Multi-colored shades of betalains: recent advances in betacyanin chemistry

Abstract

The updated classification of all known betacyanin plant pigments and a review of the current research focused on the chemical properties of the pigments are presented, in addition to the description of semi-synthesis of betalamic acid conjugates.

Dehydrogenation of Betacyanins in Heated Betalain-Rich Extracts of Red Beet (Beta vulgaris L.)

“…Several dehydrogenated betanins are known derivatives [6] which were also detected previously in the BRE extract [45]. The most hydrophobic is 2-decarboxy-xanneobetanin 20 which, together with bidecarboxylated derivatives, presumably 2,15-bidecarboxy-xanneobetanin 19 (Figure 4) as well as 2,17-decarboxy-xanneobetanin 15 (Figure 4) are generated at higher quantities at pH 7-8.…”

“…Interpretation of the LC-DAD and LC-MS spectra enabled identification of known as well as novel betanin derivatives observed during all the experiments (Table 1). Recently, an important simplification of the naming of betacyanin derivatives was proposed [6] to substitute the phrase "2,3-dehydro" by "xan" in the trivial name of the 2,3dehydrogenated betacyanins in reference to the "neo" prefix used to substitute the phrase "14,15-dehydro". [42,44].…”

“…Based on these assumptions, it can be concluded that the mechanism of betacyanin degradation may be different, and its variants were initially presented in our publications [41,[43][44][45]. In the course of many years of work on decarboxylated compounds, the above-mentioned and many other structures have been confirmed by LC-MS and/or NMR methods [6,46,47].…”

“…They are synthesized by most plants of the order Caryophyllales [3], and are also found in some species of fungi of the genera Amanita and Hygrocybe [4,5]. At present, 187 betacyanins from natural sources have been identified [6].…”

“…In addition, the physicochemical conditions of the reaction environment (pH, temperature, or the presence of metal ions) have an impact on obtained structures [41]. During the heating degradation of betacyaninrich red beetroot extract (RBE), depending on the prevailing conditions, compounds such as 2-, 15-, and 17-decarboxy-betanin, together with their corresponding neo-derivatives as well as appropriate isomers, may be formed followed by their bi-or tri-decarboxy analogues [6,21,42]. Based on these assumptions, it can be concluded that the mechanism of betacyanin degradation may be different, and its variants were initially presented in our publications [41,[43][44][45].…”