Bioavailability enhancement of formononetin by incorporation of natural bioenhancer in phospholipid complex

Formononetin (FNT) has limited application due to poor water solubility and substantial phase II metabolism. In the present study, we used phospholipid complex (PC) containing FNT and UDP-glucuronosyltransferase (UGT1A1) inhibitor piperine (PIP) to overcome FNT limitations. We characterized and compared both FNT-PC and FNT-PIP-PC complexes. Our data showed both groups improved FNT water solubility and oil-water partition coefficient. NMR, DSC, and SEM were performed to identify the interaction and the geometrical nature of complex. When compared, FNT-PIP-PC released more FNT in in vitro release and permeation through Caco-2 monolayer than FNT-PC and pure FNT. In vitro data was consistent with the in vivo pharmacokinetic profile that showed increased, Cmax and AUC(0-24) by 7.16 and 23.33-fold and 29.65 and 23.33-fold at 5 and 10 mg/kg in FNT-PIP-PC, compared to pure FNT. Additionally, co-treatment of PIP and FNT improved in vitro pharmacological action in dexamethasone-induced osteoporosis. Thus, our study showed addition of PIP in FNT-PC further increases FNT water solubility and protects it from phase II metabolism, leading to enhanced bioavailability with improved pharmacological activity.