Influence of menthol on caffeine disposition and pharmacodynamics in healthy female volunteers

Objectives: The present study was undertaken to determine whether a single oral dose of menthol affects the metabolism of caffeine, a cytochrome P 450 1A2 (CYP1A2) substrate, and pharmacological responses to caffeine in people. Methods: Eleven healthy female subjects participated in a randomized, double-blind, two-way crossover study, comparing the kinetics and effects of a single oral dose of caffeine (200 mg) in coffee taken together with a single oral dose of menthol (100 mg) or placebo capsules. Serum caffeine concentrations and cardiovascular and subjective parameters were measured throughout the study. Results: Co-administration of menthol resulted in an increase of caffeine tmax values from 43.6 ± 20.6 min (mean ± SD) to 76.4 ± 28.0 min (P<0.05). The Cmax values of caffeine were lower in the menthol phase than in the placebo phase, but this effect was not statistically significant (P=0.06). (AUG)0-24, (AUC)0-∞, terminal half-life and oral clearance were not affected by menthol. Only nine subjects' cardiovascular data were included in the analysis because of technical problems during the measurements. After caffeine, heart rate decreased in both treatment phases. The maximum decrease in heart rate was less in the menthol phase (-8.9 ± 3.9 beats/min) than in the placebo phase (-13.1 ± 2.1 beats/min) (P = 0.024). There were no statistically significant differences in systolic and diastolic blood pressures between the two treatments. Conclusions: We conclude that a single oral dose of pure menthol (100 mg) delays caffeine absorption and blunts the heart-rate slowing effect of caffeine, but does not affect caffeine metabolism. The possibility that menthol slows the absorption of other drugs should be considered.Dokuz Eylul University Research Foundation (project no: 0909.99.02.16

Reaction of dinaphthyl and diphenyl ethers at liquefaction conditions

The reactions of 2,2'-dinaphthyl ether and diphenyl ether were studied at 375-425°C using 6.9 MPa (cold) hydrogen or nitrogen, 9,10-dihydrophenanthrene (DHP) and decalin as solvents, and a molybdenum sulfide catalyst. We chose to examine these compounds as models for the cleavage of diaryl ether bridges during coal liquefaction. The molybdenum sulfide was added to the reaction as MoS3, which should transform to the active MoS2 catalyst. Cleavage of the Car-O in 2,2'-dinaphthyl ether, at reaction temperatures of 375 and 400°C, proceeded in the sequence H2 &lt; DHP-N2 &lt; DHP-H2 &lt; DHP-MoS3-N2 &lt; DHP-MoS3-H2 &lt; MoS3-H2 &lt; Dec.-MoS3-H2. At 425°C, the MoS3-H2 and Dec.-MoS3-H2 systems exchange places in this order. Diphenyl ether is less reactive than dinaphthyl ether toward hydrogenolysis reactions under these conditions. The conversion rate of diphenyl ether increases in the order H2 &lt; DHP-H2 &lt; DHP-MoS3-N2 &lt; DHP-MoS3-H2 &lt; Dec.-MoS3-H2 &lt; MoS3-H2. Although the rates of conversion of the two ethers are different, the relative effects of using a reactive gaseous atmosphere, donor solvent, catalyst - or some combination of these factors - are the same for both compounds. In liquefaction experiments, hydrogen donor solvent or hydrogen shuttling solvent seems necessary to reduce retrogressive reactions. However, a solvent interacting strongly with catalyst and scavenging hydrogen atoms can reduce the activity of catalysts in hydrocracking reactions.KTCAG-127 FEF-92-1The authors thank Dr Yasar Demirel for providing the MINUIT package program, the Computer Center of cukurova University for providing the computation facilities, and Ronald Copenhaver, Penn State University, for fabricating tubing bombs. This work was supported by Cukurova University Research Fund’s FEF-92-1 project and the Scientific and Technical Research Council of Turkey under contract number KTCAG-127

