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1,2- and 1,4-Cyclohexanediol: major urinary metabolites and biomarkers of exposure to cyclohexane, cyclohexanone, and cyclohexanol in humans.

The metabolism and toxicokinetics of cyclohexane (CH) and cyclohexanol (CH-ol), important solvents and chemical intermediates, were studied in volunteers after 8-h periods of inhalation exposure at concentrations of 1010 and 236 mg m(-3), respectively (occupational exposure limits: CH, 1050 mg m(-3); CH-ol, 200 mg m(-3)). Of the dose of absorbed parent compounds, the yields of urinary CH-ol and 1,2- and 1,4-cyclohexanediol (CH-diol) were 0.5%, 23.4%, and 11.3%, respectively, after exposure to CH and 1.1%, 19.1%, and 8.4%, respectively, after exposure to CH-ol as determined by a gas chromatography method involving hydrolysis of glucuronide conjugates. The metabolic patterns of CH and CH-ol were very similar to that of cyclohexanone (CH-one) studied in the laboratory previously. For all three compounds, peak excretion of CH-ol occurred at the end of the exposure period, after which it decayed rapidly. Excretion curves of 1,2- and 1,4-CH-diol reached maximal values within 0-6 h postexposure, with subsequent elimination half-lives being 14-18 h. The rate-limiting step in the elimination of CH compounds from the organism is renal clearance of CH-diols. Determination of CH-diols in end-of-shift urine samples is recommended as a useful new method of biomonitoring of CH, CH-ol, and CH-one at the workplace. However, due to accumulation of CH-diols in the body during repeated exposure, quantitative relationships between the exposure and the level of CH-diols have to be adjusted according to the day of sampling during the working week.

Adult↗

Cyclohexanol and methylcyclohexanols. A family of inhibitors of hepatic HMGCoA reductase in vivo.

Oral dosing of rats with cyclohexanol and methylcyclohexanols resulted in the inhibition of hepatic HMGCoA reductase. Neither cyclohexane or cyclohexane diols exerted any effects. Inhibition was not due to alcohol dehydrogenase mediated changes in redox state since 3,3',5-trimethylcyclohexanol (TMC), a non substrate for alcohol dehydrogenase, was a potent inhibitor of HMGCoA reductase. Following a single dose of TMC there was no alteration in total hepatic HMGCoA reductase activity for more than 6 hr after which the enzyme activity was depressed in a dose-dependent manner. The normal diurnal rhythm of HMGCoA reductase was reduced in amplitude following TMC administration but the phase was unaltered and the t 1/2 for activity decay following the peak of activity was unaffected. Prior to the inhibitory effect of a TMC dose becoming apparent in total HMGCoA reductase activity we found that the expressed activity of the enzyme (after isolation in F- medium to suppress endogenous protein phosphatase) was depressed by 43%. The inhibitory effect of TMC on total HMGCoA reductase activity seen 8 hr or more after dosing was reflected by inhibition of sterol synthesis in liver measured in vivo after [3H]-H2O administration.

Animals↗

Antidepressant biochemical profile of the novel bicyclic compound Wy-45,030, an ethyl cyclohexanol derivative.

The novel bicyclic compound Wy-45,030 [1-2-(dimethylamino)-1-(4-methoxyphenyl)ethyl cyclohexanol, hydrochloride] exhibited a neurochemical profile predictive of antidepressant activity. Like the tricyclic antidepressants, it inhibited rat brain imipramine receptor binding and synaptosomal monoamine uptake (dopamine as well as norepinephrine and serotonin). It did not inhibit monoamine oxidase. Unlike the tricyclic antidepressants, it was not antimuscarinic in the guinea pig ileum, nor did it have any appreciable affinity for brain alpha-1 adrenergic or histamine-1 binding sites. Wy-45,030 was also without affinity for alpha-2 or beta adrenergic, benzodiazepine, serotonin-1, serotonin-2, dopamine-2, and opiate receptors. Such a profile is predictive of antidepressant activity devoid of the side-effects common to tricyclic therapy.

Animals↗

Continuous enantioselective esterification of trans-2-phenyl-1-cyclohexanol using a new Candida rugosa lipase in a packed bed bioreactor.

