Redox Potential and Toxicity

Many examples exist that show the profound influence of oxidation-reduction reactions on the manifestation of toxicity. Examining several examples here will illustrate the effect of redox state of a molecule. 

Nitrate and nitrite are regulated in drinking water as pollutants that ean cause methaemoglobinaemia in children at elevated concentrations. However, the toxicity is dependent directly to the nitrite ion, which is the oxidized form of the nitrate anion that binds to haemoglobin and inhibits oxygen from binding. 

The toxicity of chromium is profoundly related to its oxidation state, whether the metal is in the +3 or +6 oxidation state. Chromium is a naturally occurring metal that is widely used for industrial purposes including plating, leather tanning, as a dye and as a wood preservative. Trivalent chromium (Cr ) is an essential trace nutrient required for proper glucose metabolism and other biological functions. 

The cytochrome P450 (GYP) family of enzymes are the major catalysts that are responsible for a variety of oxidation reactions associated with the biotransformation of many xenobiotics that can be used to illustrate several concepts of toxication and detoxication in a chemistry course. The main function of this group of isozymes is to insert one atom of oxygen into a substrate thereby increasing hydrophilicity or water solubility. These enzymes are haem-containing proteins containing a reduced iron species essential for transferring electrons and work in concert with coenzymes NADPH and NADPH reductase. 

The biotransformation of xenobiotics is catalysed by a number of enzymes that be divided into classes of reactions. These are hydrolysis, reduction, oxidation, conjugation. These reactions are part of the current curriculum and therefore provide an opportunity for connecting chemistry and toxicology. 

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