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PubMedDate not supplied

Determination of cyclohexanol in urine and its use in environmental monitoring of cyclohexanone exposure.

A simple and sensitive method for determining urinary cyclohexanol, the main metabolite of cyclohexanone, by hydrolysis and gas chromatography (GC) with a flame ionization detector was developed. A 2-mL urine sample was hydrolyzed with 0.4 mL of concentrated HCl and followed by extracting twice with diethylether. Two microL of the filtrate was injected into the GC with a methyl silicone column. The detection limit is estimated to be 0.4 mg/L. The coefficient of variation for the procedure is 8% and 10% for the range of concentration 5 and 50 mg/L, respectively. The within-run variation was 5.4% and between-day variation was 9.67%. The method was verified with urine samples collected from workers exposed to cyclohexanone. An excellent correlation (r = 0.88) was observed between environmental cyclohexanone exposure and cyclohexanol in urine. The procedure is relatively simple and reproducible and it can be applied for occupational health measurement of cyclohexanone exposure.

Calibration↗

PubMed2000

Role of C-5 chiral center in R-(+)-pulegone-mediated hepatotoxicity: metabolic disposition and toxicity of 5, 5-dimethyl-2-(1-Methylethylidene)-cyclohexanone in rats.

Metabolic disposition of 5, 5-dimethyl-2-(1-methylethylidene)-cyclohexanone (I) was examined in rats. Compound (I) was administered orally (250 mg/kg of body weight/day) to rats for 5 days. The following urinary metabolites were isolated and identified: 4,5,6,7-tetrahydro-3,6, 6-trimethylbenzofuran (III), 3,3-dimethylcyclohexanone (VI), 5, 5-dimethyl-3-hydroxy-2-(1-methylethylidene)-cyclohexanone (X), 5, 5-dimethyl-2-(1-hydroxymethylethyl)-cyclohexanone (IX), 3-hydroxy-5-hydroxymethyl-5-methyl-2-(1-methylethylidene)-cyclo hexano ne (XI), 5,6-dihydro-3,6,6-trimethyl-2(4H)-benzofuranone (VIII), and 5,5-dimethyl-3-hydroxy-2-(1-carboxy ethylidene)-cyclohexanone (XIII). Incubation of compound (I) with phenobarbital (PB)-induced rat liver microsomes in the presence of NADPH resulted in the formation of a metabolite, tentatively identified as a furanoterpene (III) based on proton magnetic resonance, gas chromatography, and gas chromatography-mass spectroscopy analyses. The formation of III was inhibited to a significant extent by carbon monoxide, metyrapone, SKF 525-A, and cytochrome c, suggesting the participation of PB-induced microsomal cytochrome P-450 system in the conversion of I to III. Compound I gave type I spectral change in the PB-induced liver microsomes and the dissociation constant (Ks) for I was 38.5 microM. Intraperitoneal administration of a single dose (250 mg/kg) of I to rats resulted in 26, 23, and 41% decreases in the levels of cytochrome P-450, glucose-6-phosphatase, and aminopyrine N-demethylase, respectively, at the end of 24 h. During this period, a 11-fold increase in serum glutamate pyruvate transaminase level was also observed. However, a decrease in the level of cytochrome P-450 and glucose-6-phosphatase, and an increase in serum glutamate pyruvate transaminase values were comparatively more pronounced when R-(+)-pulegone (250 mg/kg) or CCl(4) (0.6 ml/kg) was administered to rats. Pretreatment of rats with PB potentiated the hepatotoxicity caused by I, whereas pretreatment with 3-methylcholanthrene protected from it. This suggests that PB-induced cytochrome P-450-catalyzed reactive metabolites may be responsible for the toxic effects caused by I.

Aminopyrine N-Demethylase↗

PubMedDate not supplied

Gas chromatographic determination of cyclohexanone leached from hemodialysis tubing.