Enantioselective resolution of trans-2-phenyl-1-cyclohexanol (TPCH) by a Candida rugosa lipase, obtained by fermentation in the laboratory, and immobilised on EP100 polypropylene powder has been carried out using isooctane as solvent and propionic acid as esterifying agent. The study have included the utilisation of this biocatalyst in a batch process and the optimisation of the esterification conditions by means of a Box-Hunter-based experimental design. The main variables controlling the process, concentration of acid and alcohol, have been numerically optimised using initial esterification rate as objective function. The optimal concentrations for the batch process were 50 mM for the alcohol and 71 mM for the acid. This esterification reaction kinetics corresponded to a reversible Michaelis-Menten kinetic law for the optimal conditions, which has permitted to select a plug-flow packed bed bioreactor as the most appropriate configuration to minimise the residence time and to avoid shear stress effect on the biocatalyst. The behaviour of the continuous packed bed bioreactor at two different residence times (302 and 582 min) was in accordance with predictions from batch experiments, with slightly deviations (less than 10%). Continuous experiments maintained high values of enantioselectivity (enantiomeric factor was practically 1) and conversion near equilibrium value (35%) when long-time operation was carried out. Besides, long-time stability of biocatalyst has permitted to scale-up the production of enantioenriched (1R,2S)-TPCH propionate to yield gram quantities.

Bioreactors↗

Pathology of ocular irritation with acetone, cyclohexanol, parafluoroaniline, and formaldehyde in the rabbit low-volume eye test.

The ocular irritation responses to 11 different surfactants and two concentrations of acetic acid and sodium hydroxide have been shown to depend on the extent of initial injury, despite marked differences in the processes leading to tissue damage. The purpose of these studies was to determine the extent to which this fundamental relationship applies to other nonsurfactants. Ten microl of acetone (ACT). cyclohexanol (CY), parafluoroaniline (PF), or 37% formaldehyde (FA) was directly applied to the cornea of the right eye of each rabbit. Eyes and eyelids were macroscopically scored for signs of irritation beginning 3 hours after dosing and periodically until recovery or 35 days. Tissues were obtained for light microscopic examination after 3 hours and on days 1, 3, and 35. Initial corneal injury was characterized quantitatively at 3 hours and I day using in vivo confocal microscopy (CM) and by postmortem quantitation of dead corneal epithelial cells and keratocytes using a Live Dead Assay (L/D, Molecular Probes) and scanning laser CM. Corneal changes over time were characterized quantitatively using in vivo CM performed at 3 hours and 1, 3, 7, 14, and 35 days. The changes with ACT were consistent with mild irritation. Corneal injury was limited to the epithelium and superficial stroma, with the mean normalized depth of injury (NDI) being less than 10% with the majority of regions showing no stromal injury. Changes with CY and PF were consistent with moderate to severe irritation, and FA caused severe irritation. Specifically, corneal injury by CY and PF tended to involve the epithelium and anterior stroma, with the mean NDI being 10.4% to 23.8%, while injury with FA involved the epithelium, deep stroma, and at times the endothelium. Interestingly, with FA significantly less injury was observed at 3 hours with a dramatic increase in injury observed at 1 day and thereafter. In conclusion, these results continue to support and extend our hypothesis that ocular irritation is principally defined by the extent of initial injury despite clear differences in the means by which irritants cause tissue damage. We believe this approach can be applied to developing alternative assays based on injury to ex vivo eyes or injury to an in vitro corneal equivalent system.

Acetone↗

The trans-cis isomerization of trans-4'-(2-hydroxy-3,5-dibromo-benzylamino)cyclohexanol in vivo and in vitro in different species.

Isomerization of trans-4'-(2-hydroxy-3,5-dibromo-benzylamino)cyclohexanol (HDBC) in vivo has been investigated in horse, cow, dog, rat and man. Following oral administration of 4'-trans-HDBC to the horse, a very efficient first-pass trans-cis isomerization was observed. In the urine of the horse and cow, 40% and 29% respectively of the conjugated alcohols consisted of the 4'-cis isomer. Isomerization in rat and dog took place only to a small extent, and in man no 4'-cis isomer was detected. Oxidation of HDBC to the corresponding ketone, at pH 9.0, was highest with horse- and rat-liver 10 000 g supernatants and lowest with dog-liver supernatant. Reduction of the ketone with 10 000 g liver supernatants and with cryst. horse-liver alcohol dehydrogenase led to the formation of the alcohol containing 42-69% as the 4'-cis isomer, whereas after reduction with NaBH4 the alcohol contained only 20% of the 4'-cis isomer. This indicates that the conformer with the lower energy (1' and 4' position equatorially substituted) preferentially formed only during chemical reduction. A correlation between the formation of the ketone in vitro and the formation of 4'-cis-HDBC in vivo was observed in the horse, cow and dog. No similar correlation was found in the rat, where a high in vivo trans-cis isomerization might have been expected from the in vitro data.

