Milk thistle contains silymarin, as the most active component. Silymarin may potentially be beneficial in a number of diseases involving liver disease. Silymarin possess anti viral, anti bacterial, anti oxidant, anti cancer, and hepatoprotective properties (2)
Silymarin is a useful drug for hepato protection in hepatobiliary diseases and in hepato toxicity due to drugs (3). Silymarin is used for the treatment of numerous liver disorders characterized by degenerative necrosis and functional impairment. The compound also protects hepatocytes from injury caused by radiation, iron overload and viral hepatitis. As an antioxidant, silymarin scavenges free radicals that can damage cells exposed to toxins. Silymarin has been said to be ten times more potent in antioxidant activity than vitamin E. Silymarin also increases the level of the important antioxidant enzyme superoxide dismutase in cell cultures. It stimulates protein synthesis in the liver, which results in an increase in the production of new liver cells to replace the damaged ones (4).
Silymarin consists of a family of flavonoids (silybin, isosilybin, silychristin, silydianin and taxifoline) commonly found in the dried fruit of the milk thistle plant Silybum marianum.
Although silymarin's role as an antioxidant and hepatoprotective agent is well known, its role as an anticancer agent has begun to emerge. Extensive research has shown that silymarin can suppress the proliferation of a variety of tumor cells e.g., prostate, breast, ovary, colon, lung, bladder etc. this is accomplished through cell cycle arrest at the G1/S-phase, induction of cyclin-dependent kinase inhibitors (such as p15, p21 and p27), down-regulation of anti-apoptotic gene products (e.g., Bcl-2 and Bcl-xL), inhibition of cell-survival kinases (AKT, PKC and MAPK) and inhibition of inflammatory transcription factors (e.g., NF-kappaB). Silymarin can also down-regulate gene products involved in the proliferation of tumor cells (cyclin D1, EGFR, COX-2, TGF-beta, IGF-IR), invasion (MMP-9), angiogenesis (VEGF) and metastasis (adhesion molecules). Numerous studies have indicated that silymarin is a chemo-preventive agent in vivo against a variety of carcinogens/tumor promoters, including UV light, 7, 12-dimethylbenz (a) anthracene (DMBA), phorbol 12-myristate 13-acetate (PMA) and others.