Silibinin also known as 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. the mixture exhibits a number of pharmacological effects, particularly in the liver, and there is some clinical evidence for the use of silibinin as a supportive element in alcoholic and child grade a liver cirrhosis.