Massive accumulation of gallic acid and unique occurrence of myricetin, quercetin, and kaempferol in preparing old oolong tea.
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.
Lee
Viola S Y
VS
Graduate Institute of Biotechnology, National Chung-Hsing University, Taichung 402, Taiwan.
Dou
Jianpeng
J
Chen
Ronald J Y
RJ
Lin
Ruey-Song
RS
Lee
Maw-Rong
MR
Tzen
Jason T C
JT
D028241:Camellia sinensis / Q000737:chemistry; D002392:Catechin / Q000031:analogs & derivatives / Q000032:analysis; D003890:Desiccation; D005419:Flavonoids / Q000032:analysis*; D005707:Gallic Acid / Q000032:analysis*; D044949:Kaempferols / Q000032:analysis*; D018515:Plant Leaves / Q000737:chemistry; D011794:Quercetin / Q000032:analysis*; D013662:Tea / Q000737:chemistry*; D013997:Time Factors
D005419:Flavonoids; D044949:Kaempferols; D013662:Tea; D005707:Gallic Acid; C006552:kaempferol; C040015:myricetin; D002392:Catechin; D011794:Quercetin; C045651:epigallocatechin gallate