Effect of oxidant stressors and phenolic antioxidants

24 BACKGROUND. There are few studies dealing with the relationship between 25 oxidative stress and ochratoxin A (OTA). In this work we have analyzed the effect 26 of the oxidant stressor menadione and the antioxidpmants 3,5-di-tert-butyl-427 hydroxytoluene (BHT), catechin, resveratrol and a polyphenolic extract on growth, 28 generation of reactive oxygen species (ROS), OTA production and gene 29 expression of antioxidant enzymes of Aspergillus carbonarius. 30 RESULTS. Exposure to menadione concentrations higher than 20 μM led to 31 increases in ROS and OTA levels and to a decrease in growth rate. Exposure to 32 2.5-10 mM BHT also led to higher ROS and OTA levels, although growth rate was 33 only affected above 2.5 mM. Naturally occurring concentrations of catechin, 34 resveratrol and polyphenolic extract barely affected growth rate, but they produced 35 widely different effects on OTA production level depending on the antioxidant 36 concentration used. In general, gene expression of antioxidant enzymes 37 superoxide dismutase (SOD) and peroxiredoxin (PRX) was down regulated after 38 exposure to oxidant and antioxidant concentrations that enhanced OTA 39 production. 40 CONCLUSION. A. carbonarius responds to oxidative stress increasing OTA 41 production. Nevertheless, the use of naturally occurring concentrations of 42 antioxidant phenolic compunds to reduce oxidative stress is not a valid approach 43 by itself for OTA contamination control in grapes. 44 45