Showing papers on "Theobromine published in 1975"

Biosynthesis of caffeine by tea-leaf extracts. Enzymic formation of theobromine from 7-methylxanthine and of caffeine from theobromine.

Abstract: 1. Extracts prepared from tea leaves with Polyclar AT (insoluble polyvinylpyrrolidine) contained two methyltransferase activities catalysing the transfer of methyl groups from S-adenosylmethionine to 7-methylxanthine, producing theobromine, and to theobromine, producing caffeine. 2. The methyltransferases exhibited the same pH optimum (8.4) and a similar pattern of effects by metal ions, thiol inhibitors and metal-chelating reagents, both for theobromine and caffeine synthesis. Mg2+, Mn2+ and Ca2+ slightly stimulated enzyme activity but they were not essential. Paraxanthine was shown to be most active among methylxanthines, as the methyl acceptor. However, the formation of paraxanthine from 1-methylxanthine was very low and that from 7-methylxanthine was nil, suggesting that the synthesis of caffeine from paraxanthine is of little importance in intact plants. Xanthine, xanthosine, XMP and hypoxanthine were all inactive as methyl acceptors, whereas [2(-14)C]xanthine and [8(-14)C]hypoxanthine were catabolized to allantoin and urea by tea-leaf extracts. The apparent Km values are as follows: 7-methylxanthine, 1.0 times 10(-14)M; theobromine, 1.0 times 10(-3)M; paraxanthine, 0.2 times 10(-3)M; S-adenosylmethionine, 0.25 times 10(-4)M (with each of the three substrates). 3. The results suggest that the pathway for caffeine biosynthesis is as follows: 7-methylxanthine leads to theobromine leads to caffeine. In contrast, it is suggested that theophylline is synthesized from 1-methylxanthine. The methyl groups of the purine ring of caffeine are all derived directly from the methyl group of S-adenosylmethionine. Little is known about the pathways leading to the formation of 7-methylxanthine. 4. A good correlation between caffeine synthesis and shoot formation or growth of tea seedlings was shown, suggesting that the methylating systems in caffeine synthesis are closely associated with purine nucleotide and nucleic acid metabolism in tea plants.

Metabolism of xanthine and hypoxanthine in the tea plant (Thea sinensis L.)

Abstract: 1. The metabolism of xanthine and hypoxanthine in excised shoot tips of tea was studied with micromolar amounts of [2(-14)C]xanthine or [8(-14)C]hypoxanthine. Almost all of the radioactive compounds supplied were utilized by tea shoot tips by 30 h after their uptake. 2. The main products of [2(-14)C]xanthine and [8(-14)C]hypoxanthine metabolism in tea shoots were urea, allantoin and allantoic acid. There was also incorporation of the label into theobromine, caffeine and RNA purine nucleotides. 3. The results indicate that tea plants can catabolize purine bases by the same pathways as animals. It is also suggested that tea plants have the ability to snythesize purine nucleotides from glycine by the pathways of purine biosynthesis de novo and from hypoxanthine and xanthine by the pathway of purine salvage. 4. The results of incorporation of more radioactivity from [8(-14)C]hypoxanthine than from [2(-14)C]xanthine into RNA purine nucleotides and caffeine suggest that hypoxanthine is a more effective precursor of caffeine biosynthesis than xanthine. The formation of caffeine from hypoxanthine is a result of nucleotide synthesis via the pathway of purine salvage.

Inhibition of 5′-nucleotidase in rat brain by methylxanthines

Abstract: —Rat brain 5′-nucleotidase (EC 3.1.3.5) is inhibited by methylxanthines such as theophylline. Inhibition of the 5′-nucleotidase by theophylline appears more efficient than the inhibition of cAMP phosphodiesterase by this drug. A similar inhibition is observed with caffeine, theobromine, 7′-methyl-xanthine and 1-methylxanthine.

The effect of methylated oxypurines on the size of newly-synthesized DNA and on the production of chromosome aberrations after UV irradiation in Chinese hamster cells.

