Sample records for 3,7-dimethylxanthine

  1. Investigation of Xanthine Drug and some of its Dimethyl Isomers using Mass Spectrometry and Semi-Empirical Molecular Orbital Calculation

    International Nuclear Information System (INIS)

    In this paper xanthine (C5H4N4O2 , MW=152) drug (M1) as a parent molecule and three of its dimethyl substituted isomers , namely, 3,7-dimethylxanthine (M2) 1,3-dimethylxanthine (M3) and 1,7-dimethylxanthine (M4) of formula (C7H8N4O2, MW = 180), were investigated using electron ionization (EI) mass spectrometry (MS) at 70 eV. Semi-empirical MO-calculations , PM3 procedure, have been carried out on the drugs as neutral molecule and its corresponding molecular ion. These include molecular geometry (bond length), bond order, charge distribution on different atoms , heat of formation (Hf) and ionization energy. The mass spectral fragmentation pathways of the parent molecule (M1) and the isomeric molecules (M2-M4) were proposed. All compounds dissociate in the gas phase by common pathways, initiated in the same site of bond rupture resulting a loss of imide group. Subsequently, a loss of CO followed by HCN, and formation of different fragmen ions depends on the isomeric position of the methyl groups . The PM3 procedure provides information of initial bond cleavage and subsequent fragmentation of the molecules. Finally, the influence of CH3 groups in different isomeric position via the two rings of xanthine caused by significant electron-donating of this group were discussed

  2. Production of Recombinant Caffeine Synthase from Guarana (Paullinia cupana var. sorbilis) in Escherichia coli. (United States)

    Schimpl, Flávia Camila; Kiyota, Eduardo; Mazzafera, Paulo


    Caffeine synthase (CS) is a methyltransferase responsible for the last two steps of the caffeine biosynthesis pathway in plants. CS is able to convert 7-methylxanthine to theobromine (3,7-dimethylxanthine) and theobromine to caffeine (1,3,7-trimethylxanthine) using S-adenosyl-L-methionine as the methyl donor in both reactions. The production of a recombinant protein is an important tool for the characterization of enzymes, particularly when the enzyme has affinity for different substrates. Guarana has the highest caffeine content among more than a hundred plant species that contain this alkaloid. Different from other plants, in which CS has a higher affinity for paraxanthine (1,7-dimethylxanthine), caffeine synthase from guarana (PcCS) has a higher affinity for theobromine. Here, we describe a method to produce a recombinant caffeine synthase from guarana in Escherichia coli and its purification by affinity chromatography. The recombinant protein retains activity and can be used in enzymatic assays and other biochemical characterization studies. PMID:26843165

  3. Molecular and biochemical characterization of caffeine synthase and purine alkaloid concentration in guarana fruit. (United States)

    Schimpl, Flávia Camila; Kiyota, Eduardo; Mayer, Juliana Lischka Sampaio; Gonçalves, José Francisco de Carvalho; da Silva, José Ferreira; Mazzafera, Paulo


    Guarana seeds have the highest caffeine concentration among plants accumulating purine alkaloids, but in contrast with coffee and tea, practically nothing is known about caffeine metabolism in this Amazonian plant. In this study, the levels of purine alkaloids in tissues of five guarana cultivars were determined. Theobromine was the main alkaloid that accumulated in leaves, stems, inflorescences and pericarps of fruit, while caffeine accumulated in the seeds and reached levels from 3.3% to 5.8%. In all tissues analysed, the alkaloid concentration, whether theobromine or caffeine, was higher in young/immature tissues, then decreasing with plant development/maturation. Caffeine synthase activity was highest in seeds of immature fruit. A nucleotide sequence (PcCS) was assembled with sequences retrieved from the EST database REALGENE using sequences of caffeine synthase from coffee and tea, whose expression was also highest in seeds from immature fruit. The PcCS has 1083bp and the protein sequence has greater similarity and identity with the caffeine synthase from cocoa (BTS1) and tea (TCS1). A recombinant PcCS allowed functional characterization of the enzyme as a bifunctional CS, able to catalyse the methylation of 7-methylxanthine to theobromine (3,7-dimethylxanthine), and theobromine to caffeine (1,3,7-trimethylxanthine), respectively. Among several substrates tested, PcCS showed higher affinity for theobromine, differing from all other caffeine synthases described so far, which have higher affinity for paraxanthine. When compared to previous knowledge on the protein structure of coffee caffeine synthase, the unique substrate affinity of PcCS is probably explained by the amino acid residues found in the active site of the predicted protein. PMID:24856135