Five new eudesmane-type sesquiterpenoid lactones biotransformed from atractylenolide I by rat hepatic microsomes

The work presented here is the first study performed on the biotransformation and/or metabolism of atractylenolide I (1) as a valuable anti-inflammatory and chemopreventive agent, using liver microsomes from rats pre-treated with sodium phenobarbital. Two known eudesmane-type sesquiterpenoid lactones, namely 1β-acetoxyatractylenolide I (2) and 1β-hydroxy-atractylenolide I (3), and five new ones, namely 3β-hydroxy-atractylenolide I (4), 1β,13-dihydroxy-atractylenolide I (5), 1β,2α-dihydroxy-atractylenolide I (6), 1β,3α-dihydroxy-atractylenolide I (7), and 1β,3β-dihydroxy-atractylenolide I (8) were obtained. Their chemical structures were unambiguously established by both 1D and 2D NMR as well as mass spectroscopic techniques. The result indicated that the parent prototype compound 1 could be specifically oxidized at C-1, C-2 and C-3 of A-ring, suggesting that the oxidizable of 1 may contribute to its in vivo anti-inflammatory and chemopreventive effects. And the result also provided valuable information for further investigation of relationship among metabolic activation and liver microsomal cytochrome P450 enzyme isoforms.