<i>In Vitro</i> and <i>in Vivo</i> Studies of the Metabolic Activation of 8‑Epidiosbulbin E Acetate

Abstract

Furanoid 8-epidiosbulbin E acetate (EEA) is a major constituent of herbal medicine Dioscorea bulbifera L. (DB), a traditional Chinese medicine herb. Our preliminary studies demonstrated that administration of EEA caused acute hepatotoxicity in mice, and the observed toxicity required cytochromes P450-mediated metabolism. Metabolic activation studies of EEA were performed <i>in vitro</i> and <i>in vivo</i>. Microsomal incubations of EEA supplemented with <i>N</i>-acetyl lysine (NAL) and glutathione (GSH) generated six metabolites (M1–M6). M1–M4 were characterized as pyrrole derivatives, and M5 and M6 were pyrrolinones. M2–M6 were detected in bile and/or urine of rats given EEA. Dimethyldioxirane-mediated oxidation of EEA in the presence of NAL and GSH produced M1–M6, all of which were generated in microsomal incubations. The structures of M3 and M6 were confirmed by ¹H and ¹³C NMR. These findings provide evidence for the metabolic activation of EEA to the corresponding <i>cis</i>-enedial intermediate both <i>in vitro</i> and <i>in vivo</i>. Ketoconazole inhibited the microsomal production of the <i>cis-</i>enedial, and P450 3A4 was found to be the primary enzyme involved in the bioactivation of EEA