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Nα-(1 -Deoxy-D-fructos-1 -yl)-L-histidine ("D-Fructose-L-histidine") : a Potent Copper Chelator from Tomato Powder
Dried fruits and vegetables are known for their high content of D-fructose-amino acids, or Amadori compounds, which appear at the initial step of the Maillard reaction and may participate in redox reactions mediated by trace metals. In this study, we investigated complexation between Cu(ll) and Nα-(1 -deoxy-D-fructos-1 -yl)-L-histidine (D-fructose-L-histidine, FruHis). The content of FruHis in two types of commercial tomato powders was estimated by GLC-MS, using single ion monitoring of trimethylsilylated FruHis hydroxyoximate, as 40 mg/100 g, whereas the concentration of free histidine in the powder samples was about 53 mg/100 g. The Cu(ll)-binding ability of FruHis was studied along with structurally related molecules L-histidine, dipeptide L-carnosine, and Nα-(1-deoxy-D-fructos-1-yl)-L-arginine (FruArg) at 25 °C using pH-potentiometric titrations. Analysis of the titration curves showed that formation of Cu(ll)-FruHis complex species occurs at pH values as low as 2 and that the complexes were redox stable in the pH range 2-10.5, at least for the time of the experiment. At physiological pH, Cu(ll) and FruHis form a dominant coordination species of composition MLH_1 (log β = 5.67), with a presumably deprotonated anomeric hydroxyl group of the fructose portion. The apparent stability constant of 1:1 complexes formed by FruHis and Cu(ll) in neutral aqueous solutions is about 104 times higher than similar values calculated for L-histidine, L-carnosin
American Chemical Society
PMID : 18004802 ISSN : 0021-8561 CODEN : JAFCAU
Journal of agricultural and food chemistry (Print) A. 2007, vol. 55, n° 25, pp. 10373-10381 [9 pages] [bibl. : 38 ref.]
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