DISCOVERY OF ANTIFUNGAL COMPOUNDS FROM LOW VALUE/UNDERUTILIZED CROPS AND CROP CO-PRODUCTS
Location: Food and Feed Safety Research
Title: Silver enhances the in vitro antifungal activity of the saponin, CAY-1
Submitted to: Mycoses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 5, 2009
Publication Date: November 26, 2009
Citation: De Lucca II, A.J., Boue, S.M., Sein, T., Cleveland, T.E., Walsh, T.J. 2009. Silver enhances the in vitro antifungal activity of the saponin, CAY-1. Mycoses. 54:e1-e9.
Interpretive Summary: Silver has been known for hundreds of years to prevent bacteria from growing. However, little research has been performed on the antifungal properties of this element. CAY-1, a detergent-like compound produced in plants, is known to kill fungi. This work showed that, under laboratory conditions, when both are mixed together, (1) less of each compound is needed to achieve a significant reduction in fungal populations and (2) some fungi that resisted CAY-1 become susceptible to the actions of Cay-1 and sub-lethal levels of silver. This data could be used by others interested in reducing the levels of living fungi.
The separate fungicidal properties of purified CAY-1, dissolved silver, and EDTA were studied, as were the abilities of silver or EDTA to enhance CAY-1 fungicidal properties. Nongerminated and germinating conidia of A. flavus, A. fumigatus, A. niger, F. moniliforme, F. oxysporum and F. solani were incubated separately with CAY-1 (0-31ug/ml), silver (0-175ug/ml), and EDTA (0-2400ug/ml). Controls consisted of nongerminated or germinated conidia in test medium. To assess combined activity, test mixtures consisted of sub-lethal concentrations of CAY-1 combined with sub-lethal concentrations of Ag or EDTA. Controls for the mixed sets consisted of nongerminated or germinated conidia only or with the sub-lethal CAY-1 test concentrations. Alone, CAY-1 was not lethal to any nongerminated Aspergillus conidia and both conidial types of F. oxysporum and F. moniliforme. CAY-1 alone was significantly (p less than 0.001) lethal for the germinating conidia of A. flavus and A. niger (less than or equal to 5ug/ml) and F. solani (greater than or equal to 10ug/ml). Silver was inactive for nongerminated Aspergillus and F. moniliforme conidia, but significantly lethal for F. oxysporum and F. solani nongerminated conidia (19.1 and 6.4ug/ml, respectively). The germinating conidial viability of A. flavus, A. niger, A. fumigatus, F. oxysporum, F. moniliforme, and F. solani was significantly reduced when treated with silver (1.3, 0.64, 79.4, 6.4, 3.8 and 2.5ug/ml, respectively). Combinations of silver and CAY-1 (1) reduced the total amount of each needed for significant fungicidal activity and (2) was significantly active against fungi not affected by either compound alone. EDTA was not fungicidal alone and did not enhance CAY-1 fungicidal properties. Results show dissolved silver was fungicidal in vitro and enhanced the fungicidal properties of CAY-1.