Biomedical subjects

J P Freeman

Publications and source records attributed to J P Freeman.

83 records · Page 5Linked to original sources

PubMed1982

Metabolism of azo dyes derived from benzidine, 3,3'-dimethyl-benzidine and 3,3'-dimethoxybenzidine to potentially carcinogenic aromatic amines by intestinal bacteria.

The metabolism of a benzidine-based dye, Direct Black 38, a 3,3'-dimethylbenzidine-based dye, Direct Red 2 and a 3,3'-dimethoxybenzidine-based dye, Direct Blue 15 has been studied both in pure cultures of anaerobic bacteria and in bacterial suspensions derived from the intestinal contents of the rat. All of the pure cultures and the rat intestinal bacteria were able to reduce the azo linkages of Direct Black 38, Direct Red 2 and Direct Blue 15 with the subsequent formation of benzidine, 3,3'-dimethylbenzidine and 3,3'-dimethoxybenzidine, respectively. The metabolites of Direct Black 38, Direct Red 2 and Direct Blue 15 were isolated and identified by gas chromatography/mass spectrometry and had similar chromatographic and mass spectral properties with those of authentic standards. Results from this study indicate that in vitro anaerobic incubations of rat intestinal microorganisms were able to reduce and cleave the azo bonds of dyes derived from benzidine, 3,3'-dimethylbenzidine and 3,3'-dimethoxybenzidine to form potentially carcinogenic aromatic amines.

Anaerobiosis↗

PubMed1982

Glucuronide and sulfate conjugation in the fungal metabolism of aromatic hydrocarbons.

Cunninghamella elegans oxidized naphthalene to ethyl acetate-soluble and water-soluble metabolites. Experiments with [14C]-naphthalene indicated that 21% of the substrate was converted into metabolites. The ratio of organic-soluble metabolites to water-soluble metabolites was 76:24. The major ethyl acetate-soluble naphthalene metabolites were trans-1,2-dihydroxy-1,2-dihydro-naphthalene, 4-hydroxy-1-tetralone, and 1-naphthol. Enzymatic treatment of the aqueous phase with either arylsulfatase or beta-glucuronidase released metabolites of naphthalene that were extractable with ethyl acetate. In both cases, the major metabolite was 1-naphthol. The ratio of water-soluble sulfate conjugates to water-soluble glucuronide conjugates was 1:1. Direct analysis of the aqueous phase by high-pressure liquid and thin-layer chromatographic and mass spectrometric techniques indicated that 1-naphthyl sulfate and 1-naphthyl glucuronic acid were major water-soluble metabolites formed from the fungal metabolism of naphthalene. C. elegans oxidized biphenyl primarily to 4-hydroxy biphenyl. Deconjugation experiments with biphenyl water-soluble metabolites indicated that the glucuronide and sulfate ester of 4-hydroxy biphenyl were metabolites. The data demonstrate that sulfation and glucuronidation are major pathways in the metabolism of aromatic hydrocarbons by fungi.

Basidiomycota↗

PubMed1981

Biotransformation and toxicity of aniline and aniline derivatives of cyanobacteria.

Agmenellum quadruplicatum strain PR-6 and Oscillatoria sp. strain JCM grown photoautotrophically in the presence of aniline metabolized the aromatic amine to formanilide, acetanilide and p-aminophenol. The metabolites were isolated by either thin-layer, gas-liquid or high pressure liquid chromatography and identified by comparison of their chromatographic, ultraviolet absorbance and mass spectral properties with those of authentic compounds. The toxicity of aniline derivatives towards Agmenellum quadruplicatum strain PR-6 indicated that the cyanobacterium was extremely sensitive to o-, m- and p-aminophenols, and phenylhydroxylamine.

Aniline Compounds↗

PubMedDate not supplied

Stereochemistry and evidence for an arene oxide-NIH shift pathway in the fungal metabolism of naphthalene.

The mechanism of naphthalene oxidation by the filamentous fungus, Cunninghamella elegans is described. C. elegans oxidized naphthalene predominately to trans-1,2-dihydroxy-1,2-dihydroxy-1,2-dihydronaphthalene. A trans configuration was assigned for the dihydrodiol by nuclear magnetic resonance (NMR) spectroscopy at 500 MHz which showed a large coupling constant (J1,2) of 11.0 Hz. Comparison of the circular dichroism spectrum of the fungal trans-1,2-dihydroxy-1,2-dihydronaphthalene to that formed by mammalian enzyme systems indicated that the fungal dihydrodiol contained 76% (+)-(1S,2S)-dihydrodiol as the predominant enantiomer. Other naphthalene metabolites formed by C. elegans were identified as 1-naphthol, 2-naphthol and 4-hydroxy-1-tetralone. Incubation of C. elegans with naphthalene and 18O2 indicated that the trans-1,2-dihydroxy-1,2-dihydronaphthalene contained one atom of molecular oxygen which indicated a monooxygenase catalyzed reaction while similar incubations with naphthalene and H182O indicated that the other oxygen atom in trans-1,2-dihydroxy-1,2-dihydronaphthalene was derived from water. Mass spectral analysis of the acid-catalyzed dehydration products of the dihydrodiol indicated that the naphthalene dihydrodiol forms via the addition of water at the C-2 position of naphthalene-1,2-oxide. Fungal metabolism of [1-2H]naphthalene yielded 1-naphthol which retained 78% of the deuterium. NMR analysis of the deuterated 1-naphthol indicated an NIH shift mechanism in which deuterium migrated from the C-1 position to the C-2 position. The above results indicate that naphthalene-1,2-oxide is an intermediate in the fungal metabolism of naphthalene and that the fungal enzymes are highly stereo-selective in the formation of trans-1,2-dihydroxy-1,2-dihydronaphthalene.

