Additive antimicrobial effects of the active components of the essential oil of Thymus vulgaris – chemotype carvacrol

Abstract

Herbal remedies are multi component mixtures by their nature as well as by pharmaceutical definition. Being a multi component mixture is a pre-condition for interactions such as synergism or antagonism. Antibiotic activity of thyme oil and single active components were tested against six different strains of microorganisms. The degree of the detected interactions corresponded with the demarcating FICI-measure of 0.5, which separates the additive from the over additive (synergistic) effects [1]. Therefore, the observed effect was called „partial synergism“. Partial synergism was observed only in the presence of Klebsiella pneumoniae. Additive antimicrobial activity was observed for the combination of the two monosubstances carvacrol plus linalool and thymol plus linalool as well as with the combination of the two essential oils of the carvacrol and linalool chemotypes. An increase of the carvacrol-oil concentration from one to two times the MIC resulted in a considerable acceleration of the kill-rate. Carvacrol-oil (Cve) caused a faster kill-rate than the artificial combination (Ac), which was composed of the two main active monosubstances carvacrol and thymol.