Chemical investigation of the root wood of Erythrina livingstoniana led to the isolation of one previously undescribed isoflavan (3S,3″R)-7-hydroxy-2'-methoxy-[3″-hydroxy-2″,2″-dimethylpyrano (3',4')] isoflavan 1, together with eleven known compounds 2-12. The structure of compound 1 was elucidated on the basis of extensive spectroscopic and spectrometric analyses (1 D and 2 D-NMR and APCI-HRMS), with absolute configurations established by comparison of experimental and DFT calculated ECD data. The assignment of the absolute configurations of C-3 and C-3″ of compounds 2 and 3, respectively, were reported for the first time. Compounds 1 - 4 were evaluated for their antibacterial activities in vitro against E. coli ATCC 25922 and S. aureus ATCC 25923. Compound 1 exhibited moderate antibacterial activity with MIC value of 0.063 mg/mL against the clinically relevant risk-group 2 (RG-2) bacterium S. aureus.
Keywords: Erythrina livingstoniana; Staphylococcus aureus; antibacterial activity; flavanone; isoflavan; structure elucidation.