The Thistle standardized extract (Milk Thistle) is extracted from the seed of the plant. It consists of compounds called silymarins, which have antihepatotoxic (liver protective) action. Silymarin consists of many flavonolignans including silibinin, is silibinin, silicristin, silidianin, and others. Silymarin and silybin serve as antioxidants, protecting cell membranes from oxidative destruction caused by free radicals.