Simultaneous detection of monacolins and citrinin of angkak produced by Monascus purpureus strains using Liquid Chromatography-Mass Spectrometry (LC-MS/MS)

Angkak or red mold rice is produced from the fermentation of white rice using Monascus purpureus, which results in the red color of the fermented rice. Angkak has been used as a natural coloring agent for food, spices, and medicine. The active compound in angkak that contributes to lower blood cholesterol is known as monacolin (monacolin K). However, the presence of citrinin, the byproduct of angkak fermentation, needs to be considered as it can cause hepato-nephrotoxic mycotoxin. The contents of pigments, monacolins, and citrinin as secondary metabolites depends on the Monascus strain and fermentation conditions. This study aims to analyze simultaneously monacolins and citrinin in angkak produced by M. purpureus strains using Liquid Chromatography-Mass Spectrometry (LCMS/MS). The angkak was prepared by fermentation using M. purpureus FNCC 6008 and M. purpureus JK2. A total of 10⁷ M. purpureus spores/mL was inoculated into the rice. The fermentation was carried out at room temperature (25-30 °C) for 14 days. The detection using LC-MS/MS showed that the monacolin K in angkak from both strains was below LOQ (< limit of quantification). The analysis of citrinin content in angkak showed that JK2 strain produced lower citrinin (1.10±0.021µg/g) compared to FNCC 6008 (3.01±0.072 µg/g). The other monacolins found in angkak from both strains were including dehydromonacolin K, monacolin J (qualitative), and mevastatin. Based on t-test, the amount of both mevastatin and citrinin in angkak produced by two different strains were significantly different. In contrast, the amount of dehydromonacolin K in both angkak was comparable. The simultaneous detection result of LC-MS/MS could determine the choice of Monascus strains quickly. JK2 strain was considered as safe, thus it could be chosen to be applied to food products.