Multi-Omics Reveals Stage-Specific Flavonoid Accumulation in Bupleurum chinense DC. Inflorescences

The large-scale cultivation of medicinal plants generates substantial agricultural by-products that are often discarded. A notable example is the floral biomass of Bupleurum chinense DC. (B. chinense), which is routinely removed during cultivation to promote root yield. To explore the potential valorization of these discarded tissues, we performed an integrated transcriptomic and metabolomic analysis of flavonoid biosynthesis across three developmental stages: F1 (Initial Flowering Stage), F2 (Full Bloom Stage), and F3 (Late Flowering Stage). Our results revealed distinct stage-specific regulatory dynamics. Flavonoid biosynthesis was initiated at F1 through the activation of upstream structural genes, reached its peak at F2 with strong up-regulation of branch-specific genes and the accumulation of diverse flavonols and anthocyanins, and declined at F3, despite the sustained presence of several antioxidant metabolites. These findings indicate that F2 represents the optimal stage for harvesting B. chinense flowers to obtain a broad spectrum of bioactive flavonoids, while late-stage flowers may serve as a complementary source of stable antioxidant compounds. Collectively, this study highlights the potential for transforming discarded floral biomass into valuable phytochemical resources and provides a framework for exploring underutilized tissues in other medicinal plants.