Peppers Put the “Heat” on Pests

By Jan Suszkiw
March 15, 2001

Cayenne pepper, a popular spice for flavoring food, is known for its heat-producing properties from the substance capsaicin. Agricultural Research Service scientists also have found that cayenne peppers contain another potent substance in the saponin chemical family that kills several noxious fungi and yeasts.

And because this pepper saponin, called CAY-1, is not toxic to human cells at microbial-killing doses, MycoLogics, Inc., a Denver, Colorado, firm, has begun testing its potential as a candidate drug for treating patients with fungal infections. MycoLogics is doing so under an agreement with ARS's Southern Regional Research Center in New Orleans, La., according to Anthony DeLucca, a microbiologist there.

He and chemists John Bland and Craig Vigo discovered CAY-1 during research to identify plant compounds that could be used as crop protectants against spoilage microorganisms such as Aspergillus fungi, which make aflatoxins. Cayenne peppers topped an unusual list of organisms--including Cecropia moths, tree frogs, and bacteria--that produce other novel antifungal compounds.

Though CAY-1 proved active against Aspergillus and other important microbial crop pests, DeLucca speculated its properties might also interest medical researchers seeking candidate drug compounds to fight emerging fungal threats to human health. That curiosity led to collaborative studies with National Institutes of Health scientist Tom Walsh, University of Cincinnati researcher Melanine Cushion, and MycoLogic president Claude Seltrennikoff.

In a paper undergoing peer review, they report results from bioassay studies in which germinating and non-germinating cultures of four bacterial, six fungal and one yeast species were exposed to different CAY-1 concentrations. For example, in one test against Candida albicans, which causes thrush and other human infections, a 2.6 microgram-per-milliliter dose curbed the microbe's growth by 93 percent. Additionally, none of the antimicrobial concentrations used caused harm to human cervix cell cultures. CAY-1 also wasn’t toxic to cells from lung tissue, where Aspergillus and Pneumocystis carinii fungi can cause serious infections in immuno-compromised patients.

ARS, the U.S. Department of Agriculture’s chief scientific research agency, has filed a patent on CAY-1.

Scientific contact: Tony J. De Lucca, ARS Southern Regional Research Center, New Orleans, La., phone (504) 286-4253, fax (504) 286-4419, adelucca@commserver.srrc.usda.gov.