Temperature-staged liquefaction of selected Turkish coals

Four Turkish coals, along with two American coals for comparison, were liquefied at various temperature-staged conditions in bench-scale microautoclave reactors. 9,10-Dihydrophenanthrene was used as a strong donor solvent, and ammonium tetrathiomolybdate was added to some reactions as a catalyst precursor for the in situ generation of a hydrogenation catalyst. The combination of a potent hydrogen donor and good catalyst were sufficient to provide conversions ?90% (d.a.f. basis) for all coals in this study. The most important role of the solvent is in the initial breakdown of the coal. A catalyst is important for upgrading of the initial products, but it is also active in promoting hydrogen transfer from the solvent to the coal. For reactions of Çan lignite in the absence of catalyst, most of the hydrogen transferred to the coal derives from the solvent; when a sulfided molybdenum catalyst is added, most of the hydrogen consumed comes from gas-phase H2. Oil (hexane-solubles) yield increases linearly with increasing hydrogen consumption. The best results in the present study were a 98.8% conversion with 72.2% oil yield, which were obtained with Seyit Omer lignite with 2:1 solvent:coal ratio, added catalyst, and 30 minutes each at 275 and 425°C. © 1994

The effect of additives on hydrodesulfurization of dibenzothiophene over bulk molybdenum sulfide: Increased catalytic activity in the presence of phenol

The effect of various additive organic reagents on the activation of MoS3 as molybdenum sulfide catalyst precursor during hydrodesulfurization reaction of dibenzothiophene was studied. It was found that the presence of phenol or 1-naphthol greatly promoted the activity of the catalyst, while tetralin, 9,10-dihydrophenanthrene, ethylbenzene, and pyridine reagents were found to be detrimental for the activity of the catalyst. © 2007

Upgrading lignites via thermal reduction with coke-oven gas

Three Turkish lignites of varying rank were processed by using coke-oven gas under various processing conditions. Proximate and ultimate analyses and microscopic investigations with a polarized-reflected light microscope were carried out for all of these samples. Gaseous products were also determined after each process. Blends of processed lignites with coking coals were subjected to dilatation tests and cokes were produced in a laboratory scale coke oven using the same blends. The tensile strengths of the cokes produced were determined. The chemical and physical data showed that there are useful changes in lignite structures upon treatment with coke-oven gas under certain processing conditions. The dilatation and tensile-strength results showed that it would be possible to blend processed lignites with coking coals in significant proportions to produce metallurgical grade cokes. © 1991.International Science and Technology Cooperation ProgrammeThis research project is being supported by the Programme in Science and Technology Cooperation of the Agency for International Development under Grant no. DPE-5542-G-SS-8031-00

Direct liquefaction of high-sulfur coals: Effects of the catalyst, the solvent, and the mineral matter

WOS: 000178122100005Two low-rank coals with high sulfur contents (Gediz subbituminous coal: 7.6 wt % S:dry basis. Cayirhan lignite: 5.7 wt%, S:dry basis.) were subjected to hydroliquefaction. Liquefaction conditions included dry or solvent mediated runs under pressurized hydrogen without added catalyst or with the impregnated catalyst precursor ammonium heptamolybdate AHM). Gediz coal having higher sulfur content gave 90% conversion in the absence of catalyst and solvent. Maximum conversion (98%) and maximum oil + gas yield (70%) from this coal were obtained by impregnating AHM onto coal and carrying out liquefaction in H-2/tetralin system at 450 degreesC for 30 min. Under the same conditions, Cayirhan lignite gave 85% conversion and 70.5% oil + gas yield. The superior hydrodesulfurization effect of impregnated AHM on the oil fraction when used in the absence of solvent (less than 0.1% S in lignite's oil and less than 1% S in subbituminous coal's oil following one-stage hydrogenation) is a promising finding of this work. AHM was found to be much more effective in liquefaction of Cayirhan lignite and this has been ascribed to the well-dispersion of AHM throughout this lignite's structure via a cation-exchange mechanism through oxygen functionalities. Strong evidence for the catalytic effect of clay minerals in coal structure on char-forming reactions during liquefaction was observed by making use of liquefaction reactions of demineralized coal samples. It was also observed that tetralin had a retarding effect on the condensation and subsequent cross-linking reactions

Swelling Pretreatment of Coals for Improved Catalytic Temperature-Staged Liquefaction

