Inhibition of in vitro trichothecenes production by microalgae phenolic extracts

There is evidence that microalgae phenolic compounds can inhibit the growth of toxigenic fungi. This study aimed to evaluate the ability of microalgae phenolic extracts to inhibit trichothecene production by Fusarium genus and thereby identify parameters that can promote a new technology to avoid contamination of crops by mycotoxins. The microalgae phenolic acids (Spirulina sp. and Nannochloropsis sp.) were extracted with methanol, clarified and resuspended in water. The in vitro experiment involved adding the phenolic extract from each microalga (40 μg/mL) to Petri dishes containing culture medium and previously sterilized wheat grains, with subsequent inoculation of an isolate belonging to the F. graminearum species complex. The control was cultured with sterile water. Treatment with the fungicide tebuconazole (0.6 mg/mL) was also performed. Petri dishes were incubated at 25 °C, with a light/dark photoperiod of 12-12 h. After 168 h, the samples were extracted by the adapted QuEChERS method; the trichothecenes (nivalenol, deoxynivalenol and acetylates) were identified and quantified by high-performance liquid chromatography. When the phenolic extracts from microalgae were applied, the characteristic peak of nivalenol was not detected, suggesting total inhibition, whereas, the nivalenol content increased (15%) in the presence of tebuconazole. Both microalgae phenolic extracts also had a promising effect on the inhibition of deoxynivalenol, with no detection (Nannochloropsis sp. extract) and 62% reduction (Spirulina sp. extract). The application of the fungicide tebuconazole increased the deoxynivalenol concentration. Both microalgae phenolic extracts and tebuconazole decreased the detection of acetylates. Thus, phenolic extracts from microalgae were more efficient than tebuconazole as antifungal and antimycotoxigenic agents in cultures in vitro.