Antioxidant activity of flavones from Scutellaria baicalensis in lecithin liposomes.

The antioxidant effect of a trihydroxyflavone extract from Scutellaria baicalensis on oxidation induced by ultraviolet light, was studied with phosphatidylcholine liposome membrane. Also, as standards, the antioxidative activity of baicalin, wogonin, baicalein and butylated hydroxytoluene (BHT) was investigated. Comparison of the protective effects of the compounds studied against photoinduced lipid peroxidation in lecithin liposome membranes showed that: (1) the inhibitory effect of those compounds (at 1.2 mol% antioxidant content in liposomes) on TBA reactive materials from lipid peroxidation decreased in the order of baicalin > BHT approximately equal to Scutellaria baicalensis. These were found much greater than wogonin and baicalein; (2) the depressed effect of those compounds (at 1.1 mol% compounds content in liposomes) on the production of conjugated dienes (proportional to oxidation index) could be classified as follows: Scutellaria baicalensis approximately equal to baicalin > BHT, these three were found more active much greater than baicalein and wogonin. Results obtained by ESR measurement confirm that Scutellaria baicalensis extract and the BHT compound significantly depressed the effect of liposome oxidation. It was found that the new trihydroxyflavones of Scutellaria baicalensis, ensured a very satisfactory concentration-dependent protection of the liposome membrane against UV-induced oxidation. These findings suggest that some of the beneficial effects of the extract of the Scutellaria baicalensis can be mediated in certain diseases (for example in skin diseases) by their ability to scavenge free radicals and by their protective effect on lipid peroxidation caused by sunlight irradiation.