Chemical fingerprint analysis and characterization of monacolins, pigments, citrinin, sudan red G from red yeast rice samples using liquid chromatography-accurate QToF mass spectrometry

Abstract

Red yeast rice (RYR) is prepared by fermentation of rice with various strains of the yeast Monascus spp belonging to family Aspergillaceae, the genus Monascus. Depending on the Monascus strains and the fermentation conditions, the products may contain polycetides called monacolins or polyketides (pigments), which are secondary metabolites. The preparations of red yeast rice have being used in food as a preservative, spice, coloring, rice wine or been sold as dietary supplements to lower blood levels of cholesterol and related lipids. The UHPLC-QToF-MS analysis of monacolins, pigments, citrinin and sudan red G from various RYR samples and dietary supplements was performed. A separation by LC was achieved using a reverse-phase column and a gradient of water/acetonitrile each containing formic acid as the mobile phase. MS-MS detection was used to provide structural information. Under typical ESI-MS conditions, monacolins produced abundant ions corresponding to the protonated molecules, sodium ion adducts and dimers [2 M+H]+. The elimination of the ester side chain followed by dehydration and dissociation of the lactone moiety were observed as the main fragmentation pathways for most of the monacolin-type of compounds.