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

Gulyas, Jenna Lara (2017-12)

Thesis (MSc)--Stellenbosch University, 2017.

Thesis

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.

AFRIKAANS OPSOMMING: Die gebruik van ondersteunende reproduksietegnieke (ART's) soos kunsmatige inseminasie en embrio produksie, wat die gebruik van goeie gehalte sperme benodig, word beperk deur die vatbaarheid van ramsperme vir beskadiging tydens berging by lae temperature asook hitte stres. Korttermyn (koue) berging het 'n besliste uitwerking op die lewensvatbaarheid, morfologiese integriteit en die bevrugtingsvermoë van sperme, as gevolg van 'n toename in oksidatiewe stres wat veroorsaak word deur 'n oormatige opbou van reaktiewe suurstofspesies (ROS). Hitte stres het 'n aantal nadelige gevolge vir spermproduksie en rypwording, met die oormatige opbou van ROS wat lei tot 'n afname in sperm lewensvatbaarheid en -kwaliteit. Die studie het ondersoek of die diterpeen verbindings in gewone roosmaryn- en wilde roosmaryn variëteite, wat 'n natuurlike antioksidant (AO) aktiwiteit het, die skadelike veranderinge wat onderskeidelik deur koue berging en hitte stres (HS) veroorsaak word, kan verminder. Die bevindings het getoon dat sperm lewensvatbaarheid afgeneem het onder beide koue en hitte stres toestande, maar dat daar geen beduidende bydrae van die AO was om die afname in lewensvatbaarheid te voorkom nie. Die waterekstrak van die wilde roosmaryn spesie het 'n hoër vlak van morfologiese abnormaliteite as dié van die gewone roosmaryn spesie vir die koue berging en hitte stres studies. By die oorweging van die twee individuele spesies was daar egter geen beduidende verskille vir morfologie nie. Daar was geen beskermingseffek van die AO op die handhawing van spermvatbaarheid vir beide die verkoeling van koue stoor en HS nie, en die AO het ook tydens die HS-studie geen beskermende effekte op morfologie gehad nie. Koue berging het gelei tot 'n toename in die persentasie abnormale sperme wanneer die individuele effekte van die AO oorweeg word. Ter afsluiting het aanvulling van sperm verdunningsmedium met die waterekstrak van beide plantspesies nie 'n beduidende mate van beskerming getoon teen die skadelike effekte van verkoeling en HS op spermkwaliteit nie. Die onttrekkingstegniek wat vir die huidige studie gebruik is, was nie voldoende om die AO-opbrengs te optimaliseer nie. Rosmariniese suur was in hoër konsentrasies as karnosiensuur en karnosol teenwoordig in die waterekstrakte, wat toegeskryf kan word aan die hidrofobiese eienskappe van beide karnosiensuur en karnosol. Die wilde roosmaryn spesie se waterekstrak was moeilik om te filter na die onttrekking, waarskynlik as gevolg van die struktuur van die blare, wat moontlik ook die AO-opbrengs beperk het. Toekomstige studies moet gedoen word om die mees geskikte ekstraksiemetodes vir elke AO in elke plantspesie te bepaal ten einde die effekte van die AO op die verbetering van sperme te optimaliseer. Dit sal ook voordelig wees om te bepaal wat die interaksie van elkeen van die AO in die spermmembraan is, hoe hulle die effekte van die natuurlike AO verdediging meganisme kan versterk en hoe die invloed van die hitte stres reaksie beperk kan word.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/102956
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