In vitro antifungal and anti-ochratoxigenic activities of Aloe vera gel against Aspergillus carbonarius isolated from grapes

The basic objective of this study lies in determining the physico-chemical characteristics of Aloe vera gel in freshly harvested leaves, as well as evaluating its efficiency in terms of inhibiting the growth and ochratoxin A (OTA) production by Aspergillus carbonarius. The antifungal evaluation was performed by compound dissolution at the doses of 5, 10, 20, 30 and 50% in Czapek Yeast Agar medium (CYA). Our results revealed that Aloe vera gel did not display a pronounced antifungal effect on the growth of A. carbonarius. It rather showed a high anti-ochratoxigenic activity. Statistical analyses on growth rate of the fungus demonstrated that the main effect on mycelial growth was recorded at 50% of Aloe vera gel with an inhibition rate estimated at about 11.59%. At tested concentrations, Aloe vera gel could not totally inhibit the OTA production of fungus but only reduce it by 22.47-75.69% depending on concentration. However, this reduction was not positively correlated with the increase of the Aloe vera gel in the medium. The most important reduction on OTA synthesis was recorded at 20% of Aloe vera gel although no growth reduction was detected at this concentration. Overall, our results suggest that the concentration of Aloe vera gel should be between 20 and 30% to ensure an active inhibition of OTA production by A. carbonarius. This finding provides sound evidence that the use of Aloe vera gel as a biological pre-harvest treatment at the vineyard level is an effective, feasible and welcomed strategy.