| Summary: | 博士 === 國立中興大學 === 生物科技學研究所 === 97 === Oolong tea manufactured via a semifermentation process possesses a taste and color somewhere between green and black teas. Alteration of constituents, particularly phenolic compounds, in the infusion of oolong tea resulted from its manufacture, was analyzed by high-performance liquid chromatography coupled to ultraviolet absorbance or electrospray ionization tandem mass spectrometry. The identified contained 2 alkaloids, 11 flavan-3-ols, 8 organic acids and esters, 11 proanthocyanidin dimers, 3 theaflavins, and 22 flavonoid glycosides, including 6 novel acylated flavonol glycosides. The structures of two major acylated flavonol tetraglycosides were elucidated by spectroscopic methods as quercetin 3-O-[2G-(E)-coumaroyl-3G-O-β-D-glucosyl-3R-O-β-D-glucosylrutinoside] and kaempferol 3-O-[2G-(E)-coumaroyl-3G-O-β-D-glucosyl-3R-O-β -D- glucosylrutinoside]. 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 and unique occurrence of flavonols (myricetin, quercetin,and kaempferol) putatively decomposed from flavonol glycosides was observed in the old teas compared with the new one.
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