This study developed and validated an analytical stability method for trans-resveratrol by high-pressure liquid chromatography with photodiode-array detection (HPLC-PDA), which allowed its quantification in the presence of its degradation products. The quantification of trans-resveratrol occurred at a retention time of 2.6 min, with ammonium formate /acetonitrile, 70/30 v/v, as mobile phase. The validation met the ICH Q2 criteria of specificity, method linearity (2.8–4.2 μg/ml), precision and accuracy, robustness, quantification limit (0.176 μg/ml), and detection (0.058 μg/ml). As degradation products, cis-resveratrol was observed at 3.9 min, which could be resveratrone in 3.2 min and five unidentified products in 0.7, 1.0, 1.4, 1.8, and 5 min. Some solutions subjected to temperature stress of 40 and 60°C, UV light, and acidic and basic hydrolysis exhibited colour changes. An analytical method was obtained by HPLC-PDA, which allowed quantifying the stability of trans-resveratrol in a fast and specific manner in the presence of its degradation products. The c-RSV  radiation at wavelengths of 254 nm or 365 nm [Some studies have indicated that t-RSV had limited stability under the influence of light, basic pH levels, and temperature, which could cause isomerization to he c-RSV  is not fr 365 nm –26. Anotr 365 nm , 26, 27.Most analytical methods reported for the identification and quantification of t-RSV have been applied in wine –30 or inStability is the most important quality requirement for a pharmaceutical product. It allows a better choice of the components that will make part of the formulation and the appropriate packaging. Stability will also provide optimal storage conditions and expiration dates . This watrans-resveratrol in the face of different conditions of forced degradation. The goal was to develop an analytical method using high-pressure liquid chromatography (HPLC) coupled to a photodiode-array detector (PDA) that allowed the quantification of trans-resveratrol in a parenteral formulation in the presence of its isomer (c-RSV) and its degradation products. The method created was validated with respect to linearity, selectivity, precision and accuracy, robustness, and quantification and detection limit. trans-RSV was assessed under acidic, basic forced degradation, oxidative degradation, and photo degradation, as well as the effects of different temperatures.Considering the low stability and solubility of t-RSV, the hypothesis of the present study was that selection of the optimal conditions of the analytical method and its validation would allow the identification and specific quantification of 2O2) (31% purity), Fermont® ; sodium hydroxide (NaOH) (98.4% purity); RA-grade hydrochloric acid (HCl) (37.8% purity); and RA-grade glacial acetic acid (HAc) (99.9% purity), JT Baker® . The water used in all the experiments was filtered using the Milli-Q water purification system (18.2 MΩ), Millipore equipment.The following chemicals and reagents were used in the present study: resveratrol (99% purity), Sigma-Aldrich® ; resveratrol, raw material (50% purity) Alephquim® ; PEG 400 and PG; ammonium formate (AF) (99.0% purity), Sigma-Aldrich® ; RA-grade formic acid (89.2% purity), Tecsiquim® ; HPLC-grade acetonitrile (ACN) (99.9% purity); ACS-grade methanol (MetOH) (99.9% purity); ACS-grade ethanol (EtOH) (99.9% purity); ISO-grade hydrogen peroxide  chamber; under the effect of temperature at 40°C, the samples were placed in a MAPSA oven, HDP-433 model and at 60°C in a Felisa oven, model 133.μm, USA) were used at a flow of 0.3 ml/min and an injection volume of 10 μl, containing 21 μg/ml of t-RSV raw material for the selection of the mobile phase. Different mixtures of MetOH, ACN, HAc , and AF (10 mM) acidified with formic acid (pH = 4) were used to choose the mobile phase. Once the mobile phase was chosen, the t-RSV response was compared with different columns: Agilent® Zorbax Rapid Resolution High Definition (RRHD) SB-C18 ; Agilent® Zorbax Eclipse XDB C8 ; Waters® Symmetry C18 ; Inertsil® ODS-3 C18 ; and Phenomenex® Luna C18 , conditioning the flow for each column with a pressure of 1200 psi.Halo® C18 columns  was used with 10 mM ammonium formate mobile phase, acidified at pH = 4 with formic acid and acetonitrile, 70/30 v/v. The mobile phase had a flow of 0.9 ml/min and a run time of six minutes. The aliquot of the injected sample was 10 μl. The chromatograms were obtained at a wavelength of 307 nm, since it is the maximum absorbance of t-RSV. The percentage of t-RSV concentration (% t-RSV) was calculated using  and Formulation 2 (F2) contained 3.5 mg/mL of t-RSV, both formulations developed in the laboratory. The placebo of F1 consisted of a mixture of EtOH/water/PEG 400, 10/30/60 v/v/v, whereas the placebo of F2 consisted of a mixture of EtOH/water/PG, 15/25/60 v/v/v.μg/ml, corresponding to 80–120% of t-RSV. Each solution was prepared independently and randomly.Five placebos were prepared with resveratrol, in a final concentration range of 2.8–4.2 μg/ml of t-RSV. For the effect of temperature, photolysis was diluted with EtOH/water, 1/1 v/v. Acid hydrolysis was diluted with 0.1 N HCl, basic hydrolysis with 0.1 N NaOH, and oxidation with 3% H2O2. Each solution was prepared independently and randomly.Standard t-RSV (STD), F1, F2, and their corresponding placebos were used for the forced degradation method. They were diluted to a final concentration of 4.2 The validation of the analytical method was performed in accordance with the recommendations established in the ICH Q2 guideline .λ = 365 nm), 0.1 N NaOH, 0.1 N HCl, 3% H2O2, and a temperature of 60°C for 24 hours (h). In order to determine the specificity, it was first confirmed that there was no analytical response in the analyte retention time.Samples in triplicate of diluent solution were used as blank. Samples of solutions corresponding to 100% concentration of t-RSV, standard solution, placebo added of F1 and F2, placebo of both solutions, and samples of F1 and F2 were subjected to UV light stress (μg/ml). Linearity was determined by linear regression analysis, calculating the correlation coefficient, determination coefficient, relative standard deviation, and confidence interval of the y-intercept.A 6-level calibration curve was performed in triplicate and independent of t-RSV standard solutions  and the value of the slope (β1), withboth values of the calibration curve, usingThe limit of detection (LOD) and limit of quantification (LOQ) were determined using the standard deviation of the The effect of intentional variations in the analytical conditions was assessed, namely: injection volume (10 ± 1 ml); mobile phase AF 10 mM pH = 4 and ACN (70/30 ± 1%); pH of the mobile phase of AF 10 mM (pH = 4 ± 1); and equipment change to UPLC. For the assessment, six loaded placebos corresponding to 100% of the analyte were analysed for each condition, calculating the absolute difference of the arithmetic mean corresponding to the area of the normal condition and to the modified condition.μg/ml concentration. The forced degradation effect was obtained under acidic, basic, and oxidative conditions, at temperatures ranging from 40 to 60°C, and the photolysis effect  and temperature effect  were assessed for 120 h, in accordance with the recommendations established in the ICH Q1A and Q1B guidelines [The forced degradation study was conducted with samples of STD, F1, F2, and placebos, which were diluted to a 4.2 idelines , 45. TheT), respectively [K0 represents the value of the unadjusted degradation constant, a value that was used to get the adjusted degradation constant (KA) obtained from the Arrhenius graph, given by P, which are percentiles taken at two or more temperatures of the study, following an Arrhenius model , and A and E are two unknown parameters [For the kinetic analysis, the t-RSV concentration was measured at different time intervals . The recovery percentages of t-RSV were used to determine the degradation kinetics for each sample, using first order equations and logarithm of the percentage of recovered t-RSV concentration (log% RSV) as a function of time in h log  KA. The time of 90% concentration (t90) was estimated using , using the statistical software STATGRAPHICS Centurion version XV.II .All experiments were performed in at least triplicate, and data are expressed as mean ± relative standard deviation (% RSD). The results were statistically assessed by analysis of variance with 5% significance level (tR), capacity factor (k′), width (w), and peak area (A) were compared for the development of the method and its optimization. First, four mobile phases were tested with the Halo C18 column, namely: MetOH/HAc , 60/40 v/v; ACN/HAc , 30/70 v/v; ACN/Water/MetOH, 30/35/35 v/v/v; and CAN/FA acidified with formic acid, pH = 4, 10 mM, 60/40 v/v, choosing the last mentioned mobile phase, due to better chromatographic parameters  in comparison to those of the other mobile phases. Then, once the mobile phase was chosen, the column was selected assessing the Halo C18, Zorbax C18, Zorbax C8, Symmetry C18, ODS-3 C18, and Luna C18 columns. Two flow rates were used: one of 0.2 ml/min in the Zorbax C18, ODS-3, and Zorbax C8 columns and the other of 0.8 ml/min in the Luna C18, Halo C18, and Symmetry C18 columns, both columns with a pressure of 1200 psi (tR = 2.6 min), a symmetric well-defined peak, a narrow peak , and a k′ of 4.27.Retention times (λ = 254 nm) for seven days to generate c-RSV. The purpose was to obtain the best resolution of the peaks and the shortest running time. The conditions with the best resolution were 70% of 10 mM ammonium formate acidified with formic acid at pH = 4 and 30% acetonitrile at a flow of 0.9 ml/min, with a resolution value of 2.91 and a tR of 2.6 min for t-RSV and 3.9 min for c-RSV  60/40 v/v, and a sample of t-RSV subjected to UV light , and the life time at 90% of t-RSV (t90), which were obtained from the first order graph of the percentage logarithm of recovered concentration of t- RSV (log% t-RSV) with respect to time, and the Arrhenius graph at each degradation condition, respectively.On the other hand, it is worth mentioning that colour change was observed in some solutions subjected to stress . There wRegarding the results under acid hydrolysis conditions, F2 had greater degradation at a temperature of 40°C, reaching 36.58% recovery on 24 h, in comparison to the results obtained at 60°C, with 52.53% recovery after 120 h. On the other hand, F1 exhibited greater stability in comparison to F2, a fact that may have occurred due to the excipients, with a recovery percentage close to 12% at both temperatures on the 120 h. However, the standard obtained lower degradation percentage than the formulations, recovering 88.06% at 40°C and 81.06% at 60°C on 120 h. The standard obtained a t90 of 174.91 h and 77.86 h at 40 and 60°C, respectively. F2 had a t90 of 20.2 h at 60°C, and 2.51 h at 40°C. In the case of F1, a t90 of 7.02 and 5.85 h were estimated for 40 and 60°C, respectively. The F2 solutions were those that exhibited colour change -IV, whicWith respect to basic hydrolysis, it was observed that, at 40°C, F2 had better stability, with a recovery percentage of 41.39%, whereas STD and F1 tended to degrade rapidly, with 4.41% recovery on 24 h, and 19.44% on 72 h, respectively. At a temperature of 60°C, it was observed that the three samples featured the same stability pattern, obtaining on 24 h a recovery percentage of 5.49% of STD, 1.39% for F1, and 0.0% in F2. At the temperature of 40°C, there were t90 values of 2.46, 2.89, and 1.54 hours for STD, F2, and F1, respectively, whereas, for the temperature of 60°C, the t90 values obtained were 0.88, 0.22, and 0.58 h. According to the values obtained, it was considered that, in the three samples assessed, basic hydrolysis exhibited a higher rate (%) of degradation in comparison to that of acid hydrolysis. It can be seen that t-RSV STD had better stability under acidic conditions, whereas, under basic conditions, F2 was more resistant to degradation. 