Massive accumulation of gallic acid and unique occurrence of myricetin, quercetin, and kaempferol in preparing old oolong tea

Journal of Agricultural and Food Chemistry
Viola Szu-Yuan LeeJason Tze-Cheng Tzen

Abstract

Old oolong tea, tasting superior and empirically considered beneficial for human health, is prepared by long-term storage accompanied with periodic drying for refinement. Analyzing infusions of three old and one newly prepared oolong teas showed that significant lower (-)-epigallocatechin gallate (EGCG) but higher gallic acid contents were detected in the old teas compared to the new one. The possibility of releasing gallic acid from EGCG in old tea preparation was supported by an in vitro observation of gallic acid degraded from EGCG under heating conditions mimicking the drying process. Moreover, three minor flavonols, myricetin, quercetin, and kaempferol, that were undetectable in the new tea occurred in all of the three old teas. Converting the new oolong tea into an old one by periodic drying revealed the same characteristic observation, i.e., massive accumulation of gallic acid presumably released from EGCG and unique occurrence of flavonols putatively decomposed from flavonol glycosides.

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Citations

Sep 9, 2011·Journal of Agricultural and Food Chemistry·Jang-Eun LeeYoung-Shick Hong
Oct 15, 2010·Journal of the Science of Food and Agriculture·Ping-Chung KuoJason T C Tzen
Jun 2, 2016·Food Science & Nutrition·Ershad SheibaniSean F O'Keefe
Feb 13, 2015·Critical Reviews in Food Science and Nutrition·Md Wasim SiddiquiR S Dhua
Jul 6, 2017·Critical Reviews in Food Science and Nutrition·Kwan-Wai NgTao Yi
Mar 5, 2010·Rapid Communications in Mass Spectrometry : RCM·Ren-Jye LeeMaw-Rong Lee
May 29, 2019·Natural Product Research·Ping-Chung KuoJason T C Tzen
Mar 24, 2018·Journal of Food and Drug Analysis·Miki Mei-Chi WangJason Tze-Cheng Tzen
Jul 30, 2019·Journal of Food Biochemistry·Yue-Chiun LiJason T C Tzen
Mar 1, 2015·Journal of Food and Drug Analysis·Tse-Yu ChungJason T C Tzen
Sep 16, 2017·Journal of Food and Drug Analysis·Sheng-Kuo HsiehJason T C Tzen
Jun 20, 2019·Nutrients·Dylan O'Neill Rothenberg, Lingyun Zhang

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