Assessment of Antimicrobial Activity of Ocimum gratissimum and Cymbopogon flexuosus Oil against Some Selected Pathogenic Microorganism

Abstract

Essential oils are concentrated substances extracted from plant components such as leaves, flowers, fruits, stems, roots, and bark. These oils contain volatile organic compounds that are responsible for their distinctive aroma and therapeutic effects. This study investigated the antimicrobial activity of essential oils from Ocimum gratissimum L (Clove basil) and Cymbopogon flexuosus (Lemongrass) against two gram-positive bacteria, two gram-negative bacteria, and one fungus, using the agar well diffusion method. Fourier-transform infrared spectroscopy (FTIR) analysis of selected essential oils revealed the presence of functional groups, such as aldehydes, ketones, and aromatic rings. The results showed that both oils exhibited significant antimicrobial activity against all tested microorganisms, with Cymbopogon flexuosus (Lemongrass) being more effective, completely inhibiting the growth of Bacillus paramycoides and Bacillus altitudinus at concentrations up to 40%. The zone of inhibition for Cymbopogon flexuosus against Escherichia coli and Pseudomonas spp. RRC15 were 25.5 mm and 8.1 mm at 100% concentration, respectively. Ocimum gratissimum L showed lower antimicrobial activity than Cymbopogon flexuosus, with the zone of inhibition in the decreasing order of Bacillus paramycoides, Bacillus altitudinus, Escherichia coli, and Pseudomonas spp. RRC15. Both essential oils completely inhibited the growth of Colletotrichum gloeosporioides at concentrations ranging from 100% to 40%. The antimicrobial activity was attributed to the presence of bioactive compounds, such as citral, eugenol, and other monoterpenes in the essential oils, which disrupt bacterial and fungal cell membranes, leading to cell death. These findings highlight the potential of Ocimum gratissimum L. and Cymbopogon flexuosus essential oils as natural antimicrobial agents for various applications including plant-based crop protection practices and in food and textile industries.