Study of the release of gallic acid from (-)-epigallocatechin gallate in old oolong tea by mass spectrometry

Liquid chromatography combined with multiple-stage mass spectrometry (LC/MS(n)) was used to study the pathway of the release of gallic acid (GA) from epigallocatechin gallate (EGCG) in infusion of old oolong tea. The possibility of releasing GA from EGCG in old tea preparations was supported by an in vitro observation of GA degraded from EGCG under heating conditions mimicking the drying process. Negative electrospray ionization with the data-dependent mode of MS(n) was used to study the formation pathway of GA in old oolong tea. The MS(n) data show that GA was released from the dimer of EGCG, not directly degraded from EGCG. Copyright (C) 2010 John Wiley & Sons, Ltd

Rapid identification of acylated flavonol tetraglycosides in Oolong teas using HPLC-MS

A method was developed to separate and identify acylated flavonol tetraglycosides (AFFGs) by combining isocratic HPLC with electrospray ionisation tandem mass spectrometry. Better separation was obtained for oolong tea infusion using a manually packed Sephadex LH-20 mini-column than with an ACCUBOND (R) ODS solid-phase column. Seven unknown and one known AFTGs were found in oolong teas prepared by various semi-fermentation processes and their structures were identified by mass spectrometry. According to the analyses of diverse oolong teas including Dongding Oolong, Tieguanyin, Wuyi Oolong, Fenghuang Oolong, Gaoshan Shibi, Laocong Shuixian and Baihao Oolong, AFTGs seemed to be universally present, and each oolong tea could be classified into one of three groups (Dongding Oolong, Tieguanyin and Wuyi Oolong) on the basis of its AFTGs profile. The results suggest that the developed method is rapid and sensitive for identifying natural compounds. Copyright (c) 2007 John Wiley & Sons, Ltd

Identification and comparison of phenolic compounds in the preparation of oolong tea manufactured by semifermentation and drying processes

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 MSn (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

Structural determination and DPPH radical-scavenging activity of two acylated flavonoid tetraglycosides in oolong tea (Camellia sinensis)

Two major acylated flavonoid tetraglycosides were isolated from the methanol extract of oolong tea. Their structures were elucidated by spectroscopic methods as quercetin 3-O-[2(G)-(E)-coumaroyl-3G-O-beta-D-glucosyl-3R-O-beta-D-glucosylrutinoside] (1) and kaempferol 3-O-[2(G)-(E)-coumaroyl-3G-O-beta-D-glucosylrutinoside] (2). Compounds 1 and 2 exhibited scavenging activity against DPPH radical with EC(50) values of 30.5 and 487.2 mu M, respectively

Minimizing the central hydrophobic domain in oleosin for the constitution of artificial oil bodies

Oleosin, a unique structural protein anchoring onto the surface of seed oil bodies by its central hydrophobic domain, stabilizes these lipid-storage organelles as discrete entities. Stable artificial oil bodies have been successfully constituted with native or recombinant oleosins. In this study, recombinant sesame oleosin with 12 residues stepwise truncated from its central hydrophobic domain of 72 residues was overexpressed in Escherichia coli, was purified to homogeneity, and was used for the constitution. Artificial oil bodies constituted by truncated oleosins with the central hydrophobic domain longer than 36 residues were as stable as native sesame oil bodies, and those constituted by truncated oleosins lacking more than half of the original central hydrophobic domain inclined to coalesce upon collision or aggregation

Molecular cloning of the precursor polypeptide of mastoparan B and its putative processing enzyme, dipeptidyl peptidase IV, from the black-bellied hornet, Vespa basalis

Mastoparan B, a cationic toxin, is the major peptide component in the venom of Vespa basalis. Molecular cloning of its cDNA fragment revealed that this toxin was initially synthesized as a precursor polypeptide, containing an N-terminal signal sequence, a prosequence, the mature toxin, and an appendix glycine at C-terminus. Sequence alignment between precursors of mastoparan B and melittin from honeybee venom showed a significant conservation in prosequence. Alternate positions existing in both prosequences were either proline or alanine known as the potential cleaving sites for dipeptidyl peptidase IV. Subsequently, a putative dipeptidyl peptidase IV cDNA fragment was cloned from Vespa basalis venom gland. The prosequence may possibly be removed via sequential liberation of dipeptides during the processing of mastoparan B

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

High flavivirus structural plasticity demonstrated by a non-spherical morphological variant

10.1038/s41467-020-16925-yNature Communications111311

Understanding digital consumers' well-being in Asia: The moderating roles of digital natives and privacy concerns

As digital technologies permeate our lives, the effect of digital device use on well-being has become a hot-button issue. In this research, we focus on digital usage and digital shopping via online and mobile devices and investigate their relationships with well-being using a public data from South Korea. Overall, online usage and online shopping increase well-being, whereas mobile usage and mobile shopping decrease it. Interestingly, these relationships are complex and idiosyncratic as including digital natives and privacy concerns as moderators provides varied results. Among digital natives, the positive effect of online usage on well-being decreases whereas the negative effects of mobile usage and mobile shopping on well-being increase. Furthermore, privacy concerns weaken the effects of mobile usage and online shopping on well-being