Deuterium↗

PubMedDate not supplied

Use of 13C NMR spectrometric data to produce a predictive model of estrogen receptor binding activity.

We have developed a spectroscopic data-activity relationship (SDAR) model based on 13C NMR spectral data for 30 estrogenic chemicals whose relative binding affinities (RBA) are available for the alpha (ERalpha) and beta (ERbeta) estrogen receptors. The SDAR models segregated the 30 compounds into strong and medium binding affinities. The SDAR model gave a leave-one-out (LOO) cross-validation of 90%. Two compounds that were classified incorrectly in the SDAR model were in the transition zone between classifications. Real and predicted 13C NMR chemical shifts were used with test compounds to evaluate the predictive behavior of the SDAR model. The 13C NMR SDAR model using predicted 13C NMR data for the test compounds provides a rapid, reliable, and simple way to screen whether a compound binds to the estrogen receptors.

Carbon Isotopes↗

PubMedDate not supplied

Producing 13C NMR, infrared absorption, and electron ionization mass spectrometric data models of the monodechlorination of chlorobenzenes, chlorophenols, and chloroanilines.

We have developed four spectroscopic data-activity relationship (SDAR) models of monodechlorination of 32 chlorinated benzene compounds in anaerobic estuarine sediment. The SDAR models were based on combinations of 13C nuclear magnetic resonance (NMR), infrared absorption (IR), and electron ionization mass spectrometric (EI MS) data. The SDAR models segregated the 32 compounds into 17 readily monodechlorinated compounds and 15 not readily monodechlorinated compounds. The SDAR model based on 13C NMR, IR, and EI MS data gave a leave-one-out cross-validation of 93.8%. The SDAR model based on a composite of 13C NMR and IR data gave a leave-one-out cross-validation of 90.6%. The SDAR model based on a composite of IR and EI MS data gave a leave-one-out cross-validation of 84.4%. The SDAR model based on a composite of 13C NMR and EI MS data gave a leave-one-out cross-validation of 84.4%. These reliable SDAR models provide a rapid and simple way to predict whether a chlorinated benzene compound will readily go through monodechlorination. The FDA has filed a patent application on methods of using any combination of spectral data (NMR, MS, UV-vis, IR, and fluorescence, phosphorescence) to model a chemical, physical, or biological endpoint.

Carbon Isotopes↗

PubMedDate not supplied

Microsomal metabolism of 4-(N,N-diacetylamino)benzo[a]pyrene: a potent mutagenic arylamide derived from a carcinogenic polycyclic aromatic hydrocarbon.

4-(N,N-Diacetylamino)benzo[a]pyrene, a potent mutagen, is derived from a carcinogenic polycyclic aromatic hydrocarbon, benzo[a]pyrene. Metabolism of this compound by rat liver microsomes was studied. Metabolites were separated by reversed-phase high-performance liquid chromatography and were identified by analysis of their UV-vis absorption, mass, and proton nuclear magnetic resonance spectral data. Seven metabolites were identified, namely, the 9-phenol, 1,9-hydroquinone, and trans-9,10-dihydrodiol of 4-(N,N-diacetylamino)benzo[a]pyrene, 4-(N-acetylamino)benzo[a]pyrene, and the 5-phenol, 5,9-hydroquinone, and trans-9,10-dihydrodiol of 4-(N-acetylamino)benzo[a]pyrene. Comparison of these results with those of metabolism of benzo[a]pyrene indicates that the N,N-diacetylamino substitutent at the 4-carbon of benzo[a]pyrene inhibits metabolism at the peri position (3-carbon) and positions (6-, 7-, and 8-carbons) remote from the substituent. The results also indicate that while 4-(N,N-diacetylamino)-benzo[a]pyrene is a substrate of the rat liver microsomal deacetylase, the formed 4-(N-acetylamino)benzo[a]pyrene apparently is not a substrate.

Animals↗

PubMedDate not supplied

Synthesis of N-(purin-8-yl)arylamines.