A capillary gas chromatographic procedure is described for the determination of cyclohexanone leached from hemodialysis tubing by water. Recoveries were 100% at 2.0 mg/100 mL (20 ppm), 99.0% at 500 microg/100 mL (5 ppm), and 106% at 1.0 microg/100 mL (10 ppb). Reproducibility of the system was 0.152% for 3.0 microL injections of a solution containing cyclohexanone at 5.58 microg/mL. Correlation coefficients were 0.9983 for 0.3672-3.672 ng and 1.0000 for 3.672-367.2 ng. Twenty hemodialysis tubing sets from 4 manufacturers were examined. The leachable cyclohexanone ranged from 1.02 to 43.7 ppm per set. Rinsing the tubing with 1 L 0.9% sodium chloride solution did not remove significant amounts (P = 0.05) of leachable cyclohexanone.

Chromatography, Gas↗

PubMed2006

Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone in airlift sonochemical reactor.

Baeyer-Villiger oxidation of cyclohexanone to epsilon-caprolactone was studied in a new type reactor--the airlift loop sonochemical reactor. The reactor plays a synergistic effect of sonochemsity and higher oxygen transfer rate. The influences of ultrasound intensity, reaction temperature, the molar ratio of benzaldehyde to cyclohexanone and oxygen gas flow rate on the conversion and selectivity of cyclohexanone were investigated and discussed. Under ultrasound, the amount of benzaldehyde can be reduced from 75% to 67%. Ultrasound not only intensified the rates of reactions but also increased the yield of product. The optimized operation conditions are listed as follows: the reaction temperature is 30 degrees C, the molar ratio of cyclohexanone to benzaldehyde is 1:2, the oxygen gas flow rate is 1.15 cm s(-1), and ultrasonic irradiations 2h at 40 kHz, 2.25 W cm(-2). Under the optimum operation conditions, the average molar yield of epsilon-caprolactone comes up to 87.7%.

Journal Article↗

PubMed1967

Partition of porphyrins between cyclohexanone and aqueous sodium acetate as a function of pH. Determination of uroporphyrin and of hydrophilic porphyrin conjugates.

1. The partition of uroporphyrins I and III, coproporphyrins I and III, haematoporphyrin IX, porphyrin c and a hydrophilic porphyrin-peptide fraction from variegate-porphyria faeces has been studied in systems of equal volumes of cyclohexanone and sodium acetate buffers of varying pH and concentration. 2. The concentration of acetate in the aqueous phase has little effect on the partition of porphyrin c, but markedly influences that of uroporphyrin. At 50% acetate saturation and pH4.5, only 5% enters the cyclohexanone phase whereas 60% of porphyrin c is extracted under similar conditions. 3. This circumstance forms the basis of a method for the determination of hydrophilic porphyrin-peptides in variegate-porphyria urine. Its reliability has been checked in model experiments. 4. At pH1.5 and an aqueous phase half-saturated with sodium acetate, an equal volume of cyclohexanone removes 95-97% of uroporphyrin and about 55% of porphyrin c. Uroporphyrin may therefore be determined as a second step in the method. 5. For the routine determination of uroporphyrin in systems free from other hydrophilic porphyrins, cyclohexanone extraction may be performed at any pH in the range 1.0-3.0.

Journal Article↗

PubMed2002

Identification of two gene clusters involved in cyclohexanone oxidation in Brevibacterium epidermidis strain HCU.

Brevibacterium epidermidis HCU can grow on cyclic ketones and alcohols as a sole carbon source. We have previously reported the identification of two cyclohexanone-induced Bayer-Villiger monooxygenase genes by mRNA differential display. Using the related technique of Out-PCR, we have amplified large DNA fragments flanking the two monooxygenase genes. Two large gene clusters were sequenced. Several ORFs in each gene cluster encoded proteins homologous to cyclohexanol and cyclohexanone oxidation enzymes from Acinetobacter. However, the structure of these two gene clusters differs significantly from that of Acinetobacter, where the complete pathway has been described. To assess activity of these genes, they were cloned and expressed in Escherichia coli. In vivo and in vitro assays enabled us to assign functions to the expressed ORFs. These ORFs included a cyclohexanol dehydrogenase, two different epsilon-caprolactone hydrolases and two 6-hydroxyhexanoate dehydrogenases belonging to different enzyme families. Because this environmental isolate is difficult to manipulate, we cannot determine at this time which cluster is involved in the degradation of cyclohexanone under physiological conditions. However, the original differential display experiments and some of the experiments reported here suggest the involvement of both gene clusters in the oxidation of cyclic ketones.