2O2 indicated that, at 40°C, on 120 h, F1 exhibited better stability, with a recovery percentage of 43.59%, followed by F2 with 29.42%, whereas the standard degraded faster, with 15.43% recovery. The recoveries obtained at a temperature of 60°C were 28.12% on 24 h for STD, 18.35% for F1, and 0.01% for F2. The t90 value for STD, at 40°C, was 7.06 h, and at 60°C 2.05 h. For F2 40°C, it was 9.93 h and at 60°C 0.27 h. In the case of F1, t90 were 16.54 h and 1.49 h for 40 and 60°C, respectively. In this case, the formulations and the standard suffered a very rapid degradation; however, the F1 sample, at 40°C, exhibited slower oxidation in comparison to F2 and STD, which had no colour changes.Oxidation with 3% HWith respect to temperature effect, it was observed that t-RSV exhibited better stability at 4°C, temperature at which higher recovery percentages were obtained on 120 h, which were greater than 95% in the three samples. At 25°C on 120 h, the STD and F2 samples showed the same degradation trend, recovering more than 90%, whereas for F1 the degradation rate was faster, with 88.76% recovery. At 40°C, the degradation was greater for F2, recovering 65.23% on 120 h, whereas F1 exhibited the lowest degradation value (75.84%). At 60°C the degradation on 120 h for the standard was slower (67.76% recovery) in comparison to the samples of F1 and F2, which achieved 4.40 and 8.31% recovery, respectively. At 4°C, the STD sample exhibited the highest t90, with 540.24 h, whereas F1 had the lowest (457.94 h). Regarding ambient temperature (25°C), the standard sample exhibited the highest value, with a t90 of 146.77 h. The lowest value was observed in F1, with a t90 of 79.68 h. At 40°C, the t90 of the standard was 64.39, whereas those of formulations 16 and 2 were 29.60 and 26.38 h, respectively. At 60°C, the t90 of F2 and F1 were similar, i.e., 7 h, whereas the t90 of the standard was 24.09 h. In the case of thermal conditions of 60°C -III, it λ = 365 nm , the F2 and F1 samples had similar degradation behaviour (84.47% and 85.02%), whereas the STD obtained recovery of 97.48%. In ambient light, STD and F1 exhibited similar degradation values. Both formulations recovered about 85% on 120 h, whereas for F2 the recovery was 36.51%. In UV light, at a wavelength of 365 nm, on 120 h, F2 was the one that obtained the lowest degradation percentage, with 30.35% recovery, whereas the STD and F1 samples showed very similar degradation kinetics, recovering 12.26 and 11.19%, respectively. In darkness, t90 values of 701.17, 87.93, and 71.76 h were obtained for STD, F1, and F2, respectively. In ambient light, the t90 for STD was 90.51 h, in F1 85.35 h, and in F2 13.24 h. In UV light, t90 of 7.43, 6.98, and 11.64 h were obtained for STD, F1, and F2, respectively. The solutions that exhibited colour changes were those exposed to UV light at = 365 nm -VI. On 2λ = 365 nm). It was also possible to detect seven degradation products, from which their absorption spectrum was obtained. Colour change from translucent to yellow-orange was detected in the solutions subjected to forced degradation. The constant degradation for each t-RSV sample and its concentration time were determined by means of the first order equation. The samples were more stable at a temperature of 4°C and in the absence of light.An analytical method indicative of stability HPLC was developed. It allowed quantifying t-RSV in parenteral formulation and raw material. It turned out to be fast, simple, and specific in the presence of its degradation products. In addition, it featured shorter times for retention, running, limit detection, and quantification in comparison to methods reported in the literature. The method assessed in the present study met the validation parameters established in the ICH Q2 validation guidelines. Its efficiency and selectivity were confirmed by the indicative stability method, which revealed that the stability of t-RSV samples was changed by basic hydrolysis, temperatures greater than 40°C, and UV light (


The purpose of this review is to summarize data on the structure, mechanical and tribological properties, and wear patterns of composites based on high-performance polymers (HPPs) intended for use in friction units. The review includes three key sections, divided according to the tribological contact schemes regardless of the polymer matrix. In the second part, the analysis of composites is carried out in point contacts. The third section is devoted to the results of studies of HPP-based composites in linear ones. The fourth section summarizes information on flat contacts. Particular attention is paid to the formation of transfer films (TFs) in the contacts and their influence on the tribological patterns of the studied rubbing materials. As a conclusion, it is noted that the challenge of experimental methods for analyzing TFs, stated by K. Friedrich, is effectively solved in recent studies by the XPS method, which enables us to accurately determine their composition. Although this determination is completed after the tribological tests, it allows not only a more accurate interpretation of their results considering specific conditions and loading schemes, but also the ability to design HPP-based composites that form required TFs performing their preset functions. The purpose of this review is to summarize data on the structure, mechanical and tribological properties, and wear patterns of composites based on high-performance polymers (HPP) intended for use in friction units. A number of such materials are described in excessive detail in the literature, in particular, neat polyetheretherketone (PEEK) and PEEK-based composites, while a similar polyaryletherketone (PAEK) polymer has rarely been the subject of research. At the same time, polytetrafluoroethylene (PTFE) is not included in this list as a matrix material, despite the fact that it is extremely widely used as solid lubricant filler. The motivation for this critical review has been the highly ambiguous published data on the effect of the same types of fillers on the tribological properties of composites, which is illustrated many times below. The authors are aware that such an effect is associated primarily with the difference in conditions of tribological tests, including a loading scheme (a contact type), load-speed (P·V) parameters, temperatures and environments, and the counterpart material and its roughness, etc. For this reason, the conditions of the tribological tests are characterized in the description and analysis of the obtained results.As a key criterion (the top level of the classification), a contact scheme of the polymer composites and counterparts  is adopted since it determines the macroscale level of the tribological interaction of the rubbing bodies. The influence of other parameters is considered when interpreting reported values of the coefficient of friction (CoF) and wear rate (WR), as well as the characteristic mechanisms that determine an increase/decrease in wear resistance.The prospect of using HPPs to design materials for friction units is determined by their two key properties: high melting points and great strength properties. In addition to an acceptable level of melt flow index and the ability to provide interfacial adhesion to filler particles/fibers (including at a sufficiently high degree of their content), these materials are also attractive because of their ability to process and improve the stiffness/load-bearing capacity. However, advanced strength properties of this class of materials simultaneously determine great CoF levels, which in most cases can exceed 0.3 on steel under dry sliding friction (DSF) conditions. According to Brian J. Briscoe, a typical method for solving this problem is loading polymers with various types of fillers using the ‘hard and strong fillers in a softer matrix’ or ‘soft and lubricating fillers in a hard and strong matrix’ principles .2, SiC, ZnO, TiO2, Al2O3, Si3N4, CuO) with nanoparticles as a way to improve the load-bearing capacity and wear resistance of the polymer composites against counterparts . It . It 4]. HPPs include polyethersulfone (PES), polyetherimide (PEI), polyphenylene sulfide (PPS), PEEK, fluoropolymers, etc. Their attractiveness lies in the possibility of replacing metal parts with nonmetallic ones in high-tech industries . HoweverGuowei Chen named CFs, CNTs, Gr, graphene (GN) and carbon black as the key fillers for PPS in his review . AspectsA significant number of papers on the use of PEEK-based composites are devoted to orthopedic applications. The authors are looking for ways to replace metal implants (components) with polymer ones, for which neat PEEK is often loaded with CFs . In the Because the tribological properties of the polymer composites are determined by their friction surfaces, some data on the PEEK surface modification have also been reviewed. In , Singh, 2, silica (SiO2), titania (TiO2), alumina (Al2O3), CFs, aramid fibers (AFs), GF, zinc dioxide (ZnO2), zirconium dioxide (ZrO2), silicon nitride (Si2N4), and carbon nitride (C3N4). In [The unique properties of PI have determined the prospects for some practical applications of PI-based composites. The most detailed review  covers t3N4). In  nanofill3N4). In .This review consists of three key sections, divided