Epoxides cyclodiene

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). 

Chan, T.M., Gillett, J.W. and Terriere, L.C. Interaction between microsomal electron transport systems of trout and male rat in cyclodiene epoxidation. Comp. Biochem. Physiol. (1967), 20, 731-7 +2. 

Gillett JW, Chan TM. 1968. Cyclodiene insecticides as inducers, substrates, and inhibitors of microsomal epoxidation. J Agric Food Chem 16 590-593. 

Chlordane was introduced as an insecticide in 1945 and was the first cyclodiene insecticide that was used in agriculture (Eisler, 1990). It was the second most important organochlorine pesticide after toxaphene from 1976 to 1977 (Stansley Roscoe, 1999). It has been used on agricultural crops and extensively in the control of termites (Smith, 1991). Chlordane and heptachlor can be metabolized into two persistent (oxygenated) epoxides—oxychlordane and heptachlor epoxide—in mammals (Nomeir Hajjar, 1987) such that the two compounds are always measured together with chlordane and heptachlor. 

The first chlordane-related mortality was of three wild birds and was recorded between 1978 and 1981 (Blus et al., 1983). The levels of chlordanes and heptachlor epoxide from the two adult male red-shouldered hawks (Buteo lineatus) and an adult female great horned owl (Bubo virginianus) were within the critical lethal range that has been defined by experimental studies (heptachlor epoxide in brain tissue 3.4-8.3 pg g-1 wet wt. oxychlordane in brain tissue 1.1 5.0 pg g-1 wet wt.). The chlordane poisoning of birds has been reported in several studies in the United States (Blus et al., 1983, 1985 Post, 1951 Stansley Roscoe, 1999). From 1986 to 1990, 122 cases of avian mortality due to chlordane and/or dieldrin were documented in New York, Maryland and New Jersey (Okoniewski Novesky, 1993). High pesticide concentrations were found in cyclodiene-resistant insect populations. These pesticide-tainted insects, when eaten by birds, caused mortalities in the avian populations (Okoniewski Novesky, 1993). 

Cyclodienes are an important group of chlorinated pesticides. The group hep-tachlor includes insecticides such as chlordane, aldrin, dieldrin, endosulfan, and heptachlor and its epoxide. These are used for the control of a variety of plant pests in agriculture and household environments. The entry of cyclodienes to the global market has created easy management for the control of crop pests. They appeared after World War II as tools to protect food crops and control diseases from pests. In fact, humans were protected from malaria, typhus, and loss of food crops by pesticides. 

In the mid-1960s we showed firstly that the natural tolerance of houseflies to cyclodienes resulted mainly from oxidative detoxication (33 55) and secondly that another enzyme system, epoxide hydrase, converted certain dieldrin analogues into the corresponding trans-diols, (56,57) Interspecific differences in ability to attack enzymatically the unchlorinated ring systems of various analogues, either oxidatively and/or hydratively (if appropriate) can confer selective toxicity between insect species and also between insects and mammals (58) ... 

Epoxidation Epoxidation is an important microsomal reaction. For example, the cyclodiene insecticide aldrin can be oxidized to its epoxide dieldrin (as shown in Chapter 4, Figure 4.4), and heptachlor is oxidized to heptachlor epoxide. There is no great increase in toxicity in this case, but the epoxides are more environmentally persistent than their precursors. Moreover, some of the epoxides produced in the microsomal oxidation are highly reactive and can form adducts with cellular macromolecules such as proteins, RNA, and DNA, often resulting in chemical carcinogenesis. 

Epoxide rings of alkene and arene compounds are hydrated to form trans-diols. The enzymes that catalyze the addition of a molecule of water to an epoxide ring to yield diols are called epoxide hydrolases (also known as epoxide hydrases). Epoxide hydrolase activity has been detected in numerous species of insects. Enzymatic epoxide hydration of certain cyclodiene insecticides and their analogs has been demonstrated in the housefly, blowfly (Calliphora erythrocephala), yellow mealworm (Tenebrio molitor), Madagascar cockroach (Gromphadorhina portentosa), southern army worm (Spodoptera eridania), and red flour beetle (Tribolium castaneum). Epoxide hydrolase is also important in the metabolism of juvenile... 

Cyclodienes are chlorinated hydrocarbon insecticides with a polycyclic structure and, as the name implies, two unsaturated bonds. Not all of the insecticides in this class meet these criteria. Chlordane, for example, contains only one double bond in its polycyclic structure. Endrin and dieldrin are epoxides of the cyclodienes isodrin and aldrin, respectively. 

Heptachlor and Heptachlor Epoxide. Heptachlor is a cyclodiene insecticide introduced around the same time as DDT and, until recently, was used extensively. It is important to the present discussion because it was the first case where a metabolite of a pesticide was proven to be involved in the toxic response assumed... 

Table IV lists the insecticidal activity of cyclic sulfites In this case, the exo cyclic sulfites of 5,6-bis(hydroxymethyl)-7-isopropylidenebicyclo[2.2 l]hept-2-ene [20] was active whereas the corresponding endo Isomer [18] was inactive Monoepoxldation [21 and 22] and diepoxidation [23] of the exo cyclic sulfite resulted in a slight increase in activity Compound 15 was the most active among this series of compounds The LD q value of this compound was estimated to be about 1 pg/fly when topically applied to houseflies without any synergists (data not shown) The C-7 isopropylidene group proved to be unnecessary for high activity by comparison with compound 18. The activity decreased after epoxidation [16] or hydrogenation [17] of the endocyclic double bond The cyclodiene insecticide endosulfan was about 10 times as active as [15] ...

Epoxidation or the insertion of an oxygen atom into a carbon-carbon double bond can frequently result in the formation of products with greater environmental toxicity. Various microorganisms can catalyze the reaction of the chlorinated cyclodiene insecticides aldrin, isodrin, and heptachlor to their more toxic epoxide derivatives. 

Next, LLNL-Hept-2 was characterized for its ability to recognize related cyclodiene insecticides. Representative inhibition curves for LLNL-Hept-2, using, heptachlor epoxide, chlordane, aldrin and endrin, in addition to the results obtained with heptachlor, are shown in Figure 2. The degree of cross reactivity of LLNL-Hept-2 to different chemicals was calculated by comparing the Iso values obtained with each chemical to the I50 obtained with heptachlor (the heptachlor value was arbitrarily assigned a value of These cross-reactivity results are summarized in Table I. 

Figure 2. Competition ELISA results using Mab LLNL-Hept-2 with various cyclodiene insecticides as competitors heptachlor (solid circles), heptachlor epoxide (open circles), aldrin (open squares), chlordane (open diamond), and endrin (open triangle). Bars represent 1 standard deviation for heptachlor.

Our results clearly point out the critical role of sample cleanup in development of an immunoassay for lipophilic compounds. The methods should be simple, rapid, and capable of being exported into the field if the full potential of immunoassays are to be realized. The sample cleanup method we describe here meets these criteria for heptachlor, aldrin and chlordane. However, recovery experiments clearly indicate that the more polar epoxides of these insecticides are retained on the column. Thus, while the antibody binds all cyclodiene insecticides with roughly equal affinity, the cleanup method will not equally present the cyclodienes to the assay. Attempts at using mixed solvent elution systems such as ether/hexane remove the more polar insecticides but also remove more of the starting fat and interfering compound(s). Thus, further efforts in the area of sample cleanup are needed. 

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