Flavone glycosides from Erythrina caffra (Fabaceae)

The genus Erythrina (family Fabaceae) comprises over 110 species of orange or red flowered trees, shrubs and herbaceous plants [1,2]. A phytochemical investigation of the ethanolic extract of Erythrina caffra Thumb. flowers from an Egyptian origin yielded three C-flavonoidal glycosides; 5,7,4′-trihydroxyflavone-8-C-β-D-glucopyranoside (vitexin) (1), 5, 7, 4′-trihydroxyflavone-6, 8-di-C-β-D-glucopyranoside (vicenin-2) (2), 5,7,4′-trihydroxyflavone-6-C-β-D-glucopyranoyl-(1→2)-β-D-glucopyranoside (isovitexin-2((Prime))-β-D-glucopyranoside) (3) and one O-flavonoidal glycoside; Kaempferol-3-O-β-D-glucopyranosyl) (1→2)-β-D-glucopyranoside. The structures of the isolated compounds were elucidated using different spectroscopic techniques (1D and 2D NMR, IR, and UV) and HRESIMS. This is the first report for the isolation of flavonoidal glycosides from Erythrina caffra Thumb. The antibacterial, antifungal, antimalarial, and antileishmanial activites of the isolates were evaluated. Also the preliminary cytotoxic activity of the ethanolic extract and the main fractions were tested using brine shrimp bioassay.

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Acknowledgments: The authors thank Prof. Dr. Nabil El-Hadidi, Department of Botany, Faculty of Sciences, Cairo University, for his help in the plant identification. This work was supported in part by Alexandria University, Egypt. We are grateful to Dr. M. Jacob, Dr. B. Tekwani and Dr. B. Avula for bioassay and HRESIMS experiments at the NCNPR, School of Pharmacy, University of Mississippi. References: [1] Allen ON, Allen EK (1981). The Leguminosae: A Source Book of Characteristic Uses and Nodulation. Macmillan, USA. [2] Fabian A, Germishhuizen G (1997) Wild flowers of Northern South Africa. Fernwood Press, Vlaeberg.