Dietary silymarin, Silybum marianum extract ameliorates cadmium chloride toxicity in common carp, Cyprinus carpio

The present study evaluated the protective effects of silymarin extract (SIE) on cadmium chloride toxicity in common carp, Cyprinus carpio. Four experimental groups were considered for the experiment including: SIE₀ (control): non-SIE-supplemented fish, SIE₁: fish supplemented with 400 mg SIE/kg diet, SIE₂: fish supplemented with 1400 mg SIE/kg diet, SIE₃: fish supplemented with 2400 mg SIE/kg diet. Fish were fed experimental diet for 60 days and then exposed to cadmium chloride (1.5 mg/l or 25% of LC50-96 h) and antioxidant defense components and the survival rate assayed. After 60 days feeding trial, total antioxidant capacity (TAC) levels significantly increased (P<0.01) in 1400–2400 mg SIE/kg diet treatments compared to those in control and 400 mg SIE/kg diet treatment. Malondialdehyde (MDA) (P>0.01) and acetylcholinesterase (AChE) levels (P>0.01) remained unchanged during the feeding period in all treatments. Hepatic catalase (CAT) in all SIE supplemented groups and superoxide dismutase (SOD) and glutathione peroxidase (GPx) in 1400–2400 mg SIE/kg diet treatments significantly elevated (P<0.01) in response to SIE. Plasma levels of hepatic metabolic enzymes [alanine transaminase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), creatine kinase (CK), lactate dehydrogenase (LDH)] remained unchanged (P>0.01) in all experimental groups over feeding period. After exposure to cadmium chloride, TAC levels were significantly elevated (P<0.01) in all experimental groups. In control and 400 mg SIE/kg diet treatment, TAC showed lower levels (P<0.01) compared to other groups. MDA levels were significantly increased (P<0.01) in control and fish supplemented with 400 and 1400 mg SIE/kg diet. TAC in the fish of 2400 mg SIE/kg diet treatment remained unchanged (P>0.01), following the exposure. CAT (P<0.01), SOD (P<0.01) and GPx (P<0.01) were significantly elevated in response to cadmium chloride in all groups. However, the treatments, 1400 and 2400 mg SIE/kg diet, showed lower increases (P<0.01) of enzymes. AChE activity (P<0.01) in the liver were significantly decreased in control and fish fed 400 and 1400 mg SIE/kg diet. Exposure to cadmium significantly increased (P<0.01) the plasma levels of ALT, AST, ALP and LDH in control and those fed 400 and 1400 mg SIE/kg diet. The findings of the current study indicated that SIE at a rate of 1400–2400mg/kg diet might enhance antioxidant defense and protect hepatocytes against toxic effects of cadmium.