Administration, Oral↗

In vitro metabolism of (-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl) phenyl]-trans-4-(3-hydroxypropyl) cyclohexanol, a synthetic bicyclic cannabinoid analog.

The oxidative metabolism of CP-55,940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3- hydroxypropyl)cyclohexanol] was studied in mouse liver S-9 microsomal preparations. [3H]CP-55,940 was incubated in a microsomal supernatant enriched with the appropriate cofactors for cytochrome P-450 oxidative metabolism. HPLC separation of petroleum ether/diethyl ether (1:1) extracts facilitated the identification of metabolites by GC/MS after derivatization with BSTFA or [2H18]BSTFA. The mass spectral data indicated that five monohydroxylated metabolites had been formed that differed with respect to the position of hydroxylation on the 1',1'-dimethylheptyl side chain. Two additional compounds were detected whose mass spectral data suggested that these metabolites were hydroxylated at two positions on the side chain. Side chain hydroxylation is consistent with the metabolic profile of delta 9-tetrhydrocannabinol (delta 9-THC) and other cannabinoid compounds. It is possible that these side chain-hydroxylated metabolites retain activity, as is the case with similar metabolites formed from delta 9- and delta 8-THC, and thereby contribute to the pharmacological profile seen with this potent synthetic cannabimimetic agent.

Analgesics↗

Docking of cyclohexanol-derivatives into the active site of liver alcohol dehydrogenase. Using computer graphics and energy minimization.

Model building and energy minimization procedures have been used to determine a productive substrate binding mode in liver alcohol dehydrogenase for secondary alcohols. These docking results have been compared to some of the extensive amounts of kinetic data available for this enzyme. The indirect diamond lattice approach first suggested by Prelog (Prelog, V. (1964) Pure Appl. Chem. 9, 119-130) to describe the active site of an enzyme has been used to build a direct diamond lattice from the crystallographic model of the enzyme. This lattice was oriented and positioned into the active site using the productive binding mode of cyclohexanol derivatives obtained from model building. We then classified the positions as allowed, forbidden, or boundary depending on their distances to protein atoms. We found very good agreement between the classification of our direct diamond lattice points and those of the indirect lattice obtained by others from kinetic studies. Finally we have extended the lattice as an aid to predict the stereospecificity of the enzyme for molecules which cover other regions of the active site.

Alcohol Dehydrogenase↗

The effect of the acetylcholine transport blocker 2-(4-phenylpiperidino) cyclohexanol (AH5183) on the subcellular storage and release of acetylcholine in mouse brain.

The effect of the acetylcholine (ACh) transport blocker 2-(4-phenylpiperidino) cyclohexanol (AH5183) on the subcellular storage and release of acetylcholine was studied in mouse forebrain. Results indicated that AH5183 reduced the amount of ACh released from mouse forebrain minces by high K+ and veratridine over the identical concentration range as it inhibits the active transport of ACh into synaptic vesicles isolated from the electric organ of Torpedo. However, AH5183 did not block the K+- or veratridine-induced reduction of cytoplasmic (S3) ACh. Also, it did not block the loss of vesicular (P3) ACh caused by these depolarizing agents. It did, however, cause a disappearance of nerve ending ACh which was partially matched by a selective gain in the choline content of the P3 fraction. When minces of mouse forebrain were pretreated in high K+ to deplete the S3 and P3 fractions of their ACh content and then subsequently incubated in normal Krebs with [14C]choline, AH5183, at a concentration which reduces ACh release by 50%, did not affect the repletion of P3 stores with newly synthesized [14C]ACh. At somewhat higher concentrations, however, AH5183 reduced the amount of [14C]ACh in the P3 fraction without affecting the amount of [14C]ACh in the S3 fraction. At these concentrations it did not inhibit extracellular choline transport or ChAT activity. These results suggest that AH5183 may reduce the amount of ACh released from central cholinergic nerve terminals in response to depolarization through a combination of effects: (1) it may facilitate the breakdown or loss of ACh stored in the vesicular fraction; (2) it may also block the transport of newly synthesized ACh into the vesicular fraction.

Acetylcholine↗

Behavioral effects of phencyclidine and its major metabolite, (trans)4-phenyl-4-(1-piperidinyl)cyclohexanol, in mice.

