Caffeine complexes with

Higuchi, T. Pitman, I.H. Caffeine complexes with low water solubility synthesis and dissolution rates of 1 1 and 1 2 caffeine-gentisic acid complexes. J. Pharm. Sci. 1973, 62, 55-58. 

Destmction of the aluminum complex with ammonia then permits hydrocarbon extraction of the alkaloid. The alkaloid is subsequently both isolated and used as its tartrate salt. This nonnarcotic dmg, for which tolerance may develop, is frequently used orally with caffeine (16) for treatment of migraine it acts to constrict cerebral blood vessels, thus reducing blood flow to the brain. 

The principal CGA isomers identified in green coffee include three caffeoylquinic acid isomers, 3-CQA [327-97-9], 4-CQA [905-99-7], and 5-CQA [906-33-2], three dicaffeoylquinic acid isomers, 3,4-diCQA [14534-61-3], 3,5-diCQA [2450-53-5], and 4,5-diCQA [57378-72-0], and three feruloylquinic acid isomers, 3-FQA [1899-29-2], 4-FQA, and 5-FQA [40242-06-6]. The total CGA level is somewhat higher in robustas compared to arabicas. The 5-CQA is the predominant isomer both in arabicas, ie, 4—5% dry basis (db), and in robustas, 5—6% db, and is known to form in vitro and possibly in vivo complexes with caffeine [58-08-2]. Greater compositional differences between robustas and arabicas are found in the minor CGA isomers, eg, 3,4-diCQA, 5-FQA,... 

Chlorogenic acid forms a 1 1 complex with caffeine, which can be crystallized from aqueous alcohol and yields very little free caffeine on extraction with chloroform. Other compounds with which caffeine will complex in this way include isoeugenol, coumarin, indole-acetic acid, and anthocyanidin. The basis for this selection was the requirement for a substituted aromatic ring and a conjugated double bond in forming such a complex. This kind of complex does modify the physiological effects of caffeine.14 Complex formation will also increase the apparent aqueous solubility of caffeine in the presence of alkali benzoates, cinnamates, citrates, and salicylates.9... 

The methylxanthines vary in their ability to form certain metal complexes. For example, theophylline will complex with both copper and silver whereas caffeine will not.16 The interpretation of this is that the metal ion forms a pentacyclic complex involving the phenolic 0 at C-6 and N at 7.18... 

The known changes in polyphenolic material have already been noted. Fermentation also results in slight loss of extractable caffeine. Decreases of 5 to 7% have been observed.31 Higher-than-normal fermentation times and temperatures accelerate this effect. The fate of caffeine made unavailable during fermentation is not definitely known. It has been demonstrated that caffeine interacts with polyphenols,80-81 so it is likely that the alkaloid becomes complexed with the most insoluble thearubigen fractions that do not become part of the beverage.31... 

A.J. Charlton, A.L. Davis, D.P. Jones, J.R. Lewis, A.P. Davies, E. Haslam and M.P. Williamson, The self-association of black tea polyphenol theaflavin and its complexation with caffeine. J. Chem. Soc. Perkin Trans. 2 (2000) 317-322. 

Complexation with caffeine and theophylline-7-acetate depresses the rate of alkaline hydrolysis of substituted phenyl benzoates and is consistent with the formation of molecular complexes with 1 1 stoichiometry between the hosts and esters stacking of the xanthines is excluded as an explanation in the range of concentrations studied. Inhibition of hydrolysis is attributed to repulsion of the hydroxide ion from the host-ester complex by the extra hydrophobicity engendered by the xanthine host, as well as by the weaker binding of the transition state to the host compared with that in the host-ester complex. ... 

Formation of a chemical complex with other molecules in solution can change fluorescence behaviour, e.g. the presence of caffeine in solution reduces the fluorescence of riboflavin. This alteration of fluorescence upon binding is used to advantage when examining binding of fluorescent molecules to proteins or other constituents of cells. 

In aqueous solution, sodium benzoate forms a 1 1 complex with xanthine derivatives such as theophylline and caffeine [47]. 

Nogueira, T., do Lago, C. L. (2007). Determination of caffeine in coffee products by dynamic complexation with 3,4-dimethoxycinnamate and separation by CZE. Electrophoresis, 28, 3570-3574. 

Flavones contribute to plant tissue color provided that they occur in high concentrations or are complexed with metal ions. Some flavones participate in taste for example, the highly methoxylated aglycones nobiletin, sinensetin and tangeretin are responsible for the bitter taste of citrus peel. On the other hand, some glycosylated flavones (for instance neodiosmin and rhoifolin) reduce the bitterness of some substances (limonin, naringin, caffeine, quinine) [2]. 

Tphe complexing of virtually all purines with aromatic molecules seems - to have far-reaching biological significance. For example, it is known that caffeine affects the rates of many enzymatic reactions (e.g., 0.01, 0.05, and 0.10M caffeine will inhibit salivary amylase 29, 54, and 72% respectively) (12), and purine can decrease the helix-coil transition temperature of the proteins bovine serum albumin and lysozyme (2). It is not unreasonable to expect the involvement of caffeine-aromatic and purine-aromatic complexes because caffeine derivatives and purine complex with the aromatic amino acids tyrosine, phenylalanine, and tryptophan (2). (In fact tryptophan forms a stable 1 to 1 crystalline complex in 0.5M theophylline glycol.)... 

