Protective effects of the antioxidants curcumin, ellagic acid and methionine on motility, mitochondrial transmembrane potential, plasma membrane and acrosome integrity in freeze-thawed Merino ram sperm

The aim of this study was to determine the effects of curcumin, ellagic acid and methionine on sperm parameters following the freeze-thawing of Merino ram semen. Ejaculates were collected via an artificial vagina from four Merino rams, evaluated microscopically and pooled at 37 °C. The pooled semen samples were diluted in a Tris-based extender and separated into groups containing curcumin (1, 2, 4mM), ellagic acid (1, 2, 4mM), methionine (1, 2, 4mM) and no antioxidant (control). The diluted semen was cooled to 5 °C slowly and equilibrated for 3 h. After the equilibration, the samples were frozen in liquid nitrogen vapour, and plunged into liquid nitrogen (-196 °C) for storage. Frozen straws were thawed at 37 °C for 30 s in a water bath for microscopic sperm evaluation, individually. All antioxidants led to a higher percentage of sperm motility in comparison to the control group. The freezing extender supplemented with methionine (1mM), curcumin (1 and 2mM) and ellagic acid (1 and 2mM) led to higher percentage of sperm plasma membrane integrity when compared to other groups (P < 0.05). Antioxidant supplementation also resulted in a higher percentage of sperm acrosome integrity in comparison to the control. Methionine, curcumin and ellagic acid (1mM: 27.7 ± 2.4, 28.0 ± 2.1 and 26.8 ± 2.0) groups provided higher protection in terms of sperm mitochondrial activity when compared to other groups (P < 0.05). The findings of this study show that varying concentrations of curcumin, methionine and ellagic acid have markedly different effects on the spermatological variables under study.