Chemical Composition and In-Vitro Antimicrobial Screening of Leaf Essential Oil of Plectranthus gerardianus Benth., and Isolation of the Major Constituents of the Oil

Abstract

Background: The Lamiaceae (Labiatae) is one of the most diverse and widespread plant families’ in terms of ethno medicine and its medicinal value is based on the volatile oils concentration. This family is important for flavour, fragrance and medicinal properties. Manyplants belonging to this family have indigenous value. Method: The essential oil of Plectranthus gerardianusBenth. (Lamiaceae), was analysed by GC and GC-MS analysis, while the major component was isolated and conformed by NMR spectroscopy. Result: The oil was found to be rich in oxygenated monoterpenes, which contribute around 62% of the total oil. The major components identified were fenchone (22.90%) and carvenone oxide (16.75%), besides other mono and sesquiterpenoids. The in-vitro antimicrobial activity of essential oil was tested against three gram negative bacteria viz. Pasteurellamultocida, Escherichia coli, and Salmonella enterica, two gram positive bacteria viz. Staphylococcus aureus and Bacillus subtilis and two fungi viz. Candida albicans and Aspergillusflavus. The antimicrobial activity of the oil was also compared to the antimicrobial activity of leaf essential oil of another Himalayan plant viz. Nepetacoerulescens. Conclusion: The oil showed in-vitro antimicrobial activity against all the microbial strains and can lessen the ever-growing demand of potentially hazardous antibiotics for treatment.