**Author details**

those with an even number are degraded to herbicidally inactive phenols [21]. The occurrence of resistance in weeds to triallate has been attributed to reduced sulfoxidation, i.e., bioactivation, rates. The photosynthesis inhibitor *N,N*-dimethyl phenylurea diuron is converted into the corresponding *N*-methyl phenylurea DCPMU upon oxidative phosphorylation [22]. Dealkylation of the *N*,*N*,*N*\_,*N*\_-tetraethyl triazine derivative chlorazine to trietazine then to simazine increases the photosynthesis inhibitory activity by several orders of magnitude. For the rice herbicide thiobencarb (*S*-4-chlorobenzyl diethylthiocarbamate), reductive dehalogenation occurring in soil yields the *S*-benzyl derivative, believed to be responsible for phytotoxicity *in vivo.* These are meant for controlling weeds. Some of the proherbicides along with their active metabolites and activation processes are

Although commonly used structural modifications, carried out during routine structureactivity relationship studies and lead structure optimizations, affect both pharmacokinetics and pharmacodynamics, chemical alterations used in propesticide design are aimed to improve the biological profile by optimizing exclusively the pharmacokinetics of the toxicant.

Altered physicochemical properties leading to improved stability, solubility, or lipophilicity

Delayed or sustained action due to the slow release of the active agent from its derivatives.

Increased selectivity, that is, decrease toxicity toward non-target species, due to different

The structural and metabolic diversity of various pest control chemicals shown above demonstrates the usefulness of the "Trojan horse" principle of chemical formulation. Future research efforts, either capitalizing on known pesticide design practices or discovering new ones based on differences between the xenobiotic metabolisms of various organisms, will lead to new and selective agrochemicals that find and hit the target enzyme or receptor of the pest as

given in the **Table 3**.

114 Insecticides - Agriculture and Toxicology

**ii.** *Sustaining activity*

**iii.** *Increases selectivity*

**7. Conclusion**

"magic bullets."

**6. Environmental utility of propesticides**

**i.** *Alteration of physicochemical properties.*

influencing distribution in organism (systemicity).

metabolism of the parent compound and its derivatives.

Potential advantages of a propesticide can be summarized as follows:

Shaon Kumar Das<sup>1</sup> \* and Irani Mukherjee<sup>2</sup>

