Cymbopogon martinii essential oil: chemical characterization, effects on Propionibacterium acnes and immune response in lymphocytes

Cymbopogon martinii (Roxb.) Wats var. motia essential oil (EO) is usually isolated by steam distillation of the freshly harvested leaves or partially dried leaves [1]. Palmarosa has been widely used in aromatherapy as a tonic skin due its antibacterial, antiviral and anti-inflammatory activity. It has also been used in Ayurvedic medicine for skin problems and to relieve pain [1]. Propionibacterium acnes is the microorganism associated with the pathogenesis of acne; it is a gram-positive bacteria and anaerobic opportunistic [2] and is an important factor in the activation of innate immunity in acne [3]. The aim of this research was to evaluate if C. martinii EO and its major compound, geraniol (constitute ≈ 85% of the EO), are able to modify the immune stimulation caused by P. acnes. We determined the antibacterial activity of C. martinii EO and geraniol for P. acnes in vitro. Sensitivity test broth micro dilution was performed and phenotypic changes were confirmed by Transmission Electron Microscopy (TEM) and we investigated if the presence of C. martinii EO and geraniol modify the effect of P. acnes in the differentiation of T-cells. We determined the Minimum Inhibitory Concentration (MIC) to P. acnes ATCC 11828 (type II) and ATCC 6919 (type IA) [See Table 1]. Peripheral blood mononuclear cells from six volunteers were infected with P. acnes strains with a multiplicity of infection = 3 and simultaneously treated with 3 different doses of C. martinii EO and geraniol, respectively. The treatments did not modulate the production of Interferon-gamma and Interleukin-17 in CD4 + cells in PBMC's infected with P. acnes. Given these preliminary results, natural compounds tested showed antimicrobial activity against P. acnes strains and they do not modulate P. acnes- stimulated lymphocytes T helper 1 and Th17 immune response. P. acnes showed differences in sensibility test depending of subtype and probably geraniol is the responsible compound for the antimicrobial activity of the EO of C. martinii.