Abstract: Summary A comparison has been made, in Chinese hamster cells, of the ability of various methylated oxypurines to inhibit post-replication repair of DNA after UV irradiation and to potentiate UV-induced chromosome aberrations. DNA synthesized in UV-irradiated cells contains gaps, which are subsequently sealed by a process termed post-replication repair. In rodent cells this process is inhibited by caffeine and its analogues. This has been quantitated by measuring the molecular weight of the DNA synthesized in UV-irradiated cells during a 4-h pulse-labelling period in the presence or absence of inhibitors—the lower molecular weight the greater the inhibition. Eight methylated oxypurines were tested; caffeine and chlorocaffeine were always the most potent inhibitors, tetramethyluric acid was inactive, and the other five derivatives (methoxycaffeine, ethoxycaffeine, paraxanthine, theobromine and theophylline) had intermediate effects. Measurements of the potentiation of UV-induced chromosome aberrations showed that treatments with caffeine or chlorocaffeine again had the greatest effects, tetramethyluric acid and also theophylline had no potentiating activity, and methoxycaffeine was intermediate. This correlation between effects at the molecular and cytological levels is consistent with the hypothesis that the inhibition of post-replication repair by methylated oxypurines gives rise to the increased production of chromosome aberrations.

The effect of methylxanthines on chromosomes of human lymphocytes in culture

Abstract: The effect of caffeine (1,3,7-trimethylxanthine), theophylline (1,3-dimethyl-xanthine), theobromine (3,7-dimethylxanthine), paraxanthine (1,7-dimethylxanthine) 1-methylxanthine, 3-methylxanthine, and 7-methylxanthine added at the 48th h on the chromosomes of human lymphocytes in 72-h cultures has been investigated. Caffeine and the dimethylxanthines cause breakage at 750 μg/ml, with caffeine the most, and paraxanthine the least clastogenic. 1-methylxanthine and dimethylxanthines with a methyl group in the 1-position are the most effctive in depressing mitotic indices. No chromosome damage was exhibited by the monomethylxanthines.

Theobromine and theophylline

Abstract: Theobromine and theophylline have a limited therapeutic use and in addition they occur in plants used in the preparation of a number of widely consumed drinks. Thus most of the population must be exposed to both compounds. Chromosome abnormalities are caused by both theobromine and theophylline in plant cells and in mammalian cells in culture, and both have anti-mitotic activity. While they are fairly potent mutagens in Escherichia coli and other lower organisms the rather scanty available evidence suggests that they are not mutagenic in mammals. The difference in mutagenic activity may be due to the reported inability of E. coli to demethylate these compounds, a process which occurs readily in mammals including man. The structure-activity relationships of these compounds are complex but the available evidence suggests that methylation at position 1 is the most important for both mutagenic activity and the anti-mitotic effect while methylation at position 3 is of most importance in the action on chromosomes.

Effect of various nucleotides and drugs on microsomal thiamine diphosphatase activity in rat brain

Abstract: The basic properties of microsomal thiamine diphosphatase (TDPase) in rat brain were examined. It was mainly localized in the microsomal fraction. Microsomal TDPase showed an absolute requirement for divalent cation which was best satisfied by Ca++. Theophylline (1mM), NADP (0.1mM) and NADPH (0.1mM) significantly inhibited its activity. However, caffeine, theobromine, NAD and various putative neurotransmitters did not affect the enzyme activity. UDP was inhibitory and IDP was a competitive inhibitor, but ATP had no effect on the enzyme activity.

I164– Ions in crystalline (theobromine)2.H2I8; X-ray structure of (theobromine)2.H2I8

Abstract: Crystal structure analysis shows that (theobromine)2.H2I8 is a polyiodide salt composed of alternating cationic and anionic layers; the former consist of hydrogen-bonded protonated theobromine species and the latter of I164– polyiodide ions.

Identification and quantification of drugs in human amniotic fluid.

Abstract: Since drugs administered to gravid females are rapidly transferred to the fetus, transplacentally acquired drugs and drug metabolities should be excreted by the fetus into amniotic fluid. Analyses have been carried out on amniotic fluid obtained at the time of delivery using a gas chromatograph-mass spectrometer-computer system. The drugs that have been identified are caffeine, secobarbital and phenobarbital. Theobromine (3,7-dimethylxanthine) and smaller amounts of 1,7- and 1,3-dimethylxanthine, three metabolites of caffeine, were also found in amniotic fluid, but metabolites of secobarbital and phenobarbital were not detected. It is known that human fetal tissues have active enzyme systems for metabolizing drugs, but these results suggest that this may be a selective rather than general occurence.

Which of caffeine's chemical relatives are able to evoke contractures in mammalian heart?

Abstract: At concentrations between 0.5 mM and 10 mM caffeine, theophylline, theobromine, imidazole, 2-methyl imidazole, 5-amino-4-imidazole carboxamide, naphazoline, antazoline, and tolazoline in normal MacEwen solution induce contractures in rat and guinea pig myocardium. 9-Methylxanthine, 1,3,9-trimethylxanthine, hypoxanthine, or 2-imidazolidone, when similarly applied, do not. These observations, and similar results from frog heart, can be interpreted assuming that an unsaturated position 9 nitrogen in a xanthine molecule or in the equivalent position of an imidazole group is necessary for the release of calcium into the sarcoplasm to be initiated and therefore for a contraction to develop. The site of action of these compounds is likely to be the sarcoplasmic reticulum.

