Plants xenobiotics levels

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... 

Knowles and Milner, 2000). Furthermore, these compounds are thought to be involved in the inhibition of certain cytochrome P-450 enzyme-dependent bioactivations of procarcinogens and protoxicants (Brady et al., 1991), as well as to increase levels of glutathione-S-transferase (GST), an enzyme of particular importance in the detoxification of xenobiotics in the body (Wilce and Parker, 1994). Most recently, the ability of various plants and plant extracts to influence apoptosis, or programmed cell death, in cancerous cells in an attempt to arrest their proliferation, has been the topic of much research. Allicin has been shown to induce apoptosis in a variety of cell lines, including human hepatocellular carcinoma cells (KIM-1) and human lymphoid leukemia (MOLT-4B) cells (Thatte et al., 2000). 

Several xenobiotics that are metabolized by GSH conjugation In plants, Including atrazine, propachlor, and PCNB, produce significant levels of bound residue (15). It appears that the bound residue may be formed from the GSH pathway with either a cysteine conjugate or a thiol as a precursor 1 5). The chemical nature of these bound residues has not been determined. 

Figure 4. Scheme of interactions between active oxygen generating xenobiotics and the oxygen detoxification system. Light intensity, the rate constants of photogeneration of active oxygen, dissipation of the xenobiotics and the levels and rate constants of the enzymes interact to determine whether a plant will be spared or killed. 

Toxicology is a science that deals with the effects of poisons on living organisms. A poison or toxicant is a substance that, above a certain level of exposure or dose, has detrimental effects on issues, organs, or biological processes. Many toxicants are xenobiotic materials, but not only xenobiotic species are toxicants. Among the toxicants, we should mention different pollutants in air, soil, water, plant and other environments in Asia that we have discussed in previous chapters. 

Many chiral xenobiotics are lipophilic and, thus, these pollutants are absorbed into plants and may accumulate to toxic levels. The fate and bioconversion of chiral xenobiotics in plants is, therefore, of importance to the natural world as a whole, and to agriculture and human health. The levels of xenobiotics in plants can be reduced by elimination via roots and leaves, or by metabolism. Again, the rate and the fate of the phytotransformed products depend on various environmental conditions and the concentrations of the xenobiotics. 

Low ecotoxicity. Because preservatives are used with the intention to kill microorganisms, the products are dangerous for microbes in the environment. As mentioned for the human toxicity the microbiocides loose their activity when diluted below the no-effect-level. The most important outlet into the environment is the waste water treatment plant (WTP). It is important to keep in mind that the elimination of xenobiotics in the WTP is strongly depending on the adaption of the bacteria. Bacteria adapt their enzyme battery if faced to sub-lethal doses of a microbiocide. 

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