Effect of pH on the synergism of thymol and carvacrol against Saccharomyces cerevisiae

Thymol and carvacrol are natural monoterpene phenols found in high concentration in various essentials oils including the oil of thyme. These monoterpene phenols are known to possess strong antiseptic activities [1]. In this study, I detail the effect that pH has on the synergism of thymol and carvacrol against the model organism, Saccharomyces cerevisiae . For every 0.1 unit interval in the pH range (6.4-8.4), IC 50 values were measured based on the thymol content in the mixture of thymol and carvacrol. The maximum potency of 0.399 mg L -1 was achieved at pH 6.4 using a 1:9 ratio of thymol to carvacrol – over 5 times more potent than thymol alone at pH 7.4 (IC 50 = 2.05 mg L -1 ). Understanding the synergy of the components in essential oils is one of the first steps in establishing alternative treatments to fight drug-resistant microorganisms. By combining essential oils or their components with existing antibiotic or antifungal agents, effective treatment of superbugs can be elucidated [2].