A new flavonol glycoside from the Abelmoschus esculentus Linn

Abelmoschus esculentus L. belonging to the family Malvaceae is a kind of one year herbage plant, which is one of the most important vegetables widely grown in Nigeria for its tender fruits and young leaves. It's easy to be cultivated and grows well in both tropical and temperate zones, that is, it is widely planted from Africa to Asia, South European to America. A new flavonol glycoside characterized as 5,7,3',4'-tetrahydroxy-4''-O-methyl flavonol -3-O-β-D- glucopyranoside (1) has been isolated from the fruit of A. esculentus together with one known compound 5,7,3',4'-tetrahydroxy flavonol -3-O-[β-D-glucopyranosyl-(1→6)]-β-D-glucopyranoside (2). The structure of the new compound was elucidated on the basis of its spectral data, including 2-D NMR and mass (MS) spectra. The antioxidant activities of the isolated compounds 1 and 2 were evaluated by 2 assays, the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). The present work deals with the isolation, identification and antioxidant activity of the two compounds.

The compounds were isolated by Diaion HP-20, Sephedex LH-20 column chromatography methods, their structures were identified by physicochemical properties and spectroscopic analysis. The antioxidant activities of the isolated compounds 1 and 2 were evaluated by two assays, e.g., DPPH and FRAP.

Two flavonol glycosides have been isolated from the fruit of Abelmoschus esculentus L. for the first time, and the compound 1 was a new compound, the compound 2 was isolated from the plant for the first time.

The results show that the two flavonol glycosides have strong ability for scavenging DPPH and FRAP free radical by the experiment of antioxidant activities, so A. esculentus may be a natural antioxidants resource.