Isolation of a free radical-scavenging antioxidant from water spinach (Ipomoea aquatica Forsk)

Ipomoea aquatica Forsk, a green leafy vegetable that is a rich source of vitamins and amino acids with many health benefits, has been explored for the isolation and identification of its bioactive compounds. Activity-guided repeated fractionation of a methanol extract on a silica gel column followed by an XAD column yielded a compound that exhibited antioxidant activity with an EC50 value of 83 +/- 1.02 mu g ml(-1) reaction mixture. It also showed very strong lipid peroxidation-inhibitory activity in a liposome model system with an EC50 value of 72.2 +/- 0.9 mu g ml(-1). However, it showed negligible metal-chelating activity. Based on UV, 2D nuclear magnetic resonance and gas chromatography/mass spectrometry studies, the compound was tentatively identified to be 7-O-beta-D-glucopyranosyl-dihydroquercetin-3-O-alpha-D-glucopyranoside. This is the first report on the antioxidant properties of I aquatica leaf extracts. (c) 2005 Society of Chemical Industry.