Processing-Induced Metabolic Reprogramming of Litsea coreana Modulates Its Phytochemical Profile and Bioactivities

Hawk tea (Litsea coreana), a traditional caffeine-free herbal beverage, has gained increasing consumer interest owing to its health-promoting properties. Yet, how processing shapes its metabolic composition and bioactivity is not fully elucidated. In this study, we investigated the chemical composition, metabolic profile, and in vitro bioactivity of three processed hawk teas: green (GHT), yellow (YHT), and black (BHT). Chemical analysis revealed a substantial reduction in phenolic and flavonoid contents during the processing of GHT into BHT, accompanied by a noticeable color evolution from yellow-green to orange-red. Non-targeted metabolomic analysis uncovered 5163 metabolic features, with 2610 being significantly differential, primarily from flavonoids, phenolic acids, amino acids, and sugars. Molecular network analysis showed that phenylpropanoid biosynthesis and amino acid degradation were the central pathways remodeled during processing, driving the conversion of monomeric flavanols in GHT to complex polymeric pigments in BHT. This metabolic shift corresponded to a marked divergence in bioactivity, as GHT demonstrated the strongest antioxidant potential and exhibited the greatest α-amylase inhibitory activity. By systematically delineating the metabolic landscape underlying hawk tea quality, our work provides a mechanistic understanding and a scientific basis for its tailored application in functional food products.