The potential of rosmarinic acid, carnosic acid and carnosol as antioxidants to preserve sheep (Ovis aries) sperm viability and morphological integrity

[摘要] ENGLISH ABSTRACT: The use of assisted reproductive techniques (ART's) such as artificial insemination and embryo production, which requires the use of good quality sperm, is hampered by the susceptibility of ram sperm to cold stress and heat stress. Short-term (cold) storage has a definite effect on the viability, morphological integrity, and subsequently the fertilizing ability of sperm, due to an increase in oxidative stress caused by an excessive build-up of reactive oxygen species (ROS). Heat stress has a number of deleterious effects on sperm production and maturation, with the excessive build-up of ROS resulting in a decrease in sperm viability and quality. The study therefore investigated whether diterpenes in common rosemary and wild rosemary varieties, which has a natural antioxidant activity, can minimize the deleterious changes caused by cold storage and heat stress (HS). The findings indicated that sperm viability decreased over time under both cold and heat stress conditions, but that there was no significant contribution of the antioxidants (AO's) on the changes in viability. The wild rosemary species had a higher level of morphological abnormalities than the common rosemary species for the cold storage and heat stress studies. However, when considering the two species individually, there were no significant differences for morphology. There appeared to be no protection from the AO's on maintaining sperm viability for both the cold storage and HS studies, and the AO's also appeared to have no protective effects on morphology during the HS study. Cold storage resulted in an increase in the percentage of abnormal sperm when considering the individual effects of the AO's. To conclude, supplementation of sperm media with both rosemary aqueous extracts did not show a significant level of protection against the deleterious effects of cold storage and HS on sperm quality. The extraction technique that was used for the present study was not sufficient in optimizing the AO yield to its maximum potential. Rosmarinic acid was extracted at a higher concentration than that of carnosic acid and carnosol due to the hydrophobic properties of both carnosic acid and carnosol. The wild species was difficult to filter after extraction, likely due to the structure of the leaves, and this too would have hindered the AO yield. Future studies need to determine the most suitable extraction methods for each AO in each plant species in order to optimize the effects of the AO's on improving sperm quality. It would also be beneficial to determine how each of the AO's interact with the sperm membrane, how they are able to enhance the effect of the natural AO defense mechanism, and how they can minimize the negative impact of heat stress.

[发布机构] Stellenbosch University