according to the tribological contact schemes regardless of the polymer matrix. To facilitate comparison and interpretation of the presented data for each cited paper, the terms of the tribological tests are briefly outlined. This slightly complicates the possibility of generalizing the data but enables us to better identify the specific features of the obtained results.a.; B-o-D; counterpart is a ball with a diameter of 6 mm; RIn  Puhan, Da = 0.02 µm; B-o-F; DSF; LF = 0.9 and 3 N)...; P = 5 N (steel-steel); T = 25 °C). in the lubrication improvement in PEEK-steel contacts . Compareg). The PEEK TF was essentially oriented towards the steel counterpart surface. For this reason, TF formation was determined by the friction processes and the tribological contact temperature, which are not functionally dependent on the load-speed parameters a = 1.5 µm) and the 52,100 steel disc 46 mm in diameter (Ra = 10 nm); T = 25 °C; P = 1–40 N; V = 100 mm/s).. V = 100 mm/min, L = 250 mm, P = 1–30 N; (ii) P = 30 N, L = 250 mm, V = 10–500 mm/min; (iii) Ampl = 5 mm, L = 0.005–3.710 m; PEEK; RYahiaoui, M., et al. studied the tribological behavior of the PEEK-steel contact in reciprocating or unidirectional motion by varying load, speed, and sliding distance . CoF valg) glass transition temperature. Jean-Fulcrand, et al. solved this issue by combining polybenzimidazole (PBI), having one of the highest Tg points, with PEEK in a ratio of 50:50 [a(PBI) = 1.41 ± 0.43 μm; Ra(PEEK-PBI) = 1.27 ± 0.18 μm; Ra(PEEK) = 0.79 ± 0.15 μm; Ra(Steel) < 0.01 μm)..; P = 5 N; t = 30 min). under water lubrication (WL) conditions . The ‘PEeratures . Loading−4 Pa; counterpart is the GCrl5 steel ball with a diameter of 3.175 mm; Ra = n/d; V = 0.126 m/s; RR = 6 mm; P = 1 N).. = 0.15 µm; Rz(X5CrNi18-10) = 0.31 µm; Rz(Al2O3) = 0.46 µm; Rz(bronze) = 0.33 µm; P = 30.0 N; P = 21.2 N; RF = 1 Hz; V = 28.2 mm/s; L = 6 km; CP = 3–27 MPa; P·V < 0.76 MPa m/s).. as well as long woven fibers (LWF) at high sliding speeds . The prea = 0.1 μm; T = 130 and 260 °C; t = 60 min; P = 3–12 N; V = 0.25–1.00 m/s) salt can be used for improving the interface properties. As an example, Yu, L., et al. investigated ‘PI + poly-p-phenylenebenzobisoxazole (PBO)’ samples . They rea = n/d; RT; P = 100–400 N; t = 30 and 120 min). [−7 mm3/Nm (T = 350 °C at the g-C3N4 content of 5 wt.%). The observed effect was achieved due to TF formation, containing g-C3N4 with both high elastic modulus and hardness levels. This enabled the composites to effectively redistribute loads on TPI and prevent resin from abrading at the contact surfaces a(TPI) = 0.093 µm; counterpart is the GCr15 steel ring with a diameter of 3 mm; P = 5 N; V = 0.1 m/s; L = 1 km; t = 166 min; RT, 100, 200, 250, 300 and 350 °C).. Duan, C., et al. developed an effective approach for improving the high-temperature wear resistance of thermoset PI (TPI) by loading it with g-C.0 wt.%) . In a ra2-PI) in amounts of 0–15 wt.% and porous PI (0–15 wt.%) on the tribological properties of the composites. Compared to loading with neat PI, the addition of SiO2-PI and porous PI resulted in loose structures of the PTFE matrices and uneven worn composite surfaces. This promoted the formation of smooth and uniform TFs. In contrast to loading PTFE with SiO2-PI, the addition of SiO2 nanoparticles into the ‘PTFE + PI’ compounds induced the formation of rough and uniform TFs, which were detrimental to the tribological performance of the ‘PTFE + PI + SiO2′ composites a = n/d; P = 200 N; stroke length = 15 mm; frequency = 2 Hz; t = 120 min; counterpart is the GCr15 steel ball with a diameter of 9.5 mm)... . The addAs noted above, the role of nanoparticles in HPP-based composites for tribological applications narrows to (1) reinforcing the polymer matrix; (2) (solid) lubricating (with correct compositions); (3) stimulating TF fixation on counterparts. The most ‘popular’ types of nanofillers were also listed. Results of a number of papers devoted to the point composite-counterpart contacts are summarized below.2’ (0–25 wt.%) composites via in situ polymerization [2 content from 0 to 5 wt.%. Then, they enhanced CoF levels by 11% with raising the content up to 25 wt.%. At the nano-SiO2 contents of 5–10 wt.%, WR values of the composites were greater than that for neat PI. Formed TFs delaminated easily, and nano-SiO2 particles tended to be accumulated on the friction surfaces. These factors reduced wear resistance of the composites . Zhou S., et al. investigated PI-based composite coatings composed of CNTs and fluorinated graphene (FG), in which both hybrid and blend phases were mixed via solution doping [a = n/d; SF = 2 Hz; DSF; t = 30 min; P = 5 N; counterpart is the GCr15 steel ball with the diameter of 3 mm).. through grafting them onto the surfaces of hollow CNFs (HCNFs) [2 + HCNF’ composite coatings showed high wear resistance under WL conditions  and in liquid paraffin oil  a=; RT; RH = 25–30%; HCP = 112 MPa; P = 20 N; V = 1.2 cm/s (20 Hz); t = 30 min). is being extensively investigated by many researchers as a nanofiller for improving the tribological properties of PI-based composites. For example, Zhu, L., et al. showed [3N4’ composites. CoF kinetics gradually decreased with raising the g-C3N4 filler concentration but increased above 10 wt.%. At its low contents, the wear type was adhesive, while it changed to abrasive with excessive g-C3N4 levels a = n/d; DSF; reciprocating testing; P = 2, 4 and 50 N; counterpart is the GCr15 ball with the diameter of 6 mm; t = 10 min; V = 0.42 m/s; RT; RH = 40%). . The ‘PI. showed  that its2 nanosheets (0.5–20.0 wt.%) via a one-step hydrothermal method [2’ composite showed advanced tribological properties. CoF and WR values were equal to only 0.24 and 2.01 × 10−6 mm3/Nm, respectively, which were lower than those for neat PI, as well as for both ‘PI + CF’ and ‘PI + MoS2’ composites. Additionally, self-lubricating MoS2 nanosheets gradually exposed on the worn surfaces, making it easier to slide a = n/d; P = 3 N; V = 0.083 m/s; t = 30 min).. via in situ polymerization . In conta = n/d; frequency = 5 Hz; P = 10 N; t = 30 min; DSF, SLF).. under different friction conditions . CoF levomposite . Due to 2 nanoparticles  for strengthening ‘PAI + PTFE’ coatings. At a concentration of CeO2 nanoparticles of 5 wt.%, the worn coating surface was the least damaged. During friction, substance transfer was observed, accompanied by tribochemical reactions. Due to TF formation, it was possible to exclude direct contact between the components of the mating materials . = 1 μm; counterpart is the alumina ball with a diameter of 6 mm; Ra = 0.050 ± 0.002 μm; WL; T = 37 °C; P = 5 N; HCP = 37 MPa; V = 0.05 m/s; L = 0.18, 2.16 and 4.52 km). in the PEEK powder surfaces by a one-step hydrothermal method [−6 mm3/Nm for the ‘PEEK + 5% nano-ZnO’ composite, which was 68% lower than that for neat PEEK, according to a = n/d; RLS; counterpart is the CoCrMo pin with a diameter of 10 mm; Dist = 10 mm; P = 30 N; V = 5 mm/s; t = 120 min; RT; 25% CSL). to improve PEEK tribological properties . Nanocoml method . As a re2O3 and SiO2 nanoparticles, as well as with conventional SLs (Gr and PTFE). SL particles improved wear resistance at low sliding speeds, especially with negligible loads. Chelation reactions between PTFE and the steel counterpart, as well as transfer of graphitic materials deriving Gr and CF debris were the main mechanisms driving TF growth. When sliding at a P = 1 MPa and speeds from 0.05 up to 0.20 m/s, additional loading with Bi2O3 nanoparticles significantly reduced WR levels of the CF-reinforced PEEK-based composite. At higher pressures or lower speeds, the effect of Bi2O3 nanoparticles was negligible. At low loads and relatively high speeds, releasing Bi2O3 nanoparticles on the friction surface improved TF load-bearing capability. The positive role of SiO2 nanoparticles was manifested at P = 30 MPa and V = 0.1 m/s. In the case of sliding at P = 30 MPa and V = 0.01 m/s, a great load and a relatively high speed contributed to the formation of strong TF reinforced with SiO2. The antiwear role of the SLs was the most pronounced at both low loads and speeds a = 0.25 μm; DSF; RT; radius = 16.5 mm; V = 0.01–0.20 m/s; P = 1–30 MPa; t = 5 h).. However, under blowing air and sand-dust conditions, its WR values increased by 1.5–3.0 times. Blowing air resulted in reducing CoF levels of PI due to TF formation on a counterpart and raising its WR parameter. In doing so, blowing air significantly promoted the transfer of PI on the counterpart in contrast to the DSF conditions. PI exhibited the highest WR values because no TF was formed during the abrasive wear process a = 0.06–0.07 μm; RT; V = 0.424 m/s; P = 100 and 250 N). × 10−5 mm3/Nm at the maximum load in another case. The higher hardness of PI and the fragmentation of abrasive particles under high loads were responsible to the WR reduction with raising the load a = 0.06–0.07 μm; RT; V = 0.424 m/s; P = 50–250 N).. In  the samea = 0.4 μm; RT; V = 0.42 m/s; P = 100 N). × 10−5 mm3/Nm. However, since both neat PEI and PES possessed high specific WR values of 2.5 × 10−4 and 3.1 × 10−4 mm3/Nm, respectively, loading with PEEK improved their wear resistance. A TF was formed on a counterpart only in the cases of neat PEEK and PEEK-based composites, but neat PEI and PES did not form any films on the steel counterpart surface a = n/d; RT; V = 200 r/min; P = 200 N).... CFs with lengths of 28–56 μm in PEEK on the tribological behavior of the obtained composites . The ‘PEa = 0.1–0.2 µm; RT; V = 1 m/s; CP = 1.5 MPa.).... was found with the SBF content of 10 wt.%. A TF, formed on the counterpart surface, contributed to the reduction of these parameters a = 0.2 μm; V = 43.1–86.2 cm/s; P = 200–500 N).... due to the effective network structure inside the composites . and Gr (35 vol.%) contents. With rising P·V product, the CoF and WR values reduced. At V = 86.2 cm/s and P = 500 N, the composites showed the CoF = 0.07 and WR = 2.2 × 10−7 mm3/Nm a = 0.2 μm; RT; V = 43.1–86.2 cm/s, P = 200–500 N)... In  Li, J. r−7 mm3/Nm was revealed for the ‘PEEK + 10% PTFE + 10% Gr + 20% SCF’ sample. This parameter exhibited a slight dependence on the material composition, elastic modulus, and density and impact resistance opposite to its flexural properties and toughness which were not so influential a = 0.1 μm; RT; V = 1 m/s; CP = 1 MPa). and SCFs (10–25 vol.