The protective effects of propolis on hepatic injury and its mechanism

Propolis (PP) is a sticky substance that is collected from plants by honeybees. The purpose of this study was to investigate the protective effects of PP on hepatotoxicity induced by acetaminophen (AA, paracetamol) and the mechanism of its hepatoprotective effect. In rat hepatocyte culture, pretreatment with PP (1, 10, 100, 200 and 400 mug/mL, 24 h) significantly decreased the cytotoxicity of AA (0.5 mm) in a dose-dependent manner. In mice, pretreatment with PP (10 and 25 mg/kg, p.o., 7 days) also decreased the mortality and the incidence and severity of hepatic necrosis induced by AA (400 mg/kg, i.p.). After treatment with PP for 7 days, the hepatic enzyme activities of cytochrome P450 monooxygenases (P450s), UDP-glucuronyltransferase, phenolsulphotransferase (PST), glutathione S-transferase (GST) were measured in both rats and mice. In rats, PP (50 and 100 mg/kg, p.o.) decreased the activity of P4502E1, but significantly increased the activities of GST and PST. On the other hand, in mice treated with PP (10 and 25 mg/kg, p.o.), the activities of P4501A2, 2B1, 3A4 and 2E1 were dramatically inhibited, and the activity of PST was significantly enhanced. These results suggest that PP has a protective effect on hepatic injury, and that its effect may be explained by inhibition of phase I enzymes and induction of phase II enzymes. Copyright (C) 2003 John Wiley Sons, Ltd.