Anaerobic metabolism of the agro-pesticide nitroxinil by bovine ruminal fluid.

Metabolism of three different agro-pesticides widely used in Uruguay, the insecticides imidacloprid and thiamethoxam and the antiparasite nitroxinil, by bovine ruminal fluid, as supply of anaerobic microorganims, was studied. Complete ruminal fluid was incubated with each of the agrochemicals in different conditions, varying time, nutrients, and nitroethane supplementation as methanogenesis modificator. Only biotransformation was detected for nitroxinil in some of the studied variables. In the optimized condition only one product was generated and the chemical structure of this main metabolite was elucidated using combined spectroscopies evidencing a structural motive unrelated with the products of the corresponding mammal biotransformation results of reduction, and substitution processes. The ruminal generation of the metabolite was confirmed. In order to employ this anaerobic microbial system as potential bioremediator of agrochemical-contaminated soils, the toxicity, against mammal cells, and the mutagenicity, using Ames test, of the product of biotransformation were studied. The lack of toxic effects encouraged us to propose the ruminal system as a plausible system for agrochemicals bioremediation.

[Study of plasma and hepatic hydrolysis of nitroxinil derivatives]. / Etude de l'hydrolyse plasmatique et hépatique de dérivés du Nitroxinil.

Seven esters derivatives of Nitroxinil were prepared and their structures were assigned by IR and 1H-NMR spectroscopy. The rate of plasma and hepatic hydrolysis were evaluated in vitro in sheep and rabbit. In view of this profile of activity, pivaloyl derivative merits evaluation, in vivo.

In vitro metabolism of aromatic nitriles.

Studies on the metabolic fate of aromatic nitriles, in contrast to their aliphatic counterparts, have been minimal and the subject of controversy. The in vitro metabolic fate of several aromatic nitriles with varying substituents was investigated by using rat liver subcellular fractions, with a particular emphasis on the nitrile moiety. Benzonitriles and 4-cyanophenols underwent oxidative metabolism to produce ring-hydroxylated metabolites. On the other hand, 2-cyanophenol was resistant to metabolism. o-Tolunitrile was metabolized and produced o-cyanobenzyl alcohol and phthalide. Phthalide, however, was chemically derived from o-cyanobenzyl alcohol, the initial metabolite. 4-Nitrobenzonitrile was resistant to oxidation on the ring, but was readily reduced to the corresponding amine metabolite under both aerobic and anaerobic conditions. Nitroxynil (3-iodo-4-hydroxy-5-nitrobenzonitrile) was metabolized to produce 3-iodo-4-hydroxy-5-nitrobenzamide and 3-iodo-4-hydroxy-5-nitrobenzoic acid. The enzyme(s) responsible for this hydrolytic metabolism was primarily localized in the cytosol. Among the nitriles tested, o-tolunitrile and nitroxynil produced metabolites in which the nitrile moiety was modified. Nitroxynil, however, was the only compound that was directly metabolized on the nitrile moiety by the rat liver enzyme(s).

Plasma protein binding of nitroxynil in several species.

The binding of nitroxynil to total plasma proteins of cows, sheep and rabbits was characterized using equilibrium dialysis. The data indicate clearly that nitroxynil was highly (97-98%) bound to plasma protein of each animal. This linear binding would be due to the particular power exerted by serum albumin. The results are in good agreement with known pharmacokinetic properties of nitroxynil in domestic species.

Impaired in vitro metabolism of the flukicidal agent nitroxynil by hepatic microsomal cytochrome P-450 in bovine fascioliasis.

In vitro metabolism by liver tissue of the flukicidal agent nitroxynil has been studied in cattle naturally infected with Fasciola hepatica. A dramatic impairment of the cytochrome P-450-dependent nitroxynil metabolism both in the acute and in the milder stage of the disease has been observed and this is due to a loss in the integrity and functionality of the cytochrome P-450 enzyme system. These results suggest that in bovine fascioliasis the in vivo metabolism of nitroxynil will be decreased with consequent increase of nitroxynil retention in the animal's body.

The reductive metabolism of the nitroaromatic flukicidal agent nitroxinil by liver microsomal cytochrome P-450.

Hepatic biotransformation of the flukicidal agent nitroxynil (3-iodo-4-hydroxy-5-nitrobenzonitrile) (I) has been studied with rat liver subcellular fractions as the source of enzymes: two metabolites, 3-iodo-4--hydroxy-5-aminobenzonitrile (II) and 3-iodo-4-hydroxy-5-nitrobenzamide (III) have been identified by standard analytical techniques (TLC, GLC and MS). The nitroaromatic reduction product (II) is formed in the hepatocyte in a process in which cytosol and endoplasmic reticulum enzymes cooperate. This formation is maximal in anaerobic conditions, but takes also place aerobically and in the absence of electrogenic cofactors. Cytochrome P-450 plays a major role in the denitrification process, and consequently could be the cellular site most exposed to damage by the intermediate arylhydroxylamine formed by reduction.

The metabolism of nitrophenolic and 5-arylazorhodanine anthelmintics by Ascaris suum, Moniezia expansa and by mouse- and sheep-liver enzymes.

1. The anthelmintics disophenol (2,6-diiodo-4-nitrophenol), nitroxynil (3-iodo-4-hydroxy-5-nitrobenzonitrile) and nitrodan (3-methyl-5-(4-nitrophenylazo)rhodanine) were reduced in vitro to the corresponding amines by intact Ascaris suum, Moniezia expansa, by enzymes prepared from these helminths, and by mouse- and sheep-liver homogenates. Helminth reductases required NADH2 and glutathione as cofactors and were inhibited about 50% by 2.0 x 10(-7) M allopurinol. Azo bonds of nitrodan and its analogues were not reduced by the helminths but were reduced by mouse- and sheep-liver enzymes. 2. Mouse- and sheep-liver enzymes, in addition to effecting nitro reduction, metabolized nitroxynil by hydrolysis to 3-iodo-4-hydroxy-5-nitrobenzamide and 3-iodo-4-hydroxy-5-nitrobenzoic acid. No hydroxylation products were found. Nitrodan was oxidized by the mammalian microsomal oxidation enzyme system to the thiazolidinedione derivative, but not by helminth enzymes.

[Distribution and retention of nitroxinil in the tissues and fluids of large and small ruminants treated with fasciolide]. / Prouchvaniia vurkhu razpredelenieto i zadurzhaneto na nitroksinil v tukani i technosti na edri i drebni prezhivni zhivotni, tretirani s fastsiolid.

Nitroxynil distribution and the period of its retention in the organism of sheep and calves subcutaneously treated with therapeutical doses of the Bulgarian patent medicine fasciolid which contains N-methylglucaminic-nitro-xynil salt were followed. Comparative studies were carried out using the patent medicine dovenix "Specia". The polarographic method, based on nitro-group reduction over a dripping mercury electrod was applied for nitroxynil determination. It was established that fasciolid and dovenix applied to sheep and cattle in a prophylactic-therapeutic dose did not differ significantly in their distribution and retention in the organism.