%) as fillers . The low−7 mm3/Nm and a CoF value of 0.27 were determined for the sample with the nonparallel orientation a = 0.3 μm; RT; V = 1 m/s; CP = 1–5 MPa).. . The fibMPa). In  Rasheva,2 and Gr particles. Both the lowest WR and CoF levels of 0.85 × 10−6 mm3/Nm and 0.18 were found, respectively, for the ‘PI + 10% Gr-10% SCF-3% SiO2’ composite at P = 200 N and V = 43 cm/s. It was also shown that the composites exhibited better tribological properties under higher P·V products a =0.3 μm; RT; V = 43.1 and 86.2 cm/s, P = 200–700 N)... on the tribological properties of PEEK-based composites under both boundary and mixed lubrication conditions [−7 mm3/Nm, which is 62% lower than that for neat PEEK. However, further raising the fraction of CNNS from 1 up to 2 vol.% gave rise to higher CoF and WR parameters a = 0.1–0.2 µm; RT; V = 0.03–0.80 m/s, P = 400 N).. In  Zhang, Lnditions . It was 2  on the tribological properties of PEEK-based composites [2 had the highest wear resistance at a WR value of 1 × 10−5 mm3/Nm. The nanocomposites were characterized by much smoother surfaces than neat PEEK. Reduced perpendicular strains of the PEEK matrix and decreased tangential plastic flows of the surface layer, involved in the friction process, were supposed to be important for changing the tribological behavior after loading with nano-SiO2 a = 0.2 μm; RT; V = 1 m/s; CP = 4 MPa).. on the functional properties of PI-based composites [3. A further increase in the CNT content did not cause a significant change in the properties of these nanocomposites a = 0.20–0.52 µm; RT; V = 43.1 and 86.2 cm/s; P = 50–196 N). [2O3 were characterized by the lowest WR levels under a relatively high load. At P = 200 N and V = 43.1 cm/s, the wear volume loss was 3 mm3 a = 0.20–0.52 µm; RT; V = 43.1 and 86.2 cm/s; P = 50–196 N). in amounts from 0.25 up to 2.00 wt.% on the tribological properties of PI-based composites. At a high load of 300 N, a WR value decreased down to 2.64 × 10−8 mm3/Nm for the ‘PI + 0.5 wt.% TiO2@RGO’ sample. The obtained excellent mechanical and tribological properties were attributed to the structure of the composites and chemical bonds between RGO and TiO2, which were assumed to prevent the crack propagation under friction conditions and cause the WR reduction, according to a = 0.3–0.5 μm; RT; V = 42 cm/s, P = 100–300 N) particles decorated with Fe2O3 ones [−8 mm3/Nm, which was more than 28 times lower than that of neat PI, observed for the ‘PI + RGO + Fe2O3’ composite at a load of 300 N. In this case, the tribological wear mechanism was changed due to a synergetic effect of both Fe2O3 and RGO particles on the compressive and thermal properties of the composites. As a result, TF formation contributed to low WR levels under high loads a = 0.3–0.5 μm; RT; V = 42 cm/s; P = 100–300 N). . The nan6 N). In  Wu, J., 2O3 ones . Their iglass level increased by 14 °C a = n/d; RT; V = 0.26–1.04 m/s, P = 15–30 N)... on wear resistance of PI-based nanocomposites were reported in . Also, tarticles . The hig2O3 nano- or microparticles in an amount of 5 wt.% on the tribological properties of three-component ‘PEEK + 10 wt.% PTFE’ nanocomposites [2O3 filler dimensions. The ‘PEEK + PTFE’ composite loaded with 15 nm Al2O3 particles possessed the lowest WR value of 5 × 10−6 mm3/Nm. For the composites loaded with both 90 and 500 nm Al2O3 inclusions, the increased WR value was associated with abrasive and adhesive wear types, respectively, on the surface of the PEEK-based composite compared to that loaded with 15 nm Al2O3 particles. The ability of such fillers to improve wear resistance was closely related to TF formation a = n/d; RT; V = 42 cm/s; P = 196 N)... In  Wan, H.,2, 5–20 vol.%) dispersion on the tribological properties of PI-based composites reinforced with CFs [−6 mm3/Nm) was recorded for the ‘PI + 10 vol.% TiO2 + 20 vol.% CF’ sample. The incorporation of TiO2 caused a significant improvement in the matrix stiffness a = n/d; RT; V = 1.28–3.20 m/s; P = 200–1000 N). with a content of SiC nanoparticles of 5 vol.%. Enhancing tribological performance was caused by high mechanical and tribological properties of SiC nanoparticles and an improved bonding strength between CF and PI due to both high specific surface area and the surface activity of SiC inclusions. In addition, a thin and relatively uniform TF was formed on a steel counterpart a = 0.1 μm; RT; V = 0.2–0.5 m/s; P = 600–1100 N; DSF).. In  Su, C., 2O3, CuO, SiO2, and ZrO2 (1 vol.%) [2 and ZrO2 reduced both CoF and WR parameters at P·V levels above 30 N·m/s. ZrO2 inclusions were more effective (WR = 6 × 10−5 mm3/Nm) than SiO2 ones since a TF formed with ZrO2 showed higher bearing capacity than in another case. The addition of soft nanoparticles, i.e., Bi2O3 and CuO, into the polymer matrix did not allow the formation of a strong and lubricious TF, according to a = 0.27 μm; RT; P·V = 6–300 N·m/s). and loaded with various oxide nanoparticles, i.e., Bi1 vol.%) . The adda = n/d; RT; V = 1 m/s, CP = 5–60 MPa)... under WL conditions . The sam0 N). In  Fan, S.,2, ZnS, SiO2 (5–10 wt.%) [a = 0.2 μm; RT; V = 0.5–4.0 m/s; CP = 1–8 MPa). . The low2, SCFs, Gr, and PTFE were used as fillers. In both mixed and boundary lubrication regimes, the structure of the nanocomposites affected significantly their tribological performance. TF formation on the surface of a metallic counterpart played an important role in this phenomenon a = 0.2–0.3 μm; RT; V = 0.2–2.0 m/s; CP = 5 MPa). on the tribological performance of PPS-based nanocomposites in low-sulfur diesel as a lubricant. The best tribological properties were determined for the ‘PPS + SCF + Gr + AlN’ sample with a specific WR level of 1.3 × 10−7 mm3/Nm and a CoF value of 0.08. Tribochemical reactions of PPS with a steel counterpart and AlN nanoparticles resulted in the formation of a robust TF a = 0.2 μm; RT; V = 0.38 m/s; P = 100 N).. [−7 mm3/Nm under DSF conditions at P = 500 N). The filled composites exhibited both better friction and wear behavior in an oil lubricator and showed worse tribological properties under WL conditions (as compared with DSF ones). In this case, an increase in the WR level was due to the fact that water might be first absorbed into voids at the interface between SCFs and the PI matrix, diffused slowly into the matrix that caused fall out of SCFs and their ‘cutting’ effect a = 0.2–0.3 μm; RT; V = 0.431 and 0.862 m/s; P = 200–500 N)., Gr (10 vol.%). and nano-Si vol.%). . With an2 and WS2 particles (10 wt.%) in both micro and nanoforms as secondary SLs. Filling with WS2 resulted in better performance than that for the MoS2 case. Nanoparticles were more efficient than microsized ones. The sample loaded with a combination of nano and microparticles of WS2 showed the best performance compared to other bearings, since a continuous thin TF reduced both CoF and WR parameters a = 0.2 μm; RT; V = 0.5 m/s; P = 100–500 N). = 0.5 μm; RT; V = 0.1 m/s; P = 60 and 125 N; CP = 1.8 and 3.9 MPa; DSF). = 0.2 μm; counterpart is a steel pin of 56.6 HRC with a diameter of 20 mm; R Yan, et al. investigated a series of PEEK-based composites loaded with different PI contents (10–50%) [glass. The optimal PI content was 30% a = 0.5 μm; RT, 100 and 200 °C; V = 0.5 m/s; P = 10 N; DSF). . Thermala = 0.15–0.30 μm; RT; V = 1.4 m/s; P = 200 N).% C-(0.17–0.37)% Si-(0.50–0.80)% Mn steel; R For self-lubricating PPS-based composites, Wang, H., et al. showed that loading with 1 wt.% zeolite and impregnating with lithium-base grease in pores resulted in greatly lowering both CoF and WR parameters . Compared to neat PPS, the CoF level reduced by 90%, and the WR value increased by 4.67 × 104 times. Wear resistance enhanced by 3.6 times that for the ‘PPS + 30 wt.% NaCl’ composite. Due to both high load and temperature levels, grease squeezed from micro and nanopores provided the excellent lubrication effect [a = 0.15–0.30 μm; counterpart is the (0.42–0.50)% C-(0.17–0.37)% Si-(0.50–0.80)% Mn steel; RT; V = 1.4 m/s; P = 150 N; DSF...... In  Shen et a =0.2 µm;RT; V = 0.2 and 1.0 m/s; P = 50 N; CP = 3 MPa; air, high vacuum and hydrogen with a purity of 99.999%).... In  Davim eta = 0.5 µm; RT; V = 0.25 and 0.75 m/s; P = 2.68 and 8.00 MPa; DSF).. In [−16 m3/N × m, respectively. (They have decreased with raising the P·V parameters.) The limit P·V values were 112 and 100 MPa·m/s for the composites with 30 and 40 wt.% SGF, respectively. Loading with 30 wt.% SGF provided both lower CoF and WR levels at higher P·V limit values compared to the second investigated composite a = n/d; RT; V = 1.6.Davim et al. compared both CoF and WR parameters for neat PEEK, as well as the ‘PEEK + 30 wt.% CF’ and ‘PEEK + 30% GF’ composites . The lowomposite . It was DSF). In  Panda eta = n/d; RT; V = 0.1 m/s, P = 50 N; DSF, dry or slurry erosion and high stress abrasive conditions). and WR levels over a wide range of sliding speeds and loads. (The first parameter has a greater effect than the second one.) For V < 3 m/s, the CoF values decreased as speed increased if the contact pressure was stable. For V > 3 m/s, the contact pressure increased with rising speed. The ‘CFR + PEEK’ TF on the Si3N4 counterpart and water lubrication could significantly reduce the CoF levels. In this case, the contact pressure affected the WR value of the composite through its influence on the surface temperature. The WR value enhanced mainly from material transfer caused by adhesion and mechanical plowing. TF formation alleviated friction. In addition, raising the P·V product resulted in increased surface temperatures and improved PEEK ductility 3N4; Ra = 0.15 μm; RT; V = 1.36–3.70 m/s; CP = 0.45–0.92 MPa; DSF). = 200 μm; Ra(#120) = 175 μm); Ra(#150) = 125 μm; Ra(#220) = 50 μ; Ra(#320) = 45 μm; Ra(#400) = 40 μm; Ra(#600) = 30 μm; Ra(#800) = 20 μm; RT; V = 0.36 m/s; P = 2–10 N; DSF). = 0.8 μm; 30±1 °C; V = 0.012–4.000 m/s; CP = 0.25–2.00 MPa; WL).. In  Yamamotoa = 3.2 μm; RT; V = 0.35 m/s; P = 100–400 N; DSF).. were less than 5% (related to improved heat resistance properties). Compared to other compositions of the studied coatings, the ‘PPS + 45% PTFE’ coating did not show any signs of failure for 15 h a = 0.15–0.30 μm; counterpart is a steel pin; RT; V = 0.47 m/s; CP = 1.4 MPa; DSF).. In  Jones, Mcoatings . The ‘PPa = 0.5 μm; RT; V = 1 and 2 m/s; CP = 4, 8 and 10 MPa; DSF). under various load conditions [a = 0.042 μm; RT; V =2 m/s; CP = 1.0, 1.5 and 2.0 MPa; DSF).. Upon sliding, grease could be squeezed through nano/micro hierarchical pores under a coupling effect of load and friction heat. As a result, a stable layer was formed on the friction surface, providing the self-lubricating effect and improving wear resistance a = 0.15.In  Qi, H., nditions . It was DSF). In  Zhu, Y.,2. As an example, Zalaznik et al. studied the effect of micro and nanosized MoS2 and WS2 particles in PEEK upon dry sliding on the 100Cr6 stainless steel [2 and WS2 particles reduced CoF levels (down to 30%) regardless of their contents and sizes. However, nanosized particles required a higher content to form an effective TF with a low CoF value. TF formation was necessary to reduce WR levels (down to 51%) for all composites. In addition, loading with particles of all studied types caused enhanced hardness and improved wear resistance as a result. The XPS data showed that oxidation occurred upon the sliding process, reducing the beneficial effect of particles on the wear behavior a = 0.5 μm; RT; V = 0.05 m/s; CP = 1 MPa; DSF)., which is a mix of MoS2, SiO2, CuS, Al2O3, etc., as well as PTFE upon sliding on a steel counterpart [3/km. In the cases of the ‘PPS + MS + PTFE’ composites, TFs formed on the steel counterpart surface were very thin and uniform. Their XPS analysis showed that MoS2 decomposed into Mo and S to form both MoO3 and FeSO4 compounds. The presence of FeSO4 in the TFs indicates a tribochemical reaction between S and Fe on the counterpart, which contributed to the WR reduction between them. This retarded the TF loss from the counterpart and contributed to the WR reduction a = 0.06, 0.10 and 0.14 μm; RT; V = 0.5, 1.0 and 1.5 m/s; CP = 0.65 MPa; DSF).. These characteristics enhanced as the sliding conditions got harder . The composite filled with WS2 was characterized as the most wear resistant at moderate P·V products. Under the most severe conditions, the one with MoS2 showed the highest result. All studied composites proved to be excellent materials for tribological units . Loading with 3 wt.