Steam-Processed Stauntonia hexaphylla (Thunb.) Decne Fruit Stimulates Osteoblast Differentiation in MC3T3-E1 Cells and Inhibits Osteoclastogenesis in RAW 264.7 Cells

<i>Stauntonia hexaphylla</i> (Thunb.) Decne (SH), a medicinal plant from the Lardizabalaceae family, holds traditional importance in East Asia for treating rheumatism. Steam treatment is commonly applied to enhance its medicinal properties, but the chemical and biological changes resulting from this process remain unexplored. This study compared steamed and untreated SH fruit (SHF) extracts, analyzing their chemical composition, antioxidant activity, and effects on bone health using in vitro models. Steamed SHF extracts exhibited increased levels of 5-hydroxymethylfurfural (5-HMF), total flavonoids, phenolics, and enhanced antioxidant activity. Bone health assessment using osteoclasts differentiated from RAW 264.7 cells and osteoblasts from MC3T3-E1 cells revealed that steamed extracts promoted alkaline phosphatase activity, calcium nodule formation, and collagen synthesis in osteoblasts while inhibiting tartrate-resistant acid phosphatase (TRAP) activity in osteoclasts. Additionally, steamed SHF extracts effectively modulated gene expression related to osteoclastogenesis and osteoblastogenesis by downregulating TRAP, NFTAc1, RANK, MMP9, c-Fos, and TRAF6 while upregulating ALP, Runx2, BGLAP, Col1a1, and OPG. The component 5-HMF played a pivotal role in promoting alkaline phosphatase and inhibiting TRAP activities. These findings suggest that steamed SHF may offer a promising therapeutic approach for postmenopausal osteoporosis.