The milk thistle extract contains an active flavanoid-lignan (flavanolignan) group of constituents, called silymarin, which consists of four constituents: silibinin, isosilibinin, silicristin and silidianin. Among all four constituents, silibinin has the highest content in the milk thistle extract.

Silmyarin has liver-protective and regenerative properties, as well as antioxidant effect. It is used to treat a variety of liver ailments, such as liver cirrhosis, chronic hepatitis (liver inflammation), toxin-induced liver damage including the prevention of severe liver damage from Amanita phalloides ('death cap' mushroom poisoning), and gallbladder disorders.