Stereoselective metabolism of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate and its metabolites in rabbits in vivo and vitro

Abstract

The stereoselective metabolism of the enantiomers of the UV-filter 2-ethylhexyl 4-dimethylaminobenzoate (EDP) in rabbits was studied. The two major metabolites 4-(N,N-dimethylamino) benzoic acid (DMP) and 4-methylaminobenzoic acid (MMP) were also investigated in vivo and in vitro. Cytotoxicity of EDP and its two metabolites was also investigated in hepatocytes. The results showed that EDP degraded rapidly to its metabolites (DMP and MMP) and could not be detected in blood at 5 min after intravenous administration to rabbit in vivo. In almost all the tissue samples, EDP, DMP and MMP could not be detected at 3 h expect DMP was found in the liver and kidney at about 1 mg kg⁻¹ level. EDP was found to be degraded to DMP rapidly in plasma and liver microsome in vitro with t_1/2 less than 20 and 5 min and the whole process was enantioselective with preference of (+)-form. DMP was observed to be further degraded to MMP in liver microsome in the presence of NADPH. The cytotoxic effects of EDP, DMP and MMP were carried out using buffalo rat liver cell line. The results from cell viability assays indicated that the degradation of EDP was a detoxification process.