The inhibitory activity of salicylaldehyde compounds on aspergillus species and their effects on aflatoxin production and crop seed germination

Authors: Kim, Jong Heon; Chan, Kathleen - Kathy; Hart-Cooper, William; Ford, Deangela; Orcutt, Kaydren; Sarreal, Siov; Palumbo, Jeffrey - Jeff; Orts, William

Submitted to: Applied Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/30/2024
Publication Date: 11/1/2024
Citation: Kim, J., Chan, K.L., Hart-Cooper, W.M., Ford, D.E., Orcutt, K.B., Sarreal, S.L., Palumbo, J.D., Orts, W.J. 2024. The inhibitory activity of salicylaldehyde compounds on aspergillus species and their effects on aflatoxin production and crop seed germination. Applied Sciences. 14(21):10000. https://doi.org/10.3390/app142110000.
DOI: https://doi.org/10.3390/app142110000

Interpretive Summary: Fungal infections/contaminations on food crops are serious problems since effective agents for treating fungicide-resistant fungi are often very limited. Administration of fungicides at suboptimal concentrations or time-points of fungal growth can also increase toxin production by fungi, thus negatively affecting the safe production of foods/crops as well as public food safety. Natural products (NP) have been potential source of antifungal agents, food additives, etc. However, currently there are significant research gaps between the NP utilization in food/feed industry and food/feed safety (risks). We hypothesized that, as determined in conventional fungicides, if NP or their structural derivatives are applied at suboptimal concentrations, NP/derivatives could enhance mycotoxin production by the aflatoxin (AF)-producing aspergilli (Aspergillus flavus, A. parasiticus). Recent study also showed that botanicals, such as pomegranate peel extract, applied at suboptimal concentrations increased the production of AFB1 in A. flavus. In this study, we investigated the effect of sub-inhibitory doses of thirteen NP/derivatives, currently used as food/feed additives, against A. flavus and A. parasiticus by evaluating the enhancement AF production. Compounds that did not enhance AF production were tested further for their utility as potent antifungal agents in crop (corn) seeds.

Technical Abstract: Crops such as tree nuts, corn and peanut are highly susceptible to infestation by the aspergil-li Aspergillus flavus or Aspergillus parasiticus and subsequent aflatoxin (AF) contamination, a serious threat to public food safety. Conventional control of the aspergilli has been through the application of fungicides; however, certain fungicides at sub-optimal doses have been correlated with increased production of mycotoxins including AF. Natural products (NP) have been a po-tential source of antifungal agents. In this study, we performed risk assessment testing for which thirteen natural compounds/derivatives (Generally Recognized As Safe) were examined at sub-inhibitory concentrations to determine the enhancement of AF production in aspergilli. We found that benzaldehyde derivatives or thymol enhanced AF production in aspergilli, while 4-isopropyl-3-methylphenol (4I3M), a synthetic analog of the NP thymol and carvacrol, or salic-ylaldehyde (SLD) exerted a potent antifungal or mycotoxin-inhibitory effect. In seed testing (corn, pistachio kernels), SLD effectively prevented aspergilli growth as a fumigant, while 4I3M com-pletely inhibited AF production at ' 1.0 mM. Therefore, we concluded that NP/derivatives that do not have any significant environmental impact can be a potent source of antifungal or an-ti-mycotoxigenic agents, either in their nascent form or as leads for more effective derivatives; however, NP should be applied at optimum concentrations to prevent abnormal enhancement of mycotoxin production by fungi.