Identification of in vitro phase I metabolites of benzotriazole UV stabilizer UV-327 using HPLC coupled with mass spectrometry

The benzotriazole UV stabilizer (BUVS) 2-(5-chloro-benzotriazol-2-yl)-4,6-di-(tert-butyl)phenol (UV-327) is used in various plastic products to protect them against harmful UV radiation. Meanwhile, there are concerns about potential adverse health effects on humans, as residues of UV-327 and other BUVSs have already been detected in various environmental matrices. However, information on the metabolism of UV-327 is not yet available. Therefore, in vitro experiments with human liver microsomes (HLMs) were performed in order to identify phase I metabolites to be used as specific biomarkers of exposure in biomonitoring studies. The samples were analyzed by HPLC coupled with mass spectrometry (HPLC/MS). Potential metabolites, which were formed by hydroxylation and further oxidation to carboxylic acid, were tentatively identified. Special metabolite structures were suspected and custom-synthesized as reference substances for verification. In total, seven phase I metabolites, which may be suitable biomarkers for the assessment of exposure to UV-327, have been identified and quantified. The results of the present study provide initial insights into the metabolic pathway of UV-327, which is essential for further research on its human metabolism.