Melanoidin formation in ethanolic monosaccharide - arylamine - copper (II) systems

Results of studying of melanoidin formation regularities at interaction of D -glucose and D -xylose with p -amino benzoic acid (PABA) in acidic ethanolic media have been presented; features of the chosen threefold systems are, firstly, existence of the low-active amino-compound of benzene series, secondly, presence of catalytic amounts of the biogenic metal. Regularities of melanoidins structure formation from similar systems are almost not studied, at the same time some important biological properties are predicted for them that demands research of reactions' kinetics and development of techniques of their directional synthesis. Studying has been carried out by synthetic methods in total with a sample drawing technique with UV-Vis-spectrophotometry filing and engaging of FTIR-spectroscopy. Based on electronic spectra analysis more intensive melanoidin formation in case of reaction from D -xylose has been shown, this can be bound to steric hindrance and to ability of aldopentoses to give more reactionary capable intermediates in comparison with aldohexoses. The accelerating role of copper (II) ions as the complexing center catalyzing both formation and degradation of the intermediate products at different reaction stages has been confirmed, at the same time the accelerating action is considerably shown since copper ion concentrations about 60 mg/l, but Cu(II) chelation degree by final products is low. The effect of solvent has been noted, in particular the influence of ethanol on nature of amino-carbonyl interactions manifested in strengthening of carbohydrates tendency to re-cyclization, it also probably accelerates melanoidin formation. The data obtained have shown the percent of carbohydrates direct destruction (caramelization) in the presented conditions is insignificant, that allows developing based on the present researches target synthetic techniques for melanoidin products' preparation.