Comparative Analysis of Chemical Composition and Antibacterial Activities of Essential Oils from Two Ocimum Species

Background: The species of the genus Ocimum has been used since ancient times in the Indian subcontinent to cure various illnesses. Essential oil from Ocimum species has antimicrobial activity. Objective: The main objective of this study was to extract essential oils from different parts of two Ocimum species and test their antimicrobial activity. Methods: Hydrodistillation was used to extract essential oils from various parts of two basil species, GC-MS was used to identify the chemical compounds. The disk diffusion method was used to assess their antimicrobial activity. Results: A total of sixty-seven chemical compounds from Ocimum sanctum L. and Ocimum gratissimum L. were identified using GC-MS. Among them, eugenol (1.00-27.66%), methyl eugenol (0.78-28.52%), β-elemene (5.10-20.98%), caryophyllene (0.94-43.18%), caryophyllene oxide (1.1-10.81%), palmitic acid methyl ester (3.20-21.38%), oleic acid methyl ester (2.91-40.7%) and linoleic acid methyl ester (1.55-74.71%) comprised the majority of the makeup of essential oils, due to diverse plant species and body sections, the percentage differed significantly. The essential oils contained monoterpenes, sesquiterpenes, and aldehydes/ketonic derivatives in the flower and leaf parts of O. sanctum and the leaf part of O. gratissimum. The essential oils of these Ocimum species showed good antibacterial activities against the bacteria, methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, and Enterococcus faecalis with inhibition zones ranging from 10-36 mm. Conclusion: These two species of Ocimum showed significant variation in chemical composition and antibacterial activity.