New flavonoids from the stem bark of Erythrina caffra Thunb.

Abstract

Three new flavonoids 5,7-dihydroxy-2′,4′-dimethoxy-5′-formylisoflavanone (erycaffra E) (1), 5,7-dihydroxy-3′-(2″-hydroxy-3″-methylbut-3-enyl)-5′-(3‴-hydroxy-3‴-methyl-trans-but-1-enyl)-4′-methoxyflavanone (erycaffra D) (2) and 5,7-dihydroxy-4′-methoxy-3′,5′-di-(3″-hydroxy-3″-methyl-trans-but-1-enyl)flavanone (erycaffra F) (3) were isolated from the stem bark of Erythrina caffra along with four known compounds, namely 5,4′-dihydroxy-6-(3″-methylbut-2″-enyl)-5‴-hydroxyisopropyldihydrofurano[2‴,3‴:7,8]isoflavone (isosenegalensein) (4), 5,7-dihydroxy-4′-methoxy-3′-(3″-methylbut-2-enyl)-5′-(3‴-hydroxy-3‴-methylbut-1-enyl)flavanone (burttinone) (5), 5,4′-dihydroxy-5″-hydroxyisopropyldihydrofurano[2‴,3‴:7,6]isoflavone (erythrinin C) (6) and 5,4′-dihydroxy-6″-hydroxymethyl-6″-methylpyrano[2″,3″:6,7]isoflavone (erysubin B) (7). The structures were determined on the basis of spectroscopic data (1D, 2D NMR and MS) and by comparison with literature values.

Keywords::

• Erythrina caffra
• isoflavanone
• flavanone
• fabaceae
• isolation

Acknowledgements

We are grateful for the financial support from Deutscher Akademischer Austauschdienst (DAAD, German Academic Exchange Service) and Zelalem Yibralign Desta also thanks University of Gondar for study leave.