Synthesis and Evaluation of Galloyl Conjugates of Flavanones as BMP‑2 Upregulators with Promising Bone Anabolic and Fracture Healing Properties

The molecular hybridization concept led us to design a series of galloyl conjugates of flavanones that have potent osteoblast differentiation ability in vitro and promote bone formation in vivo. An array of in vitro studies, especially gene expression of osteogenic markers, evinced compound 5e as the most potent bone anabolic agent, found to be active at 1 pM, which was then further assessed for its osteogenic potential in vivo. From in vivo studies on rat calvaria and a fracture defect model, we inferred that compound 5e, at an oral dose of 5 mg/(kg day), increased the expression of osteogenic genes (RUNX2, BMP-2, Col1, and OCN) and the bone formation rate and significantly promoted bone regeneration at the fracture site, as evidenced by the increased bone volume/tissue fraction compared with vehicle-treated rats. Furthermore, structure–activity relationship studies and pharmacokinetic studies suggest 5e as a potential bone anabolic lead for future osteoporosis drug development.