Mechanisms of antifungal and mycotoxin inhibitory properties of Thymus vulgaris L. essential oil and their major chemical constituents in emulsion-based delivery system

The antifungal and mycotoxin inhibitory activity of emulsions formed with Thymus vulgaris L. essential oil (thyme oil) and four major components (thymol, p-cymene, gamma-terpinene, and linalool) on Fusarium graminearum, and their corresponding mode of action (MOA) were evaluated in this study. Among the five emulsions, thymol emulsion presented the strongest antifungal activity followed by thyme oil and linalool emulsion. The spore morphology changes and cell membrane destruction were the main reasons attributed to it supported by the SEM and CLSM observation. Moreover, significant (p< 0.05) suppression on mycotoxin inhibition were achieved by all five emulsions. We also noticed that the antifungal activity and the mycotoxin inhibitory were not always correlated. Linalool appeared to be a more effective spore germination inhibitor, while p-cymene and gamma-terpinene decreased mycotoxin production more effectively. We further investigated the MOA of thyme oil and thymol emulsions on suppression of mycotoxin production on generic level. We observed that thyme oil significantly (p< 0.05) up-regulated the expression of the key encoding genes in mycotoxin biosynthesis pathway that were studied (Tri3, Tri4, and Tri5), while thymol did not up-regulate any gene expression.