Structural and anharmonic vibrational spectroscopic analysis of artificial sweetener alitame: A DFT study for molecular basis of sweet taste

Abstract

Artificial sweeteners are synthetic and low-calorie food additives and used as sugar substitutes. Molecular basis of sweetness of them has not been fully defined and understood, yet. Alitame is among the high-intensity artificial sweeteners and has the 2000 times greater sweetness potency than that of sucrose. It is a dipeptide composed of L-aspartic acid and D-alanine with a terminal N-substituted tetra methylthietanyl-amine portion. The goal of this study was to determine alitame's molecular structure and its vibrational wavenumbers by means of quantum chemical computations and, to reveal whether there is a correlation between the sweetness of alitame and selected molecular descriptors, for the first time. Results demonstrated that a strong hydrogen bond of 1.702 Å was formed between aspartic portion backbone-side chain and C=O-OH moiety of alitame. Here, we suggest that the dihedral angles of −19.64° and 7.03° between two single NH groups and two adjacent C=O groups of alitame with respect to each other might be in association with the sweetness of alitame, for the first time. In addition, there is an inversely proportional relationship between the sweetness and the molecular shape index. In contrast, a directly proportional relationship was found between the sweetness and the total surface area. Understanding the molecular structure of such compounds and constructing a better molecular basis of sweetness may help to design further artificial sweeteners that will be important in particularly diabetes and obesity.