N^α-(1-Deoxy-d-fructos-1-yl)-l-histidine (“d-Fructose-l-histidine”): a Potent Copper Chelator from Tomato Powder

Abstract

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(II) and N(alpha)-(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(II)-binding ability of FruHis was studied along with structurally related molecules L-histidine, dipeptide L-carnosine, and N(alpha)-(1-deoxy-D-fructos-1-yl)-L-arginine (FruArg) at 25 degrees C using pH-potentiometric titrations. Analysis of the titration curves showed that formation of Cu(II)-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(II) and FruHis form a dominant coordination species of composition MLH-1 (log beta = 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(II) in neutral aqueous solutions is about 10(4) times higher than similar values calculated for L-histidine, L-carnosine, and FruArg. FruHis nearly completely protected hydroxyl radical-mediated fragmentation of polymeric DNA in the presence of the Cu/H2O2/ascorbate system, whereas neither of the reference compounds could inhibit the DNA fragmentation as efficiently in similar conditions. These results warrant further investigation of FruHis as a potential food-related antioxidant.

Interaction of Tomato Lycopene and Ketosamine against Rat Prostate Tumorigenesis

“…), 55%; fat, 0.5%; fiber, 9%; protein, 16%; organic acids, 8%; total ash, 9%. bIn tomato powder, free amino acids partially combine with glucose to form up to 8% fructose-amino acids (13), including 0.04% FruHis (20), during the tomato paste drying process at elevated temperatures.…”

“…For this study, FruHis was prepared from an aqueous solution of food-grade L-histidine, glacial acetic acid, and D-glucose, and purified, as previously described (20). It was obtained as nonhygroscopic crystalline powder (21), free of any detectable impurities.…”

“…The protective effect of FruHis against DNA oxidative degradation may be partially related not only to its reducing potential, as shown by the Folin-Ciocalteau and the FRAP assays, but also to its excellent copper-chelating properties (20).…”

“…Cancer Res 2008; 68: (11 We have recently evaluated FruHis in tomato products using an optimized analysis procedure of gas-liquid chromatography/ mass spectrometry technique (20). Thus, FruHis content in samples of cold break and hot break tomato powder was 38.2 F 0.2 and 41.4 F 0.4 mg/100 g, respectively, and correlated well with the amounts of other D-fructose-amino acids relative to the content of respective ''parent'' free amino acids.…”

Food‐Related Carbohydrate Ligands for Galectins

“…The molecular structure of lactulosamines suggests that these compounds may possess some antioxidant properties, by acting as reducing agents (70) or metal chelators. Although there are no published data on LAs, their structural analogues, fructose-amino acids, have demonstrated a superior ability to protect oxidative DNA fragmentation as compared to other water-soluble antioxidants (71). Both fructosamines and LAs tautomerize into the enol-enamine form (Fig.…”