Chemoenzymatic Preparation of Oligoglycosides of Silybin, the Flavonolignan from Silybum marianum

Abstract

Starting from 23-O-b-D-glucopyranosyl silybin (2) and 23-O-b-Dgalactopyranosyl silybin (3), a-oligoglucosides of silybin were synthesized employing cyclodextrin glucanotransferase from Bacillus stearothermophillus (E.C. 2.4.1.19).Oligoglycosides of silybin were tested for the LDL antioxidant activity in vitro.Flavonolignan silybin (1) (Figure 1), isolated from seeds of the milk thistle (Silybum marianum), is an active component in a number of phytopreparations, e.g., Flavobion, Legalon, widely used in human therapy for improving liver function. 1 Cytoprotective activity of 1 consists in several mechanisms operating at various cell levels.Silybin acts as a radical scavenger (antilipoperoxidant), removing the reactive toxic radicals resulting from oxidative detoxification of xenobiotics by liver monooxygenase systems (P-450 and others). 2 Cell regenerating activity is associated with its ability to activate the proteosynthesis by DNA-dependent RNA-polymerase I stimulation. 3 Cytoprotective activity of 1 is believed to be based on its antioxidant properties.4a Silybin is considered to act as a chain-breaking antioxidant by scavenging free radicals which induce lipid peroxidation.4b Other important antioxidative effects of 1 are due to its influence on enzyme system associated with glutathione 4a and superoxide dismutase.4c Antioxidant activity of 1 in different models is widely documented.1a,2,4 Recently, low