Role of some neosynthesized styryl heterocycles in ochratoxin a control in Aspergillus carbonarius

Ochratoxin A (OTA) is a mycotoxin whose dangers have been sufficient for many countries to regulate its presence in various foods. In Mediterranean countries, the black Aspergilli group, in particular Aspergillus carbonarius, causes the highest OTA contamination in fruit. Here we describe the synthesis of three novel styryl heterocyclic compounds and their effect on (1) the prevention of OTA biosynthesis by A. carbonarius cultured in a conducive liquid medium, (2) Reactive Oxygen Species (ROS) formation, and (3) lipoxygenase (LOX) activity. The most effective control of OTA biosynthesis was achieved with (E)-3-(3,4-dimethoxystyryl)- thiophene. In fungal cultures treated with this compound at 5, 25, 50, and 100 ppm, OTA biosynthesis decreased by 45% to 95% until the experiment's conclusion (8 days). (E)-3-(3-methoxy-4-acetoxy-styryl)-thiophene significantly inhibited OTA biosynthesis (by about 50%). However, this effect lasted for only few days when used at 5 or 25 ppm and up to 8 days when used at 50 or 100 ppm; (E)-3-(3-methoxy-4-hydroxy-styryl)-thiophene did not exert any control on OTA biosynthesis. The same compounds also were assayed for their ability to affect LOX activity and ROS formation. The compounds able to control OTA biosynthesis also significantly inhibited ROS formation and LOX activity. The nature of the substituent in para position strongly affects the molecule's reactivity. Lower reactivity enhances the inhibition of OTA biosynthesis, in particular long-term. Natural compounds present in edible plants having a styryl heterocyclic scaffold may be effective inhibitors of OTA biosynthesis.