DDT analogs

Although a lipoid-soluble group characterizes many contact insecticides, simple oil-solubility of a compound is not always a criterion of activity. Busvine (14) tested a series of DDT analogs and found that solubility in oil was not essential to activity. Kirkwood... 

Table I. Dehydrochlorination-Rate Constants and Insecticidal Activity of DDT Analogs...

These data lead to the conclusion that, contrary to the hypothesis of Martin and Wain, there is no statistically significant relationship between dehydrochlorination rate and insecticidal activity in DDT analogs, at least as regards activity against A. quadri-maculatus larvae. Similar comparisons of insecticidal data against adult houseflies (11,12),... 

Lund AE, Narahashi T (1983) Kinetics of sodium channel modification as the basis for the variation in the nerve membrane effects of pyrethroids and DDT analogs. Pestic Biochem Physiol 20 203-216... 

Gardner, D.R. and Vincent, S.R. Insecticidal and nenroexitant actions of DDT analogs on the cockroach. Periplaneta americana, Bull Environ. Contam. Toxicol, 20(3) 294-302, 1978. 

The results of the studies will be summarized. Details of the QSAR analyses are or will be published elsewhere, including intercorrelation matrices of the steric parameters mentioned. But relevant conclusions from e.g. intercorrelations will be dicussed. At this moment the STERIMOL method has been applied successfully in about 50 publications often with better results than other steric approaches, including MTD and MTD, especially in series with few substituent positions. A recent example is our study of DDT analogs. Brown et al. (9J analysed a series of 21 derivatives using the van de Waals (Vw) volumes as steric parameters. In Table I the equations are given in which the steric parameters are compared. 

Table I. Comparison of Vw, MSD, MTD, MTD and STERIMOL parameters in a series of 21 DDT analogs with activity against Culex fatigans. ...

Figure 4. Standard used in Equation 4 to obtain MTD values in a series of DDT analogs.

The choice between the STERIMOL and MTD approaches is dependent on some properties of the series studied, e.g. the number of members in relation to the number of substitution positions In those cases where the resulting degrees of freedom are sufficient, the STERIMOL approach gives the most satisfactory results (e.g. in the studies on the DDT analogs and to a lesser extent in benzoylphenylureas Table VII). But in opposite cases,... 

Holan proposed that the benzylic substituents of DDT analogs would fit into the channel of a pore in the cell membrane to induce leakage of Na+ ion 80). He demonstrated that the optimum dimension in diameter of the benzylic substituents is about... 

Another example that supports the postulate that a decrease in log Poct results when water wins the competition to a hindered P-site comes from the DDT analogs shown in Table 5.8. 

The phenomenal success of DDT stimulated further research, and by 1946 the two DDT analogs, DDD and methoxychlor (Table 1,A) had been produced (Tables are at the end of the chapter). The observation of greater insecticidal activity in those organochlorine compounds that lose their HC1 more easily led to yet another group of chlorinated derivatives, the condensed ring chlorocyclodienes (Table 1,B). Thus, nearly all of the chlorinated pesticides currently in use had been... 

When soils from two Oregon orchards were examined for residues of hdogenated insecticides, most of the residues found were DDT analogs and metabolites. Approximately 40% of the DDT applied to the orchards since 1946 is still present in the soil, most of it in the top 12 inches. Only traces of these pesticides are found at the 3-foot depth. Part per billion levels of the pesticides were present in water thought to emanate from one of the orchards. Waste land adjacent to the orchards has accumulated about 5 pounds of DDT per acre. Considering all avenues of loss except evaporation and degradation, approximately 50% of the DDT applied to the orchards has been accounted for. 

Table II. Vertical Distribution of DDT Analogs and Metabolites, Medford Orchard Soils, 1965 a...

The discovery of DDT led to the synthesis of several effective DDT analogs, such as tetrachlorodiphenylethane (TDE), methoxychlor, dicofol, and chlorobenzilate (Figure 4.1). TDE is also called DDD (dichlorodiphenyldichloroethane). These analogs are less toxic than DDT to mammals. Their oral LD50 values in rats are methoxychlor, 600 mg/kg TDE, 3400 mg/kg dicofol, 570-595 mg/kg and chlorobenzilate, 2784-3880 mg/kg. The last two compounds have very little insecticidal activity but are good acaricides. 

Bitman J, Cecil HC. 1970. Estrogenic activity of DDT analogs and polychlorinated biphenyls. J Agric Food Chem 18 1108-1112. 

Enhancement of Veratridine-Dependent Sodium Channel Activation by Pyrethroids and DDT Analogs... 

Pyrethroid insecticides (deltamethrin, NRDC 157, cismethrin), DDT analogs ( p,j> -DDT, (>,j> -DDT, methoxychlor, EDO), and a DDT-pyrethroid hybrid compound (GH401) enhanced veratridine-dependent sodium uptake by mouse brain synaptosomes The effectiveness of these compounds in the sodium uptake assay was in good agreement with their acute mammalian toxicities. , -DDT also enhanced veratridine-dependent sodium uptake by fish brain synaptosomes These findings demonstrate the utility of ion flux assays to study interactions of insecticides with sodium channels in the central nervous system and to explore species differences in insecticide target site sensitivity ... 

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