Herbicide design

One of the herbicides used extensively in this project was a herbicide designated as "Agent Orange which was formulated as a... 

Figure 22-20 Chromatograms of herbicides (designated 1-6) spiked into river water at a level near 1 ppb demonstrate increased signal-to-noise ratio in selected ion monitoring, (o) Ultraviolet detection at 240 nm (b) Electrospray reconstructed total ion chromatogram, (c) Electrospray selected ion monitoring at m/z 312. [From A. Lagana. G. Fago, and A. Marino, "Simultaneous Determination of imidazoiinone Herbicides from Soil and Natural Waters."Anal. Chem. 1998, 70.121.]...

The second step in the synthesis, catalyzed by acetohydroxyacid isomeroreductase, involves shift of an alkyl group (Fig. 24-17). Neither this reaction nor the preceding one occurs in mammals. For this reason, the enzymes required are both attractive targets for herbicide design.343 346 The third enzyme, dihydroxy acid dehydratase, catalyzes dehydration followed by tautomerization, resembling 6-phospho-... 

Where other books on this subject highlight the fuzzier aspects, this one covers the hard science. It explores the latest developments in the field, discusses structure-activity relationships and SAR studies, and provides a foundation for the development of new natural herbicides. Designed as a practical, bench-friendly book, AUelopatlty Chemistry and Mode of Action of Allelochemicals is a convenient, easy-to-use resource that puts the latest information within easy reach. 

As pointed out previously, most herbicides have been discovered using random screening programs rather than from an applied rational approach to herbicide design, target, and synthesis. A few attempts to rationally design herbicides chose Inhibition of sites of photophosphorylation uncouplers (284). glycol ate oxidase (285). oxidation of Indoleacetic acid (lAA) by peroxidase (286). and secondary plant metabolism, I.e., phenlyalanine ammonia-lyase (2SZ)... 

Xenoblotics That Alter Extractable PAL Activity. PAL Inhibition has been chosen as a site of action for herbicide design however, several herbicides and other chemicals were found to have no specific effect on PAL (I5S) Analogous results were obtained when herbicides encompassing the major herbicide classes were examined (139. 1601. 

Koblizek M, Maly J, Masojidek J et al. A biosensor for the detection of triazine and phenylurea herbicides designed using photosystem II coupled to a screen-printed electrode Biotechnol Bioeng 2002 78 110-116. 

Koblizek M., Maly J., Masoji dek J., Komenda J., Kucera T., Giardi M. T., Mattoo A. K., and Pilloton R., A biosensor for the detection of triazine and phenylurea herbicides designed using photosystem ii coupled to a screen-printed electrode, Biotechnol. Bioeng., 78(1), 110-116, 2002. 

The above mentioned molecules were pursued as targets primarily because 1) they represent new targets for herbicide design and 2) they incorporate aspects of the model compounds 3-5, which may result in new insights into SAR requirements for the herbicidal activity of amides and carbamates. Since the models for this work are photosystem II inhibitors, insight into the binding and receptor site at or near photosystem II was expected. 

Potent inhibition of the selected target may still not produce an effective herbicide. Studies of the iptake, translocation, and metabolism of the inhibitor are needed to determine if the cause of poor jn vivo performance is due to these factors or to an intrinsically poor target. Without full appreciation of each of these aspects of herbicide design, the chances for success with the target-site directed approach are reduced (Rendina, A., DuPont de Nemours and Co., Newark, DE, Personal Ocmmunication, 1992). 

The above findings demonstrated that there was good correlation between enzyme inhibition and herbicidal activity, suggesting that PDHc could be a target for new herbicide design and development. 

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