Constituents of antibacterial extract of Caesalpinia paraguariensis Burk

The Argentinean legume Caesalpinia paraguariensis Burk. (Fabaceae) was selected for further fractionation work based on the strong antimicrobial activity of its CH2Cl2-MeOH (1:1 v/v) extract against a host of clinically significant microorganisms, including antibiotic resistant strains. 1D and 2D NMR enabled the identification of the novel benzoxecin derivative caesalpinol along with the known compounds bilobetin, stigma-5-en-3-O-beta-6'-stearoylglucopyranoside, stigma-5-en-3-beta-6'-palmitoylglucopyranoside, stigma-5-en-3-beta-glucopyranoside, oleanolic acid, 3-O-(E)-hydroxycinnamoyl oleanolic acid, betulinic acid, 3-O-(E)-hydroxycinnamoyl betulinic acid, and lupeol from the active fractions. Oleanolic acid was found active against Bacillus subtilis and both methicillin-sensitive and -resistant Staphylococcus aureus with MICs of 8 (17.5 microM), 8 and 64 (140 microM) microg/ml, respectively. The rest of the compounds, however, did not show activity.