Identification and Comparison of Phenolic Compounds in the Preparation of Oolong Tea Manufactured by Semifermentation and Drying Processes

Abstract

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 resulting from its manufacture, was analyzed by high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry. The identified constituents 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 tentative structures of these 6 novel compounds were depicted according to their mass fragmentation patterns in MS(n) (n = 1-4). In comparison with caffeine as an internal standard, relative contents of the constituents in the infusions of fresh tea shoot and different oolong tea preparations were examined. Approximately, 30% catechins and 20% proanthocyanidins were oxidized during the manufacture of oolong tea from fresh tea shoots, and 20% of total flavonoids were decomposed in a follow-up drying process. Gallocatechin-3-O-gallate and theaflavins putatively produced in the semifermentation process of oolong tea were not detected in fresh tea shoots, and the majority of theaflavins were presumably transformed into thearubigins after drying.

Bioactive compounds and scavenging capacity of extracts from different parts ofVismia caulifloraagainst reactive oxygen and nitrogen species

“…Peaks 10 and 11 were tentatively identified as taxifolin deoxyhexosides with , both derived from taxifolin moiety, corresponds to the loss of a hydroxyl group (18 u) and a characteristic fragment due to retro-Diels-Alder fission (152 u) was also observed in the taxifolin standard. The glycosylation position of each sugar moiety was not assigned in this study, since, in principle, any of the hydroxyl groups in phenolic compounds can be glycosylated, but certain positions are favored: for example, the 7-hydroxyl group in flavones, flavanones, and isoflavones; the 3-and 7-hydroxyls in flavonols and flavanols; and the 3-and 5-hydroxyls in anthocyanidins are common glycosylation sites (Cuyckens & Claeys, 2004) À , corresponding to a loss of catechin or epicatechin, and these patterns match those previously reported (Dou et al, 2007). Peaks 28 and 29 presented [M-H] À at m/z 287 and 257, respectively, with UV-Vis and fragmentation pattern similar to those already reported for xanthones (dos Santos et al, 2000;Du et al, 2012), and were assigned as xanthone derivative compounds.…”

Characterisation of phenolic acids, flavonoids, proanthocyanidins and antioxidant activity of water extracts from seed coats of marama bean [Tylosema esculentum] – an underutilised food legume

“…Similar mass spectral data for (epi)catechin-3-O-gallate has been reported in green tea (Miketova et al, 1998) and oolong extracts (Dou et al, 2007).…”

“…have been reported in green tea (Miketova et al, 1998) and oolong tea (Dou et al, 2007) extracts. Terminal units of proanthocyanidins in seed coats of pinto beans, small red beans and red kidney beans were reported to be composed of (+)-catechin (7.3 -14.5%) and (-)-epicatechin (0.4 -1.1%) (Gu et al, 2003).…”

Optimization of Quercetin Extraction from Green Tea ( Camellia sinensis ) Using Central Composite Design, and the Pharmacological Activity of the Extract

“…In addition to quercetin, extraction of the bioactive compounds (gallic acid, (-)-gallocatechin, 3-O-caffeoylquinic acid, theobromine, 5-O-galloylquinic acid, (+)-catechin, caffeine, (-)-epigallocatechin-3-gallate, 4-p-coumaroylquinic acid, (-)-epicatechin-3-gallate, quercetin-3-O-rutinoside, querce tin--3-galactoside, kampferol-3-O-glucoside, apigenin glycoside, theaflavin-3,3'-digallate, thaflavin-3-gallate, kaempferol-rhamnose-hexose-rhamnose) was confirmed for optimal extraction conditions based on mass fragmentation patterns [40][41][42] . The mass spectral characteristics of the identified compounds in the optimal extract of green tea are presented in Table 4, and their structural formulas are given in Figure 8.…”