An overview of the antioxidant effects of silymarin and its role in reducing the harmful effects of some heavy metals, radiation and nicotine on sperm quality.

Oxidative stress is an imbalance between oxidants and antioxidants at the cellular level which leads to infertility in males. For several decades, reactive oxygen species have been known as destructive and damaging agents to cells and tissues. Cells produce small and controlled amounts of ROS to control their physiological activities. Under normal conditions, ROS produced in semen are continuously deactivated by antioxidants in semen, Unsaturated fatty acid chains in sperm plasma membrane are vulnerable to oxidative stress conditions, and thus spermatozoa depend on extracellular antioxidant systems to overcome oxidative stress conditions. Another reason for creating oxidative stress conditions for spermatozoa, in addition to the low level of antioxidants in semen, is excessive production of ROS by spermatozoa with abnormal morphology. so one of the reasons for the creation of oxidative stress in semen is due to the imbalance between ROS production and its inactivation by antioxidants. Exposure to high concentrations of ROS causes disruption of the mitochondrial membrane, plasma membrane, and also chromosome fragmentation, which reduces sperm motility and viability. Increased formation of ROS is associated with decreased sperm motility. There is a possibility that the increase in ROS production will ultimately cause a decrease in the phosphorylation of axonemic proteins and sperm motility. This condition leads to a decrease in fluidity of the membrane, which in turn is necessary for sperm-oocyte fusion. The use of antioxidants such as silymarin can prevent the effects of oxidative stress.Milk thistle is the most well-known English common name for this species and other names include Holy thistle, Mary thistle, St. Mary’s thistle, Marian thistle, Lady’s thistle, Christ’s crown, Venus thistle, Heal thistle, Variegated thistle, Pig leaves, Royal thistle, Snake milk, Sow thistle, and Wild artichoke. The milk thistle medicinal plant is widely used in the traditional medicine of China and most European countries in the treatment of liver and biliary disorders. The seed extract of this medicinal plant, which is known as silymarin, protects the liver against a variety of poisonings. Silymarin contains a collection of flavonoids and other compounds with antioxidant, anti-inflammatory and cellular glutathione-increasing properties. Among the various flavonoid compounds found in the Silybum marianum, are silybin, silychristian and silydianin, which are collectively called silymarin. In many cases, the antioxidant properties of Silymarin are considered to be responsible for its protective actions. Oxidative stress-induced apoptosis in spermatozoa may lead to male infertility. Environmental pollutants and heavy metals cause harmful effects on the reproductive system and sperm parameters through the induction of oxidative stress. Silymarin, as a potent antioxidant, is able to inhibit oxidative stress. Silymarin with its antioxidant properties can have reduced the effects of compounds such as; aluminum, cadmium, lithium, nickel, benzopyrene, doxycycline, tetracarbon chloride, nicotine, methotrexate, arsenic and lead acetate on the sperm. And improve the damaged sperm parameters resulting from the mentioned compounds. Silymarin is also effective in reducing the harmful effects of varicocele and radiation therapy on sperm parameters.