Base Sequence↗

PubMed2004

Validated HPLC determination of 2-[(dimethylamino)methyl]cyclohexanone, an impurity in tramadol, using a precolumn derivatisation reaction with 2,4-dinitrophenylhydrazine.

A new method for the determination of 2-[(dimethylamino)methyl]cyclohexanone (DAMC) in Tramadol (as active substance or active ingredient in pharmaceutical formulations) is described. The method is based on the derivatisation of 2-[(dimethylamino)methyl]cyclohexanone with 2,4-dinitrophenylhydrazine (2,4-DNPH) in acidic conditions followed by a reversed-phase liquid chromatographic separation with UV detection. The method is simple, selective, quantitative and allows the determination of 2-[(dimethylamino)methyl]cyclohexanone at the low ppm level. The proposed method was validated with respect to selectivity, precision, linearity, accuracy and robustness.

Chromatography, High Pressure Liquid↗

PubMed2005

A comparison of cyclohexanone and tetrahydro-4H-thiopyran-4-one 1,1-dioxide as pharmacophores for the design of peptide-based inhibitors of the serine protease plasmin.

The plasminogen system is important in the proteolytic cascade that facilitates angiogenesis, a process that is essential for tumor growth and metastasis. The serine protease plasmin has a central role in the plasminogen system. This protease acts by degrading several components of the basement membrane and by activating other proteases. Therefore, inhibition of plasmin may be an effective method for blocking angiogenesis and, as a result, inhibiting the growth of primary tumors and secondary metastases. Three pairs of plasmin inhibitors were synthesized to compare the relative potency of inhibitors that are based upon a cyclohexanone or a tetrahydro-4H-thiopyran-4-one 1,1-dioxide nucleus. Compounds 1, 3, and 5 were cyclohexanone-based inhibitors, whereas compounds 2, 4, and 6 were tetrahydro-4H-thiopyran-4-one 1,1-dioxide-based inhibitors. Compounds 5 and 6 are reasonable inhibitors with IC50 values of 25 and 5.5 microM, respectively. Comparisons of the IC50 values of the three pairs show that the electron-withdrawing sulfone functional group is a beneficial element for the design of plasmin inhibitors. The presence of the sulfone increases inhibitor potency by a factor of 3-5 when compared to inhibitors that are based upon a simple cyclohexanone core.

Antifibrinolytic Agents↗

PubMed1998

[Stereoselective epoxidation with bulky dioxiranes generated from substituted cyclohexanones].

Dioxiranes have recently been shown to be important and versatile oxidants, which are generated from potassium monoperoxysulfate (KHSO5) and ketones. Dimethyldioxirane, a dioxirane generated from acetone as a ketone, is particularly useful as an oxidation reagent with a broad scope of synthetic applications. Several papers have been reported about stereoselective epoxidation using dimethyldioxirane. However, there have been only a few examples using dioxiranes generated from other ketones. Dioxiranes derived from sterically hindered ketones are expected to be "bulky oxidant", and to be useful for stereoselective epoxidation. In a CH2Cl2-buffered water (two-phase system) in the presence of phase-transfer agent under neutral condition (pH 7.8) according to the reported procedure, the epoxidations with hindered alpha-substituted cyclohexanones proceeded in very low yields. After a survey of possible conditions we found that basic (pH 11) CH2Cl2-MeOH-buffer system was effective for the epoxidations of olefins with Oxone (active constituent KHSO5) and substituted cyclohexanones. We carried out epoxidation of cyclohexen derivatives with dioxiranes derived from alpha-substituted cyclohexanones in a CH2Cl2-MeOH-buffer solvent system at pH 11. High trans selectivities were obtained. Furthermore, according to this method acyclic silyl ethers were stereoselectively oxidized to afford erythro epoxides.

Chemistry, Organic↗

PubMedDate not supplied

Capillary gas chromatographic determination of cyclohexanone and 2-ethyl-1-hexanol leached from solution administration sets.

