W.J.A. Vandenheuvel

Environmental effects of the usage of avermectins in livestock.

Abamectin (avermectin B1) and ivermectin (22,23-dihydroavermectin B1) are high molecular weight hydrophobic compounds, active against a variety of animal parasites and insects. Numerous environmental fate and effects studies have been carried out in the development of these two compounds as antiparasitic agents and for abamectin as a crop protection chemical. They were found to be immobile in soil (Koc > or = 4000), rapidly photodegraded in water (degradation half-life (t1/2) in the summer 0.5 days or less) and as thin films on surfaces (t1/2 < 1 day), and aerobically degraded in soil (ivermectin in soil/feces mixtures (t1/2) = 7-14 days; avermectin B1a in soils, t1/2 = 2-8 weeks) to less bioactive compounds. Abamectin is not taken up from the soil by plants, nor is it bioconcentrated by fish (calculated steady-state bioconcentration factor of 52, with rapid depuration). Daphnia magna is the fresh water species found to be most sensitive to ivermectin and abamectin (LC50 values of 0.025 and 0.34 ppb respectively); fish (e.g. rainbow trout) are much less sensitive to these compounds (LC50 values of 3.0 ppb and 3.2 ppb, respectively). In the presence of sediment, toxicity toward Daphnia is significantly reduced. The metabolism and degradation of ivermectin and abamectin result in reduced toxicity to Daphnia. Abamectin and ivermectin possess no significant antibacterial and antifungal activity. They display little toxicity to earthworms (LC50 values of 315 ppm and 28 ppm in soil for ivermectin and abamectin, respectively) or avians (abamectin dietary LC50 values for bobwhite quail and mallard duck of 3102 ppm and 383 ppm, respectively), and no phytotoxicity. Residues of the avermectins in feces of livestock affect some dung-associated insects, especially their larval forms. This does not delay degradation of naturally formed cattle pats under field conditions; however, in some cases, delays have been observed with artificially formed pats. Based on usage patterns, the availability of residue-free dung and insect mobility, overall effects on dung-associated insects will be limited. As abamectin and ivermectin undergo rapid degradation in light and soil, and bind tightly to soil and sediment, they will not accumulate and will not undergo translocation in the environment, minimizing any environmental impact on non-target organisms resulting from their use.

5-Methyltetrahydrofolic Acid as a Mediator in the Formation of Pyridoindoles

Enzymes from chick and rat tissues catalyze the reaction of N-methyl tryptamine with 5-methyltetrahydrofolic acid to form 2,3,4,9-tetrahydro-2-methyl-1H-pyrido[3,4b] indole. N,N-Dimethyltryptamine was not formed. With tryptamine as substrate the product is 2,3,4,9-tetrahydro-1H-pyrido[3,4b] indole and not N-methyltryptamine. These pyridoindoles were not formed when S-adenosylmethionine was cosubstrare.

Blood and urine levels of N,N-dimethyltryptamine following administration of psychoactive dosages to human subjects

Psychoactive doses (0.7 mg/kg) of the hallucinogen N,N-dimethyltryptamine (DMT) were administered intramuscularly to 11 normal subjects. A gas chromatographic-mass spectrometric isotope dilution determination of DMT concentrations in whole blood and urine revealed that only a fraction of the injected dose was recovered and the blood DMT concentrations had a very similar time course o the subjectively reported “high”.

Dimethyltryptamine levels in blood of schizophrenic patients and control subjects

A gas chromatographic-mass spectrometric determination of blood N,N-dimethyltryptamine in normal controls and schizophrenic patients was carried out with a sensitivity limit of 0.05 ng/ml whole blood. Although the results appear to suggest that the mean DMT level was higher in the total patient group, those patients with acute psychosis, female patients and patients with suspiciousness scores on the BPRS of 4 or over, the differences were not statistically significant.

The gas—liquid chromatography of dimethylsilyl, trimethylsilyl and chloromethyldimethylsilyl ethers of steroids : Mechanism of silyl ether formation and effect of trimethylsilylation upon detector response

Abstract The GLC behavior of three pairs of epimeric hydroxysteroids and their dimethylsilyl, trimethylsilyl and chloromethyldimethylsilyl ethers has been investigated through the use of two stationary phases of different partitioning properties. In general, stereochemical differences at C-3 result in greater retention differences than those at C-17, with derivative formation leading to improved separation; at C-20 the three hydroxyl groups lead to greater epimer differentiation than do derivatives. Chloromethyldimethylsilylation leads to increased retention time with “polar” and “non-polar” stationary phases, in contrast to dimethylsilylation and trimethylsilyation which effect a reduction in retention times with the former. The formation of multiple derivatives (homogeneous and heterogeneous) of polyhydroxy steroids through the use of mixtures of different silylating reagents enhances the ability to characterize such compounds. Studies on the mechanism of formation of silyl ethers have disclosed that the disilazane and the corredsponding chlolrosilane each function as sources of silyl ether groups in the etherification reaction. On both a molar basis and a weight basis the trimethylsilyl ether of cholesterol yields a greater detector (argon ionization and flame ionization) response than the parent sterol.

