Antibacterial, antifungal, and GC–MS studies of Melissa officinalis

Abstract

Melissa officinalis L. (Lamiaceae) is a perennial plant with varied ethnomedical, therapeutic, and culinary applications. It has been traditionally used in the treatment of various conditions, including cold sores, wounds, infectious bites, ulcers, and parasitic disorders; therefore, this study was undertaken to evaluate the antimicrobial potential of the total ethanol extract and different fractions of M. officinalis against a variety of human pathogenic micro-organisms. Overall, the tested samples demonstrated varying inhibitory potencies against Staphylococcus aureus and Pseudomonas aeruginosa with MICs ranging between 1.65 and 191.40 μg/mL, whereas no antibacterial actions were recorded against Escherichia coli and Klebsiella pneumoniae. The crude extract and its derived fractions also showed noteworthy antifungal activities against Candida albicans, Candida krusei, and Candida glabrata with MICs of 0.30–345.10 μg/mL. Additionally, among the tested plant samples, the petroleum ether fraction exhibited notable antimicrobial spectrum; therefore, it was subjected to GC–MS analysis, for the first time, to ascertain the chemical principles that might underlie its antimicrobial aptitude. Accordingly, a number of metabolites with well-known antimicrobial properties were characterized, mostly dominated by fatty acids and varied terpenoids, with methyl commate A, palmitic acid, and phytol being the major identified components. Interestingly, all the identified constituents are first reported herein from the genus Melissa. The current results collectively highlight the appreciable antimicrobial potential of M. officinalis, particularly against Gram-positive bacteria and yeasts, which strongly endorse its folk use as an anti-infective herb, and reflect its potential as a source of antimicrobial metabolites with possible application both in pharmaceutical and food-related fields.