Chemical composition and in vitro activity of Origanum vulgare L., Satureja hortensis L., Thymus serpyllum L. and Thymus vulgaris L. essential oils towards oral isolates of Candida albicans and Candida glabrata

The purpose of this research was to investigate the chemical composition of essential oils (EOs) from: Origanum vulgare L., Satureja hortensis L., Thymus serpyllum L. and Thymus vulgaris L. (Lamiaceae) cultivated in Poland, and to study their antifungal activity towards clinical isolates of oral Candida spp. The hydrodistilled essential oils were analyzed using the GC-MS method. The antifungal activity was evaluated in vitro against oral isolates and reference strains of Candida albicans and C. glabrata, using the broth microdilution method according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) and Clinical and Laboratory Standards Institute (CLSI) guidelines, allowing for estimation of minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC). GC-MS analysis revealed that carvacrol was the main EO compound in oregano and summer savory, while thymol and linalool were the major ingredients of thyme and wild thyme oils, respectively. The EOs possessed fungicidal activity against C. albicans and C. glabrata, including oral isolates, with MIC = 125 – 2000 mg/L, MFC = 250 – 4000 mg/L and MFC/MIC = 1 – 4, depending on the yeast and plant species. The most active was thyme oil – with MIC = 125 – 500 mg/L, MFC = 250 – 500 mg/L and MFC/MIC = 1 – 2.