Chemical constituents of root and stem bark of Erythrina brucei

Two new isoflavanones, erybrucein A and B (1, 2), together with nineteen known compounds are reported herein from the stem and root bark of the Ethiopian medicinal plant, Erythrina brucei. All known compounds, except erythraline (19), have been isolated for the first time from E. brucei. Their structures were established on the basis of extensive spectroscopic and spectrometric analyses (1D and 2D NMR, CD, IR and ESI-HRMSn) and confirmed by comparison with reported- and DFT-calculated data. The absolute configuration of kenusanone F (3) and the 7-methyl ether (4) were determined in the same way. Antibacterial properties as well as DPPH radical scavenging activities of the new isoflavanones and selected known compounds were evaluated. Although most tested compounds showed weak activity against the tested organisms, erybrucein B (2) showed moderate activity (MIC=0.062mg/mL) against Bacillus cereus. In the DPPH radical scavenging assays, compounds 1, 2, and 3 showed moderate activity whereas two other compounds showed high activity.