Japanese butterbur (Petasites japonicus) leaves increase hepatic oxidative stress in male rats.

We investigated the adverse effects of Japanese butterbur leaves (Petasites japonicus, Compositae) in male F344/DuCrj rats. The rats were fed a control diet or a treatment diet containing 5% butterbur leaf powder for 4 weeks. No differences were observed in body weight gain, food intake or feed efficiency between treatments, but relative liver weight in the butterbur group was significantly higher than that of the control group. In addition, thiobarbituric acid reactive substances (TBARs) and glutathione levels in the serum and liver of the butterbur group were higher than those of the control group. Hepatic glutathione reductase and glutathione S-transferase activities and mRNA expression in the butterbur leaf group were higher than in the control group. Furthermore, hepatic cytochrome 2E1 mRNA expression was higher than in the control group. In vitro, an acetone extract of the butterbur leaf powder showed the strongest increase in TBARs level in a hepatic homogenate through 4 d. Our findings suggest that feeding 5% butterbur leaf powder to rats can cause adverse effects by increasing oxidative stress.