% MoS2 micro or WS2 nanoparticles greatly improved the tribological performance of the composites. In the WS2 case, this effect was less pronounced due to improper deagglomeration of these heavy particles. XPS studies found the partial formation of oxides including MoS2 or WS2 a = 0.1. Song, J., et al. evaluated PI-based composites filled with aramid fibers, Gr, and MoS2 or PTFE [2 + AF’ and ‘PTFE + AF + PI’ ones at 6 MPa and 7 Hz upon 8 h. TFs formed between a phosphor bronze pin and the ‘PI + MoS2 + AF’ or ‘PTFE + AF + PI’ composite surfaces changed both contact states and wear mechanisms that enabled a long service life of these tribological matings. a = 0.1 μm; F = 3–11 Hz, CP = 4, 5 and 6 MPa; DSF).Graphite as a solid lubricating filler was used by the authors of ,144,145.a = 0.08.–0.22 μm; RT; V = 0.2 and 1.0 m/s; P = 50 N; DSF, vacuum of 10 Rodriguez, V., et al. assessed the friction and wear response of neat PEEK, as well as the ‘PEEK + CF + Gr’ and ‘PEEK + CF + Gr + PTFE’ composites [a = 0.20 µm; RT; V = 20 and 50 mm/s; CP = 4.8 and 10.0 MPa; DSF)..; RIn  Liu, L.,sistance . The low2 or Gr in vacuum [2 demonstrated better tribological properties compared to those for the one loaded with Gr only at low temperatures. At −80 °C, both negligible CoF and WR levels of the composite filled with MoS2 were recorded due to a thin polymer TF formed on a counterpart because of a higher MoS2 content on the composite surface. A transition from severe to moderate wear was observed in a P·V range from 0.01 up to 0.10 MPa·m/s. At RT in vacuum, the optimum performance was determined at P·V = 1 MPa·m/s. Depending on both temperature and sliding speed parameters, the composites filled with MoS2 showed great wear resistance and low CoF levels a = 0.2 μm; −80, −40, −20 and +20 °C; V = 0.01, 0.10 and 1.00 m/s; CP = 1 and 7 MPa; DSF)..The tribological characteristics of SL-based composites have also been studied under various conditions and environments in ,149,150.n vacuum . PEEK fi−16 and 4 × 10−16 m3N/m and CoF levels of 0.40 and 0.32 were determined for neat PAI and the ‘PAI + 12% Gr + 3% PTFE’ composite, respectively. The wear mechanism included both adhesive and abrasive processes a = 0.2 µm; RT; V = 0.5, 1.0, 2.0 and 3.0 m/s; P = 50, 100 and 150 N; DSF with and without air cooling) . With ri2’ nanocomposite to a contact and improved the tribological properties under severe load conditions (at P·V > 8 MPa·m/s). In this case, released nanoparticles were sintered during the sliding process. As a result, a compact protective layer was formed on a steel counterpart and improved TF load-bearing capacity. Consequently, the direct contact between the composite and the counterpart were diminished and decreased both CoF and WR levels, according to a = 0.15 µm; RT; V = 0.1–4.0 mm/s; CP = 1–4 MPa; DSF).., the WR values were higher. Loading with CNFs did not affect CoF levels of the studied composites a = 0.06–0.08, 0.09–0.11, and 0.13–0.15 μm; RT; V = 1 m/s; CP = 0.65 MPa; DSF)..... nanoparticles upon sliding on the MCS35 steel and NiCrBSi alloy counterparts . During 2 and SLs (PTFE and WS2) in ‘PI + CF’ composites on their tribological performance over a wide range of load-speed parameters. Filling with nano-SiO2 particles enabled a significantly reduction in CoF levels regardless of the P·V products. Under mild P·V conditions, wear resistance of the ‘SCF + PI + SiO2 + SLs’ composite was improved through the synergistic effect of nanoparticles and the SLs. However, WR values enhanced significantly with rising P·V up to 59.26 MPa·m/s due to incorporating the SLs and their thermal instability. The fiber-matrix interface protection by nanoparticles, higher in both mechanical properties and thermal stability of SiO2, were responsible for enhancing the P·V limit up to 152.37 MPa m/s a = 0.2–0.3 μm; RT; V = 1–3 m/s; P = 100–900 N; CP = 5.65–50.85 MPa; DSF). and, consequently, reduced WR values by 90% compared to that for neat polymer due to the rapid formation of a high-quality TF because of some tribochemical reactions [a = 0.1 µm; RT; V = 0.5 m/s; P = 10 N; CP = 12.8 MPa; DSF)... The formation of a polymeric TF on a metal counterpart surface was crucial in achieving the ultralow WR and CoF levels under DSF conditions a = 0.1.Golchin, A., et al. determined the tribological characteristics of ‘PPS + SCF + MWNT + Gr’ composites under WL conditions . Loading WL). In  Panda et−8 mm3/N·m), compared to that for the composite with CNFs. This phenomenon was associated with the use of poly (DMS) that provided a cushioning effect in the matrix. Also, the phosphate grafting of poly (DMS) was implemented. In addition, the nanoscale of both fillers and their specific surface treatment using aminosilane for enhancing the matrix-filler interfacial bonding enhanced this effect. The maximum wear resistance was observed at the nano-HA contents of 7–8% a = 10 μm; RT; V = 400 rpm; P = 5, 30 and 60 N; DSF). a = n/d; RT; V = 0.072 m/s; P = 15 N; DSF). on the tribological properties of PI-based composites [−6 mm3/N·m) at its content of 15 wt.%. The lowest CoF value was 0.135. A TF, formed on the surface of this self-lubricating composite, was smooth and continuous, which was the reason for the low WR level a = 0.1–0.2 μm; RT; V = 0.48 m/s; P = 200 N; DSF). loaded with a low content of CNFs and various percentages of nano-HA particulates . FillingDSF). In  Chen, Y.mposites . Under D−6 mm3/N·m was registered, which was 60% lower than under the DSF conditions. The worn surface of neat PI was characterized by strong adhesive wear, while the main wear mechanism was abrasive for the ‘PI + PTFE + CNT’ composite. The worn surfaces of the ‘CNT + PTFE + PI’ samples were smoother after sliding in oil or alkali lubricators than those under the DSF or WL conditions a = 0.1–0.2 μm; RT; V = 1.4 m/s; P = 200 N; DSF, WL, oil- or alkali-lubrication).. lubricating medium. In this case, according to the classical patterns of tribology, rising wear resistance at a low CoF value is determined by the ability to retain a lubricating film on the contact surfaces. Materials that increase surface energy or containing functional groups contribute to this phenomenon.Under DSF conditions, a harder counterpart, which contains asperities on its surface, affects the softer polymer surface, contributing to its wear. A part of debris is transferred and fixed on the counterpart or/and polymer (composite) surfaces, depending on the tribological loading conditions . This is classified as a TF formation process in both cases. Changing tribological properties are determined by TF evolution, including its replenishment with newly formed debris from the initial polymer and the oxidized or fractured material. Filler particles can contribute to strengthening such a film, as well as its adherence on the sliding surfaces in the tribological contacts.In a liquid medium (under the boundary lubrication), the tribological properties of fiber-reinforced HPP-based composites are greatly determined by the effect of this medium on the polymer matrix or the interface with reinforcing inclusions. In doing so, the wear intensity may be increased due to degradation of the composite structure on the sliding surface even at low CoF levels. Under severe tribological test conditions, the wear process can be transformed into a (micro)abrasive type due to rising temperature and local evaporation of the liquid medium.The analysis of the above tribological test results on both HPPs and their composites using the point, line, and flat schemes has enabled us to state the following. The variety of the used fillers, the test conditions, and the achieved tribological properties show that the optimal compositions of the HPP-based composites for the given applications are highly case sensitive. There is no universal composition that has advanced functional characteristics under any circumstances. In the opinion of the authors, the following factors play an important role in the achieved tribological properties with the applied classification principle  of the hard counterpart surface, the TF purpose narrows to form smooth sliding contacts. The counterpart contact area is small, and both high specific pressure and local temperatures in the contact contribute to the TF adhering. The TF source is the entire sliding surface, so a large amount of debris is not required to form it. Especially with the addition of solid lubricant particles, this enables the achievement of extremely low wear rates at negligible CoF values. Under severe tribological test conditions (high P·V products), wear resistance is limited by the HPP matrix stability, the bonding strength with fillers, the ability of the TF to be adhered in the tribological contact zone, etc.Most studies of this contact type have been performed according to the ‘block-on-ring’ scheme. Compared to the previous case, the specific pressure is lower and the key differences are: (1) raising the number of asperities due to enhancing the contact area (which causes increasing CoF levels); (2) generally rougher counterpart surfaces (Ra > 0.1 µm); (3) due to its high roughness, a protective TF over the entire counterpart sliding surface needs to be formed