Gas chromatographic-mass spectrometric isotope dilution assay for N,N-dimethyltryptamine in human plasma

Abstract An isotope dilution assay for the determination of N,N-dimethyltryptamine in human plasma has been developed. Dideutero-N,N-dimethyltryptamine is added to the plasma as a carrier, and also serves as an internal standard in a gas chromatographic-mass spectrometric analysis of the final isolate. Mass spectrometric isotope intensity ratios for two ions are used to calculate the amount of endogenous N,N-dimethyltryptamine in the isolate at a sensitivity limit of 0.5 ± 0.2 ng/ml plasma.

Drug residue formation from ronidazole, a 5-nitroimidazole. V. Cysteine adducts formed upon reduction of ronidazole by dithionite or rat liver enzymes in the presence of cysteine

When ronidazole (1-methyl-5-nitroimidazole-2-methanol carbamate) is reduced by either dithionite or rat liver microsomal enzymes in the presence of cysteine, ronidazole-cysteine adducts can be isolated. Upon reduction with dithionite ronidazole can react with either one or two molecules of cysteine to yield either a monosubstituted ronidazole-cysteine adduct substituted at the 4-position or a disubstituted ronidazole-cysteine adduct substituted at both the 4-position and the 2-methylene position. In both products the carbamoyl group of ronidazole has been lost. The use of rat liver microsomes to reduce ronidazole led to the formation of the disubstituted ronidazole-cysteine adduct. These data indicate that upon the reduction of ronidazole one or more reactive species can be formed which can bind covalently to cysteine. The proposed reactive intermediates formed under these conditions may account for the observed binding of ronidazole to microsomal protein and the presence of intractable drug residues in the tissues of animals treated with this compound. They may also account for the mutagenicity of this compound in bacteria.

Gas-liquid chromatography and mass spectrometry of deuterium-containing amino acids as their trimethylsilyl derivatives

Abstract The gas-liquid chromatography and mass spectrometry of specially labeled deuterium-containing amino acids as their trimethylsilyl derivatives has been investigated. In many cases the retention time of the deuterated compound was measurably shorter than that of its protium analog. The small retention time differences, to a first approximation, were proportional to the number of deuterium atoms. Under our experimental conditions separation of mixtures (bifurcated peak) was observed within only two pairs of compounds—leucine and leucine-D 10 , and isoleucine and isoleucine-D 10 . Fractionation of the protium and deuterium forms within a single gas-liquid chromatography peak has been demonstrated by combined gas-liquid chromatography —multiscan mass spectrometry. Comaparison of the mass spectra of normal amino acid trimethylsilyl derivatives and their deutrium-containing analogs has facilitated the elucidation of the mass spectral fragmentation patters observed for these compounds.

Identification of N,N-dimethyltryptamine as the product of an in vitro enzymic methylation

Abstract Thin-layer chromatography, reverse isotope dilution assay, and combined gas-liquid chromatography-mass spectrometry have demonstrated that an enzyme obtained from human lung catalyzes the in vitro methylation of N -methyltryptamine by S -adenosylmethionine to form N,N -dimethyltryptamine. Isolation of the product of the enzymic reaction and its identification were facilitated by use of carbon-14 and deuterium labeling.

Preparation, gas chromatography and mass spectrometry of methyl and trimethylsilyl esters of indomethacin

The preparation and gas chromatographic-mass spectrometric behavior of the methyl and trimethylsilyl esters of indomethacin, 1-(p-chlorobenzoyl)-5-methoxy-2-methylindole-3-acetic acid, are described. Reaction of this anti-inflammatory drug with diazomethane or bis(trimethylsilyl)acetamide forms the expected esters. Derivatization with dimethylformamide dimethylacetal yields two compounds, the methyl ester (major product) and a methyl ester-dimethylaminomethylene condensation (at the alpha-carbon of the side chain) product (minor). Experiments with 5-O-desmethyl-indomethacin have demonstrated that using the described diazomethane methylation conditions no alkylation of the phenolic group occurs. Esterification combined with an isolation procedure allows the determination of indomethacin levels in plasma and aqueous humor of rabbits, the 4-fluorobenzoyl analog serving as internal standard. The derivatives exhibit excellent electron capture properties allowing quantitative assay of the drug at the submicrogram level. Precision and accuracy for plasma samples varied from 92 +/- 19% (5 ng/ml) to 96 +/- 1.5% (1000 ng/ml). The analogous values for aqueous humor are superior: 97 +/- 5.6% and 99 +/- 2.2%, resectively.