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The antifungal activity of Nerol (NEL) was evaluated against Aspergillus niger , a known cause of grape spoilage, and possible modes of action were explored. The antifungal efficacy of NEL against A. niger has been proven in a dose-dependent manner through in vitro (mycelial growth and spore germination) and in vivo (grapes) tests. An obvious increase in the membrane permeability was detected through the determination of extracellular pH and conductivity. The damage in the cell membrane was measured by monitoring the influx of Propidium iodide (PI) using flow cytometry and was further verified through the inhibition of ergosterol synthesis in the cell membrane. NEL induced morphological changes, and the integrity of the A. niger fungal cells decreased with increasing NEL concentrations. A dose-dependent decrease in ergosterol production was also seen in A. niger cell membranes upon exposure to NEL. The mechanism-of-action study revealed that NEL activated a membrane-active mechanism that inhibits ergosterol synthesis and consequently compromised the membrane integrity of A. niger . As a result, the membrane permeability changes and causes cell death. The membrane lesion mechanism makes NEL a natural alternative to commercial fungicide for control of stored grape spoilage. [ABSTRACT FROM AUTHOR]

A variety of plant products have been recognized for their antifungal activity and recently have attracted food industry attention for their efficacy in controlling postharvest fungal decay of fruits. The antifungal activity of perillaldehyde (PAE) was evaluated against Aspergillus niger, a known cause of grape spoilage, and possible mechanisms were explored. PAE showed notable antifungal activity against A. niger , with a minimum inhibitory concentration (MIC) and a minimum fungicidal concentration (MFC) of 0.25 and 1 μl/ml, respectively. The accumulation of mycelial biomass was also inhibited by PAE in a dose-dependent manner, completely inhibiting mycelial growth at 1 μl/ml. In vivo data confirmed that the vapour treatment of grapes with various concentrations of PAE markedly improved control of A. niger and suppressed natural decay. Concentrations of PAE of 0.075 μl/ml air showed the greatest inhibition of fungal growth compared to the controls. Further experiments indicated that PAE activated a membrane-active mechanism that inhibits ergosterol synthesis, increases membrane permeability (as evidenced by extracellular pH and conductivity measurements), and disrupts membrane integrity, leading to cell death. Our findings suggest that this membrane-active mechanism makes PAE a promising potential antifungal agent for postharvest control of grape spoilage. [ABSTRACT FROM AUTHOR]