Ochratoxin A (OTA) is a mycotoxin produced by some Aspergillus and Penicillium
species which is often detected in beer, cereals, coffee, feeds, figs, sultanas and
wine. Some fungicides have been found to be effective in preventing fungal
growth, but, in other cases, an increase in the synthesis of mycotoxins was
reported. Also, the pressure to use less harmful compounds to the environment
stimulates the exploration of new and more benign compounds.
Synthetic compounds were tested on the growth and OTA production of one strain
of A. alliaceus, A. ochraceus, A. carbonarius and A. niger. These new synthetic
compounds have a linear structure incorporating urea and/or a phenolic unit.
Fungi were grown in yeast extract sucrose (YES) medium supplemented with 50
μM to 200 μM of each one of 20 test compounds in triplicate, for 6 days. Growth
was recorded by measuring the diameter of colonies every 24 hours, and OTA was
quantified after 5 days of growth using HPLC and fluorescence detection.
Growth of the A. ochraceus and the A. carbonarius strains were not inhibited by
most of these compounds. However, some led to a decrease in OTA detection.
Compounds without the phenolic unit were found to be less effective, while those
compounds with urea and phenolic units were the most effective. Growth of the A.
alliaceus and of the A. niger strains were inhibited by compound-X by 22 and 27%
respectively.
This approach will lead to the selection of functional groups able to inhibit the
synthesis of OTA which could be incorporated into more powerful antifungal
compounds.Fundação para a Ciência e a Tecnologia (FCT) - SFRH/BD/11228/2002, SFRH/BD/3185/2000, SFRH/BPD/12044/2003