Submitted to: Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 7/30/2004
Publication Date: 12/1/2004
Citation: De Lucca II, A.J., Boue, S.M., Palmgren, M.S., Maskos, K., Cleveland, T.E. 2004. Reduced fungicidal properties of CAY-1 precursors. Interscience Conference on Antimicrobial Agents & Chemotherapy Proceedings. Abstract F-845. p. 208. Interpretive Summary:
Technical Abstract: Cayenne pepper contains CAY-1 (mol. wt. 1243), a steroidal saponin with four glucose and one galactose moieties. CAY-1 is fungicidal [LD90 values: Aspergillus flavus (7.5 uM), A. fumigatus (4.0 uM), A. parasiticus (20.0 uM), A. niger (10.0 uM)] but inactive against Fusarium oxysporum, F. moniliforme. High pressure liquid chromatography/mass spectrometry (HPLC/MS) showed two compounds (A, B) closely elute with CAY-1. This study determined their chemical structures and fungicidal properties. Methods: Cayenne pepper was extracted (1:4, wt:vol) overnight (4 deg C) in 1 percent potato dextrose broth (PDB). (A) and (B) were semipurified by column chromatography with final purification (is equal to or greater than 99%) by HPLC/MS. Nuclear Magnetic Resonance (NMR) determined chemical structures. Fungicidal assays: nongerminated and germinating fungal conidia (25 ul, 10**4/ml in PDB) of the aforementioned fungi were added to 225 ul of A and B (0-30 uM) in separate assays. Controls were: conidia (25 ul, 10**4/ml in PDB) + 225 ul PDB. Samples were incubated (30 deg C, 30 min) and aliquots (50 ul) spread on agar plates. After incubation (24 hrs, 30 deg C) colonies were counted. Each experiment per compound and fungal conidial type was run three times (n=12). Data were analyzed statistically by ANOVA and Holm-Sidaks or Dunn's method. Results: Compounds (A) and (B) had molecular weights of 1082 and 920, respectively, and were structurally identical to CAY-1 except (A) lacked the fourth glucose and (B) lacked the third and fourth glucose moieties. (A) was significantly (p is less than 0.05) lethal only for the germinating conidia of A. fumigatus and A. niger (15 and 10 uM, respectively); (B) was inactive. (B) required sonication to become soluble indicating all sugars were needed for aqueous solubility. Conclusions: (A) and (B), metabolic precursors of CAY-1 are either weakly fungicidal or inactive. All sugars in CAY-1 are required for its fungicidal properties and aqueous solubility.