from the wear debris; (4) the role of solid lubricant inclusions is significantly leveled, while an increase in wear resistance can be achieved by improving strength (reinforcing) of HPP-based composites. However, it is the possibility of TF formation and adherence on the harder counterpart, realized due to the chemical activity or increased surface energy of the filler, which enables the reduction in the CoF values. An alternative way is the formation of a thin modified (strengthened) layer on the wear track surface, which facilitates sliding and reduces wear intensity.This kind of tribological contact is predominantly implemented with the ‘pin-on-disk’ scheme. However, a harder counterpart (disk) rotates relative to a fixed softer pin, unlike point contacts. The disc roughness is predominantly comparable to that for the ‘block-on-ring’ scheme (Ra > 0.1 µm). An increase in the contact area and the number of asperities on the sliding surfaces impose further restrictions on the structure and properties of polymers (composites). In this regard, the TF role also increases, which can be formed not only on the sliding surface of the hard counterpart (covering hard asperities), but also on the flat pin surface. In the first case, debris should form a continuous film that can adhere on the hard counterpart (at the running-in stage). Additionally, it is necessary to minimize the transfer of  wear particles from the hard counterpart to the polymer pin to avoid enhancing CoF levels due to the solid-on-solid friction. On the other hand, the possibility of forming a modified reinforced layer on the sliding surface of the HPP pin is a way to increase both the CoF and WR values.As a final conclusion, it should be noticed that a challenge of experimental methods for analyzing TFs, stated by K. Friedrich in , is effe


Diabetes mellitus (DM) is considered to be associated with an increased risk of colorectal cancer. Recent studies have also revealed that tubulin hyperacetylation is caused by a diabetic status and we have reported previously that, under microtubule hyperacetylation, a microtubule severing protein, katanin-like (KL) 1, is upregulated and contributes to tumorigenesis. To further explore this phenomenon, we tested the effects of the ketone bodies, acetoacetate and β-hydroxybutyrate, in colon and fibroblast cells. Both induced microtubule hyperacetylation that responded differently to a histone deacetylase 3 knockdown. These two ketone bodies also generated intracellular reactive oxygen species (ROS) and hyperacetylation was commonly inhibited by ROS inhibitors. In a human fibroblast-based microtubule sensitivity test, only the KL1 human katanin family member showed activation by both ketone bodies. In primary cultured colon epithelial cells, these ketone bodies reduced the tau protein level and induced KL1- and α-tubulin acetyltransferase 1 (ATAT1)-dependent micronucleation. Resveratrol, known for its tumor preventive and tubulin deacetylation effects, inhibited this micronucleation. Our current data thus suggest that the microtubule hyperacetylation induced by ketone bodies may be a causal factor linking DM to colorectal carcinogenesis and may also represent an adverse effect of them that needs to be controlled if they are used as therapeutics. Diabetes mellitus (DM) has been associated with increased risk of multiple cancer types, including colorectal cancer (CRC) ,2. CommoKetone bodies have been well-established to be representative pathogenic substances in DM. They are small, lipid-derived molecules that serve as a circulating energy source for tissues in times of fasting or exercise. Ketone bodies include acetoacetate (AA), β-hydroxybutyrate (BHB), and acetone, and ketogenesis mainly occurs in the mitochondria of liver cells, which normally produce ketone bodies as the result of fatty acid breakdown when the blood glucose levels are low. Ketogenesis also occurs in kidney cells, brain astrocytes , and colIn terms of an association with tumorigenesis, although the ketogenic diet has been evaluated for cancer prevention and treatment purposes with the hope of attenuating tumor growth via calorie restriction, there have been studies suggesting tumor promoting effects of ketosis. A chemical induction of DM in rats with streptozotocin has been reported to be sufficient to enhance tumor growth . SimilarThe studies of both human patients and an animal model of DM have shown that enhanced tissue tubulin acetylation is a characteristic of this disorder ,15. Prevt-test, p < 0.05), 2.7 ± 0.2 (p < 0.01), 2.9 ± 0.2 (p < 0.05), and 3.9 ± 0.3 (p < 0.01), for AA at 5 and 10 mM, and BHB at 10 and 20 mM, respectively. In RFL-6 cells, these ratios were 1.6 ± 0.1, 5.9 ± 0.6 (p < 0.01), 1.3 ± 0.1, and 3.3 ± 0.2 (p < 0.01), for AA at 5 and 10 mM, and BHB at 10 and 20 mM, respectively  and 1.38 ± 0.1 (p < 0.05)-fold increases in the detyrosinated-tubulin/α-tubulin ratio in AA at 5 and 10 mM treatment, respectively, and a significant 1.6 ± 0.1 (p < 0.01)-fold increase in the polyglutamylated-tubulin/α-tubulin ratio following 10 mM AA treatment of HCT116 cells. Notably however, the BHB treatment produced no enhancement of detyrosination or polyglutamylation  and 2.7 ± 0.2 (p < 0.01), and 2.9 ± 0.1 (p < 0.01) and 3.3 ± 0.2 (p < 0.01), for AA at 5 and 10 mM, and BHB at 10 and 20 mM, respectively. The transcript levels of α-tubulin acetyltransferase 1 gene were examined by RT-PCR but showed no change (N-acetyl-l-cysteine (NAC) [To further elucidate the mechanisms by which the AA and BHB ketone bodies increase microtubule acetylation, we first examined whether the TCA cycle intermediates generated through ketone body oxidation in mitochondria are required to induce microtubule hyperacetylation. We tested the effects of the TCA cycle entry inhibitor aminooxyacetate (AOA)  for thato change . It has o change B. We nexne (NAC) . Both agne (NAC) , which lne (NAC) . We therne (NAC)  and confne (NAC)  in ketonne (NAC) .p < 0.01) compared with the siHDAC3 alone, whereas BHB treated cells did not (1.0 ± 0.1), under a HDAC3 knockdown , and 3.6 ± 0.1 (p < 0.01) for 10 mM AA- and 20 mM BHB-treated cells, respectively, and 0.4 ± 0.1, 0.5 ± 0.1, and 0.7 ± 0.1, for untreated-, AA-, and BHB-treated cells under siATAT1 transfection, respectively. Western blot analysis confirmed these increases . These data support our hypothesis.Microtubule hyperacetylation has been shown to have carcinogenesis promotive effects ,18 and AHCT116 cells have been demonstrated to be chromosomally stable  and we tp < 0.01) in the BHB-treated HCECs.Since we observed significant effects of BHB upon HCT116 in micronucleation, we further tested this ketone body on primary cultured normal human colon epithelial cells (HCEC) that have been used in CRC studies . Previoup < 0.01) and 1.0 ± 0.2 for BHB alone and BHB + resveratrol, respectively; p < 0.01) and 0.9 ± 0.1  for BHB alone and BHB + siATAT1, respectively; We also transiently transfected HCECs with siRNAs against ATAT1 and KL1. Significantly, more than 80% reductions in both ATAT1 and KL1 proteins were achieved C,D. A nap < 0.01), and 1.1 ± 0.3%  for control, BHB, and BHB + siATAT1, respectively), supporting the microtubule acetylation-dependence of the micronucleation  supporting the causal role of KL1  [Under these same experimental conditions, we further performed immunofluorescence analyses of the HCECs with nuclear and anti-centromere antigen  staining  .These results suggest that exposure to BHB generates aneuploidy, a tumor cell trait, in normal human colon epithelial cells.We have here evaluated the relationships between ketone bodies and carcinogenesis. Our data show that at a more than 10 mM concentration, both the AA and BHB ketone bodies commonly induce cellular microtubule hyperacetylation, whether the cells were transformed or not, and that this effect causes chromosome aberrations in colon epithelial cells. This may indicate that although a lower than 10 mM dose of a ketone body has beneficial effects for human health , which mThe mechanisms through which ketone bodies elicit microtubule hyperacetylation may involve stress response signal cascades driven by ROS . BHB see+ reduction causes similar perinuclear microtubule acetylation enhancement in stimulated macrophages [The functional role of perinuclear region-centered microtubule hyperacetylation is an important question to emerge from our current study and prior reports. For example, NADrophages . The mitrophages . Given trophages . AlternaAPC) is known to be frequently mutated in human colon cancer. The APCMin/+ mouse is an established animal model of human adenomatous polyposis and these mice spontaneously develop multiple polyps in the small intestine [Adenomatous polyposis coli -3-Hydroxybutyric acid  was purchased and dissolved in phosphate-buffered saline, as described previously  (as BHB)Mouse monoclonal antibody anti-polyglutamylated tubulin, mAb (GT335) was purchased from Enzo Life Sciences . Commercially sourced mouse monoclonal anti-α-tubulin , Cy3-conjugated-β-tubulin (Sigma) , anti-SIRT2 (A-5), anti-HDAC3 (A-3), anti-β-actin (AC-15)  and anti-acetylated-α-tubulin (clone 6-11B-1) (Sigma) were used in the experiments. Mouse monoclonal phospho-independent anti-Tau antibody (T1029) was obtained from USBiological . A rabbit polyclonal antibody against DDDDK-tag was used as the anti-Flag antibody . Rabbit polyclonal Anti-Tubulin Antibody, Detyrosinated  was also used. Rabbit polyclonal antibody against KATNAL1  was obtained from Sigma and rabbit polyclonal anti-ATAT1 was sourced from Epigentek  for use in ATAT1 detection. The detected major bands were isoform 3 (NCBI Reference Sequence: NP_001177653.1) in HCT116 cells and isoform 1 (NCBI Reference Sequence: NP_001026892.1) in both IMR90-SV cells and HCECs. Rabbit monoclonal anti-p53 antibody  and anti-FOXO3A  were used as was a human anti-centromere antibody  (as ACA). Rabbit anti-phospho-AMPKα (Thr-172) and anti-AMPKα1/2 were from Cell Signaling Technology.Human FKat, FKL1, and FKL2 expression vectors were purchased from GenScript : KATNA1_OHu05824C_pcDNA3.1 + N-DYK, KATNAL1_OHu10589C_pcDNA3.1 + N-DYK, and KATNAL2_OHu103129C_pcDNA3.1 + N-DYK, for FKat, FKL1, and FKL2, respectively.5 and 1.5 × 105 cells/well were seeded onto six-well plates for RFL-6 and IMR90-SV cells, respectively. For immunofluorescence studies, approximately 1.0 × 105 RFL-6 or IMR90-SV cells/dish were plated onto 3.5 cm glass-bottom dishes. In the microtubule sensitivity test IMR90-SV cells were plated one day before siRNA transfection, transfected with 4 μg of each plasmid using Nucleofector II  with program X-005 from the manufacturer. The cells