Effective microbiocidal activity of Ocimum sanctum L. and Ocimum gratissimum L. extracts

Innovation of effective antimicrobial agents in terms of resistance against various pathogenic microorganisms is a universal challenge for the pathologists and researchers, leading to improvement of innovative technologies that have great potential and efficacy. With this intention, we investigated and compared the antimicrobial activities of leaf extracts of Ocimum sanctum L. and Ocimum gratissimum L. against few bacteria, such as Escherichia coli, Agrobacterium tumefaciens and Bacillus megaterium, and fungi such as Fusarium oxysporum and F. solani. Methanol, petroleum ether, nhexane as well as water were used to prepare the extracts; the antimicrobial activities were tested using the well-diffusion method. As expected, irrespective of the solvent, the highest concentration (100%) of the extract generally showed the highest efficacy with the largest zones of inhibition of the three bacterial and two fungal species. Among the solvents, overall, the methanolic extract was the most effective (showing the largest zones of inhibition) against bacteria; but the solvents did not show any difference in their activity between the two fungal species. Meanwhile, the most susceptible bacterial species against both the species of tulsi was A. tumefaciens, and the most susceptible fungal species was F. oxysporum. The extracts of O. gratissimum showed relatively higher antimicrobial activity against both bacteria and fungi; this finding correlated with the higher vigour, stronger aroma and higher eugenol content of this species of tulsi. HPLC-fingerprinting of them showed different patterns that correlated with their antimicrobial activities.