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At least 19 recordsLinked to original sources
PubMed1977

Quinoxalinol derivatives of aliphatic 2-oxocarboxylic acids. Infrared and mass spectra of the O-trimethylsilylated compounds.

In acidic media o-phenylenediamine and 2-oxoacids react to yield quinoxaline derivatives. On derivatization in pyridine with silylating reagents quinoxalinol-O-TMS ethers or O-TMS-ether-TMS-esters are formed exclusively as shown by gas chromatography infrared spectrometry and gas chromatography mass spectrometry. These derivatives have very favourable properties for gas chromatographic detection and quantitation of the parent 2-oxoacids. The mass spectra have characteristic fragments which facilitate easy identification. In addition, 'single ion monitoring' of all aliphatic 2-oxoacids can be performed with only three fragments at m/e 217,232 and 245. In some aspects the mass spectra resemble those of other heterocyclic compounds which contain an O-alkyl sidechain. The fragmentation mechanisms were deduced by low resolution mass spectrometry with and without deuteration, high resolution mass spectrometry and metastable ion evidence. A new type of rearrangement alpha-beta-elimination of ethylene or propylene from the aliphatic sidechain, is proposed for some O-TMS quinoxalinols.

Chemical Phenomena↗
PubMed1992

Antimalarial activity of new dihydroartemisinin derivatives. 5. Sugar analogues.

A series of dihydroartemisinin derivatives containing a sugar moiety was prepared in the search for analogues with good water solubility and high antimalarial activity. The preparation of the new compounds was achieved by treatment of dihydroartemisinin (2) with chlorotrimethylsilane in pyridine solution at -10 degrees C to give a nearly quantitative yield of 10-O-(trimethylsilyl)dihydroartemisinin (3), which was then condensed with 1-hydroxypolyacetylated sugars 5 to give dihydroartemisinin derivatives 7a-d. Deacetylation of intermediates 7 gave the desired sugar derivatives 8. The resulting derivatives, tested in vitro against Plasmodium falciparum, were found to be more effective against W-2 than D-6 clones and were not cross-resistant with existing antimalarials. Trimethylsilylated compound 3 is more effective than derivatives 7a-d, which possess activity comparable to or better than that of artemisinin itself. Deacetylated compounds 8a-d were substantially less active than 7 in both cell lines. In P. berghei-infected mice, 7a-c showed 5/5, 2/5, and 3/5 cures, respectively, at 320 mg/kg per day x 3, whereas 7d showed no activity at the same dosage. However, 7d did prolong the life span in 3/5 of the infected mice at 640 mg/kg per day x 3 dose level. Trimethylsilylated compound 3 was also the most effective among the compounds studied, with 5/5 cures at 80 mg/kg per day x 3. The deacetylated sugar derivatives 8a-d showed only slight in vivo antimalarial activity.

Animals↗
PubMed1977

Structural analysis by mass spectrometry of the major mammalian retinal ganglioside, a sialyl-sialyl-dihexosyl-ceramide.

The major mammalian retinal ganglioside was analysed by mass spectrometry. Three types of derivatives were used, the fully methylated, the methylated and reduced and the methylated, reduced and trimethylsilylated compound. The mass spectra unambiguously showed the ganglioside to be a sialyl-sialyl-dihexosyl-ceramide. This is the first conclusive proof that the two N-acetylneuraminic acids are bound to each other constituting the terminal disaccharide. The major species contained sphingosine and stearic acid.

Animals↗
PubMed1975

N-dimethylaminomethylene derivatives for the gas-liquid chromatography of primary sulfonamides.

Dimethylformamide dialkylacetals have been found to react readily with primary sulfonamides to form N-dimethylaminomethylene derivatives. These compounds possess excellent gas-liquid chromatographic properties and can be conveniently prepared at the submicrogram level. Their retention times are much greater than those of other sulfonamide derivatives (e.g., N,N-dimethyl) but their ease of preparation and lack of absorptive properties make them attractive for gas-liquid chromatographic studies. The practical applicability of this derivatization approach to biological studies is illustrated by the gas-liquid chromatographic determination of 3-bromo-5-cyanobenzenesulfonamide in ovine blood using 3,5-dibromobenzenesulfonamide as the internal standard. The method has a detection limit of 25 ppb with electron capture detection.

Animals↗
PubMed1978

O-trimethylsilylquinoxalinol derivatives of aromatic alpha-keto acids. Mass spectra and quantitative gas chromatography.

As an extension of earlier work on aliphatic alpha-keto acids, a method is described for the quantitative gas chromatographic determination of urinary aromatic alpha-keto acids. The keto acids are derivatized with o-phenylenediamine to yield the quinoxalinols. These compounds are chromatographed after trimethylsilylation. The aromatic keto acids are stabilized by sodium dithionite (4 mg/ml urine) and storage below 0 degrees. The final derivatives are stable for weeks at room temperature. Low resolution mass spectra are reported. The fragmentation mechanisms are elucidated by analysis of O-trimethylsilyl-(TMS)-quinoxalinois, O-(TMS-d9)-quinoxalinois and O-TMS-6(7)-chloroquinoxalinois.