Methods for direct synthesis of N-(purin-8-yl)arylamines were investigated. N-(Purin-8-yl)arylamines are adducts from reaction of electrophilic metabolites of arylamines with DNA and have not been readily available by direct synthesis. Ability to generate significant quantities of this class of DNA adduct by synthetic means would facilitate basic research in molecular toxicology. Two routes with common thiourea intermediates were developed for this purpose. In the first route, 6-hydroxy-2,4,5-triaminopyrimidine was caused to react in aqueous medium with dithiocarbamate derivatives of o-, m-, or p-toluidine to form corresponding 2,4-diamino-5-(tolylthioureido)aminopyrimidin-6-ones in 60-70% yields. The thiourea intermediates were converted to carbodiimides and isolated in 20-25% yields after treatment with HgO in dimethylformamide. The carbodiimides were cyclized at 125 degrees C in dimethylformamide under N2 for 45 h to yield N-(guanin-8-yl)(o-, m-, or p-)toluidines in 65-75% yields. In the second route, direct reaction of p-tolyl isothiocyanate with 6-hydroxy-2,4,5-triaminopyrimidine or with 4,5,6-triaminopyrimidine in dimethylformamide and triethylamine led to the formation of 2,4-diamino-5-(p-tolylthioureido)aminopyrimidin-6-one and 4,6-diamino-5-(tolylthioureido)aminopyrimidine, respectively, in 77-79% yields. Methylation of the two thiourea derivatives by methyl iodide in dimethylformamide gave the corresponding methylisothiuronium derivatives, which were isolated in 71% and 84% yields (as HI salts), respectively. Conversion of the methylisothiuronium derivatives to N-(guanin-8-yl)-p-toluidine or N-(adenin-8-yl)-p-toluidine was accomplished by heating in dimethylformamide for 5-7 h at 80-90 degrees C, in 70% and 62% yields, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Carcinogens↗

PubMedDate not supplied

Peroxidase-catalyzed oxidation of pentachlorophenol.

Pentachlorophenol (PCP) was shown to function as a reducing substrate for horseradish peroxidase (HRP) and to stimulate the HRP-catalyzed reduction of 5-phenyl-4-penten-1-yl hydroperoxide (PPHP) to 5-phenyl-4-penten-1-ol. HRP catalyzed the hydroperoxide-dependent oxidation of PCP, using H2O2, PPHP, or ethyl hydroperoxide as substrates, as evidenced by UV spectroscopic and reverse phase HPLC analysis of reaction mixtures. The major oxidation product was tetrachloro-1,4-benzoquinone which was identified on the basis of electronic absorption spectroscopy, mass spectrometry, and cochromatography with authentic standard. HRP-catalyzed oxidation of PCP yielded relatively stable, ESR-detectable pentachlorophenoxyl radical intermediates whose ESR spectra consisted of a symmetrical single line without hyperfine structure. Substitution of natural abundance isotopically-labeled PCP with 13C-labeled PCP resulted in broadening of the ESR signal line width from 6.1 G to 13.5 G. ESR spin trapping studies, with alpha-(1-oxy-4-pyridyl)-N tert-butylnitrone (4-POBN) as the spin trap demonstrated identical spectra using natural abundance isotopically-labeled PCP versus 13C-labeled PCP, suggesting oxyl addition, rather than carbon-centered radical addition to 4-POBN. The computer simulation of the observed spectra is consistent with two distinct 4-POBN adducts, with relative abundances of approximately 3:1, and hyperfine coupling constants of alpha N = (14.61 G)/alpha H = 1.83 G and alpha N = (14.76 G)/alpha H = 5.21 G, respectively. Mechanisms for the hydroperoxide-dependent, HRP-catalyzed oxidation of PCP are presented that are consistent with these results.

Catalysis↗

PubMedDate not supplied

Characterization of the antihistamines tripelennamine, methapyrilene, and thenyldiamine and their N-oxides by thermospray mass spectrometry.

This study describes an investigation of the thermospray (TS) mass spectrometric analysis of tripelennamine, methapyrilene, thenyldiamine, and their N-oxide derivatives. These compounds were analyzed by direct injection TS mass spectrometry in the column bypass mode and with 0.1M ammonium acetate/methanol (80:20, v/v) as the mobile phase. Typically, the parent antihistamines produced only [MH]s ions under these conditions. The N-oxides provided strong [MH]s ions and multiple fragment ions. A scheme to explain the fragmentation patterns is proposed.

Aminopyridines↗

PubMedDate not supplied

Determination of amoxicillin in catfish and salmon tissues by liquid chromatography with precolumn formaldehyde derivatization.

A liquid chromatographic (LC) method with fluorescence detection was developed for analysis of amoxicillin in catfish and salmon tissues. The tissue was extracted with phosphate buffer (pH 4.5), followed by trichloroacetic acid (TCA) precipitation of proteins and solid-phase (C18) extraction. Trace amounts of nonpolar interfering substances present after solid-phase extraction were removed by ether liquid-liquid extraction. The extract was reacted with formaldehyde and TCA at 100 degrees C for 30 min. A fluorescent derivative was extracted with ether, concentrated, and analyzed by reversed-phase LC with fluorescence detection. Average recoveries of amoxicillin spiked at 2.5-20 ppb were > 80% for catfish and > 75% for salmon muscle tissue, with coefficients of variation of < 6%. Limits of detection (LOD) and quantitation (LOQ) for catfish tissue were 0.5 and 1.2 ppb, respectively. LOD and LOQ for salmon muscle tissue were 0.8 and 2.0 ppb, respectively.

Amoxicillin↗