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Qingzhuan tea (QZT) is a unique type of dark tea exclusively produced in Hubei Province of China. In the current study, liquid chromatography–mass spectrometry (LC-MS) coupled with multivariate analysis was applied to characterize the chemical composition of QZT and investigate the effect of QZT processing on its metabolic profile and sensory quality. The contents of polyphenols and flavonoids decreased significantly while the polysaccharides content remained stable, while the theabrownin content inversely increased during QZT processing. LC-MS-based metabolomics analyses revealed that the tea sample after microbial fermentation (MFT) was dramatically different from the sample before microbial fermentation (UFT), while MFT was very similar to QZT. A total of 102 compounds were identified as critical metabolites responsible for metabolic changes caused by QZT processing, with the contents of catechins and flavonoids significantly decreased, and some novel phenolic acids and catechin derivatives were formed. The sensory quality of QZT was mainly formed during microbial fermentation, which greatly reduced the astringency and bitterness of raw tea leaves and produced its characteristic woody and stale aroma as well as mellow taste. These results suggested that microbial fermentation is the critical process in changing the metabolic profile of raw tea leaves and forming the sensory quality of QZT.

BackgroundResveratrol (RSV), a naturally occurring polyphenolic stilbenoid, is known to possess potent anti-atherogenic properties; however, the effect of RSV on hypercholesterolemia is not fully understood. We hypothesized that RSV decreases blood cholesterol levels through the activation of cholesterol 7α-hydroxylase (CYP7A1)-mediated bile acid synthetic pathway pathways in vitro and in vivo.MethodsIn this study, we evaluated body weight, serum lipid concentrations, hepatic lipid content and the size of the bile acid pool in high-fat diet (HFD)-fed C57BL/6 J mice that were treated with RSV. In addition, we characterized the underlying mechanism of the effects of RSV in HepG2 hepatocytes by Western blot analysis.ResultsRSV (200 mg/kg per day) reduced body weight and liver weight gains, improved serum lipid parameters, reduced hepatic cholesterol accumulation and increased the bile acid pool size in mice fed an HFD for 8 wks. RSV significantly increased liver expression of CYP7A1 mRNA and protein and CYP7A1 enzyme activity. Furthermore, RSV treatment upregulated CYP7A1 expression and induced liver X receptor alpha (LXRα) activation in a time- and dose-dependent manner in HepG2 cells. In addition, the specific liver X receptor alpha (LXRα) inhibitor geranylgeranyl pyrophosphate (GGPP) inhibited the RSV-induced expression of CYP7A1 in HepG2 hepatocytes.ConclusionThe beneficial effects of RSV on HFD-induced hypercholesterolemia are mediated through LXRα signaling pathways, suggesting a potential target for the prevention of dyslipidemia.