Tree Nut Research May Unexpectedly Lead to Medical Advances

Petri-dish experiments conducted by now-retired Agricultural Research Service (ARS) research leader Bruce C. Campbell, ARS molecular biologist Jong H. Kim, and their co-investigators suggest that pairing conventional antifungal medicines with natural, edible compounds from plants—such as thymol, extracted from the popular herb thyme—can boost the healing effects of some of these drugs. ARS is the chief intramural scientific research agency of USDA.

Campbell and Kim's work at the ARS Western Regional Research Center in Albany, Calif., with species of Aspergillus mold, for example, has attracted the attention of medical and public health researchers. Found worldwide in air and soil, Aspergillus can infect corn, cotton, pistachios, almonds and other crops, and can produce aflatoxin, a natural carcinogen.

Aflatoxin-contaminated crops must be identified and removed from the processing stream, at times resulting in large economic losses. Since 2004, Campbell, Kim, and colleagues have carefully built a portfolio of potent, plant-based compounds that kill a target Aspergillus species, A. flavus, or thwart its ability to produce aflatoxin.

Further research and testing might enable tomorrow's growers to team the best of these natural compounds with agricultural fungicides that today are uneconomical to use, according to Kim.

A. flavus and two of its relatives, A. fumigatus and A. terreus, may impact the health of immunocompromised individuals exposed to the fungus in moldy homes. In a 2010 article in Fungal Biology, the team reported that thymol, when used in laboratory tests with two systemic antifungal medications, inhibited growth of these fungi at much lower-than-normal doses of the drugs.

A related study provided new evidence to support earlier findings, at Albany and elsewhere, which had suggested that plant compounds such as thymol may sabotage a target fungi's ability to recover from oxidative stress triggered by antifungal drugs. A 2011 article published by Kim, Campbell and others in Annals of Clinical Microbiology and Antimicrobials documents this research.

Using plant-derived compounds to treat fungal infections is not a new idea, nor is that of pairing the compounds with antifungal medicines. But the Albany team's studies have explored some apparently unique pairs, and have provided some of the newest, most detailed information about the mechanisms likely responsible for the impact of powerful combinations of drugs and natural plant compounds.

Read more about this research in the October 2012 issue of Agricultural Research magazine.