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.

Epiphyllum, Hylocereus, and Opuntia plants belong to the Cactaceae family. They are mostly known as ornamental plants but also for their edible fruits, which can potentially be sources of betalains, such as betanin, a natural pigment used in the food industry, e.g., under the European label code E 162. The aim of this work was the identification of betalains (using LC-MS/MS), evaluation of total betalain content (spectrophotometrically), analysis of functional groups (using FT-IR), evaluation of antioxidant activity (using DPPH, ABTS, FRAP, DCFH-DA, and reducing power methods) and evaluation of antimicrobial activity (S. aureus, E. coli, and C. albicans) in fruits of Epiphyllum, Hylocereus, and Opuntia taxa. A total of 20 betalains were identified in the studied Cactaceae fruits. The Epiphyllum pink hybrid had the highest values of total betalains amongst all samples. The highest antioxidant activity was observed in the Epiphyllum pink hybrid, in Opuntia zacuapanensis and O. humifusa fruits. The antimicrobial activity assay showed that cacti fruits were not able to effectively inhibit the growth of E. coli, S. aureus, or C. albicans. Our results prove that these fruits are good sources of natural pigments—betalains. They do not contain toxic compounds in significant amounts and they exhibit antioxidant activity.

Betacyanins are a group of water-soluble red-violet compounds containing nitrogen in their structure. These are biosynthesized in red beetroot (Beta vulgaris L.), a widely consumed vegetable that contains significant amounts of nutritious and bioactive compounds which are also found in dietary supplements. This contribution presents results of betacyanin thermal oxidation (resulting in dehydrogenation) interrelated with decarboxylation in selected acetate/phosphate buffers at pH 3–8 and at 85 °C, which may be of particular significance for formulation and performance of foods. Most of the reaction products were detected at the highest concentrations in the acidic solutions (pH 3–4). The main dehydrogenation reaction pathways were monitored by LC-DAD-MS/MS and were associated with decarboxylation of the principal extract pigments, betanin/isobetanin and neobetanin, at carbon positions C-2 and C-17. Additional reactions are accompanied by the 2,15-decarboxylation processes at different dehydrogenation levels with 15-decarboxy-betanin and 2,15-bidecarboxy-betanin, structurally elucidated by NMR analysis, as the distinct indicators of this route type. For other novel pigments detected, 2,15-bidecarboxy-xanbetanin, 2,15-bidecarboxy-xanneobetanin and 2,15,17-tridecarboxy-neobetanin, additional high resolution mass spectrometric analyses were performed and confirmed their molecular formulas.

Betalains are one of the most common groups of plant pigments found in nature, especially in red beetroot ( Beta vulgaris L.) which is the main commercially exploited source of betalains produced in the form of concentrates or powders. This report presents results of thermal decarboxylation...

The influence of stabilizing activity of citric buffers on betacyanins, as well as their thermal dehydrogenation and decarboxylation in a beetroot betalain-rich extract (BRE), was studied at pH 3–8 and temperature 30, 50 and 85 °C with an additional effect of EDTA. In acetate/phosphate buffers, the highest stability is observed at pH 5 and it decreases toward pH 3 as well as pH 8, which is more remarkable at 85 °C. For the citrates, a contradictory effect was observed. Citric buffers tend to stabilize the substrate pigments and their intermediary products in acidic solutions, although increase their reactivity at pH 6–8. The highest impact of EDTA addition on pigment retention in acetate buffers is observed at 85 °C and pH 3–5 as well as 8, reflecting the preserving activity of EDTA at the most unfavorable conditions. At lower temperatures, pigment stability in more acidic conditions is still at higher levels even without addition of citrates or EDTA. The most striking effect on generation of betanin derivatives during heating is 2-decarboxylation which preferentially proceeds in the most acidic environment and this generation rate at 85 °C is much higher in the citrate buffers compared to acetates.

Identification of betacyanins in Basella alba L. and Basella alba L. var. ‘Rubra’ fruits was performed by low- and high-resolution mass spectrometry (LRMS and HRMS) as well as ¹H, ¹³C and two-dimensional NMR which revealed hitherto completely not known betacyanin classes in the plant kingdom. Especially, the presence of unique nitrogenous acyl moieties in the structures of the pigments was ascertained by the HRMS Orbitrap detection. Except for detected polar betacyanin glycosylated derivatives, presence of a series of previously not reported pigments such as malonylated betanidin 6-O-β-glusosides with their acyl migration isomers along with the evidence of the 3′′-hydroxy-butyrylated betacyanins is reported. The first complete NMR data were obtained for novel and principal acylated gomphrenins with hydroxycinnamic acids: 6′-O-E-caffeoyl-gomphrenin (malabarin), 6′-O-E-sinapoyl-gomphrenin (gandolin), 6′-O-E-4-coumaroyl-gomphrenin (globosin) and 6′-O-E-feruloyl-gomphrenin (basellin).