Plasma lipoproteins in transport of silibinin, an antioxidant flavonolignan from Silybum marianum.

To assess the role of plasma lipoproteins in the transport of silibinin, an antioxidant flavonolignan, ¹²⁵I-labelled silibinin (¹²⁵I-SB) administered perorally to the rat was used. The plasma ¹²⁵I-SB derived radioactivity was distributed among plasma lipoproteins according to their lipophilicity (TAG-rich lipoproteins 30–40% > LDL 15% > HDL 5%), and in the fraction of d > 1.215 containing albumin and other proteins a minority amount of radioactivity was found. Administration of ¹²⁵I-SB in a complex with phosphatidylcholine resulted in proportionally higher radioactivities in all fractions as well as in tissues. Dietary olive oil had a slightly decreasing effect on plasma concentrations of silibinin measured by HPLC as well as on ¹²⁵I-SB derived radioactivity in plasma and liver. In the TAG-rich lipoprotein fraction and HDL no effects of olive oil on the levels of ¹²⁵I-SB derived radioactivities were observed, however, at a 30 min interval the levels of ¹²⁵I-SB derived radioactivity in LDL and the heart were significantly decreased in the olive oil group. These results suggest that (i) silibinin is not resorbed by the chylomicron pathway, and (ii) the endogenous lipoprotein pathway VLDL → LDL may play a role in the transport of silibinin from the liver to the extrahepatic tissues concurrently facilitating the lipoprotein antioxidant influence of silibinin. Copyright © 2003 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]