Thesis (MTech(Biomedical Technology) -- Cape Peninsula University of Technology, 2010 / Defective sperm function is the most prevalent cause of male infertility. Mammalian sperm are rich in polyunsaturated fatty acids (PUFA) and are susceptible to attack by reactive oxygen species (ROS), an important mediator of sperm function. Normally, a balance is maintained between the amount of ROS produced and the antioxidant defense system. When an imbalance exists between ROS production and antioxidants protection in the favour of ROS activity, oxidative stress (OS) occurs which could lead to cellular damage. A shift in the levels of ROS towards pro-oxidation in semen can induce oxidative stress on sperm. This study compares the modulation of OS by an indigenous herbal tea (rooibos), Chinese green tea, commercial rooibos and green tea supplements in rat epididymal sperm and testicular function. Sixty male Wistar rats were supplemented with fermented or “green” rooibos, Chinese green tea, rooibos supplement, green tea supplement or water for ten weeks while inducing OS during the last two weeks. Rats consuming fermented rooibos and “green” rooibos showed a significant higher sperm concentration and motility. The superoxide dismutase (SOD) activity was significantly higher in the sperm of rats that consumed fermented rooibos, “green rooibos” and green tea compared to the control. Also, the superoxide dismutase activity of the groups that received fermented rooibos, rooibos supplement and green tea increased significantly in the testicular tissue compared to control. Catalase (CAT) activity in the epididymal sperm was significantly increased in the rats consuming fermented rooibos, “green rooibos” and both rooibos and green tea supplements compared to the control. None of the tea treatments showed a significant effect on catalase activity in the testicular tissue. A tendency to increase this activity was observed in fermented rooibos, green tea, rooibos and green tea supplements. The glutathione levels of rats fed with fermented rooibos and “green” rooibos were significantly higher in the rat epididymal sperm compared to the control while the glutathione level of rats consuming green tea supplement also increased significantly in the testicular tissue compared to the control. None of the tea treatments showed a significant effect on lipid peroxidation and ROS levels in the rat sperm. Although rooibos fermented, “green” rooibos and rooibos supplements showed a tendency to lower the levels of these biomarkers when compared with the control group in epididymal sperm. However, the rooibos supplement showed a significantly reduced ROS levels in the testicular tissue. In conclusion, our study demonstrated that rooibos extract and green tea are effective as antioxidants by increasing the antioxidant enzyme activities and glutathione levels in oxidative stress-induced rats and could offer a measure of protection against oxidative damage, thereby improving sperm quality and function.