Phase II - Introduction
Phase II reactions are also known as conjugation reactions. Conjugation reactions are anabolic processes which, in general, form compounds of higher molecular weight with greatly reduced biological activity, increased water solubility and usually reduced mobility. Major herbicide conjugates in plants are: simple and complex glucosides, glutathione conjugates and amino acid conjugates. Phase I metabolites of xenobiotics or those molecules which contain phenolic, N-arylamine, or carboxylic groups are rapidly conjugated in plants. In mammals, however, sulfate, glucuronic acid, and glutathione conjugates usually predominate. Although conjugates are excreted from animal systems, they remain in plant systems as conjugates or the conjugates are incorporated into insoluble polymers during Phase III reactions. Any toxicity remaining after Phase I is usually reduced further by Phase II reactions.