Metabolite differentiation and antiobesity effects between different grades of Yuexi Cuilan green tea

Comprehensive applications of metabolomics on tea science and technology: Opportunities, hurdles, and perspectives

With the development of metabolomics analytical techniques, relevant studies have increased in recent decades. The procedures of metabolomics analysis mainly include sample preparation, data acquisition and pre-processing, multivariate statistical analysis, as well as maker compounds' identification. In the present review, we summarized the published articles of tea metabolomics regarding different analytical tools, such as mass spectrometry, nuclear magnetic resonance, ultraviolet-visible spectrometry, and Fourier transform infrared spectrometry. The metabolite variation of fresh tea leaves with different treatments, such as biotic/abiotic stress, horticultural measures, and nutritional supplies was reviewed. Furthermore, the changes of chemical composition of processed tea samples under different processing technologies were also profiled. Since the identification of critical or marker metabolites is a complicated task, we also discussed the procedure of metabolite identification to clarify the importance of omics data analysis. The present review provides a workflow diagram for tea metabolomics research and also the perspectives of related studies in the future.

Sustainable and effective approach to recover antioxidant compounds from purple tea (Camellia sinensis var. assamica cv. Zijuan) leaves

Camellia sinensis var. assamica cv. Zijuan (purple tea) is known for its content of anthocyanins, flavan-3-ols, and bioactivities. This study aimed to verify the influence of solvent polarity, in a solid-liquid extraction, on the content of phenolic compounds and chlorophylls, instrumental color, and antioxidant activity. Different proportions of water and ethanol (0:100, 25:75, 50:50, 75:25, and 100:0 v/v) were used for extraction. The results showed that the hydroalcoholic extract (75 % ethanol + 25 % water) had the highest contents of total flavonoids, total anthocyanins, chlorophyll A, and total carotenoids, as well as presenting the highest color intensity, proportion of yellow pigments, and antioxidant activity (total reducing capacity and scavenging of the DPPH free radical). Twenty-two compounds were identified, with chlorogenic acid, hesperidin, (-)-epicatechin, (-)-epigallocatechin gallate, and isoquercitrin being the main phenolics. This phenolic-rich extract inhibited lipoperoxidation induced in egg yolk homogenate (IC₅₀ = 455 mg/L), showed no hemolytic behavior when human erythrocytes were subjected to osmotic stress, and exerted in vitro cytotoxic effects against cancer and hybrid cells. The extract obtained with the mixture of non-toxic solvents presented critical bioactivities, as well as a comprehensive identification of phenolic compounds in the cultivar, and has potential to be used in technological applications.

Huangshan Maofeng Green Tea Extracts Prevent Obesity-Associated Metabolic Disorders by Maintaining Homeostasis of Gut Microbiota and Hepatic Lipid Classes in Leptin Receptor Knockout Rats

Huangshan Maofeng green tea (HMGT) is one of the most well-known green teas consumed for a thousand years in China. Research has demonstrated that consumption of green tea effectively improves metabolic disorders. However, the underlying mechanisms of obesity prevention are still not well understood. This study investigated the preventive effect and mechanism of long-term intervention of Huangshan Maofeng green tea water extract (HTE) on obesity-associated metabolic disorders in leptin receptor knockout (Lepr^−/−) rats by using gut microbiota and hepatic lipidomics data. The Lepr^−/− rats were administered with 700 mg/kg HTE for 24 weeks. Our results showed that HTE supplementation remarkably reduced excessive fat accumulation, as well as ameliorated hyperlipidemia and hepatic steatosis in Lepr^−/− rats. In addition, HTE increased gut microbiota diversity and restored the relative abundance of the microbiota responsible for producing short chain fatty acids, including Ruminococcaceae, Faecalibaculum, Veillonellaceae, etc. Hepatic lipidomics analysis found that HTE significantly recovered glycerolipid and glycerophospholipid classes in the liver of Lepr^−/− rats. Furthermore, nineteen lipid species, mainly from phosphatidylcholines (PCs), phosphatidylethanolamines (PEs), and triglycerides (TGs), were significantly restored increases, while nine lipid species from TGs and diglycerides (DGs) were remarkably recovered decreases by HTE in the liver of Lepr^−/− rats. Our results indicated that prevention of obesity complication by HTE may be possible through maintaining homeostasis of gut microbiota and certain hepatic lipid classes.