Chemical properties of catechols and their molecular modes of toxic actionin cells, from microorganisms to mammals

Catechols can undergo a variety of chemical reactions. In this review, we p articularly focus on complex formations and the redox chemistry of catechol s, which play an inportant role in the toxicity of catechols, In the presen ce of heavy metals, such as iron or copper, stable complexes can be formed. In the presence of oxidizing agents, catechols can be oxidized to semiquin one radicals and in a next step to o-benzoquinones. Heavy metals may cataly se redox reactions in which catechols are involved. Further chemical proper ties like the acidity constant and the lipophilicity of different catechols are shortly described as well. As a consequence of the chemical properties and the chemical reactions of catechols, many different reactions can occu r with biomolecules such as DNA, proteins and membranes, ultimately leading to non-repairable damage. Reactions with nucleic acids such as adduct form ation and strand breaks are discussed among others. Interactions with prote ins causing protein and enzyme inactivation are described. The membrane-cat echol interactions discussed here are lipid peroxidation and uncoupling. Th e deleterious effect of the interactions between catechols and the differen t biomolecules is discussed in the context of the observed toxicities, caus ed by catechols.