A capillary gas chromatographic method is described for the determination of cyclohexanone and 2-ethyl-1-hexanol leached from solution administration sets. A preliminary study was made of compounds leached from solution administration sets by 5% sodium bicarbonate solution (pH 8.1), 0.9% sodium chloride solution (pH 6.8), and water. Water was selected as the leaching solvent because similar quantities of the compounds were leached into water and into both types of parenteral solutions. The correlation coefficients were 0.99977 for cyclohexanone and 0.99974 for 2-ethyl-1-hexanol, and recoveries were good (93-94%). Five administration sets from each of 2 manufacturers were analyzed by this method. The amounts of cyclohexanone that were leached from the individual sets varied considerably; however, similar quantities were leached from sets of both manufacturers. 2-Ethyl-1-hexanol was also found in extracts from each of the sets analyzed.

Chromatography, Gas↗

PubMed1987

Studies on the resistance of activated sludge bacteria to high concentrations of methanol, butanol, glycol, cyclohexanone and cyclohexylamine.

The resistance of bacterial strains isolated from activated sludge purifying petrochemical wastewaters to high concentrations of methanol, butanol, glycol, cyclohexanone and cyclohexylamine was examined. The strains were found to be resistant to up to 5000 mg/l of methanol, butanol and glycol. Cyclohexylamine in concentration 1500 mg/l completely inhibited the growth of all examined strains whereas cyclohexanone even at concentration 4500 mg/l eliminated only about half of the isolated strains. The highest resistance to cyclohexane derivatives was shown by bacteria belonging to Pseudomonas III. None of the studied strains was, however, able to utilize cyclohexanone and cyclohexylamine as a source of barbon and energy.

Alcohols↗

PubMed1989

Effect of cyclohexanone derivatives on in vitro percutaneous absorption of indomethacin.

We have previously shown that cyclohexanone derivatives exert a promoting effect on the in vivo percutaneous absorption of indomethacin (IMC), and now describe in vitro permeation studies to gain understanding of the mechanism of action. The results of the in vitro experiment were consistent with those of the previous in vivo experiments. 2-tert-Butylcyclohexanone was the most effective of six enhancers examined. The partition coefficient of IMC was determined in a buffer-octanol system containing the cyclohexanone derivatives, and the lipophilicities of these derivatives are discussed using a lipophilic index. We conclude that the cyclohexanone derivatives penetrate into the stratum corneum and alter the skin permeability of IMC by fluidizing or modifying the hard hydrophobic barrier of the corneum.

Animals↗

PubMed2001

Purification and characterization of hexahistidine-tagged cyclohexanone monooxygenase expressed in Saccharomyces cerevisiae and Escherichia coli.

Cyclohexanone monooxygenase (CMO) is a soluble flavoenzyme originally isolated from Acinetobacter spp. which carries out Baeyer-Villiger reactions with cyclic ketone substrates. In the present study we cloned the Acinetobacter CMO gene and modified it for facile purification from heterologous expression systems by incorporation of a His(6)-tag at its C-terminus. A single purification step employing metal (Ni(2+))-affinity column chromatography provided essentially homogeneous enzyme in yields of 69-72%. The properties of the purified, recombinant enzymes (rCMO) were compared with that of native CMO (nCMO) isolated from Acinetobacter cultures grown in the presence of cyclohexanone. The specific activities of His(6)-tagged rCMO and nCMO toward their index substrate, cyclohexanone, were similar and ranged from 14 to 20 micromol/min/mg. nCMO and rCMO from the Escherichia coli expression system exhibited molecular masses, determined by electrospray mass spectrometry, of 60,800 and 61,615 Da, respectively, an increase for the recombinant enzyme equivalent to the mass of the His(6)-tag. However, rCMO expressed in Saccharomyces cerevisiae consistently exhibited a mass some 50 Da larger than rCMO expressed in bacteria. Edman degradation confirmed that rCMO purified from the E. coli system and nCMO shared the same N-terminal sequence, whereas no sequence information could be obtained for rCMO expressed in yeast. Therefore, the yeast-expressed enzyme possesses an additional posttranslational modification(s), possibly acylation, at the N-terminus. Expression in E. coli is the preferred system for future site-directed mutagenesis studies and crystallization efforts.

Acinetobacter↗

PubMed2001

A theoretical study of the reaction of lithium aluminum hydride with formaldehyde and cyclohexanone.

