Objective: To identify the main chemical classes of compounds from aqueous extract of Enterolobium contortisiliquum (E. contortisiliquum) seed bark and to evaluate its anti-bacterial activity, as well as its potential to increase the activity of antibiotics against strains of Staphylococcus aureus,Pseudomonas aeruginosa and Escherichia coli. Methods: Different classes of compounds in the aqueous extract of E.contortisiliquum were evaluated based on the visual changes in the coloration and the formation of pre-cipitate after the addition of specific reagents.The antibacterial activity of the extract and its potential to increase of antibiotic activity of antibiotics drugs, gentamicin and nor-floxacin was determined by using the microdilution method. Results: Our results demonstrated that the following secondary metabolites were pre-sented in E. contortisiliquum seed bark: flavones, flavonols, xanthones, flavononols, chalcones, aurones,flavones and catechins. The extract itself had very low antibacterial activity against all bacterial strains tested (MIC ≥ 1 024 μg/mL), but there was an in-crease in the antibiotic activity of gentamicin and norfloxacin when combined in the sub-inhibitory concentration (i.e.,MIC/8). Conclusions: Our data suggests that E.contortisiliquum seed bark may be an alternative source for new drugs with the potential to increase antibiotic activity against different strains of bacteria.

Objective To identify the main chemical classes of compounds from aqueous extract of Enterolobium contortisiliquum (E. contortisiliquum) seed bark and to evaluate its antibacterial activity, as well as its potential to increase the activity of antibiotics against strains of Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli. Methods Different classes of compounds in the aqueous extract of E. contortisiliquum were evaluated based on the visual changes in the coloration and the formation of precipitate after the addition of specific reagents. The antibacterial activity of the extract and its potential to increase of antibiotic activity of antibiotics drugs, gentamicin and norfloxacin was determined by using the microdilution method. Results Our results demonstrated that the following secondary metabolites were presented in E. contortisiliquum seed bark: flavones, flavonols, xanthones, flavononols, chalcones, aurones, flavones and catechins. The extract itself had very low antibacterial activity against all bacterial strains tested (MIC ≥ 1 024 μg/mL), but there was an increase in the antibiotic activity of gentamicin and norfloxacin when combined in the sub-inhibitory concentration (i.e., MIC/8). Conclusions Our data suggests that E. contortisiliquum seed bark may be an alternative source for new drugs with the potential to increase antibiotic activity against different strains of bacteria.