The purpose of this study was to examine the effects of antioxidants, including vitamin C, chitosan or a combination of both, on oxidative stress markers in muscles, as edible tissues of fish, exposed to paraquat. Fish exposed to 0.02 mg/L paraquat for 21 days were fed different diets: a normal diet, a diet containing chitosan (1000 mg/kg diet), a diet with vitamin C (1000 mg/kg diet) or both vitamin C and chitosan. Oxidative stress markers, including the activity of catalase, total antioxidant and malondialdehyde (MDA), as well as biochemical parameters including the activity of aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine phosphokinase (CPK), lactate dehydrogenase (LDH) and acetylcholinesterase (AChE), were measured in muscles. Fish exposure to paraquat increased LDH, CPK, catalase and MDA activity significantly, while it significantly decreased AST, ALT and AChE activity and total antioxidant capacity in muscles. Administration of vitamin C, combined with chitosan, to fish exposed to paraquat was effective in regulating AChE, AST, ALT, LDH, CPK and catalase activity. A significant increase in the total antioxidant status and a significant decrease in MDA levels were observed in fish fed chitosan-vitamin C complex. In conclusion, it is suggested that combined supplementation with vitamin C and chitosan may improve the detoxification system in the muscles of fish and protect common carp from paraquat toxicity.

Background: Paraquat is nonselective bipyridyl herbicide that induces hepatotoxicity through oxidative stress. Vitamin C and chitosan have antioxidant as well as radical scavenger properties and show protective effects against reactive oxygen species (ROS). In the present study, hepatoprotective effects of chitosan and vitamin C were evaluated in common carp exposed to paraquat. Methods: While exposed to 0.02 mg. L-1paraquat for 21 days, common carp were fed chitosan (1000 mg. kg‑1 feed), vitamin C (1000 mg. kg-1 feed), and vitamin C combined with chitosan. At the end of the experiment, activities of hepatic enzymes and oxidative stress biomarkers were evaluated. Results: Paraquat induces changes in the activity of alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase, alkaline phosphatase and lactate dehydrogenase in liver tissue of fish. However, these enzymes were restored to normal levels in fish fed with vitamin C and vitamin C combined with chitosan following exposure to paraquat. Increased levels of malondialdehyde were observed in liver after exposure to paraquat, while glucose-6-phosphate dehydrogenase and catalase activities and the total antioxidant levels decreased. Administration of vitamin C combined with chitosan significantly reduced malondialdehyde levels and increased the total antioxidant capacity, glucose-6-phosphate dehydrogenase and catalase activities. Conclusion: Administration of vitamin C is effective in reducing liver toxicity of paraquat. However, administrating both vitamin C and chitosan is more effective. In other words, chitosan and vitamin C have a synergic effect. They could be used as hepatoprotective agents against paraquat-induced hepatotoxicity in fish.