Abstract
The metal complexes can demonstrate various interesting biological activities in the human body. However, the role of certain metal ions for specific cell activities is still subject to debate. This study is aimed at comparing the thermochemical properties of neotame (artificial sweetener) and α, β-fructose in gas phase and water medium. The interaction of α and β-fructose, neotame with monovalent and divalent metal ions was studied and comprehended by density functional theory (DFT) using B3LYP functional, 6–311 + G (d, p) and D3 basis set. Metal ion affinities (MIA) values depicted that ionic radius of metal ions played an important role in the interaction of α, β-fructose and neotame. The ∆G parameter was calculated to predict and understand the interaction of metal ions with α and β-fructose, neotame. The results suggested that the presence of hydroxyl groups and oxygen atoms in sugar molecules acted as preferred sites for the binding and interaction of mono and divalent ions. For the first time computational study has been introduced in the present study to review the progress in the application of metal binding with sugar molecules especially with neotame. Moreover, voltammetric behaviour of neotame-Zn2+ was studied using cyclic and differential pulse voltammetry. The obtained results suggest that the peak at −1.13 V is due to the reduction of Zn2+ in 0.1 M phosphate buffer medium at pH 5.5. Whereas, addition of 6-fold higher concentration of neotame to the ZnCl2.2H2O resulted in a new irreversible cathodic peak at −0.83, due to the reduction of neotame-Zn2+ complex. The Fourier transform infrared spectroscopy (FTIR) results indicates that the β-amino group (-NH) and carboxyl carbonyl (-C = O) groups of neotame is participating in the chelation process, which is further supported by DFT studies. The findings of this study identify the efficient chelation factors as major contributors into metal ion affinities, with promising possibilities to determine important biological processes in cell wall and glucose transmembrane transport.
Highlights
Neotame, (3 S)-3-(3,3-Dimethylbutylamino)-4-[[(2 S)-1-methoxy-1-oxo-3-phenylpropan-2-yl amino]-4-oxobutanoic acid is an artificial sweetener and chemically synthesized from aspartame
The interaction of sucrose or fructose with different metal ions is vital in biological processes such as metal ions binding to cell wall[17] and transmembrane transportation of glucose-Na+18, which has been established in the gas phase, thereby resulting in the key information on the chemical properties of the glucose or fructose and various metal ions
The second step included the coordination of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Fe2+, Zn2+) with the optimized structures of α-fructose, β-fructose and neotame using B3LYP/6–311 + G (d, p) and B3LYP/D3 basis set in gas phase as well as in solvent medium
Summary
Neotame, (3 S)-3-(3,3-Dimethylbutylamino)-4-[[(2 S)-1-methoxy-1-oxo-3-phenylpropan-2-yl amino]-4-oxobutanoic acid is an artificial sweetener and chemically synthesized from aspartame It has similar physical properties as aspartame in terms of sweetness and comparable with sucrose without a metallic or bitter after taste at high concentrations. To the best of our knowledge, no reports have been available in the literature on the interaction of α or β-fructose and neotame with mono, divalent metal ions in gas phase and water medium (intrinsic) using B3LYP/6–311 + G (d, p)/D3 level of theory. Anions pierce directly through the cell wall faster than the cations[18] To overcome this challenge, present study on the neotame-metal ion complexes were performed to better understand the active functional groups participating in the binding, electrochemical behavior as well as metal ion affinities of complex. Metal ion affinity (MIA) for α-, β-fructose and neotame was calculated by considering the negative of the enthalpy variation (ΔH) for the following ion association process[23]:
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