To elucidate the biological activity of natural metabolites of phencyclidine (PCP), we examined the behavioral effects of a major metabolite, the trans isomer of 4-phenyl-4-(1-piperidinyl)cyclohexanol [(trans)PPC], in mice, (Trans)PPC caused dose-related increase in locomotor activity and rearing in mice when injected intraperitoneally at the doses ranging from 10 to 30 mg/kg. (Trans)PPC at any dose tested failed to produce swaying and falling. On the other hand, PCP at the doses ranging from 1 to 10 mg/kg caused swaying and falling as well as hyperlocomotion in a dose-related manner. These indicate that unlike PCP, hyperlocomotion and rearing may be the predominant behavioral responses to (trans)PPC in the 10-30 mg/kg dose range. Furthermore, it is feasible to surmise that not only PCP but also its major metabolite (trans)PPC is involved in psychotic reactions produced by PCP.

Animals↗

Inhibition of non-quantal acetylcholine leakage by 2(4-phenylpiperidine)cyclohexanol in the mouse diaphragm.

The drug 2(4-phenylpiperidine)cyclohexanol (AH 5183) caused hyperpolarization by 1.8 +/- 0.6 mV in an end-plate zone of mouse diaphragm fibers without any change in the amplitude of miniature end-plate potentials. This supports the idea that the drug inhibits the non-quantal leakage from motor nerve terminals, probably at those parts of the nerve terminals which were incorporated into the terminal membrane after vesicle exocytosis.

Acetylcholine↗

The effect of 2-(4-phenylpiperidino)cyclohexanol (AH-5183), tityustoxin and ouabain on the release of acetylcholine and its mobilization from cytoplasmic and vesicular pools of rat brain cortical slices.

The effect of vesicular acetylcholine (ACh) transport blocker 2-(4-phenylpiperidino)cyclohexanol (AH-5183) on the subcellular storage and release of ACh was studied in rat brain cortical slices. AH-5183 reduced the release of ACh from cortical slices stimulated by tityustoxin and ouabain. Tissue stimulated in the presence of AH-5183 contained more ACh in both the nerve terminal synaptic vesicles and cytoplasmic fraction than did tissue stimulated in drug's absence. Thus, AH-5183 blocked the tityustoxin and ouabain induced release of ACh from both cytoplasmic and vesicular pools. AH-5183 also depressed the spontaneous release of ACh from incubated slices and, in this condition, the drug had no effect in the subcellular distribution of ACh. It is suggested that AH-5183 interferes with the process of ACh release independent of its blocking action on ACh transport into the synaptic vesicles.

Acetylcholine↗

[3H]2-(4-phenylpiperidino)cyclohexanol (AH5183) binding to synaptosomes and subcellular fractions obtained from rat brain.

We investigated the binding of [3H]AH5183 (2-(4-phenylpiperidino)cyclohexanol) to rat brain synaptosomes and subcellular fractions. A high content of specific binding was observed in crude synaptosomes obtained from the striatum, cerebral cortex and hippocampus. The highest density of subcellular binding sites was observed in the synaptic vesicle-rich fraction. The affinities of AH5183 binding to crude synaptosomes and the synaptic vesicle-rich fraction were almost equivalent, but the density of binding sites was higher in the synaptic vesicle fraction. The present findings indicate that [3H]AH5183 binding to both synaptosomes and the synaptic vesicle-rich fraction is useful as a cholinergic marker, and that for quantitative studies, binding to the latter fraction is more preferable.

Animals↗

Effects of the major metabolite of phencyclidine, the trans isomer of 4-phenyl-4-(1-piperidinyl)cyclohexanol, on [3H]N-(1-[2-thienyl] cyclohexyl)-3,4-piperidine ([3H]TCP) binding and [3H]dopamine uptake in the rat brain.

The major metabolite of phencyclidine (PCP), the trans isomer of 4-phenyl-4-(1-piperidinyl)cyclohexanol [(trans)-4-PPC], inhibited [3H]N-(1-(2-thienyl)cyclohexyl)-3,4-piperidine ([3H]TCP) binding to well-washed rat cortical membranes with much less activity than PCP itself. In contrast, it inhibited [3H]dopamine ([3H]DA) uptake in rat striatal synaptosomes to a similar extent as PCP. Considering our previous observations that intraperitoneally administered (trans)-4-PPC elicits dose-related increases in locomotor activity and rearing in mice, (trans)-4-PPC as well as PCP may be involved in psychotomimetic effects of PCP due to its inhibitory effect on DA uptake.

