Essential oils of Cymbopogon nardus (L.) Rendle and Cymbopogon schoenanthus (L.) Spreng exert additive antibacterial effects and low cytotoxicity

The application of essential oils against resistant pathogenic microorganisms is a promising strategy, particularly when combined with conventional antibiotics. The genus Cymbopogon (Poaceae) is an important source of bioactive essential oils with antimicrobial potential. This study evaluated the chemical composition, antimicrobial activity, synergistic interactions, and cytotoxicity of Cymbopogon nardus and Cymbopogon schoenanthus essential oils. Major constituents of C. nardus were geranyl acetate (17.5%) and trans-methyl isoeugenol (12.6%), while C. schoenanthus was rich in neral (26.3%) and limonene (19.0%). Antimicrobial interactions with ampicillin, sulfadiazine, ciprofloxacin, and tetracycline were assessed against Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 8739 using the checkerboard microdilution method. Additive effects were observed for C. schoenanthus + ampicillin (FICI = 0.562) and C. nardus +sulfadiazine (FICI = 0.625) against S. aureus. Both essential oils showed no cytotoxicity toward NIH/3T3 fibroblast cells.