Preparation of curcumin and quercetin multicomponent crystals via solvent-drop grinding

Abstract

Curcumin, a major component of Curcuma longa L. (turmeric), has several pharmacological activities; however, its use in pharmaceuticals is limited by poor water solubility. This work sought to improve the solubility of curcumin by preparing it as multicomponent crystals (MC) with quercetin as the co-former. The optimal mole ratio for preparing the curcumin-quercetin MC was determined from a binary phase diagram of their binary mixtures (BMs) at mole ratios of 0.1:0.9 to 0.9:0.1. This ratio was used to prepare the MC by the solvent-drop grinding method in ethanol. MC were characterized using powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FT-IR) spectroscopy. A simple eutectic mixture formed in the BM at a 0.7:0.3 mole ratio. PXRD results showed a decrease in the intensity of the diffraction patterns, indicating a decrease in the MC crystallinity. Similarly, the DSC thermogram revealed a reduced curcumin endothermic peak in the MC at 171.74 °C. The FT-IR spectrum showed minimal shift of the MC absorption peak. Following sonication in 40 % ethanol for 30 min, the quantity of dissolved curcumin was determined by high performance liquid chromatography at 422 nm using methanol:distilled water (80:20) as the mobile phase. The solubility of the MC and pure curcumin were 124.28 ± 7.076 mg/100 mL and 93.93 ± 6.656 mg/100 mL, respectively, indicating that the curcumin-quercetin MC were more soluble than pure curcumin.