Dietary Curcumin Protects Common Carp (Cyprinus carpio) Against Potassium Permanganate-Induced Toxicity: Hematological, Immunological, Oxidative, and Molecular Docking Evidence

Potassium permanganate treatment can adversely affect fish physiology despite its usefulness in aquaculture. This study evaluated the protective effects of dietary curcumin against potassium permanganate-induced disturbances in common carp (Cyprinus carpio). Fish were fed a basal diet or diets supplemented with 1%, 2%, or 4% curcumin for eight weeks, with or without subsequent exposure to potassium permanganate at 2 mg/L for 30 min daily for seven days. Hematological and immune parameters and oxidative status in the liver, kidney, spleen, and gill were assessed. Potassium permanganate exposure altered blood and immune parameters, increased lipid peroxidation, and weakened antioxidant defenses. Curcumin supplementation alleviated these effects, with protection evident at 1%, the lowest dietary inclusion level tested, and further improvements in selected parameters at 4%. Inclusion levels below 1% were not evaluated, so the minimum effective level remains unknown. Molecular docking predicted interactions between curcumin and the antioxidant enzymes SOD, CAT, GPx, and GST at structurally plausible binding sites. These computational findings were interpreted alongside the biological results as supportive, hypothesis-generating evidence rather than confirmation of functional effects on these enzymes in vivo. Overall, dietary curcumin showed potential to reduce the physiological disturbances associated with repeated potassium permanganate exposure. Further dose–response studies should evaluate inclusion levels below 1% to identify effective and economically viable supplementation rates and determine whether curcumin affects the antiparasitic or antibacterial efficacy of potassium permanganate.