Taxifolin is a plant flavonoid occurring in the fruit of milk thistle [S. marianum]. This fruit has been used since ancient times as a medicinal plant for the treatment of liver diseases . The extract, known as sylimarin, contains flavonoids such as sylibin and taxifolin. Sylibin has been well-studied and its hypocholesterolemic effect has also been noticed.
In a study of rats, Krecman et al.  studied found that pure silybin was not as effective as silymarin. This suggested that other constituent(s) of silymarin, in addition to silybin, also have hypocholesterolemic effects. Subsequently, the minor constituent of silymarin, taxifolin, has attracted Andre TheriaultÂ’s attention, because taxifolin constitutes the flavonoid moiety in the flavolignan silybin. Hence, Andre Theriault and coworkers investigated how taxifolin affected lipid profiles in a study using human hepatoma cell-line, HepG2, as the model system. They had a few key findings: (1) taxifolin inhibits cholesterol synthesis in a dose- and time- dependent manner, (2) taxifolin suppresses HMG-CoA reductase activity and cholesteryl ester formation (3) taxifolin inhibits the synthesis and secretion of triacylglycerol and phospholipids and (4) taxifolin decreases the secretion of apoB into LDL-like particles.
Taxifolin also demonstrated anti-inflammatory activities in in-vitro studies. Taxifolin down-regulated the expression of intercellular adhesion molecule-1 (ICAM-1). It impeded the calcium influx induced by fMLP (a receptor-mediated activator) or AlF(4)(-) (a G protein-mediated activator) and effectively inhibited the fMLP- or PMA-induced ROS production with 50% inhibitory concentration (IC (50)) less than 10microM, possibly through impairing the activation of NADPH oxidase.
 Morazzoni, P., Bombardelli, E. 1995. Silybum marianum. Cardus marianus Fitoterapia. 66:6-42.  Krecman, V., Skottova, N., Walterova, D., Ulrichova, J., Simanek, V. 1998. Silymarin inhibits the development of diet-induced hypercholesterolemia in rats. Planta Med. 64:138-142.  Casaschi A et al, Inhibitory activity of diacylglycerol acyltransferase (DGAT) and microsomal triglyceride transfer protein (MTP) by the flavonoid, taxifolin, in HepG2 cells: potential role in the regulation of apolipoprotein B secretion. Atherosclerosis. 2004 Oct;176(2):247-53.  Wang YH Prevention of macrophage adhesion molecule-1 (Mac-1)-dependent neutrophil firm adhesion by taxifolin through impairment of protein kinase-dependent NADPH oxidase activation and antagonism of G protein-mediated calcium influx. Biochem Pharmacol. 2004 Jun 15; 67(12):2251-62.
Researchers found pure silybin was not as effective as silymarin for cholesterol-lowering. Based on this research result, researchers found another element inside silymarin having cholesterol-lowering activities. And, that is taxifolin.
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