Metabolic stability plants

Metabolism studies of methoprene in nonaquatic organisms have provided background data which must be considered prior to discussing the fate of methoprene in aquatic systems. All nonaquatic metabolic studies reported to date have utilized [5-1 C]methoprene. The location of radiocarbon was selected both for ease of synthesis and for anticipated metabolic stability. However, studies in plants and bovines (25, 30, 31) revealed many presumed "metabolites" to be radiolabeled natural products, or "nonmetabolite residues". Primary metabolites of methoprene resulting from ester cleavage and/or (O-demethylation have been... 

In this review, conjugation reactions utilized In xenobiotic metabolism In plants will be discussed In reference to functional groups, phase I reactions necessary to produce a functional group suitable for conjugation, relative rates of reactions, competing metabolic pathways, frequency of occurence, plant species, stability of conjugates, and the relationship between metabolism and herbicide selectivity. Pesticides discussed herein are listed In Table I. 

As already mentioned in Chapter 4.2, all known HPPD inhibitors are chelating agents. To exhibit not only in vitro but also in vivo activity additional requirements such as uptake, transport and metabolic stability in plants (especially weeds) are necessary. The market compounds and the long list of published HPPD molecules with the general structure 1 (Fig. 4.4.1) fulfill, normally, all these needs [1],... 

The same molecular properties - high water solubility and a low log Pow, combined with high metabolic stability in plants - were in the focus of our R D... 

The highest metabolic stabilities are seen with the oximino amides (orysastro-bin, metominostrobin and dimoxystrobin) and with the dihydrodioxazine (fluox-astrobin). This high level of stability is one of several prerequisites for applications where long-lasting fungicidal efficacy should be maintained while the active compound is intensively exposed to plant metabolic processes, e.g., after root uptake in rice. 

Besides its influence on biological activity, the pharmacophore is also responsible for some specific physicochemical properties such as photolytic stability, degradation behavior in soil, metabolism in plants and insects, and toxicity to different animals as well [3, 4, 5, 6, 7, 8]. 

In contrast, no insecticide has been developed to interfere specifically with the process associated with the steroidal insect molting hormone, 20-hydroxyecdysone. Although active ecdysteroids can be obtained from plant and animal sources (S), the main reason for the failure to develop them as insecticides has been that (a) their structures are too complex to produce economically, (b) their hydrophilic nature prohibits their penetration into insect cuticle, and (c) insects have powerful mechanisms to eliminate ecdysones between molts. One approach to solve these problems is to synthesize a simple molecule which can mimic ecdysone, but with appropriate chemical and transport properties, and acceptable metabolic stability. 

Possible exposure to pesticide-derived N,-nitroso compounds depends on environmental processes that influence formation, movement, and degradation of the compounds. Although laboratory studies have shown the feasibility of environmental nitrosamine formation, there has been little evidence that it is an important process. Nitrosamines vary greatly in their environmental stabilities, but all seem to be susceptible to one or more modes of decomposition including photolysis, microbiological degradation, and plant metabolism. 

PVP is a metabolically inert, water-soluble polymer with excellent protein stabilizing properties. As an example of the beneficial effect of PVP on foreign protein accumulation in plant tissue culture, data for growth and IgO, antibody levels in transgenic... 

In plants, catalase appears to have two functions. First is the ability to dispose of the excess H202 produced in oxidative metabolism, and second is the ability to use H202 in the oxidation of phenols, alcohols, and other hydrogen donors. The difference in heat stability of catalase and peroxidase was demonstrated by Lopez et al. (1959). They found that blanching of southern peas for one minute in boiling water destroys 70 to 90 percent of the peroxidase activity and 80 to 100 percent of the catalase activity. 

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