Submitted to: Molecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/5/2014
Publication Date: 11/12/2014
Publication URL: http://handle.nal.usda.gov/10113/60059
Citation: Kim, J.H., Chan, K.L. 2014. Augmenting antifungal activity of oxidizing agent with kojic acid: Control of Penicillium strains infecting crops. Molecules. 19:18448-18464. doi: 10.3390/molecules191118448.
Interpretive Summary: The filamentous fungi in the genus Penicillium are frequently involved in food contamination or postharvest decay. For example, P. expansum is the main producer of the mycotoxin patulin in crops that triggers harmful effects on human health. Meanwhile, P. digitatum is the most devastating citrus pathogen, causing significant economical losses to the industry during post-harvest practices. Therefore, development of strategies, which warrant early intervention of mycotoxin production and/or fungal contamination in foods/crops, is urgently needed. Kojic acid (KA) is one of the main secondary metabolites produced by the aflatoxigenic aspergilli. In this study, antifungal efficacy of hydrogen peroxide (H2O2), kojic acid (KA) and abiotic stress (heat), alone or in combination, was investigated in the pathogenic strains of Penicillium. Antifungal activity of the oxidizing agent (H2O2) could be enhanced when KA was co-applied. This potential appears to be greatest with P. expansum strains. Of note, antifungal efficacy of H2O2 was enhanced further when Penicillium strains were treated with high temperatures. Collectively, KA, a safe, natural compound, possesses a potential to serve as an antifungal chemosensitizing agent in combination with oxidizing agents.
Technical Abstract: Oxidative treatment is a strategy for preventing Penicillium contamination in foods or crops. Antifungal efficacy of oxidant [hydrogen peroxide (H2O2)], biotic effector [kojic acid (KA)] and abiotic stress (heat), alone or in combination, was investigated in Penicillium. The levels of antifungal interactions between KA and H2O2 were determined in vitro by the method outlined by Clinical and Laboratory Standard Institute. Co-application of KA with H2O2 resulted in the incremental increase of antifungal activity of both KA and H2O2, when compared to the individual treatment of each agent, alone. Of note, heat enhanced the antifungal activity of H2O2 to a greater extent, where the minimum inhibitory or fungicidal concentrations of H2O2 at 35 to 45oC were lowered 7 - 13 folds, comparing to that determined at 28oC. However, similar heat treatment did not enhance the activity of KA. Effect of co-treatment was also strain-specific, where P. expansum, both parental and fludioxonil-resistant mutant strains, exhibited relatively higher susceptibility to KA + H2O2 comparing to other Penicillium strains. Collectively, combined application of antifungal agents can serve as a potent antifungal strategy to lower effective dosages of toxic antifungal substances (e.g., H2O2). This can lead to lowering of environmental and health risks.