FIG. 1.

Antifungal activities of oregano oil and component terpenoid phenols. (A) Filter disks were soaked in serial dilutions of oregano oil and placed on a lawn of S. cerevisiae. Clear areas or halos were observed up to a dilution of 1:8 and revealed inhibition of yeast growth. Controls show growth in the absence of essential oil. (B) FUN-1 fluorescence (green) following treatment of yeast with oregano oil (described in Materials and Methods) but not with mineral oil indicates loss of metabolic activity. (C) Dose-dependent effects on yeast growth of a panel of terpenoid phenols reveal structure-activity relationships. Inhibition of yeast growth followed the order carvacrol ≥ thymol > eugenol ≫ γ-terpinene, vanillin, and guaicol. (D) Time course of growth inhibition in the presence of 0.005%, 0.0075%, and 0.01% carvacrol. (E) Dose-dependent loss of metabolic activity in response to carvacrol was monitored using FUN-1 green fluorescence. Data represent averages of the results of triplicates. Error bars show standard deviations. Ab600, absorbance at 600 nm.