Co-fermentation of Ampelopsis grossedentata with Camellia sinensis reduces bitterness, enhances sweet aroma, and generates novel bioactive theaflavin analogues

Co-fermentation significantly improves vine tea flavor, reducing bitterness and enhancing sweet aroma. • Two new theaflavin analogues were discovered and structurally characterized. • These new compounds and the co-fermented product exhibit potent antioxidant and α -glucosidase inhibitory activities. • A balanced co-fermentation approach achieves both enhanced flavor and retained bioactivity in vine tea. This study developed a co-fermentation strategy to process the leaves of Ampelopsis grossedentata (vine tea) and Camellia sinensis (tea), which significantly improved the sensory quality of fermented vine tea by reducing its bitterness while enhancing sweet aroma. Untargeted metabolomics and GC–MS revealed significant metabolic changes, discovering two novel theaflavin analogues, dihydromyriflavin ( 1 ) and dihydromyriflavin-3′-gallate ( 2 ), (0.48 and 0.53 mg/g in co-fermented-vine-black tea (CVBT), respectively), formed via enzymatic oxidation. Compound 2 and the CVBT extract exhibited strong antioxidant (SC 50  = 42.91 μM and 227.05 μg/mL, respectively) and α -glucosidase inhibitory (IC 50  = 2.86 μM and 19.86 μg/mL, respectively) activities. Molecular docking confirms that 1 and 2 bind strongly (binding energies = −10.1 and − 10.9 kcal/mol) to α -glucosidase active sites. This work provides a foundation for developing high-value fermented tea products from underutilized resources and highlights the potential of co-fermentation to generate novel bioactive natural products. Download: Download high-res image (239KB) Download: Download full-size image