Theobromine acidity

C8H10N4O2. An alkaloid occurring in tea, coffee and guarana, from which it may be prepared by extraction, It is also manufactured by the methylation of theobromine and by the condensation of cyanoacetic acid with urea. Crystallizes with H2O or anhydrous from organic solvents. M.p. (anhydrous) 235"C, sublimes at 176 C. Odourless, and with a very bitter taste. Caffeine acts as a stimulant and diuretic, and is a constituent of cola drinks, tea and coffee. 

Pyrimidines and purines occur naturally in substances other than nucleic acids Coffee for example is a familiar source of caffeine Tea contains both caffeine and theobromine... 

Care must be exercised in the choice of acid employed in chloramine T — mineral acid reagent since the detection sensitivity and also the color of the fluorescences produced depend to a significant extent on the choice of acid. This is illustrated for the purine derivatives caffeine, theobromine and theophylline in Figure 1 and Table 1. 

Fig. 1 Comparison of the detection sensitivity after derivatization of three purine derivatives with chloramine T - sulfuric acid (A) and chloramine T - hydrochloric acid (B). Measurement X. (. = 365 nm, A.(, = 440 nm (monochromatic filter M 440) 1 = theophylline, 2 = theobromine, 3 = caffeine.

Much research has centered on identifying the source of the purine ring in caffeine. Two possible sources are likely methylated nucleotides in the nucleotide pool and methylated nucleotides in nucleic acids. Extensive experimental work by Suzuki and Takahashi27-30 proposes a scheme whereby caffeine is synthesized from methylated purines in the nucleotide pool via 7-methylxanthosine and theobromine. Information relating to the formation of 7-methylxanthine from nucleotides in the nucleotide pool is sparse. They also provide data that demonstrate that theophylline is synthesized from 1-methyladenylic acid through 1-methylxanthine as postulated by Ogutuga and Northcote.31... 

Seasonal variations in the metabolic fate of adenine nucleotides prelabelled with [8—1-4C] adenine were examined in leaf disks prepared at 1-month intervals, over the course of 1 year, from the shoots of tea plants (Camellia sinensis L. cv. Yabukita) which were growing under natural field conditions by Fujimori et al.33 Incorporation of radioactivity into nucleic acids and catabolites of purine nucleotides was found throughout the experimental period, but incorporation into theobromine and caffeine was found only in the young leaves harvested from April to June. Methy-lation of xanthosine, 7-methylxanthine, and theobromine was catalyzed by gel-filtered leaf extracts from young shoots (April to June), but the reactions could not be detected in extracts from leaves in which no synthesis of caffeine was observed in vivo. By contrast, the activity of 5-phosphoribosyl-1-pyrophosphate synthetase was still found in leaves harvested in July and August. 

Jalal and Collin19 used paper chromatography and TLC to determine caffeine in both coffee and tea, and theobromine in tea. Their TLC method used cellulose plates that were developed with butanokhydrochloric acid water (I 00 1 1 28) for 4 h. The spots were eluted from the plates with ammonium hydroxide and measured spectrophotometrically against a blank at 272 nm for caffeine and 274 nm for theobromine. 

HPLC allows a quantitative determination with relatively simple extractions. In many cases, extraction only involves a heating of the commodity with water, followed by filtration and injection onto an HPLC column. In the determination of caffeine, theobromine, and theophylline in cocoa, coffee, or tea, as well as in other foods, there is scarcely a month that passes without a new paper on this assay. Kreiser and Martin provide typical conditions for analysis.28 In their studies, samples were extracted in boiling water and filtered prior to injection onto the HPLC column. The HPLC conditions used a Bondapak reversed phase column and a mobile phase of water methanol acetic acid (74 25 1) with detection at 280 nm. This method is accurate, precise, and conserves time. It has also been adopted by the AOAC as an official method for the determination of theobromine and caffeine in cocoa beans and chocolate products.29... 

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. 

Fig. 11. Mechanism for formation of parabanic acids from the methylated uric acid-4,5-diol derived from theobromine (3,7-dimethylxanthine) and caffeine (1,3,7-trimethylxan-thine). Molar amounts of products are those formed in 1 M HOAc...

