Liquid and Vapor-Phase Activity of Artemisia annua Essential Oil against Pathogenic Malassezia spp.

Abstract Artemisia annua essential oil has given us many encouraging results for its numerous antimicrobial properties. In this study, the essential oil, both in liquid and in vapor phases, was tested against various Malassezia species closely related to many skin disorders in humans and animals. Malassezia treatment and eradication are mainly based on old azole drugs, which are characterized by poor compliance, unpredictable clinical efficacy, emerging resistance, and several side effects. Monoterpenes (ca. 88%) represent the most abundant group of compounds in the essential oil, mainly the oxygenated derivatives (ca. 74%) with camphor (25.2%), 1,8-cineole (20%), and artemisia ketone (12.5%). In vapor phase, monoterpenes represent more than 98% of the constituents, α-pinene being the main constituent (22.8%), followed by 1,8-cineole (22.1%) and camphene (12.9%). Essential oil of A. annua, both in vapor phase and liquid, showed strong antimicrobial activity towards almost the tested twenty strains of Malassezia analyzed. The minimum fungicidal concentrations from most of the strains tested were from 0.78 µL/mL to 1.56 µL/mL, and only three strains of Malassezia sympodialis required a higher concentration of 3.125 µL/mL. Overall, the minimal inhibitor concentrations obtained by vapor diffusion assay were lower than those obtained by the liquid method. The average values of minimal inhibitor concentrations obtained by the two methods at 72 h are 1.3 – 8.0 times higher in liquid compared to those in the vapor phase.