Adult↗
PubMed1979

Analysis of the venom of the Sydney funnel-web spider, Atrax robustus using gas chromatography mass spectrometry.

Thirteen compounds have been identified using gas chromatography mass spectrometry in the venom of the Sydney funnel-web spider, Atrax robustus. The compounds were identified as their trimethylsilyl or pentafluoropropionate derivatives and were citric acid, lactic acid, phosphoric acid, glycerol, urea, glucose, gamma-aminobutyric acid, glycine, spermidine, spermine, tyramine and octopamine. Female venom contained trace quantities of 5-methyoxytryptamine which was not detected in male venom. Quantitative determination of tyramine and octopamine was achieved using chemical ionization (CH4) gas chromatography mass spectrometry and deuterated internal standards.

Arthropod Venoms↗
PubMed1976

Determination of urinary monohydric and dihydric phenols by gas chromatography of the acetate and TMS derivatives. 4-Dimethylaminopyridine as a catalyst for acetylation reactions.

A procedure is described for the quantitative extraction of phenols from human urine. The compounds were chromatographed as the trimethylsilyl derivatives on wall-coated glass capillary columns. A more specific method of extraction involving the formation of acetate derivatives is also described. The acetates were prepared by treating dilute solutions of phenols at room temperature with acetic anhydride in the presence of 4-dimethylaminopyridine, which is a far more powerful catalyst than pyridine. Under these conditions N-acylamino acids are converted to azlactones.

4-Aminopyridine↗
PubMed1979

New procedure for isolation of amino acids based on selective hydrolysis of trimethylsilyl derivatives.

A rapid procedure for the isolation of amino acids from physiological fluids by class separation suitable for gas chromatographic and gas chromatographic-mass spectrometric analysis is described. A physiological fluid such as plasma is adjusted to pH 2 and extracted with diethyl ether to remove organic acids and neutrals. After precipitation of proteins with trichloroacetic acid, the aqueous plasma is dried and derivatized by trimethylsilylation. Organic compounds like sugars and amino acids are rendered soluble in petroleum ether leaving inorganic salts when the soluble layer is transferred. Separation of sugars from amino acids is achieved by taking advantage of the different rates of aqueous hydrolysis of the trimethylsilyl (TMS) derivatives. Mixing the petroleum ether extract with a small volume of water results in two phases. The petroleum ether layer contains TMS-Sugar constituents of plasma and the aqueous layer contains free amino acids and amines. This procedure was used to isolate L-dopa, 3-O-methyldopa and tyrosine from human plasma in a quantitation assay using 18O-labelled amino acids and gas chromatography-mass spectrometry.

Amino Acids↗
PubMed1978

Surface kinetic test method for determining rate of kill by an antimicrobial solid.

An antimicrobial-surface kinetic test which maximizes probability of cell-to-surface contact has been developed. The measurement of rate of kill by a nonleaching antimicrobial surface is based on the number of surviving bacterial cells at specific times of exposure to various amounts of total treated surface area of test substrate. This method gives information for direct comparison of rate of kill for a variety of antimicrobial surfaces in terms of rate of kill per square centimeter of surface area. Data obtained by this method can also give valuable dose response application information as an indication of the exponential efficiency of concentration in terms of treated surface area.

Bacteriological Techniques↗
PubMed1976

Synthesis and mass spectrometry of crufomate metabolites and related compounds.

Phosphates and phosphoramidates related to 2-chloro-4-t-butylphenyl methyl methylphosphoramidate (crufomate) were synthesized to aid in the identification of crufomate metabolites. Deuterium labeling metastable determinations and precise mass measurements were used to establish fragmentation pathways. Evidence was obtained for the rearrangement of an N-formyl phosphoramidate (the expected result of oxidative metabolism of N-methyl phosphoramidates) to an iminomethyl phosphate.

1-Propanol↗
PubMed1975

Estimation and identification in blood plasma of paracetamol (N-acetyl-p-aminophenol) in the presence of barbiturates.

Barbiturates are a source of interference in the estimation of paracetamol by both UV spectrophotometry and gas-liquid chromatography (GLC). Experiments have shown that the interference by barbiturates on GLC can be avoided by benzoylation (in aqueous solution) of the paracetamol. This O-benzoyl derivative can be N-silylated to give an additional identification parameter. The method, which requires ml of sample, will quantitatively and qualitatively estimate "free" paracetamol in plasma and in post mortem blood in the range of 2-40 mug of drug per millilitre of sample.

Acetaminophen↗
PubMed1977

Gas chromatographic separation of histamine and its metabolites.

