Rabu, 3 Oktober 2012
Silymarin officinalis, or milk thistle, is an herb that contains a polyphenoloic flavonoid antioxidant, silymarin. Silymarin is composed of silybin, dehydrosilybin, silydianin, silycristin. Of these, silybin has been most well studied. European herbalists have used milk thistle for hundreds of years for the treatment of liver diseases, specifically alcoholic liver disease.
Data on milk thistle in chemoprevention is almost entirely preclinical. These data describe apoptogenic, antiproliferative and anti-angiogenesis effects of milk thistle extracts in a variety of cancers. However, the estrogenic characteristics of milk thistle flavonoids may preclude its use in breast carcinomas.
Preclinical in vitro studies have shown that Silybinin inhibits growth of tumor cells in human prostate, breast and cervical carcinoma cells. In vivo models have confirmed this effect. Using the SENCAR mouse skin tumorigenesis model, silymarin has been shown to be a highly effective inhibitor of stage I tumor promotion.
Silybin has also been studied for its protective activity against cisplatin toxicity in an animal model of testicular cancer. When silybin was infused into rats prior to infusion with cisplatin, there was a significant reduction in glomerular and tubular kidney toxicity. Dose-response curves of human testicular cell lines for cisplatin combined with silybin did not deviate significantly from those of cisplatin alone.
Of particular interest is the indication of a synergistic effect of milk thistle extracts with various chemotherapy agents. For example, silybin has been shown to potentiate the cytotoxic effect of cisplatin. Orally delivered silibinin suppresses human non-small cell lung carcinoma A549 xenograft growth and enhances the therapeutic response of doxorubicin in athymic BALB/c nu/nu mice while simultaneously preventing doxorubicin-caused adverse health effects.
Milk thistle is considered safe in concentrations used by over the counter supplements, unless the patient is allergic to the plant or related plants (such as ragweed, chrysanthemum, marigold, and daisy). In large, carefully designed studies in patients with liver disorders silymarin have shown in a few cases a laxative effect, nausea, heartburn, or stomach upset. At high doses (more than 1,500 milligrams a day), some mild allergic reactions have been observed.
Milk thistle is often prescribed by to protect from the hepatoxic effects of chemotherapy drugs. While not a cytochrome P450 inducer or inhibitor its concurrent use with chemotherapy is still experimental. Current data suggest that it be used in secondary prevention of liver cancer, both primary and metastatic, and in lowering iron in patients with iron overload.