Two coals, a Texas subbituminous C and a Utah high-volatile A bituminous, were used to examine the effects of solvent swelling and catalyst impregnation on liquefaction conversion behavior in temperature-staged reactions for 30 min each at 275 and 425 °C in H2 and 95:5 H2:H2S atmospheres. Methanol, pyridine, tetrahydrofuran, and tetrabutylammonium hydroxide were used as swelling agents. Molybdenum-based catalyst precursors were ammonium tetrathiomolybdate, molybdenum trisulfide, molybdenum hexacarbonyl, and bis(tricarbonylcyclopentadienylmolybdenum). Ferrous sulfate and bis(dicarbonylcyclopentadienyliron) served as iron-based catalyst precursors. In addition, ion exchange was used for loading iron onto the subbituminous coal. For most experiments, liquefaction in H2–H2S was superior to that in H2, regardless of the catalyst precursor. The benefit of the H2S was greater for the subbituminous, presumably because of its higher iron content relative to the hvAb coal. Tetrabutylammonium hydroxide was the only swelling agent to enhance conversion of the hvAb coal significantly; it also caused a remarkable increase in conversion of the subbituminous coal. The combined application of solvent swelling and catalyst impregnation also improves liquefaction, mainly through increased oil yields from the hvAb coal and increased asphaltenes from the subbituminous. A remarkable effect from use of ammonium tetrathiomolybdate as a catalyst precursor is substantial increase in pristane and phytane yields. Our findings suggest that these compounds are, at least in part, bound to the coal matrix. © 1993, American Chemical Society. All rights reserved

Direct liquefaction of high-sulfur coals: Effect of the catalyst, the solvent, and the mineral matter

Two low-rank coals with high sulfur contents (Gediz subbituminous coal: 7.6 wt % S:dry basis. Çayirhan lignite: 5.7 wt% S:dry basis.) were subjected to hydroliquefaction. Liquefaction conditions included dry or solvent mediated runs under pressurized hydrogen without added catalyst or with the impregnated catalyst precursor ammonium heptamolybdate (AHM). Gediz coal having higher sulfur content gave 90% conversion in the absence of catalyst and solvent. Maximum conversion (98%) and maximum oil + gas yield (70%) from this coal were obtained by impregnating AHM onto coal and carrying out liquefaction in H2/tetralin system at 450 °C for 30 min. Under the same conditions, Çayirhan lignite gave 85% conversion and 70.5% oil + gas yield. The superior hydrodesulfurization effect of impregnated AHM on the oil fraction when used in the absence of solvent (less than 0.1% S in lignite's oil and less than 1% S in subbituminous coal's oil following one-stage hydrogenation) is a promising finding of this work. AHM was found to be much more effective in liquefaction of Çayirhan lignite and this has been ascribed to the well-dispersion of AHM throughout this lignite's structure via a cation-exchange mechanism through oxygen functionalities. Strong evidence for the catalytic effect of clay minerals in coal structure on char-forming reactions during liquefaction was observed by making use of liquefaction reactions of demineralized coal samples. It was also observed that tetralin had a retarding effect on the condensation and subsequent cross-linking reactions

Catalyst dispersion and activity under conditions of temperature- staged liquefaction

The general objectives of this research are (1) to investigate the use of highly dispersed catalysts for the pretreatment of coal by mild hydrogenation, (2) to identify the active forms of the catalysts under reaction conditions and (3) to clarify the mechanisms of catalysis. The ultimate objective is to ascertain if mild catalytic hydrogenation resulting in very limited or no coal solubilization is an advantageous pretreatment for the transformation of coal into transportable fuels. The experimental program will focus upon the development of effective methods of impregnating coal with catalysts, evaluating the conditions under which the catalysts are most active and establishing the relative impact of improved impregnation on conversion and product distributions obtained from coal hydrogenation. Liquefaction experiments of solvent-treated and untreated Blind Canyon (DECS-6) and Texas lignite (DECS-1) have been performed using ammonium tetrathiomolybdate (ATTM) and bis (dicarbonylcyclopentadienyl) iron (CPI) as catalyst precursors using temperature-staged conditions (275{degrees}C, 30 min; 425{degrees}C, 30 min). Solid state {sup 13}C NMR analysis was carried out for each coal and for selected residues. 12 refs., 14 figs., 9 tabs

Catalyst dispersion and activity under conditions of temperature- staged liquefaction

The general objectives of this research are (1) to investigate the use of highly dispersed catalysts for the pretreatment of coal by mild hydrogenation, (2) to identify the active forms of catalysts under reaction conditions and (3) to clarify the mechanisms of catalysis. The ultimate objective is to ascertain if mild catalytic hydrogenation resulting in very limited or no coal solubilization is an advantageous pretreatment for the transformation of coal into transportable fuels. The experimental program will focus upon the development of effective methods of impregnating coal with catalysts, evaluating the conditions under which the catalysts are most active and establishing the relative impact of improved impregnation on conversion and product distributions obtained from coal hydrogenation