Vanadate reduction by caffeic acid: a mechanism of biological importance

In the apoplasm, the toxicity of V(V) and V(IV) can be limited through redox and complexation reactions involving phenolic substances and polyuronic components. In such a context, we report about the reducing activity of caffeic acid (CAF) towards V(V) and the role of polygalacturonic acid (PGA) on this redox reaction. The results show that the reaction, particularly fast in the 2.0-3.0 pH range, leads to the formation of oxidation products of caffeic acid, also active in the reduction of V(V). The redox reaction is faster in presence of polygalacturonic acid that acts as a complexing agent of V(IV) ions in the whole pH range (2.5-6.0) investigated.