Caffeine, pentoxifylline and theophylline form stacking complexes with IQ-type heterocyclic aromatic amines
ABSTRACT Methylxanthines (MTX), in particular caffeine (CAF), are known as the most widely consumed alkaloids worldwide. Many accumulated statistical data indicate the protective effect of CAF intake against several types of cancer. One of the possible explanations of this phenomenon is direct non-covalent interaction between CAF and aromatic mutagen/carcinogen molecules through stacking (π-π) complexes formation. Here we demonstrate that CAF and other MTX, pentoxifylline (PTX) and theophylline (TH), form stacking complexes with carcinogenic imidazoquinoline-type (IQ-type) food-borne heterocyclic aromatic amines (HCAs). We estimated neighborhood association constants (K(AC) of the order of magnitude of 10(2)M(-1)) in neutral and acidic environment and enthalpy changes (ΔH values between -15.1 and -39.8kJ/mol) for these interactions using UV-Vis spectroscopy, calculations based on thermodynamical model of mixed aggregation and titration microcalorimetry. Moreover, using Ames test with Salmonella typhimurium TA98 strain and recently developed mutagenicity assay based on bioluminescence of Vibrio harveyi A16 strain, we demonstrated a statistically significant reduction in HCAs mutagenic activity in the presence of MTX.
SourceAvailable from: Maxim P Evstigneev[Show abstract] [Hide abstract]
ABSTRACT: Knowledge of the physical chemistry of small molecules complexation (the hetero-association) in aqueous solution is increasingly important in view of the rapidly emerging branch of supramolecular chemistry dealing with the formation of heterogeneous polymeric structures having specific functional roles. In this paper, the 50-year history of scientific studies of hetero-association of heterocyclic aromatic molecules in aqueous solution has been reviewed. Some important correlations of structural and thermodynamic parameters of complexation have been reported based on large data-set of hetero-association parameters accumulated to date. The fundamental problem of ‘energetic composition’ of π-stacking is extensively discussed. The review has shown that there are some gaps in our understanding of hetero-association, which provides a challenge for further studies in this area.International Reviews in Physical Chemistry 04/2014; 33(2). DOI:10.1080/0144235X.2014.926151 · 4.92 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: The formation of it-stacked complexes between water-soluble porphyrins: 4,4',4 '',4'''-(21H,23-Hporphine-5,10,15,20-tetrayl)tetrakis-(benzoic acid) (H2TCPP), 5,10,15,20-tetrakis(4-sulfonatophenyl)-21 H,23H-porphine (H2TPPS4), 5,10,15,20-tetrakis[4-(trimethylammonio)phenyl]-21H,23H-porphine tetra-p-tosylate (H2TTMePP), 5,10,15,20-tetrakis(1-methyl-4-pyridyl)-21H,23H-porphine tetra-p-tosylate (H2TMePyP), the Cu(II) complexes of H2TTMePP and H2TMePyP, as well as chlorophyll a with xanthine, theophylline (1,3-dimethylxanthine) and theobromine (3,7-dimethylxanthine) has been studied analysing their absorption and steady-state fluorescence spectra in aqueous (or acetone in case of chlorophyll a) solution. During titration by the compounds from xanthine group the bathochromic effect in the porphyrin absorption spectra as well as the hypochromicity of the porphyrin Soret maximum can be noticed. The fluorescence quenching effect observed during interactions in the systems examined suggests the process of static quenching. The association and fluorescence quenching constants are of the order of magnitude of 10(3) - 10(2) mol(-1). The results obtained show that xanthine and its derivatives can quench the fluorescence of the porphyrins according to the number of methyl groups in the molecule of quencher.Journal of Molecular Structure 02/2015; 1081. DOI:10.1016/j.molstruc.2014.10.032 · 1.60 Impact Factor
[Show abstract] [Hide abstract]
ABSTRACT: The influence of solvent polarity on the nature and extent of non-covalent interactions responsible for BPA:4-Vinlypyridine complex formation has been investigated in the pre-polymerization mixture and correlated with polymer-ligand recognition. The combination of FTIR, 1H NMR and UVeVis spectroscopy has made possible the development of a more comprehensive understanding of pre-polymerization events at a molecular level, and how they govern the properties of subsequent polymerized MIPs. The MIP ATR characterization provides direct insight into the bonding within matrix-template system, confirming that monomer:template H-bonded complexes survived the polymerization process and the presence of two functional monomers in the binding sites. The polymer has shown an excellent affinity for BPA in aqueous solutions with poor recognition in organic solvents. Loss of affinity in organic solvents together with selectivity studies suggested that the binding mechanism depended critically on the conformation of the polymeric binding pockets, which when combined with H-bonding and weak electrostatic interactions allowed for selective recognitionMaterials Chemistry and Physics 01/2013; 141:461. · 2.13 Impact Factor