Stable isotope ratio analysis for authentication of red yeast rice

Red yeast rice (RYR) is a dietary supplement obtained from rice fermented with the mould Monascus purpureus. It contains Monacolin K which is a hypocholesterolemic statin used to prevent cardiovascular diseases. The homologous prescription biosynthetic statin, lovastatin, is not chemically distinguishable from monacolin K. In this work we investigated whether delta C-13 and delta H-2 can distinguish monacolin K from lovastatin and can detect the presence of lovastatin in RYR. 18 samples of red yeast rice powder and 18 samples of lovastatin were collected. Monacolin K was isolated from RYR using preparative HPLC and together with lovastatin, was subjected to analysis of delta C-13 and delta H-2 using Isotope Ratio Mass Spectrometry. Thanks to the different photosynthetic cycles of the matrices used for their synthesis, monacolin K and lovastatin have different delta C-13 values (-29.6% +/- 0.6 and -16.7% +/- 2.6 respectively). delta H-2 is significantly (p < 0.001) lower in monacolin K but the ranges of values partially overlap with those of lovastatin. By defining a delta C-13 threshold value of -28.3%o for monacolin K, addition of lovastatin from a minimum of 10% can be identified. delta C-13 analysis can be therefore proposed as a suitable tool for detecting the authenticity of RYR on the market.