“This study describes the use of curcumin to inactivate spores of Aspergillus flavus, one of the major aflatoxin producing fungi in foods and feeds,” they reported in the journal Food Control.
The compound curcumin is a derivative of turmeric, and has natural polyphenolic properties, the Australian researchers said. The study demonstrates that the plant may be an “effective photosensitizer when combined with visible light,” they added.
“The results indicated curcumin mediated photosensitization had a significant effect on viability of A. flavus spores both in suspension and when inoculated in maize kernel surface,” said the authors. “Both in vitro and in vivo treatments had significant reduction of fungal spores when appropriate light intensities and dye concentrations were combined in photosensitization.”
Mycotoxin contamination can cause serious health problems to humans and animals including instant death in acute cases, and cancers; and studies also suggest that they cause immunosuppression, retard growth, and reproductive disorders with chronic exposures, said the researchers.
There are several ways to treat mycotoxins, ranging from the application of fungicide and pesticides to decontamination efforts after a crop has been harvested, they said. But no strategy has been completely effective.
“Photosensitization is a technique in which microbial cells are killed by cytotoxic reactions induced by energy derived from photosensitizer molecules that have been excited by light of specific wavelength,” said the scientists.
The best dye to use in the process would be edible, inexpensive and stable, they said. And, curcumin fits that description. However, only limited research has been done using the compound to counter mycotoxins.
In the study, researchers examined the effects of curcumin-mediated photo-inactivation of the mycotoxin both in an aqueous suspension and on maize kernels.
For the aqueous solution, reductions of mycotoxin spore count of up to three magnitudes of log were recorded using irradiation at 420 nm, a visible light range, researchers reported.
“The decrease in spore viability was directly proportionate to the dose of light and dye concentrations of 15–50 μM,” they said. “Reduction of viable spore count greater than 3 magnitude of log (close to zero count) was achieved when 84 J cm−2 light dose and 15, 25 and 50 μM curcumin dye concentrations were used,” they added.
There were no marked differences between the control groups – one of which received light with no curcumin and the other curcumin but no light.
Results were similar for the treated maize kernels, with a significant difference found in aflatoxin spore counts between treated and control groups, said the authors.
“Samples treated by photosensitization (light and dye applied, L+/PS+) had a significant CFU reduction of nearly 2 magnitude of log for both whole and milled kernels,” they reported.
In the aqueous experiment six levels of curcumin solution were exposed to four different levels of light along with control samples, said researchers. The solutions were exposed to visible light four times and each experiment was then run three times.
In the maize experiment, sterilized maize kernels were soaked in a spore suspension containing A. flavus and then dried, they said. Several whole kernels were treated with immersion in 0µM, 25 µM or 45 µM solutions of curcumin and then illuminated. The kernels were again dried and a spore count was taken.
Other kernels of maize were similarly immersed in curcumin solution and dried, the scientists reported. However, those kernels were thin milled and exposed to light before a spore level determination was made.
Although the trials were an initial test of the compound’s mycotoxin reduction abilities, results suggest that it could be used to help reduce contamination levels in food and feed sources as the curcumin solution could be applied before crops are sun dried, said the researchers.
"For this study we only studied the effect of photosensitization on the spores of Aspergillus flavus and not the aflatoxin," said Yasmmina Sultanbawa, senior research fellow at the Queensland Alliance for Agriculture and Food Innovation at the University of Queensland.
She told FeedNavigator: "Our next study is targeting the effect on aflatoxin to determine if the light treatment would result in the breakdown of the aflatoxin to less toxic metabolites. At this stage it will reduce the number of spores if used as a post-harvest decontamination treatment."
Source: Food Control
Title: Inactivation of Aspergillus flavus spores by curcumin-mediated photosensitization
Authors: B Temba, M Fletcher, G Fox, J Harvey, Y Sultanbawa