Structural and physicochemical characterization and purity assessment of myrsinoic acids A and B, active compounds isolated from Rapanea ferruginea barks

The present study provided a chemical, physical and physicochemical characterization of myrsinoic acids A (MAA) and B (MAB) isolated from stem bark of Rapanea ferruginea Mez (Myrsinaceae). In previous pre-clinical studies these compounds have shown important anti-inflammatory, anticholinesterasic and antimicrobial activities. A gradient stability-indicating LC-UV method was developed, and a forced degradation study was carried out. Purity, log P, solubility, and pKa were determined. Thermal analysis (DSC/TG) was conducted for both compounds. MAB was characterized by X ray powder diffraction (XRPD) and scanning electron microscopy (SEM). When submitted to stress conditions, both markers showed degradation, with MAA presenting higher lability. The purity of MAA (oil) was 76.20%, while that of MAB (powder) was 98.90%. MAA and MAB exhibited log P values of 3.30 and 3.22, respectively. MAA was very slightly soluble in methanol and acetonitrile, while MAB was slightly soluble in both solvents. Both were practically insoluble in water. MAA and MAB showed pKa of 4.5 and 4.8, respectively. In the SEM analysis, MAB showed a semi-crystalline morphology and high purity when analyzed by XRPD and DSC. This data will contribute to the development, quality control and standardization of pharmaceuticals using MAA and MAB.