Caffeine oxide

Daniel et al. [136] investigated the effects of phenothiazine neuroleptics on the rate of caffeine demethylation and hydroxylation in the rat liver. The influence of several phenothiazine neuroleptics, such as chlorpromazine, levomepromazine, thioridazine and perazine, on the cytochrome P-450 activity was measured by means of the caffeine oxidation in rat liver micro-somes. The obtained results demonstrated that all of the neuroleptics under study competitively inhibited their caffeine oxidation in the rat liver, although their potency to inhibit the particular metabolic pathways was not equal. Levomepromazine exerted the most potent inhibitory effect on the caffeine oxidation pathways, and had the most pronounced influence on 8-hydroxylation. 

It is known that not all reactions proceed in the same manner on all adsorbent layers because the material in the layer may promote or retard the reaction. Thus, Ganshirt [209] was able to show that caffeine and codeine phosphate could be detected on aluminium oxide by chlorination and treatment with benzidine, but that there was no reaction with the same reagent on silica gel. Again the detection of amino acids and peptides by ninhydrin is more sensitive on pure cellulose than it is on layers containing fluorescence indicators [210]. The NBP reagent (. v.) cannot be employed on Nano-Sil-Ci8-100-UV2S4 plates because the whole of the plate background becomes colored. 

Geen tea Camellia sinensis Reduces cancer, lowers lipid levels, helps prevent dental caries, antimicrobial and anti oxidative effects Contains caffeine (may cause mild stimulant effects such as anxiety, nervousness, heart irregularities, restlessness, insomnia, and digestive irritation) Contains caffeine and should be avoided during pregnancy, by individuals with hypertension, anxiety, eating disorders, insomnia, diabetes, and ulcers. 

In addition the role played by the sorbent on which the chromatography is carried out must not be neglected. For instance, it is only on aluminium oxide layers and not on silica gel that it is possible to detect caffeine and codeine by exposure to chlorine gas and treatment with potassium iodide — ben2idine [37]. The detection limits can also depend on the sorbent used. The detection limit is also a function of the h/ f value. The concentration of substance per chromatogram zone is greater when the migration distance is short than it is for components with high h/ f values. Hence, compounds with low h/ f values are more sensitively detected. 

J (1999) Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in hiunans , AmJ Clin Nutr, 70, 1040-45. 

A method for determining the caffeine content of regular and decaffinated green and roasted coffee beans and of regular and decaffeinated coffee extract powders, using HPLC, is specified in a British Standard Instruction.34 Caffeine is extracted from the sample with water at 90°C in the presence of magnesium oxide. The mixture is filtered and an aliquot purified on a silica microcolumn modified with phenyl groups. The caffeine content is then determined by HPLC with UV detection.35... 

Extractable caffeine levels increase on storage, presumably because of decomplexation from theaflavins as the latter decrease. Since caffeine binding with thearubigens is weaker than that with theaflavins, more caffeine may become available.94 An increase in free caffeine may be responsible for decreased value because of the bitterness imparted to the beverage. Caffeine in combination with the normal tea complement of oxidized polyphenolic matter does not exhibit bitterness.95... 

The combination of caffeine with the oxidation products of gallated flavanols produces the characteristic described as tangy astringency , probably equivalent to the term briskness applied by professional tea-... 

The organoleptic properties of black tea depend to a considerable extent on the astringency resulting from the interaction of caffeine with the oxidized galloyl ester of the flavanols. The aroma components of black tea also constitute a unique flavor profile that blends well with the taste of the nonvolatile materials. The caffeine provides a moderate level of stimulation, which adds further to the appeal of the beverage, although tea has been shown to provide relaxation as well as revival of character.119... 

Evidence that caffeine contributes antioxidative activity has been shown by the detection of the oxidized caffeine product, 8-oxocaffeine (1,3,7-trimethyluric acid) in roasted, ground and instant coffees, in the range 4 to 35 ppm.160... 

Stadler, R. H., Fay, L. B., Antioxidative reactions of caffeine formation of 8-oxocaffeine (1,3,7-trimethyluric acid) in coffee subjected to oxidative stress, J. Agric. Food Chem., 43(5), 1332, 1995. (CA122 289398f)... 

The key metabolites of caffeine (a trimethylxanthine) found in plasma, are the dimethylxanthines paraxanthine, theophylline, and theobromine the monomethylxanthine 1-methylxanthine the C-8 oxidized monomethylxanthine 1-methyluric acid and the ring oxidized uracil 5-acetyl-amino-6-amino-3-methyluracil. 

Carrillo, J. and Benitez, J., Caffeine metabolism in a healthy Spanish population N-Acetylator phenotype and oxidation pathways. Clinical Pharmacological Therapeutics 55, 293-304, 1994. 

Fig. 10. Mechanism of primary electrochemical oxidation of theobromine (1, R=H) and caffeine (I, R=CH3) at the PGE...

In the case of the methylated xanthines, particularly theophylline, theobromine and caffeine, the preponderance of data on the metabolism of these compounds in man suggests that a methylated uric acid is the principal product. However, the data presented earlier proposes at best a 77 per cent accounting of the methylated xanthine administered. The question can be raised as to whether the final products observed upon electrochemical oxidation of these compounds aids these studies. Very recently studies of metabolism of caffeine have revealed that 3,6,8-trimethylallantoin is a metabolite of caffeine 48>. This methylated allantoin is, of course, a major product observed electrochemically. The mechanism developed for the electrochemical oxidation seems to nicely rationalize the observed products and electrochemical behavior. The mechanism of biological oxidation could well be very similar, although insufficient work has yet been performed to come to any definite conclusions. There is however, one major difference between the electrochemical and biological reactions which is concerned with the fact that in the former situation no demethylation occurs whereas in the latter systems considerable demethylation appears to take place. 

The trimethylsilyloxy (TMSO) group is stable under the coupling conditions in acetonitrile (Table 12, number 6). After oxidative dimerization the TMS-ether can be mildly hydrolyzed (H+ and H2O) to the phenol or converted to a dibenzofuran. 1,2-Dialkoxybenzenes have been trimerized to triphenylenes (Table 5, numbers 7, 8). The reaction product is the triphenylene radical cation, which is reduced to the final product either by zinc powder or in a flow cell consisting of a porous anode and cathode [188]. Anodic trimerization of catechol ketals yields triphenylene ketals, which can function as a platform for receptors, for example, in an artificial caffeine receptor [190]. 

A primary kinetic isotope effect (kn/ko = 6.03 at 298 K) was observed for the oxidation of formic and oxalic acids by benzyltrimethylammonium tribromide (BTMAB) to carbon dioxide. The kinetics of oxidation of pyridoxine to pyridoxal by broma-mine-T and bromamine-B ° and caffeine by bromamine-B have been investigated. 

According to the data available in the literature, both nicotine and caffeine reach much higher concentrations in winter than in summer. The ambient temperature probably influences the net amounts of compounds in the particulate phase, through promoting volatilization in the warm season for instance, nicotine was 2.2 times more abundant in winter than in summer. Nonetheless, atmospheric oxidants seem to play a complementary role in fact, with regard to nicotine this hypothesis is in... 

Alcohols are oxidized to aldehydes by the liver enzyme alcohol dehydrogenase, and aldehydes to carboxylic acids by aldehyde dehydrogenase. In mammals, monooxygenases can be induced by plant secondary metabolites such as a-pinene, caffeine, or isobornyl acetate. Reduction is less common and plays a role with ketones that cannot be further oxidized. Hydrolysis, the degradation of a compound with addition of water, is also less common than oxidation. 

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