Parasiticides

Avermectins and Ivermectin. The avermectias are pentacycHc lactones isolated from fermentation products of Streptomjces avermitilis and ivermectin is a semisynthetic chemical, 22,23-dihydroavermectia (46). Ivermectin is effective in very low doses for the control of red spider mites on deciduous fmits, in baits for the control of imported fire ants, and as a parasiticide for Onchocerca volvulus in humans and for catde gmbs. These insecticides appear to function as agonists for the neuroinhibitory transmitter y-aminobutyric acid (GABA) (see Antiparasitic agents, avermectins). 

Parasiticides can be roughly divided according to parasites, host species, or chemical classification (see Antiparasitic agents—anthelmintics Antiparasitic AGENTS—ANTiPROTOZOALs). By any classification, these are ubiquitous in the management and control of parasites of both companion and food-producing animals (2,3). 

Other Parasiticides. The parasiticides described below have a relatively limited usage owing to a narrow spectmm of antiparasitic activity or because of the introduction of inherently safer or more effective products. 

Droncit), C H24N202, for use as a parasiticide. Ivermectic [70288-86-7] and an experimental, pyrethmm-based compound (Py-Sal 25) are both involved ia clinical trials ia Europe to determine if they can control sea Hce on salmon (see Antiparasitic AGENTS, AVERMECTINS). 

Nonmedical uses claimed for pyridopyridazines include fungicides, growth promotion agents, parasiticides, UV absorbants and dyestuff intermediates. 

Thiirane is more bactericidal than oxirane, and derivatives of 2-mei captomethylthiirane inhibit tuberculosis. The following pharmacological uses have been reported for compounds derived from thiirane derivatives gold complexes of the adducts of diethylphosphine and thiirane (antiarthritic), adducts of thiiranes and malononitrile (antibacterial, blood vessel dilators, muscle relaxants, sedatives), thermolysis products of thiirane 1-oxides and adducts of thiirane 1-oxides with sulfenyl chlorides (antibacterial), adducts of 2,3-diarylthiirene 1,1-dioxides with ynamines (antibacterial, parasiticidal), adducts of 2,3-diarylthiirene 1,1-dioxides with enamines (antifertility), adducts of p-aminophenylacetic esters with thiirane (immunosuppressants), adducts of amines and thiiranes (radioprotective drugs). 

A few commercial applications of benzofuroxans have been suggested in the Patent literature and elsewhere. A wide range of biological activity (fungicidal or fungistatic,bactericidal,i -parasiticidal,i3i and insecticidaP i i jj s been claimed for... 

Parasite unde, /. parasitology, parasitentdtend, a. parasiticidal, -cide. parasitisch, a. parasitic, parastindig, a. in the para position. Parastellung, /, para position. 

The term pharmaceutical includes more than 4,000 chemicals used to control and treat different kinds of diseases in humans and animals. Pharmaceuticals include analgesics, anti-inflammatories, anti-epileptics, (l-blockers, compounds used to prevent and treat parasites and microbial infections (parasiticides and antibiotics) and those for combating cancer. Hormones are also a class of pharmaceuticals but due to their particular involvement in endocrine disruption, they have been discussed in a separate section (see above). 

Sangster, N. C. (2001). Managing parasiticide resistance . Veterinary Parasitology, 98, 89-109. 

As the causative parasites for these diseases are closely related, and the genome of each has been sequenced, it is not surprising that a number of common biochemical pathways have been targeted by drug discovery efforts [6]. In addition, screening for parasiticidal activity of compounds has frequently been performed simultaneously against representative strains of the three major parasites, hence many of the chemotypes described in this chapter exhibit activity against all three. 

Silver(T) oxide is used for polishing and coloring glass yellow. Also, it is used in purifying drinking water as a catalyst and as a germicide and parasiticide. 

In addition to artemisinin, other synthetic trioxanes and endoperoxides (fenozan BO-7 4 and arteflene 5 " ) have enjoyed some success arteflene reached Phase II pre-clinical trials. More recently, Vennerstrom and coworkers have reported on the outstanding antimalarial properties of several 1,2,4-trioxolanes, one of which, OZ 277 (6), has entered clinical trials in man . These exciting, easily prepared drugs will be discussed in detail later in this chapter. In order to determine the parasiticidal action of this class of antimalarial, many research groups have focused their efforts on artemisinin and its semi-synthetic derivatives (artemether, arteether and artesunate Ic, Id and le), and this is the point where our discussion will begin. 

They concluded that the parasiticidal action of trioxanes involved reductive cleavage of the peroxide bond by intracellular iron-sulphur redox centres (rather than heme) and subsequent alkylation of the redox centre. This type of redox centre is known to exist in many enzymes and Wu and coworkers proposed that structural differences between those in the parasite and those in mammalian systems could account for the high selective cytotoxicity of artemisinin. 

Haynes and Vonwiller reported that artemisinin displayed multifarious reactivity in the presence of heme and non-heme iron(II) and also iron(III) °. The THF product 21 and artennuin D 13 were generally observed in varying ratios that were dependent upon the conditions used. Other products were also formed and the authors concluded that it was not possible to assign the parasiticidal species. However, they proposed an alternative mechanism of action that did not involve reductive ring opening of the peroxide bridge (Scheme 17). 

O Neill and coworkers were also able to spin-trap the previously proposed C-centred radical 63b with sodium 3,5-dibromo-4-nitrosobenzenesulphonate (DBNBS) and the EPR of the adduct 64b was characteristic of a secondary radical (Scheme 19B). It was suggested that the parasiticidal action of arteflene stems from the alkylating properties of the radical intermediate or possibly from the enone 63a, which may be able to react with intracellular nucleophiles by a Michael addition. The enone itself did not exhibit antimalarial activity, possibly due to extracellular detoxification by glntathione before reaching its intraparasitic site of action. 

C-H bond unreactive to insertion, 1160 dioxirane oxidation, 1156 Sulfonic acids, C-H bond unreactive to insertion, 1160 Sulfonyl endoperoxides parasiticidal activity, 1309 synthesis, 1306-9, 1332 Sulfonyl peroxides, 1001-2, 1004-7 Sulfonylperoxy radical, superoxide reactions, 1035-9 Sulfoxidation... 

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