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United States Department of Agriculture

Agricultural Research Service

Research Project: DISCOVERY OF ANTIFUNGAL COMPOUNDS FROM LOW VALUE/UNDERUTILIZED CROPS AND CROP CO-PRODUCTS

Location: Food and Feed Safety Research

2008 Annual Report


1a.Objectives (from AD-416)
Enhance value and utilization of low value/underutilized crops and crop co-products through discovery and purification of novel, constituent antifungal compounds and determine commercial potential of discovered antifungals.


1b.Approach (from AD-416)
Barley and cotton 3-day old cotyledons will be extracted aqueously as will okra fruit and peanut and rice hulls. Filtered, freeze-dried extracts will be tested for fungicidal properties. Active compounds will be purified by HPLC/MS and activity monitored with bioassays using Aspergillus flavus and Fusarium oxysporum. NMR will determine chemical structure of antifungal compounds. Novel compounds will be patented and all active compounds will be tested for their antifungal spectra of activity. Commercial potential of compounds as agricultural fungicides and medical antifungals will be determined by collaborators. Discovered protein antifungals will be cloned. Construct genes will be incorporated into gene expression systems to obtain a protective effect against fungal pathogens.


3.Progress Report
The action plan of NP 306, component 2, concerns new uses and development of value-added foods and bio-based products.

Our research this year showed that the fungicidal properties of CAY-1, our patented fungicide from cayenne, are enhanced by mixing it with two structurally related cayenne saponins (detergent-like compounds), 1081 and 919, which have little and no antifungal properties independently, respectively. The active ratios (4:3:3 [naturally present in cayenne] and 6:2:2) of CAY-1:1081:919 are more active than the equivalent weight of CAY-1 alone. Of potential interest to pesticide companies is that the naturally occurring saponin ratio (4:3:3) can be more easily purified from the plant than pure CAY-1. This work has been approved for a U.S. patent application. We also learned that dissolved silver acts synergistically with CAY-1. Since silver and CAY-1 can be bound to cotton gauze, it may be possible to develop CAY-1 and silver impregnated gauze to protect wounds from infections. We also found that wheat histones (proteins involved in plant DNA structure) are potent fungicides. This suggests that these proteins could be candidates for genetic modification of plants to provide enhanced resistance to fungal plant pathogens.


4.Accomplishments
1. FUNGICIDAL PROPERTIES OF CAY-1 AND CAYENNE SAPONINS 1081 AND 919.

These saponins, which have detergent-like properties, are present in cayenne pepper (Capsicum frutescens). They elute together when purified using sophisticated separation techniques, which makes it easy to harvest them. Compounds 1081 and 919 are structurally similar to CAY-1 except for the number of glucose molecules present. CAY-1 is known to be a potent fungicide against a number of fungi that are plant and human pathogens. In contrast, compounds 1081 and 919 have little and no fungicidal activity, respectively. However, when mixed together, these three saponins show greater fungicidal activity than CAY-1 alone. Moreover, the ratio (4:3:3) of CAY-1:1081:919, which is the ratio found in cayenne pepper, is overall the most active of the mixture ratios tested.

This research addresses NP 306, Quality and Utilization of Agricultural Products and NP 303, Plant Diseases.

2. FUNGICIDAL PROPERTIES OF WHEAT HISTONES.

Histones are proteins that serve as a “pole” on which deoxyribonucleic acid (DNA) forms its famous spiral, so it was not expected that they would have antimicrobial properties. However, mixtures of wheat histones (H1 – H4, and H2 –H4) and pure H1 were provided by our cooperator, at the University of Lund, Sweden. These mixtures as well as the pure histone H1 were found significantly fungicidal below 20µM against the fungi Fusarium verticiliodes (moniliforme), Fusarium solani and F. oxysporum. The first two fungi cause rots in various crops, especially cereal grains, while the latter is a serious lung pathogen in immnunocompromised patients. However, these proteins were not active against other fungi: (1) Aspergillus flavus, which produces potent cancer compounds on oilseeds; (2) A. niger, which produces several minor toxins on food and feed; and (3) A. fumigatus, another lung pathogen of immunocompromised patients.

This research addresses NP 306, Quality and Utilization of Agricultural Products and NP 303, Plant Diseases.

3. ENHANCED FUNGICIDAL PROPERTIES OF SYRINGOMYCIN-E AND RHAMNOLIPID.

Syringomycin-E, a protein produced by the bacterium, Pseudomonas syringae, was determined in our lab in the past to be a potent fungicide. We determined that this protein, supplied by our cooperator at Utah State University, when combined with rhamnolipid, a microbially-produced detergent, was superior as a fungicide to syringomcin-E alone against many fungi such as A. flavus; A. niger; A. fumigatus; F. verticilioides (moniliforme); F. oxysporum; and F. solani, (see item 2 for the importance of these fungi) and a number of primary and secondary fungal pathogens of grapes.

This research addresses NP 306, Quality and Utilization of Agricultural Products and NP 303, Plant Diseases.


6.Technology Transfer

Number of Invention Disclosures Submitted1
Number of Non-Peer Reviewed Presentations and Proceedings1
Number of Other Technology Transfer1

Review Publications
Stergiopoulou, T., De Lucca II, A.J., Meletiadis, J., Sein, T., Boue, S.M., Schaufele, R., Roilides, E., Ghannoum, M., Walsh, T.J. 2008. In vitro activity of CAY-1, a saponin from Capsicum frutescens, against microsporum and trichophyton species. Medical Mycology. 46(8):805-810.

De Lucca Ii, A.J., Klich, M.A., Sien, T., Boue, S.M., Cleveland, T.E., Walsh, T.J. 2008. Fungicidal activity of the plant saponin, CAY-1, for fungi isolated from diseased Vitis fruit and stems. American Journal of Enology and Viticulture.59:67-72.

Last Modified: 4/20/2014
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