An updated review at molecular pharmacological level for the mechanism of anti-tumor, antioxidant and immunoregulatory action of silibinin

Silibinin, from milk thistle (Silybum marianum), is a flavonolignan with anti-oxidative and anti-inflammatory properties.  It has been therapeutically used for the treatment of hepatic diseases in China, Germany and Japan.  Recently, increasing evidences prove that silibinin is also a potent antitumor agent, and the major anti-tumor mechanism for silibinin is the prominent inhibition of the activities of receptor tyrosine kinases (RTKs) and their downstream signal molecules in a variety of tumor cell lines, such as epidermal growth factor receptor 1 (EGFR) and insulin-like growth factor 1 receptor (IGF-1R) signaling pathways.  Meanwhile, the  evidences that silibinin selectively scavenges hydroxyl free radical (•OH) and specifically inhibits the action of nuclear factor κB (NF-κB) provide more complicated explanations for its antioxidant and anti-inflammatory   effects.  Some new findings such as that silibinin attenuating the cognitive deficits induced by amyloid β protein (Aβ) peptide through its antioxidative and anti-inflammatory properties is valuable to broad the medical prospect of silibinin.  In this review, we discuss the molecular pharmacological mechanisms of silibinin, focusing on   its inhibition of tyrosine kinases, actions of antioxidation, free radical scavenging, immunoregulation and anti- inflammation.