Changes in Phytochemical Composition of Black Soybean (Glycine max) During Germination: Enhanced Anti-Osteoarthritis Efficacy and Identification of Apigenin as the Active Compound

Black soybean (Glycine max) is an edible plant belonging to the legume family that have been consumed for a long time. Germination causes compositional changes in beans, altering their nutritional and bioactive properties. Herein, we germinated black soybeans under controlled light conditions in the vertical farming system for durations ranging from 0- to 4-week. We aimed to identify the optimal germination period of black soybean in terms of bioactivity and to analyze the compositional differences in order to discover the bioactive compound responsible. Among various germination periods, black soybean germinated for three-week (GBS) demonstrated the most potent anti-OA efficacy. Comprehensive untargeted profiling using UHPLC-HRMS, combined with quantitative analysis via UHPLC-MS/MS, revealed that 37 compounds were increased, and 20 novel compounds were synthesized in GBS compared to NBS. Particularly, the apigenin content in GBS was approximately 260-fold higher than in NBS, which showed a strong correlation with anti-OA effect. GBS and apigenin showed inhibitory effects against inflammation and cartilage degradation in OA patient-derived chondrocytes/synoviocytes and collagen-induced osteoarthritis mouse model. We also identified that GBS and apigenin inhibited the activation of TAK1/MAPKs/AP-1 signaling pathways associated with OA progression. Additionally, in silico molecular docking analysis revealed that apigenin directly bound to the TAK1 kinase domain, thereby inhibiting its activity. Thus, GBS with increased apigenin content is a promising edible plant for the management of OA. Our findings demonstrate that optimizing germination processes can aid in the development of therapeutic plants by maximizing bioactive components.