Antibacterial, resistance modulation action and time-kill kinetics of crude alkaloidal constituents from three different medicinal plants

Abstract

Globally, millions of people die from drug-resistant infections. The World Health Organization (WHO) estimates that a resistant variant is 64% more likely than a non-resistant variant to kill an infected victim. As a result, new anti-microbial sources are extensively being explored, and medicinal plants may serve as promising starting point. Alkaloids are a wide group of naturally occurring nitrogenous organic compounds produced by organisms. The study aimed at determining the antibacterial, anti-biofilm properties and the rate of activity of the crude alkaloidal extracts of three medicinal plants; Occimum gratissimum, Zanthozylum zanthoxyloides and Phyllanthus fraternus. Combination therapy has shown promise in overcoming AMR as the active ingredient act in synergy to inhibit the causative microorganism. In the present study, the alkaloids in the three plants showed fairly good in-vitro inhibition properties against ten clinical pathogenic strains. Time-kill kinetic results revealed complete bactericidal action of crude alkaloidal constituents from Z. zanthoxyloides against S. aureus and S. poona. Bactericidal action was also revealed by crude alkaloidal constituents from P. fraternus against E. Coli (ATCC 43888). Modulation of tetracycline (a standard antibiotic) with the crude alkaloidal constituents from P. fraternus and O. gratissimum resulting in additive effects successfully improved tetracycline’s potency against S. poona and Shigella. LC-ESI-MC analysis revealed four known Z. zanthoxyloide alkaloids, two P. fraternus alkaloids and one known O. gratissimum alkaloid in the crude alkaloid extracts.