On the one hand, reactive oxygen species (ROS) are mandatory mediators for essential cellular functions including the function of germ cells (oocytes and spermatozoa) and thereby the fertilization process. However, the exposure of these cells to excessive levels of oxidative stress by too high levels of ROS or too low levels of antioxidative protection will render these cells dysfunctional thereby failing the fertilization process and causing couples to be infertile. Numerous causes are responsible for the delicate bodily redox system being out of balance and causing disease and infertility. Many of these causes are modifiable such as lifestyle factors like obesity, poor nutrition, heat stress, smoking, or alcohol abuse. Possible correctable measures include foremost lifestyle changes, but also supplementation with antioxidants to scavenge excessive ROS. However, this should only be done after careful examination of the patient and establishment of the individual bodily antioxidant needs. In addition, other corrective measures include sperm separation for assisted reproductive techniques. However, these techniques have to be carried out very carefully as they, if applied wrongly, bear risks of generating ROS damaging the germ cells and preventing fertilization.

Aspalathus linearis (rooibos tea) may improve sperm function owing to its antioxidant properties. To test this hypothesis, male rats were given 2% or 5% rooibos tea for 52 days. No significant alterations were observed in body and reproductive organs weight, serum antioxidant capacity and testosterone level. Seminiferous tubules displayed complete spermatogenesis. However, a significant (P < 0.05) decrease in tubule diameter and germinal epithelial height was observed. Epithelial height of caput epididymides showed a significant increase. Unfermented rooibos significantly enhanced sperm concentration, viability and motility. Fermented rooibos also significantly improved sperm vitality (P < 0.01), but caused a significant increase in spontaneous acrosome reaction (P < 0.05), whereas unfermented did not. Creatinine was significantly enhanced in all treated rats, consistent with significant higher kidney weights. Rooibos significantly reduced alanine transaminase level, while 2% fermented rooibos significantly decreased aspartate transaminase level (P < 0.01). In conclusion, treatment with rooibos improved sperm concentration, viability and motility, which might be attributed to its high level of antioxidants. However, prolonged exposure of rooibos might result in subtle structural changes in the male reproductive system and may induce acrosome reaction, which can impair fertility. Intake of large amounts of rooibos may also harm liver and kidney function.

Flavonoids are major compounds of Aspalathus linearis and Camellia sinensis. They are classified as endocrine disruptors and some have been shown to inhibit testosterone production. TM3 Leydig cell cultures were treated with 250-5000 μg mL(-1) A. linearis (unfermented or fermented rooibos) or Camellia sinensis (green or black tea) for 24 h in the absence or presence of 6 mIU/200 μl human chorionic gonadotropin (hCG). Under nonstimulated conditions, all teas tend to decrease testosterone production (3.9-31.8%). However, under hCG-stimulation, a significant reduction in testosterone production was observed at all concentrations by both rooibos and tea (16.3-37.9%). MTT assay and phase contrast microscopy, revealed that at 250-1000 μg ml(-1) , both plants maintained the viability, proliferation and morphology of the cells, while 5000 μg ml(-1) was cytotoxic to the cells (P < 0.05). In conclusion, the results here demonstrate the anti-androgenic property of A. linearis and C. sinensis.

Green tea is a popularly consumed beverage worldwide and contains polyphenols, whose antioxidant activities could improve sperm parameters and fertility thereof. We investigated the effect of green tea on the male rat reproductive system as well as its safety. Male Wistar rats were administered 2 and 5% aqueous extract of green tea for 52 days’ ad libitum, while the control group received tap water. Total polyphenol, flavanol, flavonol and soluble solids significantly increased in a concentration-dependent manner in vitro (P < 0.01). Weights of body, testis, epididymis, prostate gland, seminal vesicles, and liver, serum levels of testosterone, ferric reducing antioxidant power, creatinine, and sperm motility, remained unchanged (P > 0.05). Kidney weight, sperm concentration and vitality, spontaneous acrosome reaction increased (P < 0.05), while alanine transaminase and aspartate transaminase levels decreased (P < 0.05). Catalase, superoxide dismutase, glutathione and lipid peroxidation remained unchanged in the testes, liver and kidney (P > 0.05). Histological sections of testis, epididymis, kidney and liver showed no conspicuous alteration. Diameter and epithelial height of seminiferous tubule decreased, while caudal epididymis epithelial height increased (P < 0.01). Consumption of green tea in the conditions used in the present study seems to be safe and improved sperm parameters. However, subtle structural changes observed in the decreased diameter and epithelial height of the seminiferous tubule and increased acrosome reaction needs further investigation.

The effects of aqueous leaf extract of Moringa oleifera (MO) on human sperm functions and integrity was studied in vitro. Semen was obtained by masturbation after 3-5 days' abstinence from 34 healthy donors in Western Cape, South Africa. Liquefied semen was washed in human tubular fluid supplemented with 1% bovine serum albumin (HTF-BSA;1:5) with 10 min centrifugation at 300 g. Sperm suspensions were subsequently incubated with MO extract (0.625, 6.25, 62.5 and 625 µg/ ml) for 1 hr, where HTF-BSA served as control. Sperm motility, vitality, DNA fragmentation, reactive oxygen species production, mitochondrial membrane potential, capacitation and acrosome reaction were assessed. Sperm motility, vitality, mitochondrial membrane potential and capacitation remained unchanged (p > .05). A dose-dependent decrease in sperm reactive oxygen species production (p < .0001), DNA fragmentation (p < .0001) and acrosome reaction (p < .001) was observed. An increase in the percentage of non-capacitated sperm (p < .01) was noted at 625 µg/ ml. The antioxidant properties of MO actively maintained basic sperm functions, inhibited excess sperm free superoxide production and preserved acrosome reaction and DNA integrity. Further studies are needed to confirm the effect of aqueous MO leaf extract on fertility potential.