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 EC 50 value of 83 ± 1.02 µg ml −1 reaction mixture. It also showed very strong lipid peroxidation‐inhibitory activity in a liposome model system with an EC 50 value of 72.2 ± 0.9 µg 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 ‐β‐ D ‐glucopyranosyl‐dihydroquercetin‐3‐ O ‐α‐ D ‐glucopyranoside. This is the first report on the antioxidant properties of I aquatica leaf extracts. Copyright © 2005 Society of Chemical Industry