Abstract

RADICAL SCAVENGING POTENTIAL OF COMPOUNDS FROM MELALEUCA ERICIFOLIA SM.

Fatma M. Abdel Bar*

Abstract

Plants belonging to genus Melaleuca are economically important plants as the leaves of most species contain volatile oils. In this study, the non-volatile constituent of the leaf and bark of Melaleuca ericifolia Sm. grown in Egypt was investigated. The leaf extract afforded (E)- 3`,4`-dimethoxy cinnamaldehyde 1, methyl tri-O-methyl gallate 2, kaempferol 3, 3,3`,4`-trimethoxy ellagic acid-4-O--glucoside 4 and 3- methoxyellagic acid 4-O--rhamnopyranoside 5. While the bark extract afforded melaleucic acid 6 and gallic acid 7. The structures of the isolated compounds were identified using 1D and 2D NMR spectroscopy. The antioxidant activities represented by %inhibition and free radical scavenging profile of ABTS+ radical was evaluated at 25, 50, 100 and 200 M, for 30 min. The results showed that gallic acid 7 (88% inhibition, at 25 M) and kaempferol 3 (85% inhibition, at 100 M) respectively, were the most active compounds with comparable activity to ascorbic acid as a positive control. Remarkably, the lupane-type triterpene melaleucic acid 6 showed considerable ABTS+ radical bleaching activity (53.7 %inhibition at 200 M, after 5 min). In conclusion, this study reported for the first time the isolation of compounds 4 and 6 from this plant and the antioxidant activity of melaleucic acid.

Keywords: Melaleuca ericifolia; melaleucic acid; 3,3,4`-trimethoxy ellagic acid-4-Oglucoside; antioxidant activity; radical scavenging activity.