Using the Cocrystal Approach as a Promising Drug Delivery System to Enhance the Dissolution and Bioavailability of Formononetin Using an Imidazole Coformer

Natural isoflavones are recognized for their diverse pharmacological activities; however, their low aqueous solubility presents a significant challenge for further development. Here, we aimed to develop a cocrystal of formononetin (FMN) to improve its solubility. The formononetin-imidazole (FMN-IMD) cocrystal was prepared using liquid-assisted grinding method. The prepared cocrystal was identified through a thermal analysis of physical mixtures with various coformers. FTIR and solid-state NMR confirmed the presence of hydrogen bonds and π-π interactions in the FMN-IMD cocrystal. The solubility of FMN-IMD was two to three times higher than that of crystalline FMN. The FMN-IMD cocrystal showed a 4.93-fold increase in the Cmax value and a 3.58-fold increase in the AUC compared to FMN after oral administration in rats. There were no changes in the PXRD of the FMN-IMD cocrystal after six months of storage at 40 °C. Thus, the FMN-IMD cocrystal is proposed as an effective solid form for oral delivery, offering enhanced solubility and physical stability.