Formononetin–piperine–phospholipid complex: enhancement of anti-osteoporotic activity and bioavailability in bone marrow in rats

Abstract Background Formononetin (FNT), a phytoestrogen, has shown osteogenic effects in ovariectomy-induced osteoporosis, but its therapeutic use is limited by poor bioavailability. This study aimed to compare the osteogenic potential of pure FNT and formononetin–piperine–phospholipid complex (FNT-PIP-PC) in OVX-induced osteoporosis and to quantify free FNT concentration in rat bone marrow. An in vivo study was conducted using an OVX-induced osteoporosis rat model. Adult female Sprague–Dawley (SD) rats were ovariectomized and treated orally with FNT or FNT-PIP-PC at 5mg/kg for 12 weeks. Therapeutic efficacy was evaluated using body composition analysis, µCT, L5 compression, bone markers, and pharmacokinetics parameters in the bone marrow via LC–ESI–MS/MS. Results FNT-PIP-PC treatment significantly restored trabecular bone volume and microarchitecture in the femur and tibia, improved uterine mass, increased osteocalcin (OCN), and reduced C-terminal telopeptide of type 1 collagen (CTX) levels. These findings aligned with enhanced mRNA expression of RUNX, RANKL, BMP2, and OPG. Additionally, FNT-PIP-PC improved pharmacokinetic parameters like Cmax, AUC0-t, and AUC0-∞ of free FNT from FNT-PIP-PC compared to pure FNT. Conclusion Oral administration of FNT through complexation with PIP reduced phase II metabolism and enhanced free FNT concentrations, leading to a significant increase in its bioavailability in bone marrow, supporting the targeted delivery. Furthermore, the FNT-PIP-PC complex demonstrated a marked improvement in the osteogenic potential of FNT on OVX-induced osteoporosis rats with no significant adverse effects. Collectively, these findings support the FNT-PIP-PC potential as a safe and effective therapeutic option for postmenopausal osteoporosis. Graphic abstract