Allium Discoloration: Color Compounds Formed during Pinking of Onion and Leek.
Structures and formation pathways of compounds responsible for pink discoloration of onion and leek were studied. A procedure was developed for the isolation and purification of the color compounds from various model systems and their identification by HPLC-DAD-MS/MS. In total, structures of 15 major color compounds were tentatively determined. It was found that the pigment is a complex mixture of highly conjugated species composed of two N-substituted 3,4-dimethylpyrrole-derived rings linked by either a methine or a propenylidine bridge. These two-ring units are further modified by various C1- and C3-side chains. Experiments with isotope-labeled thiosulfinates revealed that the methine bridge and C1-side chains originate from the methyl group of methiin, whereas the C3 units are derived from the propenyl group of isoalliin.
['Kubec|Roman|R|', 'Urajová|Petra|P|', 'Lacina|Ondřej|O|', 'Hajšlová|Jana|J|', 'Kuzma|Marek|M|', 'Zápal|Jakub|J|']
D002851:Chromatography, High Pressure Liquid D003116:Color D003545:Cysteine D019697:Onions D010860:Pigments, Biological D013441:Sulfinic Acids D053719:Tandem Mass Spectrometry
Allium discoloration pinking onion leek thiosulfinate isoalliin dipyrromethane plant pigment pyrrole