were plated on 3.5 cm glass-bottom dish  as described previously [Rat RFL-6 fibroblasts were purchased from Health Protection Agency , and were cultured as described previously ,19. Humaeviously . The tra5 cells/well were seeded onto six-well plates. For immunofluorescence studies, approximately 1.0 × 105 cells/dish were plated on 3.5 cm glass-bottom dishes. In the experiments testing AOA, cells were plated one day before the experiments. For the knockdown of HDAC3, two siRNAs were used in an equimolar cocktail . For the first siRNA, the oligomers sense: ggaaugcguugaauauguc and antisense: gacauauucaacgcauucc  were anescribed . We used2 in accordance with the manufacturer’s instructions. For immunoblotting analysis, approximately 2.5 × 105 cells/well were seeded onto six-well plates. For immunofluorescence studies, approximately 1.5 × 105 cells/dish were plated onto collagen-coated 3.5 cm glass-bottom dishes. Transfection of HCECs with siRNAs was performed using TransIT-X2 Dynamic Delivery System . For the knockdown of KL1, the Dharmacon siRNA smart pool  was used, as described previously [Primary cultured normal human colonic epithelial cells (HCoEpiC) were purchased from ScienceCell Research Laboratories . These cells were generated from human colonic tissues and cryopreserved at passage one. Experiments were performed within five passages. Cells were cultured in Colonic Epithelial Cell Medium  at 37 °C and 5% COeviously ,19,81. FCell viability was determined following all treatments to rule out cell death using a Trypan Blue  exclusion assay, as described previously .t-test.Western blotting and subsequent quantification of the signals was performed using LumiCube  as described previously ,19. WholHuman colon tissue lysate test strips  and -2 ) were purchased from Protein Biotechnologies . The strips were immunoblotted with anti-acetylated-tubulin and anti-α-tubulin antibodies in accordance with the manufacturer’s instructions using ECL reagents. All cases on the strip were stage I-IV adenocarcinomas. The following cases could be evaluated without experimental artifacts: T7-013, T7-017, T7-018, and T7-022 on the ST7-6X-1 strip and T7-037, T7-041, T7-044, and T7-046 on the ST7-6X-2 strip. Three independent experiments were performed for each blot. The expression levels were evaluated by densitometry with cut off values of 1.5 and 0.67. Data analysis was performed as done for the western blots.5 HCT116 cells/well were seeded onto six-well plates and were treated with ketone bodies and cultured for two days. One microgram of total cellular RNA, extracted from cells by applying TRI Reagent , was transcribed into cDNA using All-In-One 5X RT MasterMix . For the comparison of the ATAT1 mRNA levels, 1 μL of reaction product was analyzed. PCR was performed using EconoTaq Plus Green 2X Master Mix  with the following conditions: 2 min at 94 °C, 30 cycles of 20 s at 94 °C, 20 s at 55 °C, 30 s at 72 °C, and a final incubation for 10 min at 72 °C, using an ASTEC PC320 thermocycler . β-actin was used as an internal control . The MEC-17 (f) and MEC-17 (r) primers were used for ATAT1 amplification, as described previously [t-test.Approximately 4.0 × 10eviously . Three it-test.Immunostaining experiments were performed as described previously ,19. For 5 cells/dish onto 3.5 cm glass-bottom dishes, treated with ketone bodies, and cultured for two days. Cells were further incubated with 10 μM DCFDA for 30 min at 37 °C, rinsed twice with Hank’s balanced salt solution (HBSS) (Life Technologies) then maintained in HBSS and analyzed at a 200× magnification under a fluorescent microscope. ROS signals were then quantified as described previously [t-test.DCFDA was used as a cell-permeable fluorogenic probe to quantify the ROS level. This compound is rapidly de-esterified in cells and is oxidized to form fluorescent 2′,7′-dichlorofluorescein, which displays excitation/emission spectra of 492/515 nm. HCT116 cells were plated at about 1.0 × 10eviously . The opt


Pseudallescheria boydii SNB-CN85 isolated from termites produces ovalicin derivatives resulting from the esterification of the less hindered site of the ovalicin epoxide by long-chain fatty acids. Their structures were elucidated using spectroscopic analysis and semisynthesis from ovalicin. For ovalicin, these compounds displayed antiprotozoal activities against Plasmodium falciparum and Trypanosoma brucei, with IC50 values of 19.8 and 1.1 µM, respectively, for the most active compound, i.e., ovalicin linoleate. In parallel, metabolomic profiling of a collection of P. boydii strains associated with termites made it possible to highlight this class of compounds together with tyroscherin derivatives in all strains. Finally, the complete genome of P. boydii strains was obtained by sequencing, and the cluster of potential ovalicin and ovalicin biosynthesis genes was annotated. Through these metabolomic and genomic analyses, a new ovalicin derivative named boyden C, in which the 6-membered ring of ovalicin was opened by oxidative cleavage, was isolated and structurally characterized.Social insects are in mutualism with microorganisms, contributing to their resistance against infectious diseases. The fungus  Insects might be the most represented and diverse living creatures on earth . In natuTermites (Blattodea: Isoptera) are eusocial insects comprising more than 3000 species, mostly distributed in tropical and subtropical regions. All termites live in nests containing 1 to 1.5 million individuals divided into castes  that cooperatively perform colony tasks. These insects play an important role in ecosystems through the decomposition of plant lignocellulose, having a positive impact in nutrient cycling and soil–water dynamics through their nest construction and tunnel networks in the soil . TermiteThe investigation of under-explored microbial niches, such as termite-associated microorganisms, can provide original active metabolites ,7,8,9,10Pseudallescheria from three different termite colonies (out of eight nests harvested) . It. ItP. bonetworks . These tumigatus . The eig_Ova_A–H , and the_Pse_A–F . Their f3.1 ppm) . A hydro of 0.34 . Finally2–6 and sheds light on subunits’ ovalicin absolute configurations.This biosynthetic scheme was fully consistent with experimental data proposed previously, concerning configurations of compounds P. boydii metabolome, we looked for nodes with intense signals but could not annotate them by searching standards and analogs in MetGem databases. It was chosen to isolate the specialized metabolites showing an ion signal at m/z 323.1433 , indicating the presence of two additional oxygen and the lack of one carbon compared with the molecular formula of ovalicin (1). The 1H NMR spectra of Compounds 1 and 7 displayed some similarities, suggesting that 7 was an analog of 1. The remarkable difference between Compounds 1 and 7 in 1H NMR was the absence, in 7, of the singlet methoxy signal integrating for 3H at δH 3.49 , δH 1.73 , and 1.67 . The examination of the COSY correlations allowed us to link this dimethylallyl moiety to H-8 at 3.26,  D) were measured on an Anton Paar MCP 300 polarimeter in a 100 mm long 350 μL cell . IR spectra were recorded using a Perkin Elmer Spectrometer BX FT-IR . Nuclear magnetic resonance (NMR) spectra were recorded on a Bruker 600 MHz spectrometer equipped with a 3 mm inverse detection cryoprobe or a Bruker 500 and 800 MHz spectrometer equipped with a 5 mm inverse detection probe . Chemical shifts (δ) are reported as ppm based on the TMS signal. HR-ESI-MS measurements were performed using a Waters Acquity UPLC system with column bypass coupled to a Waters LCT Premier time-of-flight mass spectrometer equipped with an electrospray interface (ESI) . Flash chromatography was performed on a Grace Reveleris system with dual UV and ELSD detection equipped with a 40 g C18 column. Analytical and preparative HPLCs were conducted with a Gilson system equipped with a 322 pump device, a GX-271 fraction collector, a 171 diode array detector, and a prepELSII electrospray nebulizer detector . Columns used for these experiments included a Phenomenex Luna C18 5 μm 4.6 × 250 mm analytical column and a Phenomenex Luna C18 5 μm 21.2 × 250 mm preparative column. The flow rate was set to 1 or 21 mL/min using a linear gradient of HTermes cf. hispaniolae and Nasutitermes corniger by Prof. Reginaldo Constantino . The workers were surface-sterilized by successive soakings in 70% EtOH (2 min), 5% NaOCl (2 min), and sterile water. The termite was subsequently placed in a Petri dish containing solid PDA medium. After 1 week at 25 °C, the first fungal hyphae to emerge from the insect were sampled and transferred into other Petri dishes. One of the microbial colonies consisted of a pure fungus, which was saved in triplicate at −80 °C in H2O−glycerol (50/50). A sample was submitted for amplification of the nuclear ribosomal internal transcribed spacer region ITS. Sequencing allowed for strain identification by NCBI sequence comparison . The sequences have been registered in the NCBI GenBank database  under the registry numbers KJ023743 (SNB-CN85), KC684883 (SNB-CN73), KJ023735 (SNB-CN71), and KJ023720 (SNB-CN81).Termite workers were collected from an aerial termite nest located in Rémire-Montjoly, French Guiana, in July 2011. The termites were identified as P. boydii strains were cultivated on PDA at 26 °C for 15 days, initially on a small scale. The fungus and culture medium were then transferred into a large container and macerated with EtOAc for 24 h. The organic solvent was then collected by filtration, washed with H2O in a separatory funnel and evaporated, yielding the four crude extracts.The P. boydii strain SNB-CN85 was cultivated on a large scale in 150 × 14 cm Petri dishes, yielding 3.57 g extract. A portion of the extract (1.13 g) was subjected to reversed-phase flash chromatography using a gradient of H2O mixed with an increasing proportion of CH3CN to afford 6 fractions (A to E). The column was then eluted with CH3CN/CH2Cl2 1:1 (Fraction F). Fraction D  was purified by reversed-phase flash chromatography using the same solvent system as mentioned above with a modified gradient. The major compound was collected in pure form and was identified as ovalicin (1) (28.1 mg). Fraction F (89 mg) was subjected to preparative HPLC  to afford ovalicin linoleate (2) , ovalicin oleate (3) , fraction i (RT = 22.3–22.5 min), and fraction ii (RT = 24.8–30.1 min). Fraction i was subjected to preparative HPLC (Luna PFP(2), H2O/ACN 25:75) to afford demethylovalicin linoleate (6)  and ovalicin palmitoleate (5) . Fraction ii was subjected to preparative HPLC (Luna PFP(2), elution gradient