Effect of isoespintanol and thymol on the antioxidant activity of equine semen diluted for freezing purposes

Abstract

A wide variety of antioxidants that were evaluated for freezing equine semen failed to yield satisfactory results in maintaining their quality and fertility. Isoespintanol and thymol are molecules of natural origin with a high antioxidant activity, which makes them potentially useful for reducing semen oxidative stress during cryopreservation. This study aimed to evaluate the effect of isoespintanol and thymol on total antioxidant and enzymatic activity of equine semen diluted for freezing purposes. The semen of five Colombian creole horses was diluted in a freezing medium, divided into three aliquots that were randomly assigned to treatments with isoespintanol (40 μM), thymol (50 μM), or control (no antioxidant). Total antioxidant capacity (TAC) was evaluated using ORAC and FRAP tests. Catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity were evaluated by enzymatic assays. The statistical evaluation was performed using mixed models, correlation analysis, and comparison of means by Tukey’s test. SOD and GPx activities were lower for isoespintanol (6.7 ± 2.2 U/ml and 0.16 ± 0.02 U/ml), compared to thymol (6.9 ± 2.2 U/ml and 0.20 ± 0.02 U/ml) and to control (7.2 ± 2.2 U/ml and 0.22 ± 0.02 U/ml) (p < 0.05). There were no differences for TAC or CAT in semen (p > 0.05). Isoespintanol reduces SOD and GPx activity in equine semen diluted for freezing purposes.