The effect of cinnamaldehyde on the lesions caused by zinc oxide (ZnO) in the gills of common carp (Cyprinus carpio)

Nowadays, the use of plants as one of the treatment methods of heavy metal pollution is considered. Cinnamon is one of the plants that has many therapeutic properties due to its effective ingredients. One of the most important effective ingredients of cinnamon is cinnamaldehyde. In the current study, the therapeutic effect of cinnamaldehyde on the lesions caused by zinc oxide (ZnO) in the gills of common carp (Cyprinus carpio) was investigated. In this study, common carp were divided into 5 groups in triplicates. Group 1 was considered as a control, group 2 was exposed to 3mg/L of zinc oxide, and groups 3, 4, and 5, in addition to receiving zinc oxide received concentrations of 3.6, 7.2, and 10.8mg of cinnamaldehyde in 100g diet, respectively for a period of 45 days. Then, 6 fishes were randomly selected from each group and their gills were sampled. The highest amount of zinc concentration, the lowest amount of total antioxidant activity and the highest amount of lipid peroxidation index were observed in group 2. Also, the most severe damage was observed in group 2 including epithelial cells hyperplasia, adhesion, atrophy and destruction of secondary lamellae, hyperemia, telangiectasia and infiltration of inflammatory cells. In the treatment groups with increase of cinnamaldehyde in the diets, zinc concentration, histopathology symptoms and lipid peroxidation index decreased, while the amount of total antioxidant activity increased. The results of this study showed that cinnamaldehyde has a protective and therapeutic effect against the damage caused by zinc oxide. The most protective effect was observed in group 5 including decrease of Zn bioaccumulation, improving histopathology symptoms, reducing the value of lipid peroxidation index and increasing the value of total antioxidant activity.