Simultaneous determination of two Monascus metabolites in red yeast rice by HPLC using fluorescence detection

A reversed-phase HPLC method with fluorescence detection for the determination of two Monascus metabolites, monasfluore A (MFA) and monasfluore B (MFB), in red yeast rice was carried out. Optimum conditions for the extraction and chromatographic separation were investigated. The method was validated through the following performance criteria: linearity, stability, limit of detection (LOD), quantification (LOQ), etc. This assay was successfully used for determination of the MFA and MFB in 20 samples inoculated from different Monascus sp. The results revealed that significant variations were demonstrated in the contents of the MFA and MFB in these samples. The high contents of both MFA and MFB in sample 13 were found to be 81.400 and 26.300 mg g−1, respectively. The low contents of both MFA and MFB in sample 14 were also found to be 0.010 and 0.003 mg g−1, respectively.

Research highlights
► A HPLC method has been established for the quantitative analyses of two Monascus metabolites MFA and MFB in red yeast rice. The method is simple, sensitive and reliable.
► The high contents of both MFA and MFB in red yeast rice (sample 13) were found to be 81.400 and 26.300 mg g−1, respectively.
► The low contents of both MFA and MFB in red yeast rice (sample 14) were also found to be 0.010 and 0.003 mg g−1, respectively.
► It will be interesting in future research to investigate the factors led to the variation in the MFA and MFB content of different the red yeast rice samples.