Background: Cyclophosphamide is an alkylating anticancer agent with high efficacy; however, it also causes oxidative stress, which can lead to biochemical disorders. Antioxidants play a very important role in dealing with oxidative damage. We aimed to investigate the effect of silymarin as an antioxi- dant on testis function in adult male mice after treatment with cyclophosphamide. Materials and Methods: In this study, 24 NMRI male mice (37±2 g) were divided into 4 groups (n=6): control; cyclophos- phamide (100 mg/kg bw/week, ip); Silymarin (200 mg/kg bw/ interval day, ip) and cyclophosphamide + silymarin. After 35 days of treatment, the serum samples were collected to meas- ure the testosterone level, total antioxidant capacity (TAC) and malondialdehyde (MDA) level. The obtained data were statisti- cally analyzed using one-way ANOVA and Tukey's test and the means were considered significantly different at P<0.05. Results: A significant decrease in the level of testosterone hor- mone and the total antioxidant capacity (TAC) was observed in the cyclophosphamide group compared to the control group, while the level of malondialdehyde (MDA) significantly in- creased in the cyclophosphamide group compared to the control group. In the cyclophosphamide + silymarin group, compared to the cyclophosphamide group, there was a significant de- crease in the amount of MDA (P<0.01), a significant increase in the TAC (P<0.05) and an increase in the testosterone hormone level. The mentioned parameters did not show any significant difference in the silymarin group when compared to the control group (p>0.05). Conclusion: Our results indicated that silymarin, as a strong antioxidant, can prevent the adverse effects of cyclophospha- mide and improve the function of mice testis through reducing oxidative stress and increasing total antioxidant capacity.
