Location: Food and Feed Safety Research
2010 Annual Report
Research concerned the extraction and purification of plant antifungals. A patent was received in 2001, on CAY-1, a cayenne fungicidal compound known as a saponin, and we have continued its study where we purified two novel cayenne saponins, 1081 and 919, which are structurally very similar to CAY-1. Neither was antifungal; however, a mixture of these saponins (CAY-1, 1081, 919) in the ratio present in cayenne pepper is more antifungal than CAY-1 alone (data used to file a U.S. patent application).
Agricultural Research Service (ARS) collaborators (Winter Haven, FL) found CAY-1 active in lab studies against rot fungi in post harvest citrus. ARS collaborators (Poplarville, MS) found CAY-1 reduced plant pathogenic fungal growth in lab tests and prevented anthracnose lesions leaf tissue. However, semi-pure CAY-1 did not control foliar or fruit rot of strawberries in field trials.
Colleagues (National Institute of Health (NIH), Bethesda, MD) found CAY-1 acted synergistically in separate studies with Amphotericin B, Itraconazole (antifungal drugs), and dissolved silver against fungal pathogens, including two skin pathogens. Additional studies are needed to determine whether CAY-1 can possibly be used as a topical antifungal.
Bay leaf, okra, cotton seedlings, and barley were studied for their antifungal properties. The semi-purified extracts had antifungal properties, but the antifungal compounds were not purified.
The antifungal properties of commercial plant compounds were studied. Trans-2-hexenal and trans-2-heptenal (both from soybeans) were significantly lethal at low concentrations against Aspergillus and Fusarium species. Pumped, volatilized trans-2-hexenal killed Aspergillus flavus inoculated onto wet corn and prevented aflatoxin (a potent fungally produced carcinogen) production by this fungus. Bisabolol (plant oils) and dragosantol (synthetic bisabolol) are highly bactericidal and fungicidal against the fungal Aspergillus and Fusarium. Pinene and limonene, potent fungicides, may be useful as vapors or in an edible coating, to protect fruits and vegetables from fungal storage rot.
Volatiles produced by aflatoxin- and non-aflatoxin producing strains of Aspergillus flavus grown on corn were identified. Volatiles unique for the aflatoxin-producing strains used by Sensor Development Corporation to develop a prototype sensor, which will undergo Beta testing by the company in grain silos.
Studies into the microbicidal properties of visible light were initiated. Blue light (470nm) killed the harmful bacteria Leuconostoc mesenteroides, Pseudomonas, Staphylococcus, and Bacillus species. Exploratory experiments showed for the first time that a photosensitizing dye (Rose Bengal) in combination with visible blue light killed the fungus Aspergillus flavus conidia (spores or seeds).
Abril, M., Curry, K.J., Smith, B.J., De Lucca Ii, A.J., Boue, S.M., Wedge, D.E. 2009. Greenhouse and Field Evaluation of the Natural Saponin CAY-1, for Control of Several Strawberry Diseases. International Journal of Fruit Science. 9:3,211-220.