Factors affecting the levels of tea polyphenols and XXXX in tea leaves.

@entity23382 @entity5834 @entity3089 @entity3090 @entity3787 @entity842 @entity1068
An isocratic HPLC procedure was developed for the simultaneous determination of @entity5834 and six @entity23382 in tea samples. When 31 commercial teas extracted by boiling water or 75% @entity1068 were analyzed by HPLC, the levels of @entity3089 ( @entity3090 ), and total @entity23382 in teas were in the order green tea (old leaves) > green tea (young leaves) and oolong tea > black tea and pu-erh tea. Tea samples extracted by 75% @entity1068 could yield higher levels of @entity3090 and total @entity23382 . The contents of @entity5834 and @entity23382 also have been measured in fresh tea leaves from the Tea Experiment Station in Wen-Shan or Taitung; the old tea leaves contain less @entity5834 but more @entity3090 and total @entity23382 than young ones. To compare @entity5834 and @entity23382 in the same tea but manufactured by different fermentation processes, the level of @entity5834 in different manufactured teas was in the order black tea > oolong tea > green tea > fresh tea leaf, but the levels of @entity3090 and total @entity23382 were in the order green tea > oolong tea > fresh tea leaf > black tea. In addition, six commercial tea extracts were used to test the biological functions including @entity3787 radical scavenging, @entity842 suppressing, and apoptotic effects. The pu-erh tea extracts protected the plasmid DNA from damage by the Fenton reaction as well as the control at a concentration of 100 microg/mL. The @entity842 suppressing effect of tea extracts was in the order pu-erh tea >/= black tea > green tea > oolong tea. The induction of apoptosis by tea extract has been demonstrated by DNA fragmentation ladder and flow cytometry. It appeared that the ability of tea extracts to induce HL-60 cells apoptosis was in the order green tea > oolong > black tea > pu-erh tea. All tea extracts extracted by 75% @entity1068 have stronger biological functions than those extracted by boiling water.
