DISCOVERY OF ANTIFUNGAL COMPOUNDS FROM LOW VALUE/UNDERUTILIZED CROPS AND CROP CO-PRODUCTS
Location: Food and Feed Safety Research
Title: Synergy studies of the fungicidal plant saponin, CAY-1, with EDTA and silver
Submitted to: Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: July 30, 2007
Publication Date: September 17, 2007
Citation: De Lucca II, A.J., Lovisa, M.P., Cleveland, T.E. 2007. Synergy studies of the fungicidal plant saponin, CAY-1, with EDTA and silver. In: Proceedings of 47th Interscience Conference on Antimicrobial Agents & Chemotherapy, September 17-20, 2007, Chicago, IL. Abstract F1-1672.
Background: CAY-1 is a fungicidal saponin produced by Capsicum species. Silver (Ag) and EDTA inhibit Aspergillus and Fusarium growth. This study determined Ag and EDTA fungicidal properties for several Aspergillus and Fusarium species both alone and with CAY-1.
Methods: CAY-1 was purified by column chromatography and HPLC/MS. Silver nitrate and EDTA were dissolved in 1 percent potato dextrose broth (PDB). Nongerminated (NG) and germinating (G) conidia (25ul) of A. flavus (AFLAV), A. fumigatus (AFUM), A. niger (AN), F. moniliforme (FM), F. oxysporum (FO), and F. solani (FS) were incubated separately (30 min, 30 degrees C) with CAY-1 (0-31ug/ml), Ag (0-175ug/ml), and EDTA (0-2400ug/ml). Final test volume was 250ul. Final conidial concentration was 1.2 X 10**4/ml. Post incubation, 50ul aliquots were spread on PDA plates, incubated for 48 hrs (30 degrees C) and viable colonies counted. Controls consisted of broth (225ul) and NG or G conidia (25ul). Synergy studies consisted of CAY-1 of at least the second non-lethal concentration below the minimum lethal dose mixed with sub-lethal Ag or EDTA doses. Synergy controls consisted of NG or G conidia (25 ul) in PDB only or with CAY-1 at the test level for a total of 250ul. Remaining protocol was as described above. SigmaStat was used to determine statistical significance (p<0.001).
Results: CAY-1 was not lethal to all NG Aspergillus conidia and both conidial types of the tested Fusarium species. CAY-1 was significantly lethal for the G conidia of AFLAV, AFUM, and AN (7.2, 5, and 5ug/ml, respectively). Ag was lethal for the NG conidia of FM and FS (75 and 10ug/ml, respectively) and for the G conidia of AFLAV, AFUM, FM, FO, and FS (4, 125, 1, 4, 30, and 4ug/ml, respectively). EDTA was not lethal for any fungi. CAY-1 and Ag showed synergy against the G conidia of all fungi (range: CAY-1: 5-80 ug/ml; Ag: 10-12 ug/ml). CAY-1 and EDTA were not synergistic.
Conclusions: EDTA is not lethal to the tested fungi. Ag, not EDTA, enhances CAY-1 lethality for the tested Fusarium and Aspergillus species.