Thymoquinone improves motility, plasma membrane integrity and DNA integrity of frozen–thawed ram semen

The aim of this study was to determine the effects of thymoquinone (TQ), which is the most essential active compound of Nigella sativa, on the spermatological parameters of ram semen during cryopreservation. Ejaculates were collected from five Sonmez rams using an artificial vagina and extended with Tris-based extender not containing TQ (control, 0 μg/ml TQ) and containing 10, 25, 50 and 100 μg/ml TQ. The extended semen samples were equilibrated in a + 4°C cold cabinet for 2 h. After 2 h, the samples were loaded into 0.25 ml French straws. The straws were frozen by liquid nitrogen vapour and stored in a liquid nitrogen container (-196°C). The frozen straws were thawed in a water bath (37°C for 30 s) and evaluated in terms of motility characteristics, plasma membrane and acrosome integrity, mitochondrial reactive oxygen species levels, lipid peroxidation levels, DNA damage and biochemical alterations (oxidative stress index, malondialdehyde and glutathione). TQ100 had higher total motility (53.59 ± 3.01) and progressive motility (19.84 ± 1.44; not significantly different from TQ25 and TQ50) compared to the control and TQ10 (p ˂ 0.05). According to the results of the analyses on motility characteristics, there were significant differences between the groups in terms of curvilinear velocity (VCL), amplitude of lateral head displacement (ALH) and linearity (LIN; p ˂ 0.05). The highest DNA damage was detected in the control group (p ˂ 0.05). TQ50 had higher plasma membrane and acrosome integrity (59.56 ± 5.92) compared to the control and TQ25 (p < 0.05) but not significantly different from TQ10 and TQ100. The lowest mitochondrial reactive oxygen species levels were detected in TQ50 and TQ100 (p ˂ 0.05). There were no significant differences among the groups in terms of their oxidative stress index, lipid peroxidation, malondialdehyde and glutathione levels (p > 0.05). According to the results, it could be concluded that supplementing 50 or 100 μg/ml TQ to Tris extenders that were used for ram semen cryopreservation showed a positive effect on motility, plasma membrane integrity and acrosome integrity, and it reduced DNA damage and mitochondrial reactive oxygen species levels.