Plant xenobiotic conjugates in animals

EDWARDS AND HUTSON Plant Xenobiotic Conjugates in Animals... 

The fate of plant xenobiotic conjugates I.e. glycosides, malonates, N-acyl-amlno acids, alkyl/aryl glutathiones and derivatives, lipophilic conjugates and polymer conjugates (bound residues). In animals Is reviewed. Some classes are reasonably well-studied but no Information Is available for others. 

The conjugation of xenobiotic compounds In plants has been described In relation to that In some other life forms In the first section of this Symposium. It Is apparent that the processes are similar among among the various taxa but that some notable differences are found both In the chemistry and the disposition of the conjugates. This chapter deals with a relationship between plants and animals, mostly mammals, and therefore a comparison of conjugation In plants and animals Is shown In Table I. The observed differences are Important because It Is from these differences that the requirement to study the fate of xenobiotic plant conjugates In animals Is derived. 

A number of enzyme systems have evolved in animals and plants which effectively convert lipophilic xenobiotics to more polar compounds that are efficiently excreted. Phase I enzymes, responsible for oxidation, reduction, and/or hydrolysis, are integrated with phase II or conjugation enzymes for reactions of both types and are normally required for the formation of products polar enough to be readily excreted. The intracellular level of these enzymes, and thus, the capacity for biotransformation, increases in a coordinate fashion in response to exposure to xenobiotic compounds. This response is... 

While the conjugates are safely trapped to the cell wall as the plant is alive, the soluble conjugates in the vacuole may become liberated quickly after the plant is dead. Research showed that polymerization of xenobiotics into lignin did not prevent the bioavailability. Sandermann demonstrated that dichloroanilin in wheat straw was liberated when feeding animals. Research about the availability of residues is mainly focused on pesticides, insecticides, and drugs. A similar research on ordinary contaminants will shed light on the study of phytoremediation. 

Xenobiotics that contain a free or potential carboxyl group can be metabolized by amino acid conjugation in both plants and animals. This reaction is illustrated by the conjugation of 2,4-D with aspartic acid (Equation 31). In higher plants, amino acid conjugation is... 

Most xenobiotic conjugation reactions in plants and animals lead Initially to the fornation of polar products such as glycoside or glutathione conjugates, but several reports indicate that plants (144-148) and animals (249) may also form lipophilic conjugates. 

This paper sumnarlzes the occurrence of unusual xenobiotic conjugates which are substantially Ionized In animals and plants. Such conjugates generally are deemed "unusual" either because they occur rarely or because their existences seldom are documented, often by virtue of recent discoveries. 

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