Processing-driven flavor remodeling and gut-protective effects of black and green Forsythia suspensa leaf teas

Forsythia suspensa leaves, as a traditional edible functional raw material for beverage production, are often processed into tea beverages with diverse flavor profiles. However, how processing influences flavor chemistry and health benefits remains unclear. We produced black- and green-leaf teas and integrated sensory evaluation, electronic nose, multiple metabolomic techniques, and a dextran sulfate sodium (DSS)-induced colitis model with 16S rRNA profiling. Black tea showed a rose-like sweet aroma with a higher relative contribution of 2-phenylethanol, whereas green tea retained fresh green notes associated with isobutyraldehyde and phenylacetaldehyde. Processing was associated with distinct differences in non-volatile metabolite profiles, including variations in flavonoids and taste-active amino acids (bitter/umami enriched in green tea; sweet amino acids in black tea). Both teas alleviated colitis, restored Claudin-1/ZO-1 and MUC2, and corrected dysbiosis, including enrichment of Akkermansia muciniphila and suppression of Bacteroides. These findings demonstrated that processing-associated metabolite differences contribute to variations in flavor characteristics, while both tea products exhibited protective effects against DSS-induced colitis, supporting high-value utilization of F. suspensa leaf teas.