Evaluation of oxidative stress induced by cadmium and comparative antioxidant effects of Shirazi thyme (Zataria multiora Boiss) and vitamin E in common carp (Cyprinus carpio)

Shirazi thyme is an active phytobiotc contains phenolic compounds and flavonoids which have strong antioxidant properties. This study was conducted to investigate the potential protective effects of Shirazi thyme compared to that of vitamin E against cadmium toxicity. Common carp juveniles (34±3 g) were divided into four groups and fed by three different diets including commercial diet without any additive (for control and metal only group) and supplemented with either 1% ground Shirazi thyme or 100 mg/kg vitamin E. All treatments except the control were exposed to sublethal concentration of waterborne cadmium (1.5 mg/L free ion) for 15 d and liver, kidney and gill were sampled 3, 7, 10 and 15 days after the metal exposure. Results showed that treatment of the fish with cadmium for 15 days resulted in a significant reduction in glutathione reductase (GR), glutathione-S-transferase (GST) and catalase (CAT) and led to liver, kidney and gills dysfunction. On the other hand, the level of malondialdehyde (MDA) significantly increased during metal exposure. Supplementation of diets with Shirazi thyme and vitamin E led to a significant protection against metal exposure in different tissues. Moreover, Shirazi thyme was found to be as effective as vitamin E. The current finding can provide a useful reference for stress protective effects of thyme and its beneficial role in aquaculture.