Protective effect of quercetin against oxidative stress induced by oxytetracycline in muscle of silver catfish

Protective or ameliorative effects of quercetin on the oxytetracycline (OTC) induced oxidative stress and presence of OTC residues in the muscle of silver catfish (Rhamdia quelen) were assessed. Fish were divided into four different experimental groups and received the following experimental diets for 14 or 21days: (i)-control; (ii)-quercetin; (iii)-OTC; or (iv)-quercetin plus OTC. Muscle samples were collected at the end of the experiment and analyzed for the oxidant/antioxidant status and presence of OTC residues. The OTC values in muscle of fish were lower than the quantification limit. There was a significant increase on lipid peroxidation and protein carbonyl content in the muscle of OTC-treated fish at 14 and 21days. Treatment with quercetin avoided this increase in the groups that received diet with quercetin plus OTC. Superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities decreased in the muscle of OTC-treated fish at 14days. Quercetin was able to avoid the decrease of GPx activity in the group that fed diet with quercetin plus OTC. After 21days of treatment there was a decrease of SOD, GPx and glutathione S-transferase activities in the muscle of OTC-treated fish. Quercetin was able prevent the decrease of SOD activity in the group that received diet with quercetin plus OTC. The glutathione reductase activity was higher in quercetin group at 14 and 21days of treatment. Ascorbic acid (AA) content increased in quercetin and quercetin plus OTC groups after 14days of treatment. After 21days of treatment, the AA and non-protein thiols content decreased in the muscle of OTC-treated fish. Thus, the present study demonstrates that quercetin protects the muscle from the OTC-induced oxidative stress, suggesting that it may be a useful compound to minimize the adverse effects in fish requiring treatment with OTC.