Enhanced antimicrobial activity of palmarosa (Cymbopogon martinii) essential oil against gram-positive bacterial pathogens

Abstract

Palmarosa (Cymbopogon martinii) essential oil is widely valued for its antimicrobial properties, largely attributed to its high geraniol content. This study evaluated oils extracted from fresh and dried Palmarosa samples for antibacterial activity against Bacillus cereus using agar well diffusion and broth microdilution (MIC) assays. Zones of inhibition (ZOI), MIC, and IC₉₀ values were determined to compare potency. Dried-sample oil exhibited significantly larger ZOI (24.44 mm) than fresh-sample oil (18.50 mm), indicating stronger antibacterial activity. MIC assays showed concentration-dependent inhibition between 2-4 µL/mL, with IC₉₀ values of 3.18 µL/mL for dried oil and 3.60 µL/mL for fresh oil. These findings demonstrate that drying Palmarosa biomass can optimize essential oil bioactivity, offering a promising strategy for developing natural antibacterial agents in therapeutic and preservative applications.