Thymol and Carvacrol Binary Mixtures to Control Fusarium and Rhizopus spp

Introduction: In recent years Rhizopus and Fusarium had been the main cause of postharvest decay as well as major economic losses and food spoilage in various horticultural products. For years, fungal chemical control has been used; however, these products represent a potential hazard to the environment and the human being. An alternative is searching for natural antimicrobial compounds, such as thymol and carvacrol which could be used in fungal control. 

Purpose: The aim of this study was to evaluate the in vitro antifungal activity of thymol and carvacrol mixtures against Rhizopus and Fusarium species.

Methods: Mold radial growth was evaluated to determined minimal inhibitory concentration (MIC) with thymol or carvacrol concentrations of 0 to 1600 ppm. Binary mixtures were evaluated using concentrations below the MIC values. In order to evaluate synergism or antagonism effects. Radial growth curves were described by the Gompertz modified equation.

Results: MIC carvacrol values were 200 ppm for both molds. Meanwhile, MIC thymol values ranged between 500 and 400 ppm for Rhizopus spp. and Fusarium spp., respectively. A synergistic effect below MIC concentrations for carvacrol (50 ppm) and thymol (300-375 ppm) was observed. Significant differences (P < 0.05) between the Gompertz parameters for the antimicrobial concentrations and their tested binary mixtures established an inverse relationship between antimicrobial concentration and mycelial development of both molds.

Significance: Thymol and carvacrol possess a synergistic antifungal activity on Rhizopus spp. and Fusarium spp. when applied as binary mixtures.