Geometries and energies of the reactants, complexes, and transition states for the reactions of lithium aluminum hydride with formaldehyde and cyclohexanone were obtained using ab initio and density functional (Becke3LYP/6-31G**) molecular orbital calculations. Two pathways for reaction with formaldehyde and four transition states corresponding to axial and equatorial attack at cyclohexanone were located. The transition state structures had reactant-like geometries. Predicted stereoselectivity of the reduction of cyclohexanone strongly favors axial approach of hydrogen, in agreement with experimental data. Analysis of the transition state structures suggests that electronic effects are more important than torsional effects in controlling stereoselectivity.

Journal Article↗

PubMed1999

Empirical Relationship between the Conformation and the Direction of Carbonyl Group Pyramidalization of Cyclohexanones.

A statistical investigation of precise crystal structures from the Cambridge Structural Database shows that cyclohexanones have a predictable pyramidalization of the carbonyl group in the chair conformation that depends on the puckering of the ring. Flattened cyclohexanones are usually "axially pyramidalized" (see Figure 1), whereas more strongly puckered cyclohexanones are usually "equatorially pyramidalized". It is conceivable that a cooperation between electronic effects (hyperconjugation) and steric effects (relief from torsional strain) leads to this unique correlation. No such conformation/pyramidalization correlations are observed for other ketones.

Journal Article↗

PubMed2005

Catalytic oxidation with air of cyclohexanone to dicarboxylic acids on synthetic carbons. Effect of supported metals and solvents.

The oxidation with air of cyclohexanone was conducted in the presence of synthetic carbons catalysts. The effect of carbon activation treatment (CO2 or air burnoff), phosphorus additive, platinum loading, and nature of the solvent (water or water/acetic acid mixture) were studied. Cyclohexanone oxidation at 140 degrees C yielded a mixture of C6, C5, and C4 dicarboxylic acids. Air activated carbons, including those containing phosphorus or those supporting platinum, resulted in a higher yield of adipic acid. The activity and selectivity was associated with the oxygenated functional groups, essentially carbonyl/quinone groups, created during air activation of the carbon. The incorporation of phosphorus into the carbon increased slightly the selectivity to 34.3%, probably because this additive increased the density of oxygenated functional groups. The deposition of platinum by impregnation and liquid-phase reduction with formaldehyde increased the reaction rate and improved the selectivity to adipic acid, where the highest figure was 38.8%. It was suggested that platinum contributed to molecular oxygen activation. In contrast platinum deposition by cationic exchange followed by reduction under H2 resulted often in a detrimental effect probably because the density of the oxygenated groups on carbon is decreased upon H2 reduction in the presence of platinum. When the oxidation of cyclohexanone was carried out in mixtures of water/acetic acid, the selectivity given by the different samples were quite close and generally smaller than those obtained in water which indicates that acetic acid interacts with the oxygenated surface functional groups responsible for the activity and selectivity. Oxidation experiments with methyl-labeled 4-methylcyclohexanone indicated that glutaric acid was produced by oxidative decarbonylation of both the C1 and C2 carbon atoms of the molecule.

Journal Article↗

PubMed2002

Construction of substituted cyclohexanones by reductive cyclization of 7-oxo-2,8-alkadienyl esters.

[reaction: see text] Cyclization of 7-oxo-2,8-alkadienyl esters upon reaction with triphenylphosphinecopper hydride hexamer stereoselectively yields substituted cyclohexanones having a cis relationship of carbon side chains at C2 and C3. This cyclohexanone construction is particularly useful for preparing 4-alkoxy- or 4-siloxy-2,3-disubstituted cyclohexanones, in which instance stereoselection is > or = 20:1.

Journal Article↗

PubMed1976

Multiple forms of cyclohexanone oxygenase from Nocardia globerula CL1.

The cyclohexanone 1,2-monooxygenase of Nocardia globerula CL1 exists as two electrophoretically distinct forms. These are present in crude cell extracts and are not artifacts of enzyme purification or electrophoresis. They have been separated in mg amounts by preparative polyacrylamide gel electrophoresis and shown to have essentially identical kinetic, spectral and physical characteristics. They do differ in pH-activity profile and temperature stability. Whether or not they are conformational isoenzymes or arise by gene duplication and divergent evolution has not been established. Cyclohexanone oxygenase constitutes 8% of the soluble protein of induced cells. This high level would correlate well with the presence of duplicate genes. It is proposed that the presence of a large amount of cyclohexanone oxygenase may confer an ecological advantage on the organism.

Drug Stability↗