Four new eudesmane-type sesquiterpenoid lactones from atractylenolide II by biotransformation of rat hepatic microsomes

The biotransformation of atractylenolide II, a major bioactive principle of the rhizomes of Atractylodes macrocephala Koidz., was investigated in vitro by incubation with rat hepatic microsomes pretreated with sodium phenobarbital. The biotransformation products were extracted and purified by chromatographic methods. Seven biotransformation products (BP1BP7) were obtained and their structures were elucidated by NMR and MS data analyses and by comparison with the previously reported values, including four new compounds, namely 4(R),15-epoxy-atractylenolide II (BP1), 4(R),15-epoxy-13-hydroxyatractylenolide II (BP5), 4(R),15-epoxy-1-hydroxyatractylenolide II (BP6), and 4(R),15-dihydroxyatractylenolide II (BP7). The biotransformation pathway of atractylenolide II by hepatic microsomes was deducted based on the structure resolution of the products.