from 20:80 to 15:85 over 30 min) to afford ovalicin stearate (4) .The P. boydii SNB-CN73 was also cultivated on a large scale, similar to SNB-CN85. It yielded 2.46 g of extract. A portion of the extract (1.23 g) was purified by flash chromatography with a linear gradient of hexane−EtOAc followed by another gradient of EtOAc−MeOH. Twelve fractions were gathered based on their TLC profiles. Fraction 11 (29.6 mg), which contained Compound 7, was subjected to preparative HPLC  to afford 7 .Ovalicin (1), white powder, [α]20D −55.7 /−77.7 (c 0.13 CDCl3), 1H NMR    , ESI-HRM97.1702) .Ovalicin linoleate (2), white amorphous solid, [α]20D −26.2 , 1H and 13C NMR   .Ovalicin oleate (3), colorless amorphous solid, [α]20D −15.7 , 1H and 13C NMR   .Ovalicin stearate (4), colorless amorphous solid, [α]20D −20.4 , 1H and 13C NMR   .Ovalicin palmitoleate (5), colorless amorphous solid, [α]20D −21.7 , 1H NMR,   .Demethylovalicin linoleate (6), colorless amorphous solid, [α]20D −30.2 , 1H and 13C NMR,   .Boyden C (7), white powder, [α]20D −10.0 , 1H and 13C NMR,   .2  and Compound 3  were each dissolved in a 1:4 MeOH/THF solution (500 μL). LiOH  and distilled water (50 μL) were added, and the mixture was stirred for 4 h at 60 °C. The solution was concentrated under reduced pressure, and the residue was dissolved in distilled water (700 μL). After the addition of 0.1 M HCl (300 μL), the aqueous layer was extracted with distilled heptane (3 × 0.5 mL). The combined organic layers were filtered on Na2SO4 and concentrated to afford free fatty acids.Compound 2  was added, and the solution was stirred for 1 h at 50 °C. The solution was concentrated under reduced pressure, and H2O (500 μL) was added. The aqueous solution was extracted with a mixture of Et2O/heptane, 5:95 (2 mL). The organic layers were filtered on a Na2SO4/SiO2 column and concentrated to afford fatty acid methyl esters.The free fatty acids were dissolved in MeOH (500 μL). Each solution was cooled down to 0 °C. SOCl1, 17.9 mg, 0.06 mmol), linoleic acid , and KOH  were dissolved in anhydrous DMSO (0.5 mL). The mixture was stirred for 72 h at 60 °C. The solution was concentrated under reduced pressure, and the residue was dissolved in distilled water (1.5 μL). After addition of 0.1 M HCl (0.1 mL), the aqueous solution was extracted with Et2O (2 × 2.0 mL). The combined organic layers were washed with water (2 mL), filtered, and evaporated to afford a crude mixture (32.2 mg), which was subjected to preparative HPLC  to afford synthetic ovalicin linoleate (2) .Ovalicin : Yield: 35%, white amorphous solid, [α]22D −28.7 , 1H NMR spectrum identical to that of natural 2, m/z 599.3911 [M + Na]+ .3 was synthetized according to the procedure mentioned above, with 1 , oleic acid , and KOH . The crude mixture obtained (19.6 mg) was subjected to preparative HPLC to afford synthetic ovalicin oleate (3) .Compound Synthetic ovalicin oleate (3b): Yield: 22%, white amorphous solid, [α]22D −22.4 , 1H NMR spectrum identical to that of natural 3, m/z 601.4056 [M + Na]+ .4 was synthetized according to the procedure mentioned above with 1 , stearic acid , and KOH . The crude mixture obtained (31.0 mg) was subjected to preparative HPLC  to afford synthetic ovalicin stearate (4) .Compound Synthetic ovalicin stearate (4b): Yield: 22%, white amorphous solid, [α]22D −17.0 , 1H NMR spectrum identical to that of natural Compound 4, ESI-HRMS m/z 603.4229 [M + Na]+ .2) and ovalicin oleate (3) were determined using the method developed by Vrkoslav et al.  an2O/formic acid (99.9/0.1) (A)–acetonitrile/formic acid (99.9/0.1) (B). The column oven was set at 45 °C. Compounds were eluted at a flow rate of 0.4 mL·min−1 with a gradient from 5% B to 100% B in 20 min and then 100% B for 3 min. The injection volume was fixed at 5 μL for all analyses. Mass spectra were recorded in electrospray ionization positive ion mode with the following parameters: gas temperature 325 °C, drying gas flow rate 10 L·min−1, nebulizer pressure 30 psi, sheath gas temperature 350 °C, sheath gas flow rate 10 L·min−1, capillary voltage 3500 V, nozzle voltage 500 V, fragmentor voltage 130 V, skimmer voltage 45 V, Octopole 1 RF Voltage 750 V. Internal calibration was achieved with two calibrants, purine and hexakis  phosphazene (m/z 121.0509 and m/z 922.0098), providing a high mass accuracy better than 10 ppm. The data-dependent MS/MS events were acquired for the five most intense ions detected by full-scan MS, from the 200–1000 m/z range, above an absolute threshold of 1000 counts. Selected precursor ions were fragmented at a fixed collision energy of 30 eV and with an isolation window of 1.3 amu. The mass range of the precursor and fragment ions was set as m/z 200–1000.LC–MS/MS experiments were performed with a 1260 Prime HPLC  coupled with an Agilent 6540 Q-ToF  tandem mass spectrometer. LC separation was achieved with an Accucore RP-MS column  with a mobile phase consisting of Hm/z tolerance of 0.008 (or 20 ppm). Deconvolution was performed with the ADAP wavelet algorithm according to the following settings: S/N threshold = 10, minimum feature height = 1000, coefficient/area threshold = 10, peak duration range 0.01–1.5 min, and Rt wavelet range 0.00–0.04 min. MS/MS scans were paired using a m/z tolerance range of 0.05 Da and Rt tolerance range of 0.5 min. Isotopologues were grouped using the isotopic peak grouper algorithm with a m/z tolerance of 0.008 (or 20 ppm) and a Rt tolerance of 0.2 min. Peaks were filtered using a feature list row filter, keeping only peaks with MS/MS scans (GNPS). Adduct identification, i.e., sodium- or potassium-cationized species, was performed on the peak list with a retention time tolerance of 0.1 min, a m/z tolerance of 0.008 or 20 ppm, and a maximum relative peak height of 150%. A complex search, such as dimers, was performed with a retention time tolerance of 0.1 min, a m/z tolerance of 0.008 or 20 ppm, and a maximum relative peak height of 150%. Peak alignment was performed using the join aligner with a m/z tolerance of 0.008 (or 20 ppm), a weight for m/z at 20, a retention time tolerance of 0.2 min, and weight for Rt at 50. The MGF file and the metadata were generated using the export/submit to GNPS option .The data files were converted from the .d standard data format  to .mzXML format using MSConvert software, part of the ProteoWizard package 3.0 . All mzxhttps://metgem.github.io/, accessed on 1 March 2019) -hypoxanthine incorporation as described previously [3H]-hypoxanthine  per well. After a further incubation of 24 h, plates were frozen and thawed. Cell lysates were then collected onto fiberglass filters and counted in a liquid scintillation spectrometer. The growth inhibition for each drug concentration was determined by comparison of the radioactivity incorporated in the treated culture with that in the control culture maintained on the same plate. The concentration causing 50% growth inhibition (IC50) was obtained from the drug concentration–response curve, and the results are expressed as the mean values ± standard deviations determined from several independent experiments. Chloroquine was used as an antimalarial drug control (IC50 = 0.072 ± 0.0074 μM).The FcB1/Colombian strain of eviously . Drug so2. Cell viability was assessed using Promega  CellTiter-BlueTM reagent according to the manufacturer’s instructions. Cells were seeded in 96-well plates (5 × 103 cells per well) containing 50 mL growth medium. After 24 h of culture, the cells were supplemented with 50 mL of test compound dissolved in DMSO (<0.1% in each preparation). After incubation for 72 h, 20 mL resazurin was added for 2 h before recording fluorescence  using a Victor microtiter plate fluorimeter . IC50 values correspond to the concentration of test compound that elicited a 50% decrease in fluorescence for drug-treated cells relative to untreated cells. Experiments were performed in triplicate. Fumagillin was used as a positive control and showed an IC50 of 0.006 ± 0.002 μM.Human umbilical vein endothelial cells (HUVECs) were obtained from Clonetics  and cultured according to the supplier’s instructions. Briefly, HUVECs from three to six passages were subcultured to confluence onto 0.2% gelatin-coated tissue culture flasks in endothelial cell growth medium (EGM2) containing growth factors and 2% FCS. All cell lines were maintained at 37 °C in a humidified atmosphere containing 5% COPseudallescheria genus. It allowed the annotation of tyroscherin analogs previously described, as well as pseurotin A, but also new ovalicin analogs.This study combined genomic and metabolomic approaches to study metabolome produced by mutualistic fungal strains of termites from French Guiana of P. boydii strain collection is a source of diverse ovalicin derivatives, including new fatty acid esters of ovalicin and boyden C that have been isolated and structurally characterized. Compounds 2–4, similar to ovalicin, exhibited antiplasmodial and antitrypanozomal properties. Our work also confirms that P. boydii strains are associated with termite biosynthesized compounds with biological activities. We were able to demonstrate that antiparasitic compounds such as Compounds 1 to 4 are produced in different amounts by the different strains of P. boydii. These same compounds reduce cytotoxicities, with IC50s greater than 10 µM on HUVECs.Our Pseudallescheria sp. strains of our collection. The biosynthesis also permitted the deduction of absolute configurations of ovalicin analogs.The molecular networking analysis allowed the annotation of all isolated compounds and many other ovalicin analogues, together with the isolation and identification of the new ovalicin analog boyden C. Finally, it was possible by genome mining to propose a common biosynthetic pathway for the ovalicin analogs compounds produced by Fungal natural products possess biological activities that are of great value for medicine, agriculture, and manufacturing. Recent “omics” studies accentuated the immense taxonomic diversity of fungi, and the accompanying specialized metabolic diversity provides a significant and still largely untapped resource for natural product discovery. Particular attention will be given in the future to integrative pan-genomic approaches that use a combination of genomic and metabolomic data for parallelized natural product discovery across multiple strains. Such novel technologies will not only expedite the natural product discovery process but will also allow the assembly of a high-quality toolbox for the re-design or even de novo design of biosynthetic pathways using synthetic biology approaches, while continuing to focus on specific environments such as symbiotic microorganisms.