Erylivingstone A–C with antioxidant and antibacterial activities from Erythrina livingstoniana

The chemical study of Erythrina livingstoniana has led to the isolation of three new flavanones namely 5,7,3′-trihydroxy-4′-methoxy-5′-formylflavanone (erylivingstone A) (1), 5,7,3′-trihydroxy-5′-(2-hydroxy-3-methylbut-3-enyl)-4′-methoxyflavanone (erylivingstone B) (2) and 5,7,3′-trihydroxy-5′-(3-hydroxy-3-methyl-trans-but-1-enyl)-4′-methoxyflavanone (erylivingstone C) (3) together with three known compounds (4–6). Their structures were elucidated on the basis of NMR data, HRMSn fragmentation pathway and by comparison with literature data. We evaluated the antibacterial efficacies and free-radical scavenging potential of the isolated compounds (1–6). The typical environmental strains of Gram-positive Bacillus subtilis, Gram-negative Escherichia coli, as well as against the clinically important Staphylococcus aureus, Streptococcus pyogenes and E. coli (risk-group 2) were used for the antibacterial assay. Compounds 5 and 6 exhibited the most pronounced efficacy against tested environmental bacteria as well as against the pathogenic strain of E. coli. Compound 3 was also quite active against these three bacterial strains. The isolated compounds showed weak radical scavenging properties with compound 6 being the most active, followed by compounds 2, 3 and 5.

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