Effects of methanol extract of Alisma orientale rhizome and its major component, alisol B 23-acetate, on hepatic drug metabolizing enzymes in rats treated with bromobenzene

In the course of screening for hepatoprotective agents from natural products, the effects of the methanol extract (ME) of the rhizome of Alisma orientale (Alismataceae) and its major component, alisol B 23-acetate (ALB) on hepatic lipid peroxidation and drug-metabolizing enzymes were evaluated in rats intoxicated with bromobenzene (BB). Pretreatment with ME and ALB had no effect on hepatic antioxidant enzymes such as glutathione reductase and a-glutamylcysteine synthetase. ME and ALB had also no effect on the reduction in glutathione content caused by BB. In contrast, ME recovered the BB-induced decrease in epoxide hydrolase and glutathione S-transferase, enzymes that remove toxic epoxides. ME also attenuated the BB-induced increase in aminopyrine N-demethylase and aniline hydroxylase, enzymes that produce toxic intermediates. This effect was greater than that seen with ascorbic acid, which was used as a positive control. ALB had similar effects on the activities of antioxidant enzymes to ME, and may be partly responsible for the effects of ME.