Silibinin (Silybin) is the major active constituent of silymarin, a standardized extract of the milk thistle seeds, containing a mixture of flavonolignans consisting of silibinin, isosilibinin, silicristin, silidianin and others. Silibinin itself is a mixture of two diastereomers, silybin A and silybin B, in approximately equimolar ratio. Both in vitro and animal research suggest that silibinin has hepatoprotective (antihepatotoxic) properties that protect liver cells against toxins. Silibinin has also demonstrated in vitro anti-cancer effects against human prostate adenocarcinoma cells, estrogen-dependent and -independent human breast carcinoma cells, human ectocervical carcinoma cells, human colon cancer cells, and both small and nonsmall human lung carcinoma cells.

研究显示,silibinin可保护肝脏细胞免受毒素损害,有保肝作用。 在体外试验中,Silibinin对人类前列腺癌细胞,雌激素依赖/非依赖型人乳腺癌细胞,人结肠癌细胞,人子宫颈癌细胞,小和非小人肺癌细胞等均表现出抗癌效应。Silibinin是对映异构体silibinin A和silybinin B的混合物（约1:1）。