Animals↗

Evaluation and structure-activity relationship of synthesized cyclohexanol derivatives on percutaneous absorption of ketoprofen using artificial neural network.

The effect of 35 newly synthesized O-ethylmenthol (MET) derivatives on percutaneous absorption of ketoprofen was investigated in rats. In order to understand the relationship between the structure of compounds and promoting activity (structure-activity relationship), an artificial neural network (ANN) was employed. In the in vivo percutaneous absorption study, male Wistar rats, weighing 160-180 g, were used. The apparent penetration rate (Rp) was estimated based on a pharmacokinetic model with a constant rate of penetration through the skin after a lag time. As an index of the promoting activity of each compound, an enhancement factor (Ef), defined as follows, was used: Ef=Rp(with enhancer)/Rp(without enhancer). An irritation evoked on rat skin was microscopically judged at the end of the in vivo percutaneous absorption experiment and evaluated as a total irritation score (TIS). Ef and TIS were selected as output variables to determine the ANN structure. Calculated logP, molecular weight, steric energy (SE), van der Waals area, van der Waals volume, dipole moment, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were used as factors to determine the structural nature of cyclohexanol derivatives. Among these parameters, logP, SE and LUMO significantly affected the prediction of Ef and TIS. The predicted values of Ef and TIS coincided well with in vivo percutaneous absorption experimental values. However, results observed with a linear regression method were poor compared with the ANN approach. The contribution index of logP was approximately 50% in the prediction of Ef, suggesting that lipophilicity among physicochemical properties contributes most of the promoting activity of these compounds.

Animals↗

Spirovesamicols: conformationally restricted analogs of 2-(4-phenylpiperidino)cyclohexanol (vesamicol, AH5183) as potential modulators of presynaptic cholinergic function.

In an effort to develop selective inhibitors of vesicular acetylcholine storage, we have synthesized a series of semirigid vesamicol receptor ligands based on the structure of 2-(4-phenylpiperidino)-cyclohexanol (vesamicol, AH5183, 1). In these compounds, the planes of the phenyl and piperidyl moieties of the parent ligand 1 are held at right angles by vinyl, ethylene, and propylene bridges to form N-substituted derivatives of spiro[indene-1,4'-piperidine], 2,3-dihydrospiro[indene-1,4'-piperidine], and 3,4-dihydrospiro[naphthalene-1(2H),4'-piperidine], respectively. Preliminary evaluation of these compounds in electric organ synaptic vesicles revealed several potent vesamicol receptor ligands, such as 1'-(2-hydroxy-1,2,3,4-tetrahydronaphth-3-yl)spiro[1H-indene-1,4'-p iperidine (11b) and 1'-(2-hydroxy-1,2,3,4-tetrahydronaphth-3-yl)spiro[2-bromo-1H-in den e- 1,4'-piperidine] (14), which display subnanomolar affinity for this receptor. In general, the vinyl and ethylene bridges yielded the most potent analogs while the propylene-bridged analogs were among the least potent compounds. The increased rigidity of these spiro-fused compounds, relative to the corresponding simple 4-phenylpiperidine derivatives of vesamicol, is expected to confer greater selectivity for the vesamicol receptor.

Acetylcholine↗

Acyclic analogues of 2-(4-phenylpiperidino)cyclohexanol (vesamicol): conformationally mobile inhibitors of vesicular acetylcholine transport.

Several 1,3-disubstituted propan-2-ols and one alpha,beta-disubstituted ethanol (11i) were synthesized and evaluated as potential acyclic mimics of the vesicular acetylcholine transport inhibitor 2-(4-phenylpiperidinyl)cyclohexanol (1, vesamicol, AH5183). Analogues containing the 4-phenylpiperidyl fragment (11a, 11b) were more potent than those containing the 4-phenylpiperazyl moiety (11e, 11f). Substitution at the second terminal carbon of the propyl (or ethyl) fragment with simple lipophilic aryl substituents yielded potent inhibitors of vesicular acetylcholine storage, including (-)-11a and d-11i, which are equipotent with vesamicol. However, the activity of analogues containing bicyclic aryl groups was susceptible to aryl substitution patterns (11g vs 11h), indicating a definite receptor site topography. In addition, the inhibitory activity of these acyclic analogues was enantioselective, exhibiting a preference, similar to the parent vesamicol, for the levorotatory isomer [(-)-11a vs (+)-11a]. Therefore, the simple lipophilic acyclic vicinal amino alcohols may successfully mimic the biological activity of vesamicol.

Acetylcholine↗