Improved solubility of quercetin by preparing amorphous solid with transglycosylated rutin and isoquercitrin

Abstract

The effect of isoquercitrin (IQC) addition on quercetin (QUE) solubility was investigated. Evaporated particles (EVPs) were prepared by rotary evaporator with QUE, a-glucosyl rutin (Rutin-G), and IQC. Differential scanning calorimetry and powder X-ray diffraction analysis revealed the amorphization of QUE and IQC by evaporation with Rutin-G. No diffraction peaks were detected in EVPs even after storage in sealing condition for 8 weeks at 40°C. The amount of dissolved QUE from the physical mixture was enhanced according to the increase of Rutin-G ratio because QUE was solubilized in the aggregated structure of Rutin-G formed in proportion to Rutin-G concentration. In the case of EVPs, the concentration of dissolved QUE increased when IQC was added in QUE/Rutin-G binary formulation. The concentration of dissolved QUE from EVPs of QUE/Rutin-G/IQC (1/7/3, w/w/w) and QUE/Rutin-G/IQC (1/5/5, w/w/w) was much higher than that with QUE/Rutin-G/IQC (1/10/0, w/w/w). These results suggested that IQC inhibit the re-crystallization from an amorphous QUE in dissolution medium, resulted in the enhancement in stability of an amorphous QUE in the supersaturated state. In conclusion, the addition of IQC into QUE/Rutin-G binary system could obviously improve the solubility of QUE.