Effect of methylxanthines (theophylline, theobromine, caffeine) and catecholamines on nicotinamide coenzyme content in the rat myocardium

Abstract: In experiments on rats, after intraperitoneal injection of theophylline the content of oxidized forms of pyridine nucleotides (NAD+NADP) was reduced by 19.4%, the level of the reduced forms (NAD·H2+NADP·H2) showed a tendency to decrease, and the total content of nicotinamide coenzymes was significantly reduced. After administration of caffeine the content of NAD+NADP and the total pyridine nucleotides showed a tendency to decrease. Theobromine had no significant effect on these parameters. The action of catecholamines and methylxanthines was compared. Isoproternol (exciting β-adrenergic receptors) lowered the NAD+NADP content, but adrenalin (25 μg/kg) increased the content of both oxidized (by 24%) and reduced (48%) forms of pyridine nucleotides. An increase in the dose of adrenalin (1000 μg/kg) led to a decrease in the level of oxidized forms (by 22.2%) and of the total nicotinamide coenzymes (by 18%).

Actions of various methylxanthines and papaverine on the synthesis of corticosterone in vitro.

Abstract: Actions of various methylxanthines (theophylline, theobromine, caffeine) and papaverine, i.e. drugs which are known to inhibit phosphodiesterase (PDE), were studied on the basal and stimulated synthesis of corticosterone in vitro by using rat adrenal slices. When slices were incubated with methylxanthines, the synthesis of corticosterone was slightly increased. The order of potency, expressed as the efficacy (intrinsic activity) was: theophylline greater than caffeine greather than theobromine. Papaverine did not stimulate the synthesis. The synthesis stimulated by ACTH or the dibutyryl derivative of c-AMP (DBA) was reduced by all of the inhibitors of phosphodiesterase. The molar concentration of the inhibitors which reduced the stimulated steroidogenesis by 50% was lowest for papaverine, higher for theobromine and theophylline and highest for caffeine. Papaverine was active in concentrations of about 10(-5)M, while the methylxanthines were effective in concentrations of 10(-3)--10(-2)M. When the PDE-inhibitors were added to the incubate simultaneously with the stimulant (ACTH or DBA), there was a delay of 60 min before the synthesis was completely blocked. When the stimulant was added 30 min before the administration of an inhibitor, the inhibitory action was no more evident. The inhibitory action of theophylline, but not that of papaverine, was reversed by washing adrenal slices free from the inhibitor, before adding the stimulant. The type of inhibition for papaverine as well as for methylxanthines in antagonizing both the ACTH- and DBA-stimulated synthesis of corticosterone was not competitive but of a mixed type.

[Level of nicotinamide coenzymes in the myocardium of rats during the effects of methylxanthines (theophylline, theobromine, caffeine) and catecholamines].

Abstract: It was shown in acute experiments on rats that one hour after an intraperitoneal injection of theophylline (50 mg/kg) there was a decrease in the NAD + NADP content by 19.4%, a tendency to a fall of NAD.H2 + NADP.H2 was expressed, and the total nicotinamide coferment level was reduced. A tendency to decrease NAD + NADP and the total pyridine nucleotide level was seen after caffeine administration. The action of catecholamines and methylxanthines was compared. Theobromine produced no significant effect on the indices under study. It was shown that isadrine decreased the NAD + NADP level; adrenaline (25 mkg/kg) increased the content of both the oxidized (by 24%) and of the reduced (by 48%) forms of pyridine nucleotides. An increase of adrenaline dose to 1000 mkg/kg was accompanied by reduction of the oxidized forms (by 22.2%) and of the total nicotinamide coferment level (by 18%).

The synthesis and purification of 8-14C-theophylline

Abstract: The enzymes responsible for the metabolism of methylated xanthines suah as theophylline, theobromine, and caffeine have until now escaped identification (1, 2). However, a sensitive radiometric method of analysis of theophylline metabolism (3) was made possible by the synthesis and purification of 8-14C-theophylline (14C-Theo). 14C-Theo was synthesized by the incorporation of 14C from 14C-formic acid into the 8-position of the purine ring. Purification of the 14C-Theo was accomplished by subjecting the crude produot to cation-exchange column chromatography with AG50W-X12, 50–100 mesh resin of the hydrogen ion form.