Cytochrome P450 mediates the formation of four new citrinin metabolites

Citrinin (CIT) is one of by-products by Monascus fermentation with known nephrotoxicity. Except dihydrocitrinone, no other metabolites including the possible metabolic pathways have been found in vivo metabolism. In this study, we applied ultra-performance liquid chromatography-mass spectrometry (UPLC-MS) to analyze and identify potential CIT metabolites in the human cytochrome 450 (P450) subtype system. Four new metabolites with liver microsomes incubation were first found, namely 3-hydroxy-citrinin (M1), 4,5-ene-citrinin (M2), 5-hydroxymethyl-citrinin (M3), and 7-hydroxy-citrinin (M4). We also found the distinguished levels of the four metabolites with the incubation of various P450 subtypes. According to the results of molecular docking prediction, it showed the metabolic correlation of CYP3A4 with M1, CYP1A2, CYP2C9, and CYP2D6 with M2, M3, and M4. The maximum level of M1 metabolite was found in the incubation with liver microsome and P450 subtypes. Moreover, M1 and M4 metabolites were found in mice's duodenum, jejunum, ileum, liver, kidney, and hippocampus, but not M2 and M3. These results indicated the mediation of citrinin metabolism by P450s. It also suggested the concentration differences of metabolites with the incubation of different P450 subtypes.