Antimicrobial activity, cytotoxicity and chemical analysis of lemongrass essential oil (Cymbopogon flexuosus) and pure citral

• Published in: Applied microbiology and biotechnology 2016-11, Vol.100 (22), p.9619-9627
• Main Authors: Adukwu, Emmanuel C., Bowles, Melissa, Edwards-Jones, Valerie, Bone, Heather
• Format: Article
• Language: English
• Subjects: Acinetobacter baumannii; Acinetobacter baumannii - drug effects; Analysis; Analytical chemistry; Anti-Infective Agents - chemistry; Anti-Infective Agents - isolation & purification; Anti-Infective Agents - pharmacology; Anti-Infective Agents - toxicity; Antibiotics; Antimicrobial agents; Applied Microbial and Cell Physiology; Bacteria; Biomedical and Life Sciences; Biotechnology; Cell culture; Cell morphology; Cell Survival - drug effects; Cells, Cultured; Chemical analysis; Citronella grass; Cosmetics; Cymbopogon - chemistry; Cymbopogon flexuosus; Cytotoxicity; Drug resistance; Essences and essential oils; Essential oils; Fibroblasts; Fibroblasts - drug effects; Fruits; Grapeseed oil; Grasses; Health aspects; Humans; Infections; Inhibitory Concentration 50; Life Sciences; Microbial Genetics and Genomics; Microbial Sensitivity Tests; Microbial Viability - drug effects; Microbiology; Monoterpenes - chemistry; Monoterpenes - isolation & purification; Monoterpenes - pharmacology; Monoterpenes - toxicity; Oils & fats; Oils, Volatile - chemistry; Oils, Volatile - isolation & purification; Oils, Volatile - pharmacology; Oils, Volatile - toxicity; Studies; Toxicity
• ISSN: 0175-7598; 1432-0614
• DOI: 10.1007/s00253-016-7807-y

The aim of this study was to determine the antimicrobial effects of lemongrass essential oil ( C. flexuosus ) and to determine cytotoxic effects of both test compounds on human dermal fibroblasts. Antimicrobial susceptibility screening was carried out using the disk diffusion method. Antimicrobial resistance was observed in four of five Acinetobacter baumannii strains with two strains confirmed as multi-drug-resistant (MDR). All the strains tested were susceptible to both lemongrass and citral with zones of inhibition varying between 17 to 80 mm. The mean minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of citral ( mic —0.14 % and mbc —0.3 %  v / v ) was lower than that of Lemongrass ( mic —0.65 % and mbc —1.1 %  v / v ) determined using the microtitre plate method. Cell viability using human dermal fibroblasts (HDF; 106-05a) was determined following exposure to both compounds and a control (Grapeseed oil) using the XTT assay and the IC 50 determined at 0.095 % ( v / v ) for citral and 0.126 % ( v / v ) for lemongrass. Grapeseed oil had no effect on cell viability. Live cell imaging was performed using the LumaScope 500 imaging equipment and changes in HDF cell morphology such as necrotic features and shrinkage were observed. The ability of lemongrass essential oil (EO) and citral to inhibit and kill MDR A. baumannii highlights its potential for use in the management of drug-resistant infections; however, in vitro cytotoxicity does suggest further tests are needed before in vivo or ex vivo human exposure.