From chemical characterization to functional validation: Screening of anti-hyperglycemic components and their action mechanisms in differentially fermented teas

Single-source Jinxuan (Camellia sinensis) tea leaves were processed into teas with varying fermentation degrees to minimize genetic and environmental interference. Non-volatile component differences between fermented and non-fermented teas were identified, with fermented teas showing reduced tea polyphenols and soluble sugars but elevated theaflavins and theasinensin A(TSA). Fermented teas exhibited stronger in vitro digestive enzyme inhibition, particularly α-glucosidase (α-Glu), with TSA ( R = 0.97) and theaflavin-3-gallate ( R = 0.93) showing the strongest correlations ( p < 0.001). In vivo, TSA's hypoglycemic effect in diabetic mice was mediated by enhanced insulin secretion, linked to lipid, amino acid, and fatty acid metabolism. These findings elucidate fermented tea's superior digestive enzyme inhibition and provide a foundation for optimizing hypoglycemic effects through processing. • Fermented teas show stronger digestive enzyme inhibition in vitro. • Theasinensin A and theaflavins positively correlate with enzyme inhibition. • Theasinensin A lowers postprandial glucose via enhanced insulin secretion. • Theasinensin A regulates blood glucose and links to lipid/amino acid metabolism.