Mechanisms of action of roots crude extract and adianthifolioside GS1 from Albizia adianthifolia (Fabaceae) against MDR Gram-negative enteric bacteria

Abstract

Background: The Cameroonian pharmacopoeia is full of many plants used amongst population to treat various infections. Albizia adianthifolia (Schum.) is one of these plants and therefore several previous studies have reported the antibacterial activities of the crude methanol extract of the roots of this plant as well as those of some of its isolated compounds. In this study, the methanol root extract, and its isolated compound "adianthifolioside GS1" were evaluated on bacterial growth kinetics, bacterial membrane, biofilms, and sheep erythrocytes. Adianthifolioside GS1 was tested for its antibiotic stimulation activity against multidrug resistant (MDR) Gram-negative bacteria. Methods: The antibacterial activities of adianthifolioside GS1 in combination with the usual antibiotics were evaluated using the modified p-iodonitrotetrazolium chloride (INT) rapid colorimetric test. Determination of the effect of "crude extract and adianthifolioside GS1" samples on bacterial growth kinetics, bacterial membrane, biofilms, and sheep erythrocytes was carried out using spectrophotometric methods. Results: In combination with erythromycin (ERY), gentamicin (GEN), streptomycin (STR) and tetracycline (TET), adianthifolioside GS1 showed the most significant synergistic effects on all bacteria tested. Adianthifolioside GS1 and the crude root extract of Albizia adianthifolia showed a bacteriostatic effect on the strains tested and caused membrane lysis in Klebsiella pneumoniae KP55 and Escherichia coli AG102 strains at the concentrations tested. Albizia adianthifolia root extract showed significant inhibition of the biofilms of the strains tested, unlike adianthifolioside GS1. The crude extract and its isolated compound (adianthifolioside GS1) exhibited low toxicity to red blood cells. Conclusion: All the results obtained in the framework provide important information on the crude root extract of Albizia adianthifolia and its isolated compound "adianthifolioside GS1" as good candidates for the elaboration of phytomedicines and drugs respectively, and the association of adianthifolioside GS1 with the usual antibiotics that can be used to potentiate the action of the latter. Keywords: Albizia adianthifolia; adianthifolioside GS1; Mechanisms of action; Fabaceae; multi-drug resistance; enteric bacteria.