Fig. 11) would likely proceed by different mechanisms. Protonation of the diol (IV, Fig. 12) derived from theobromine would lead to ring opening at the C6— Cs position giving an imidazole isocyanate (XVI, Fig. 12). This could readily form XVII which after hydrolysis and loss of C02 would give dimethyl-allantoin (XVIII). On the other hand, the uric acid diol derived from caffeine (X, Fig. 12) cannot fragment by this mechanism. Accordingly, either or both of the processes could Occur via the form of the diol hydrated at the C6 carbonyl group (XIX, Fig. 12) which could readily lose C02 to give XX followed by rearrangement to trimethylallantoin (XXI).

Secondary rearrangement of the uric acid-4,5-diol derived from theobromine or caffeine to give a methylated alloxan is shown in IV - XXII and X XXIII, Fig. 13 respectively. 

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. 

Methyl succinyl chloride, ml95 Methylsulfonic acid, m34 Methyl theobromine, cl... 

Chocolate flavored syrup, theobromine and caffeine content, 6 367t Chocolate liquor, 6 355-358 amino acid content, 6 368t composition, 6 369t... 

I = theogallin 2 = gallic acid 3 = theobromine 4 = isochlorogenic acid 5 = gallocatechin 6 = epigallocatechin 7 = catechin 8 = p-coumarylquimc acid 9 = chlorogenic acid 10 = caffeine ... 

Potentially tautomeric pyrimidines and purines are /V-alkylated under two-phase conditions, using tetra-n-butylammonium bromide or Aliquat as the catalyst [75-77], Alkylation of, for example, uracil, thiamine, and cytosine yield the 1-mono-and 1,3-dialkylated derivatives [77-81]. Theobromine and other xanthines are alkylated at N1 and/or at N3, but adenine is preferentially alkylated at N9 (70-80%), with smaller amounts of the N3-alkylated derivative (20-25%), under the basic two-phase conditions [76]. These observations should be compared with the preferential alkylation at N3 under neutral conditions. The procedure is of importance in the derivatization of nucleic acids and it has been developed for the /V-alkylation of nucleosides and nucleotides using haloalkanes or trialkyl phosphates in the presence of tetra-n-butylammonium fluoride [80], Under analogous conditions, pyrimidine nucleosides are O-acylated [79]. The catalysed alkylation reactions have been extended to the glycosidation of pyrrolo[2,3-r/]pyrimidines, pyrrolo[3,2-c]pyridines, and pyrazolo[3,4-r/]pyrimidines (e.g. Scheme 5.20) [e.g. 82-88] as a route to potentially biologically active azapurine analogues. 

The major pharmacological constituents of tea are the purine alkaloids caffeine (2.9-4.2%), theobromine (0.15-0.2%), and theophylline (0.02-0.04%). Also present are triterpene saponins (including barringtogenol C and Rl-barringenol), catechins (theaflavine, theaflavin acid, thearubigine), and caffeic acid derivatives (chlorogenic acid and theogallin). A cup of brewed tea contains approximately 20-100 mg of caffeine... 

Mate contains both caffeine (0.4-2.4%) and theobromine (0.3-0.5%). Also found are triterpene saponins and the caffeic acid derivatives—chlorogenic acid, neochlorogenic acid, and cryptochlorogenic acid. Flavonoids in mate are rutin, isoquercetin, and kaemferol glycosides. A nitrile glycoside, menisdaurin, is also present, which is noncyanogenic. 

Caffeine pharmacokinetics are nonlinear. For example, when comparing a 500 mg dose to a 250 mg dose, the clearance is reduced and elimination half-life is prolonged with the higher dose (Kaplan et al. 1997). Thus, larger doses prolong the action of the drug. Active metabolites of caffeine are paraxanthine, and to a lesser degree, theobromine, and theophylline. Urinary metabolites are I-methylxanthine, l-methyluric acid, and an acetylated uracil derivative. 

The generic name of the cacao tree (Theobroma) means food of the Gods and gives its name to a caffeine-like stimulant, theobromine (a methylxanthine). It has been claimed that the theobromine in chocolate is responsible for its addictive characteristics. This is based on the fact that methylxanthines bind to adenosine receptors in the central nervous system and act as antagonists to this neurotransmitter (Chapter 14). However, another group of substances, the amides formed between ethanolamine and unsaturated fatty acids, are also possible candidates for the title of the chocolate drug . 

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