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.
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.