An improved method for the purification and structural analysis of rubropunctatin from red yeast glutinous rice

Abstract

An improved method for the separation and purification of rubropunctatin from red yeast glutinous rice was developed. In this method, silica gel column chromatography and thin layer chromatography were used to separate the Monascus pigments. Pure methanol and a mixture of ethyl acetate and methanol (13:7, v/v) were selected as the eluent and running solvent, respectively. When compared with previously reported methods, the developed method required fewer types of solvents, and could be suitable for large-scale laboratory production. The extracted pigment was analysed by ultra-high performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-Q-TOF-MS) and nuclear magnetic resonance (NMR) (1H NMR, 13C NMR). Structural analysis revealed a molecular mass of 353.2 m/z [M-H]-, and a structure including an azaphilone body with two side chains. This structure was consistent with that reported for rubropunctatin. Therefore, the improved purification method reported herein could efficiently be used for the extraction of rubropunctatin from red yeast glutinous rice.