Milk thistle (Silybum marianum) has been used for centuries for the treatment of liver disorders and as a hepatoprotectant. The primary extract of milk thistle is termed silymarin, a complex mixture that contains a number of structurally-related flavonolignans, the flavonoid, taxifolin, and a number of other constituents. The major flavonolignans present in most extracts are silybin A, silybin B, isosilybin A and isosilybin B, silydianin, silychristin and isosilychristin. Isosilybin A has been identified as the first flavonolignan PPAR-gamma agonist. Isosilybin A, elicited the strongest anti-NF-kappaB and anti-HCV actions. The data suggest that silymarin-derived compounds may influence HCV disease course in some patients. Isosilybin A activates apoptotic machinery in prostate cancer cells via targeting Akt-NF-κB-AR axis; thereby, indicating a promising role for this phytochemical in the management of clinical prostate cancer.