Identification and analysis of the reactive metabolites related to the hepatotoxicity of safrole.

1. Safrole is the main component of the volatile oil in Xixin, which has a strong antifungal effect. However, safrole has been shown to be associated with the development of hepatocellular carcinoma. Methylenedioxyphenyl and allyl-benzene substructures of safrole may cause a mechanism-based inhibition (MBI) of CYP450 enzymes (CYPs) and produce reactive metabolites (RMs), resulting in inhibition of enzyme activity and toxic effects. 2. Based on the experiments of CYPs cocktail screening, glutathione (GSH) capture and the IC50 data, we found that safrole had an inhibitory effect on CYP1A2. The test of enzyme activity recovery when adding GSH may help to verify the MBI of safrole. 3. Two metabolites, 1,2-dihydroxy-4-allylbenzene (M1) and 1'-hydroxy safrole (M2) could be captured by GSH. The ultra performance liquid chromatography - tandem mass spectrometer (UPLC-MS/MS) method was used to identify the RMs through a detailed characterization of the safrole cleavage processes and the GSH-M1 adduct. The RMs identified are quinone and its tautomer. Thus, preliminary conclusion can be obtained that safrole is a mechanism-based inhibitor of CYP1A2. 4. The cleavage process of the GSH-M1/M2 adduct was analyzed in further detail. We believe the safrole hepatotoxicity mechanism is related to the RMs mediated by CYP1A2. This work provides important information on predicting in vivo drug induced liver injury.