Flavonoids from Centaurea glomerata and antioxidant activity of its extract
In the early nineties the presence of flavonoids in herbal began to attract the attention of a number of researchers, as a result of their biological and physiological importance . The present study deals with the isolation and identification of flavonoids from Centaurea glomerata Vahl. and evaluation of antioxidant activity of the extract. The aqueous alcoholic extract (MeOH:H2O 7:3) of Centaurea glomerata aerial parts was subjected to extensive repeated column chromatography on polyamide, and Sephadex LH-20 resulted in two new flavonoids named quercetin 6- methoxy -7-O-galactoside (1) and quercetin 6,4- dimethoxy -7-O-galactoside (2) as well as apigenin 8-C-glucoside, apigenin 6-C-glucoside, quercetin 6-methoxy, quercetin and apigenin. Structures of the isolated compounds were established by chromatography, UV, HRESI-MS and 1D/2D 1H/13C NMR spectroscopy.
The radical scavenging activity of the extract was quantified spectrophotometrically, using DPPH radical. The effective dose 50 (ED50) of the extract was compared with that of standard antioxidants as vitamin C.
References: 1. Havsteen B (2002) Pharmacology & Therapeutics 96: 67–202