protective effects of silymarin extract on malthion-induced zebra cichlid (cichlasoma nigrofasciatum) hepatotoxicity

background: there is much evidence indicating that natural substances from edible and medicinal plants possess powerful antioxidant and hepatoprotective activities. the objective of the present study was to investigate the potential hepatoprotective effect of silymarin in fish exposed to malathion. methods: zebra cichlid fish were allocated into five groups of which one group received normal feed and served as control. fish from group 2 were treated with 0.1 mg.l-1 malathion. fish from group 3 and 4 were fed with enriched diet with 1400 mg and 2100 mg silymarin per 1 kg feed, respectively. while fish from group 5 and 6 were fed with enriched diet with 1400 mg and 2100 mg silymarin per 1 kg feed, respectively and simultaneously were treated with 0.1 mg.l-1 malathion for 15 days. activities of hepatic enzymes including alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase and lactate dehydrogenase were evaluated. oxidative stress was ascertained by measuring malondialdehyde as marker of lipid peroxidation and total cellular antioxidant capacity. results: exposure to malathion caused a significant increase in mda levels and altered ast, alt, alp and ldh activities in liver tissues (p<0.05). the hepatic antioxidant capacity was significantly lowered in malathion treated fish as compared to the control group (p<0.05). treatment with silymarin significantly ameliorated these changes in the malathion-treated groups. conclusion: these finding demonstrated that silymarin have protective effects against the toxic influence of malathion on the examined biochemical parameters in liver tissue of fish.