From other planar structures which have been studied, specifically planar complexes such as the tetramethyluric acid-pyrene complex, it is known that the molecules tend to stack plane to plane at a distance of about 3.4 A. (6). One unit cell dimension in this case is 6.99 A. Thus, it would be reasonable to expect the caffeine and pyrogallol molecules to be stacked with their planes roughly perpendicular to this short axis, and it would be likely that a projection of the caffeine-pyrogallol complex down this axis to the x,y plane would result in a two-dimensional picture of the complex with a small amount of distortion owing to the tilt of the planes of the molecules with respect to the x,y plane. 

ATP, ADP, and adenosine are among the purines that are present in some synapses and activate a variety of receptors. Adenosine receptors are blocked specifically by methylated xanthines such as caffeine (Fig. 25-18) and theophylline.808 80813 A drug almost 105 times as potent as theophylline is l,3-dipropyl-8-(2-amino-4-chlorophenyl)xanthine.809 Adenosine receptors, which are present in large numbers in the hippocampus,149 form functional complexes with metabotropic glutamate receptors.678 Adenosine... 

Caffeine (Fig. 11.3), widely used by humans as a stimulatory drug, has so far been detected only in a few plant species. The biological roles of caffeine are believed to be in defense against herbivory or as an allelopathic response to potential competitors.83 Caffeine is derived from the purine alkaloid xanthosine. From xanthosine, three methylations are necessary to produce caffeine. First, xanthosine is methylated on N7 by 7-methylxanthosine synthase (MXS or 7NMT) to produce 7-methylxanthosine, which is enzymatically hydrolyzed to produce 7-methylxanthine and ribose.85,86 The methylations of N1 and N3 of 7-methylxanthine to produce 1,3,7-trimethylxanthine (caffeine) occur in young leaves of tea, and the same enzyme, caffeine synthase, apparently catalyzes both reactions.55 In coffee plants, caffeine is mainly found in the beans but also occurs in the leaves. Caffeine is stored in the vacuoles of coffee leaves as a complex with polyphenols such as chlorogenic acid.87 In contrast to tea, coffee plants appear to have separate enzymes for each step of N-methylation.57... 

Carbon dioxide, 4 an important green house gas,45 is obtained in combustion of carbon and hydrocarbons, calcination of CaC03, and so on. It forms complexes with transition metals (Section 7-14) and inserts into MH and other bonds (Section 21-3). The gas is very soluble in ethanolamines, which are used to scrub C02 from gas streams. Liquid C02 at pressures up to 400 bar is a solvent for some organic compounds and is used to extract caffeine from coffee beans many studies of other applications of supercritical C02 have been conducted.46... 

The principal IR absorptions of 3,20,23 5, and 913,18 (which compounds have been recommended for the identification of alcohols24 25 and primary or secondary amines18) and of 2-substituted saccharins (10)20,23 recorded under identical conditions appear as sets of relatively constant frequencies. For structures with an acidic hydrogen, e.g., compounds (l)16 (2), (9), self-association and complex formation is expected, but the dipolar 3-dialkylamino derivatives (5b) also tend to associate in various solvents.14 Saccharin (1) has been reported to form 1 1 complexes with purines, e.g., theophylline and caffeine, and with amides and... 

Caffeine and related purines are uncharged under physiological conditions and, due to their dual hydrophilic and lipophilic character, easily penetrate cell-, tissue- and organ-related barriers. In Coffea arabica, compartmentation of purine alkaloids, e.g. caffeine, depends exclusively on the physical chemistry of their vacuolar complexation with chlorogenic acid (Waldhauser and Baumann, 1996). 

Electrochemical reduction of oxo- and amino-purines tends to be more complex. With a lead cathode in dilute sulfuric acid, caffeine was found to lose the 6-oxo function and afford the 1,6-dihydro derivative (159) in 70% yield (1899CB68) see also (B-71MI40903, p. 428) for additional confirmatory comment. 

Co is available as an isomorphous replacement for Fe in haems (cobaltmyoglobin, for example, still binds oxygen) and structural information has been obtained about cobalt porphyrin molecular complexes with steroids [89] and caffeine [90] in solution. 

In fact, traditional oxygen carrier molecules are dissolved in organic solvents. Only very few works focus on water-soluble carriers, such as Co-histidine which, however, suffers from very short lifetimes [28]. Therefore, a new type of water-soluble of Co-porphyrin with oxygen affinity was developed by Fiamrnengo et al. [43] for the PBM membrane. This novel carrier was based on the assembly of porphyrins with calixarenes. The self-assembly was driven by electrostatic interactions. The oxygen was assumed to complex inside the cavity of the porphyrin-calixarene assembly. Furthermore, the Co of the porphyrin was shielded from the other side by complexation with a nitrogenous base (1-methylimidazole or caffeine). 

Complexation. It has been well established in the literature that complexation is an effective way to solubilize hydrophobic compounds. Nicotinimide is known to complex with aromatic drugs through tt donor-7r acceptor interaction (101). Similar tt-tt interaction also occurs between salts of benzoic acid or salicylic acid and drugs containing aromatic rings such as caffeine (102).Obviously, aromaticity is an important factor in this type of complexation. Unfortunately, from a safety perspective the use of these types of complex-ing agents for products is not really very viable. 

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