Bioavailability of silymarin, a purified extract from Silybum marianum

Silymarin, a purified extract from Silybum marianum, is the active principle in several hepatoprotective drugs. It is chemically well defined and consists mainly of four flavonoid isomers (approx. 80 %). Among these silibinin is the most abundant (Fig. 1) and most pharmacological data were obtained with this isomer. The pure isomers, especially silibinin, have low solubilities in water. Their absorption is dissolution limited and the rate of dissolution is practically zero from the crystalline state.