Evaluation of Antimicrobial Activity & Phytochemical Analysis of Leaf Extracts of Acacia rigidula and Acacia berlandieri

Abstract

The emergence and spread of antibiotic resistance, as well as the evolution of new strains are of great concern to the global health community. The search for novel agents to combat the rapid evolution of bacterial pathogens becomes ever more important as current methods are proving ineffective. Plant species within the Fabacae family have been reported to exhibit antimicrobial activity; therefore, we hypothesize that these two species will display antibacterial properties. The objectives of this study were to (1) determine the presence of antimicrobial activities, (2) qualitatively determine secondary metabolites of plant extracts from Acacia berlandieri (Guajillo) and Acacia rigidula (Blackbrush), (3) analyze extracts using Nuclear Magnetic Resonance spectroscopy (NMR), infrared spectroscopy (IR), and ultraviolet‐visible spectroscopy (UV‐Vis) to identify different secondary metabolites within a test sample, and (4) determine antioxidant activities within both plant species.Plant leaves were sequentially extracted using acetone, methanol, and acetic acid that were then subjected to susceptibility testing against nine microorganisms. Results provided evidence of antimicrobial activity from the crude extracts of both species. The activity was significantly higher (p<0.001) from the leaves of species A. rigidula. Among the nine microorganisms, two gram‐negative and two gram‐positive bacteria were susceptible. Qualitative phytochemical testing revealed important secondary metabolites: phenols, flavonoids, saponins, terpenoids, and tannins. Each of which have been shown to possess antimicrobial properties and exert different modes of action. NMR, IR, and UV‐Vis spectroscopy revealed the basic structures within our unknown samples that are commonly found in flavonoids, saponins, and tannins, reinforcing the results of phytochemical testing. Preliminary results revealed some antioxidant activity within selected A. rigidula extracts. Analysis of the leaves extracts of A. berlandieri and A. rigidula have revealed the presence of medicinally valued bioactive components. This study confirms the efficacy of selected plant extracts as natural antimicrobials and suggests the possibility of employing them in drugs for the treatment of infectious diseases caused by the test organisms.