Silymarin is a mixture of flavonoids extracted from seeds of milk thistle (Silybum marianum [L] Gaertn ). Extracts of S. marianum have been used in the treatment of liver diseases for more than 2000 years.
Flavonoids are a large group of polycyclic phenols of plant origin. Flavonoids displaying estrogenic effects (phytoestrogen).
Phytoestrogens show an estrogenic activity owing to the structural similarity with the estrogen skeleton ,mimicking natural estrogens, it binds to estrogen receptor and modulates its activity . These effects cause complex changes inducing a shift in an overall hormonal balance of the individual. Long term intake of feeds with a higher content of phytoestrogens can induce transient or permanent infertility.
Silybum marianum leaves have been traditionally used in Egypt for their antifertility effects .Also, the antifertility property of silybum marianum leaves was investigated in female albino rats. This property highlights the impotance to clarify the role of silymarin (420mg /day ) a human therapeutic dose on both female and male albino rats.
Silymarin (151.2 mg/kg BW) prevented pregnancy in adult female albino rats on days 1-5 post coitum. In female rats the follicle stimulating hormone (FSH) displayed marked increase, while the luteinizing hormone (LH) and estradiol remained within normal levels. These results showed a distinct increase in number and size of ovarian growing follicles while the effect of silymarin on the uterine wall was in the form of hypertrophy of endometrial epithelium, also increase in the number of uterine glands. Ovaries taken from females treated with silymarin for one and two months contained a large number of growing follicles.
In male rats treated with silymarin (151.2 mg/kg BW) for one month, testosterone and LH were increased significantly, meanwhile estradiol not changed. Testes of rats treated with silymarin for one month showed well developed spermatogenesis with lot of sperms. The epididymis of the same group contained a heavy number of sperms. While rats treated with silymarin for two months displayed significant decrease in serum testosterone levels, while LH and estradiol not changed. These rats displayed some tubules contained well developed spermatogenic layer and normal leyding cells, others appeared moderated by affected. The epididymis contained less number of sperms.
These results indicated that silymarin (151.2mg /kgBW) a dose equivalent to human therapeutic dose (420mg/ day) prevented pregnancy in female rats and caused some histological changes in the ovary and uterus, while it has biological benefits for male rats during short treatment.