A new, rapid and simple gas-liquid chromatographic method is described for the simultaneous determination of histamine, 1-methylhistamine, 4-imidazoleacetic acid and 1-methyl-4-imidazoleacetic acid. These compounds are derivatized at 60 degrees in one fast 30-min reaction with bis(trimethylsilyl)acetamide-trimethylchlorosilane and are then separated on OV-17. No previous methylation of the acids is needed. A complete profile of the four metabolites can be obtained in 8 min with baseline resolution, and there are no tailing effects. The quantitative response curves are linear in the nanogram range, with detection limits of the order of 10 ng for the acids and 100 ng for the amines. The structures of these new trimethylsilyl derivatives have been verified by combined gas-liquid chromatography-mass spectrometry.

Chromatography, Gas↗
PubMed1978

Mass spectra of aniline glucuronides.

Mass spectra of TMS derivatives of aniline glucuronide and pentachloroaniline glucuronide are presented, and the fragmentation of these derivatives is compared with that of TMS aryl-O-glucuronides. Fragmentation yielding ions entirely from the glycone moiety was sufficiently similar to establish these N-glucuronides as TMS glucuronides in the same manner used for TMS-O-glucuronides; however, differences observed may be diagnostic for TMS-N-glucuronides.

Aniline Compounds↗
PubMed1977

Selective introduction of TMS groups in tryptamines: preparation of N1-TMS derivatives of tryptamines.

Indolethylamines (tryptamines) with a primary animofunction react with Regisil under controlled conditions to yield a mono TMS derivative. Mass spectrometry to these derivatives shows that the TMS group is substituted on the indolic nitrogen (N1) and not the primary amino nitrogen. This is confirmed by converting these compounds to their isothiocyanate derivatives. The GC and GC-MS data of some typical compounds are presented.

Amino Acids↗
PubMed1978

GLC--mass spectrometry of several important anticancer drugs I: pertrimethylsilylation and O-methoxime formation.

Procedures are reported for the formation of pertrimethylsilyl and pertrimethylsilyl methoxime derivatives of the aglycones of doxorubicin, daunorubicin, carminomycin, chromomycin A3, and mithramycin. The mass spectra are consistent with the formation of these derivatives. Fragmentation patterns highly specific for these derivatives are proposed, and the potential application for the identification of metabolites of these compounds is discussed.

Antibiotics, Antineoplastic↗
PubMed1979

Acylglycines. the gas chromatograph/mass spectrometric identification and interpretation of their spectra.

The gas chromatographic retention time (methylene units) and mass spectra of a series of acylglycine compounds as their trimethylsilyl (TMS) derivatives are presented. A general scheme for the interpretation of these compounds is developed from the mass spectra of known compounds and is shown to be in agreement with data derived from other sources (e.g. stable isotope and high resolution mass spectra). These data should provide information for the identification of these compounds in physiological fluid of both normal and diseased patients. In addition, the general interpretation scheme should provide the investigator with an approach to the interpretation of the spectra of unknown acylglycines.

Chromatography, Gas↗
PubMed1976

Mutagenicity and cytotoxicity of benzo(a)pyrene benzo-ring epoxides.

Four benzo-ring epoxides of the environmental carcinogen benzo(a)pyrene (BP) were tested for mutagenic and cytotoxic activity in 3 strains of Salmonella typhimurium (TA1538, TA98, and TA100) and in Chinese hamster V79 cells. Although very unstable in aqueous solution, 7beta,8alpha-dihydroxy-0beta,10beta-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene (diol epoxide 1), with the 7-hydroxyl group on the same face of the molecule as the epoxide oxygen, was 1.5 to 4 times as mutagenic in the bacterial strains as was its more stable stereoisomer 7beta,8alpha-dihydroxy-9alpha,10beta-epoxy-7,8,9.10-tetrahydrobenzo(a)pyrene (diol epoxide 2). In V79 cells, diol epoxide 1 had one-third the mutagenic activity of diol epoxide 2 but was at least 10 times more labile than diol epoxide 2 in the tissue culture medium. The half-life of diol epoxide 1 in tissue culture medium was about 30 sec, whereas the half-life of diol epoxide 2 was between 6 and 12 min. 9,10-Epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene, which is saturated in the benzo ring, is also very unstable and has mutagenic activity equal to or greater than diol epoxide 1 in the bacterial and mammalian cells. 7,8-Epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene was more stable in aqueous solution than any of the 9,10-epoxides of BP but was much less mutagenic in both the bacterial and mammalian cells. In v79 cells, diol epoxides 1 and 2 and 9,10-opoxy-7,8,9,10-tetrahydrobenzo(a)pyrene were more than 40 times more cytotoxic than 7,8-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene. The mutagenicity of the 2 tetrahydro epoxides toward strain TA98 of S. typhimurium was readily abolished by purified epoxide hydrase, whereas the mutagenic activity of the 2 diol epoxides was relatively unaffected by coincubation with the enzyme.

Animals↗