New sulphated rhamnoside of ellagic acid monomethylether from Eugenia supra-axillaris of potent antioxidant activity

New methoxyllagic acid possessing the naturally unknown sugar moiety, rhamnoside 3-sulphate[1 – 2]; [3-O-monomethoxyellagic acid 4'-O-α-(rhamnopyranoside-3”-O-sulphate)], (4) together with 12 known phenolics were separated and characterized for the first time from n-butanol extract of Eugenia supra-axillaris wood as follow; gallic acid (1), 3,4-di-O-galloyl quinic acid (2), 3,4,5-tri-O-galloyl quinic acid (3), myricetin-3-O-β-xylopyranosyl (1'''-> 2'')-α-rhamnopyranoside (5), quercetin-3-O-β-xylopyranosyl (1'''-> 2'')-α-rhamnopyranoside (6), quercetin-3-O-β-glucopyranoside (isoquercetin) (7), myricetin-3-O-a-rhamnopyranoside (8), 3-O-monomethoxy ellagic acid-4'-O-α-L-rhamnopyranoside (9), ellagic acid (10), 3-O-monomethoxyellagic acid (11), myricetin (12) and quercetin (13). All structures were elucidated on the basis of spectroscopic analyses including 2D NMR and HPLC/UV/MS spectral data. The extract exhibited a distinct radical scavenging effect using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method [3]. The new sulphated metabolite (4) showed potent antioxidant activity IC50 10.8 µg/ml compared to non sulphated one (9) of IC50 40.0 µg/ml.

Keywords: Eugenia supra-axillaris, plant phenolics, sulphated rhamnoside of ellagic acid, free radical scavenging activity

References:

[1] Hussein, S. A. M., Hashim, A. N. M., Seliem, M. A., Lindequist, U., Nawwar, M. A. M. Polyoxygenated flavonoids from Eugenia edulis. Phytochemistry, 2003, 64: 883 – 889.

[2] Hussein, A.M., Hashim, A. N. M., El-Sharawy, R. T., Seliem, M. A., Linscheid, M., Lindequist, U., Nawwar M. A. M. Ericifolin: An eugenol 5-O-galloylglucoside and other phenolics from Melaleuca ericifolia, Phytochemistry, 2007, 68: 1464 – 1470.

[3] Miliauskas, G., Venskutonis, P. R., van Beek, T. A. Screening of radical scavenging activity of some medicinal and aromatic plant extracts, Food Chemistry, 2004, 85:231 – 237.