Synergistic activity from Hymenaea courbaril L. and Stryphnodendron adstringens (Mart.) Coville against multidrug-resistant bacteria strains

Abstract

Infections caused by multidrug-resistant bacteria are a problem of public health, turning the search for natural products an alternative to antibiotics of great importance. The aim of this study was to investigate the in vitro antimicrobial activities of Hymenaea courbaril and Stryphnodendron adstringens against bacterial clinical isolates. The crude extracts of both vegetal species in study showed bacteriostatic activity against almost all bacteria evaluated, with minimum inhibitory concentration (MIC) ranging from 125 to 1250 µg/ml. The bacteriostatic activity was observed in all the fractions of H. courbaril and S. adstringens against at least one bacterial strain, except in the fraction dichloromethane of S. adstringens. In regard to bactericidal activity, H. courbaril was active only against E. faecalis, and S. adstringens showed activity against all bacterial strains, except to Enterococcus faecalis. The combination of extracts showed potent synergistic antimicrobial activity, with MIC values of 31.25 µg/ml against Acinetobacter baumannii, Escherichia coli and Staphylococcus aureus. S. adstringens were considered less cytotoxic compared to H. courbaril and the half-maximum cytotoxic concentration (CC 50) resulting from the combination of the two plants was 0.0082 ± 3.19 mg/ml. The results showed for the first time the synergic antibacterial activities of H. courbaril and S. adstringens against resistant bacteria, suggesting their potential use to development of new drugs.

Extracts from jatobá (Hymenaea courbaril L.) peel and seeds: Antioxidant and antimicrobial activities and synergistic effect of extract combinations

“…For B. subtilis , B cereus , P. aeruginosa and S. aureus the MIC values of peel and seed extracts in the combination were of 0.125 mg/mL. This result meant that the combination of extracts exhibited strong inhibition (MIC value <0.5 mg/mL) against these bacteria when compared with the extracts used alone, probably due to increased concentrations of compounds such as flavonoids and terpenes, known for their antimicrobial effect against gram-positive and gram-negative bacteria (Aleixo et al, 2015).…”

“…Higher values of concentrations were used with hydroalcoholic extracts of exocarp and farinaceous pulp of H. courbaril , 300 and 500 mg/mL, respectively, to inhibit bacteria clinical isolates (Martins et al, 2010). On the other hand, ethanol and 70% ethanol extracts from H. courbaril tree bark were effective against E. faecalis in lower concentrations of 0.125 mg/mL, due to the presence of antimicrobial compounds such as coumarins, alkaloids, flavonoids, steroids/triterpenoids and tannins (Aleixo et al, 2015).…”

“…The bioactive compounds present in the extracts can act simultaneously on the microbial cell and have several molecular targets, leading to their synergistic inhibition (Álvarez-Martínez et al, 2018). The antimicrobial compounds of the combination may also have affected the membranes of the microorganisms and mechanism of transport, resulting in greater inhibition efficiency (Aleixo et al, 2015).…”