HPLC profile and antibiotic-modifying activity of Azadirachta indica A. Juss, (Meliaceae)

Abstract The rising of resistant bacterial lineages as well as the development of significant side effects of antibacterial drugs have made urgent the development of researches for identification of new bioactive antibacterial compounds. Azadirachta indica is a plant species popularly known as “Nim”. This plant originates from Southeast Asia, and is amply found in Africa, Australia and in the Americas. It has been reported that it presents an insecticidal action, which affects many species. The study aimed to evaluate the antibacterial and modulatory potential of the ethanolic extracts obtained from leaves and bark of A. indica against standard and multiresistant bacteria. The extracts were tested alone or in combination with aminoglycosides and carbapenems antibiotics against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa using the broth microdilution method in Brain Heart Infusion (BHI) medium. The association between antibiotics and A. indica extracts presented synergistic or antagonistic effects, which might be due to the diversity of metabolites found in the plant. Among these metabolites, quercetin, kaempferol and coumarin were found as major constituents and gallic acid, catechin and chlorogenic acid were found as minor constituents. In conclusion, A. indica modulated the activity of antibiotics against multiresistant bacterial strains, which may involve multiple mechanisms of antimicrobial action, which resulted in a potentiation of the antibacterial activity of the tested antibiotics that was strain and drug-dependent.