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The decline of fertility in modern society is a serious worldwide concern, and the reasons behind it are complex and difficult to unveil. The fact that a big percentage of infertility cases remain diagnosed as idiopathic, turn the strategies to treat such conditions very limited. Nevertheless, one must agree that keeping the oxidative balance of the reproductive tissues should be one of the first lines of treatment for infertile patients. As reported, 30-80% of male infertile individuals present high levels of prooxidant species in the seminal fluid. Thus, antioxidant therapies, which consist of dietary supplementation therapy with one or more antioxidant compound, remain the first step in the treatment of male infertility. Nevertheless, the efficacy of such therapies is variable between individuals. The most common prescribed antioxidants are carnitines and vitamins C and E, but recently phytochemical quercetin has emerged as a potential compound for the treatment of oxidative stress in the male reproductive system. Although there are several animals' evidence about the great potential of quercetin for the treatment of infertility, clinical trials on this subject remain scarce.

BACKGROUND/AIMS: Oxidative Stress (OS) is reported as one of the main causes of male infertility. Infertile couples often resort to assisted reproductive technology (ART) to achieve parenthood. However, preparation for ART protocols increases the exposer of gametes to OS. Thus, it is crucial to find suitable preservation media that can counteract the OS-induced damages in spermatozoa. In this work, we tested and compared the efficiency of vitamin C (VC) and hyperoside (HYP) as potential antioxidant supplements for sperm preservation media. METHODS: We evaluated the cytotoxicity of HYP (0, 5, 50, 100, and 500 µM) in spermatozoa. After incubation of sperm cells with VC (600 µM) and HYP (100 and 500 µM), in the presence and absence of H2O2 (300 µM), the following parameters were assessed: total sperm motility and vitality, OS biomarkers expression, total antioxidant capacity (TAC) of the media, percentage of DNA fragmentation, mitochondrial membrane potential (MMP), and metabolite quantification of the media by proton nuclear magnetic resonance (1H-NMR). RESULTS: The supplementation with VC (600 µM) and HYP (100 and 500 µM) did not induce any deleterious effects to the physiology and metabolism of the spermatozoa, after 1-hour of treatment. In the presence of H2O2 (300 µM), both VC and HYP were able to prevent some of the deleterious effects of H2O2 in sperm, which were represented by an increase in sperm motility, a decrease in DNA fragmentation, and a decreasing trend in lipid peroxidation levels. However, these antioxidants were not able to prevent the decrease of MMP associated with H2O2 treatment, nor were able to prevent the conversion of pyruvate into acetate (a reaction promoted by H2O2). CONCLUSION: The supplementation of sperm preservation media with VC and HYP could be beneficial for the preservation of sperm physiology. From the antioxidant conditions tested, the supplementation of media with HYP (100 µM) demonstrated the best results regarding sperm preservation, evidencing the higher antioxidant capacity of HYP compared to VC. Nevertheless, none of the antioxidants used was able to prevent the metabolic alterations promoted by H2O2 in spermatozoa.