Large-leaf yellow tea (LYT) is made from mature tea leaves with stems and has unique sensory characteristics different from other teas. To study the chemical changes of LYT during processing, samples were collected from each step for quantitative and qualitative analyses by high-performance liquid chromatography and liquid chromatography−mass spectrometry (LC-MS). LC-MS-based nontargeted and targeted metabolomics analyses revealed that the tea sample after roasting was markedly different from samples before roasting, with the levels of epicatechins and free amino acids significantly decreased, but the epimerized catechins increased dramatically. After accounting for common compounds in tea, N-ethyl-2pyrrolidinone-substituted flavan-3-ols were found to be the marker compounds responsible for the classification of all samples, as they rapidly rose with increasing processing temperature. These findings suggested that the predominant changes in the tea constituents during large-leaf yellow tea roasting were the thermally induced degradation and epimerization of catechins and the formation of N-ethyl-2-pyrrolidinone-substituted flavan-3-ols from L-theanine.

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Nonalcoholic fatty liver disease (NAFLD) is a typical chronic liver disease highly correlated with metabolic syndrome. Growing prevalence of NAFLD is supposed to be linked with the unhealthy lifestyle, especially high-calorie diet and lacking enough exercise. Currently, there is no validated pharmacological therapy for NAFLD except for weight reduction. However, many dietary strategies had preventive effects on the development of liver steatosis or its progression. As one of the most common beverages, green tea contains abundant bioactive compounds possessing antioxidant, lipid-lowering, and anti-inflammatory effects, as well as improving insulin resistance and gut dysbiosis that can alleviate the risk of NAFLD. Hence, in this review, we summarized the studies of green tea and its components on NAFLD from animal experiments and human interventions and discussed the potential mechanisms. Available evidence suggested that tea consumption is promising to prevent NAFLD, and further mechanisms and clinical studies need to be investigated.