Studies in selective toxicity. III.—Benzenesulphonanilides as DDT‐synergists

Abstract

Benzenesulphonanilides with halogen or methyl substituents in the phenyl radicals, with or without N‐alkyl substituents, were assayed as DDT‐synergists against DDT‐resistant houseflies. Contrasting test methods provided a guide to the intrinsic biological activity of the synergists, and to their ‘availability’ for insects by pick‐up from residual deposits and by absorption through the cuticle. The homologous series of N‐n‐alkyl‐4‐chloro‐ and ‐4‐bromo‐benzenesulphon‐4′‐chloro‐anilides were studied. In both series the biological response to topical application of dilute toxicant solutions was highest for the N‐methyl compounds. The ‘availability’ from deposits appeared highest in the intermediate range C4 to C8. In this range the ‘availability’ appeared to oscillate between homologues having an odd number and those having an even number of carbon atoms. The homologues in the medium range showed a high solubility in kerosene. Homologues above C9 showed no biological activity. The possible modes of action and penetration of the benzenesulphonanilide synergists are discussed.

Century of DDT

“…The high activity of synergists such as p-chlorobenzenesulfon-pchloroanilide (SR 108) was described by Speroni (1952) and emphasized the structural similarity of such compounds to DDT. This led to the development of p-chlorobenzene N,IV-dibutylsulfonamide as an oil-soluble synergist for DDT (Neeman et al, 1957).…”

The inhibition of 1,1,1-trichloro-2,2-bis-(p-chlorophenyl)ethane (DDT) dehydrochlorinase and gluthathione S-aryltransferase in grass-grub and housefly preparations

“…These compounds represent new types of structure, which may serve as synergists for the insecticide in resistant insects where the resistance is due to increased detoxication. Previous attempts to find synergists for DDT have concentrated on compounds having a structural similarity to DDT (March, Metcalf & Lewallen, 1952;Speroni, 1952;Neeman, Mer, Cwilich, Modiano & Zacks, 1957;Metcalf, 1965). These compounds have been assumed to compete with DDT for the detoxication enzyme and to decrease the amount of detoxication product formed (Moorefield & Kearns, 1955).…”

DDT substitutes

“…This compound was found by Perry, Mattson, and Buckner (1953) to inhibit the in vivo detoxication of DDT to DDE, as shown in Table 3. Subsequent study of a variety of DDT analogues, i.e., compounds with 2 bridged phenyl rings and p, p'-substituents (March et al, 1952, Speroni, 1952, Neeman et al, 1957, Blum et al, 1959, and Tahori, 1955, showed many compounds that act strongly as synergists by their synergistic ratios (SR) or the LD SO of DDT/LD 50 of DDT plus synergist. Examples of the most active compounds and their synergistic ratios include:…”

“…Thus its contact LD 50 to the American cockroach Periplaneta americana is 10 mg/kg body weight and its intraperitoneal LD 5 0 is 8 mg/kg. For the rat, however, the contact (dermal) LD S0 is about 3,000 mg/kg as compared to an intraperitoneal LD 50 of 150 mg/kg and an intravenous LD SO of 50 mg/kg (O'Brien, 1967). This differential absorption puts insects at a great disadvantage in an environment contaminated with DDT and provides a large margin of safety in the use of DDT.…”