Insecticides cyclodienes

Cyclodienes. These are polychlorinated cycHc hydrocarbons with endomethylene-bridged stmctures, prepared by the Diels-Alder diene reaction. The development of these insecticides resulted from the discovery in 1945 of chlordane, the chlorinated adduct of hexachlorocyclopentadiene and cyclopentadiene (qv). The addition of two Cl atoms across the double bond of the ftve-membered ring forms the two isomers of chlordane [12789-03-6] or l,2,4,5,6,7,8,8-octachloro-2,3,3t ,4,7,7t -hexahydro-4,7-methano-lJT-indene, QL-trans (mp 106.5°C) and pt-tis (32) (mp 104.5°C). The p-isomerhas signiftcantiy greater insecticidal activity. Technical chlordane is an amber Hquid (bp 175°C/267 Pa, vp 1.3 mPa at 25°C) which is soluble in water to about 9 fig/L. It has rat LD qS of 335, 430 (oral) and 840, 690 (dermal) mg/kg. Technical chlordane contains about 60% of the isomers and 10—20% of heptachlor. It has been used extensively as a soil insecticide for termite control and as a household insecticide. 

Lindane is one of eight different hexachlorocyclohexane (HCH), C H Cl, isomers and its Chemical Abstract n.2cniQ is la, 2a 3P, 4a, 5a 6P-hexachlorocyclohexane [58-89-9] (y-HCH or y-BHC, ben2ene hexachloride) (80). Commercial products containing lindane are marketed as either a mixture of isomers or as the pure y-BHC isomer. Not unexpectedly, lindane is a highly stable lipophilic compound and it has been used extensively worldwide as an insecticide. In contrast, hexachloropentadiene, C Cl, is an extremely reactive industrial intermediate used as a chemical intermediate in the synthesis of a broad range of cyclodiene-derived pesticides, which include endosulfan, endrin, heptachlor, and several different organohalogen flame retardants (81). 

Balasubramaniam E, Paul V, Jayakumar AR, et al. 1996. The effect of chronic cyclodiene insecticide treatment on some pharmacological actions of diazepam in rats. Environ Toxicol and Pharm(2) 141-146. 

Flodstrom S, Warngard L, Hemming H, et al. 1988. Tumor promotion related effects by the cyclodiene insecticide endosulfan studied in vitro and in vivo. Pharmacol Toxicol 62 230-235. 

Gant DB, Eldefrawi ME, Eldefrawi AT. 1987. Cyclodiene insecticides inhibit GABA receptor-regulated chloride transport. Toxicol Appl Pharmacol 88 313-321. 

Tumer KO, Syvanen M, Meizel S. 1997. The human acrosome reaction is highly sensitive to inhibition by cyclodiene insecticides. J Androl 18(6) 571-575. 

The organochlorine insecticides (henceforward OCs) can be divided into three main gronps, each of which will be discnssed separately in the sections that follow. These are (1) DDT and related componnds, (2) the cyclodiene insecticides, and (3) isomers of hexachlorocyclohexane (HCH Brooks 1974 Fignre 5.1). 

The cyclodiene insecticides aldrin, dieldrin, endrin, heptachlor, endosulfan, and others were introduced in the early 1950s. They were used to control a variety of pests, parasites, and, in developing countries, certain vectors of disease such as the tsetse fly. However, some of them (e.g., dieldrin) combined high toxicity to vertebrates with marked persistence and were soon found to have serious side effects in the field, notably in Western European countries where they were extensively used. During the 1960s, severe restrictions were placed on cyclodienes so that few uses remained by the 1980s. 

Apart from the oxidations just mentioned, cyclodienes are rather stable chemically. It should, however, be noted that dieldrin can undergo photochemical rearrangement under the influence of sunlight to the persistent and toxic molecule photo dieldrin, which occurs as a residue following the application of this insecticide in the field. 

In one example (Lawrence and Casida 1984, Abalis et al. 1985) rat brain microsacs were used to test the action of cyclodiene insecticides such as dieldrin and endrin on the GABA receptors contained therein. The influx of radiolabeled CL into the microsacs via the pore channel of the receptor was inhibited by these chemicals. A similar assay was developed using microsacs from cockroach nerve. Assays with this preparation showed again the inhibitory effect of a cyclodiene (this time heptachlor epoxide) on CL influx. Also, that microsacs from cyclodiene resistant cockroaches were insensitive to the inhibitory effect of picrotoxinin, which binds to the same site on the GABA receptor (Kadous et al. 1983). 

Cyclodienes A group of organochlorine (OC) insecticides, some of which are highly toxic and persistent (e.g., aldrin, dieldrin, and heptachlor). 

Abalis, I.M., Eldefrawi, M.E., and Eldefrawi, A.T. (1985). High affinity stereospecific binding of cyclodiene insecticides and gamma HCH to GABA receptors in rat brain. Pesticide Biochemistry and Physiology, 24, 95-102. 

Walker, C.H. and Newton, 1. (1998). Effects of cyclodiene insecticides on the sparrowhawk in Britain—a reappraisal of the evidence. Ecotoxicology 7, 185-189. 

TR. Dombrowski, E.M. Thurman, and G.B. Mohrman, A first application of enzyme-linked immunosorbent assay for screening cyclodiene insecticides in ground water, in Environmental Immunochemical Methods, ed. J.M. Van Emon, C.L. Ger-lach, and J.C. Johnson, American Chemical Society, Washington, DC, pp. 148-154 (1996). 

L.H. Stanker, B. Watkins, M. Vanderlaan, R. Elhs, and J. Rajan, Analysis of heptachlor and related cyclodiene insecticides on food products, in Immunoassays for Trace Chemical Analysis, ed. M. Vanderlaan, L.H. Stanker, B.S. Watkins, and D.W. Roberts, American Chemical Society, Washington, DC, Chapter 12, pp. 108-123 (1991). 

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