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.

Red beetroot (Beta vulgaris L.) is the main commercially exploited source of betalain pigments which are produced in the form of concentrates or powders [Ciriminna et al., 2018]. The most abundant pigments present in red beet are betanin (red betacyanin) and vulgaxanthin I (yellow betaxanthin). Due to their satisfying nutritional value and disease-preventing effects, such extracts are regarded benefi cial to human health and applied as food additives, colorants, and dietary supplements [Nemzer et al., 2011]. They are also characterized by the best quality in terms of the color and its intensity. In addition, betanin is approved by the US FDA and European Union as a natural colorant used for coloring dairy products, cosmetics, and pharmaceuticals [Esatbeyoglu et al., 2015]. Beetroot extracts are utilized to emphasize the redness of such products as tomato soups, sauces, pastes, desserts, jams, sweets, and jelly beans. They are also used to protect meat from discoloration and to extend its shelf-life [Chhikara et al., 2019; Tang et al., 2015]. Several studies have attributed a wide spectrum of bioactive properties to betalain pigments and betalain-rich extracts. They may serve as biologically active nutraceuticals

Hypochlorous acid (HOCl) produced by neutrophils is a part of the natural innate immune response system in the human body, but excessive levels of HOCl can ultimately be detrimental to health. Recent reports suggest that betacyanin plant pigments can act as potent scavengers of inflammatory factors and are notably effective against HOCl. In this contribution, chlorination mechanism and position of the electrophilic substitution in betacyanins was studied by high-resolution mass spectrometry and further structural analyses by NMR techniques, which completed the identification of the chlorinated betacyanins. For the study on the influence of the position of decarboxylation on the chlorination mechanism, a comparison of the chlorination position between betanin as well as 17-, and 2,17-decarboxylated betanins was performed. The structural study confirmed that the chlorination position in betanin occurs within the dihydropyridinic moiety at carbon C-18. Therefore, out of the aqueous free chlorine equilibrium species: HOCl, OCl−, Cl2, and Cl2O, the most potent chlorinating agents are HOCl and Cl2O postulated previously and the attack of the Cl⁺ ion on the carbon C-18 with a cyclic intermediate version is considered.

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.

Betacyanin pigments were studied in edible fruits of four Melocactus species, M. violaceus Pfeiff., M. bahiensis (Britton & Rose) Luetzelb, M. amoenus (Hoffm.) Pfeiff., and M. curvispinus Pfeiff., by means of chromatographic and mass spectrometric techniques. The main pigment constituent, melocactin, endogenously present in the Melocactus species, was identified as betanidin 5- O -β-sophoroside betacyanin, previously known as “bougainvillein-r-I”. The highest total concentration of betacyanins was found in fruits of M. amoenus (∼0.08 mg/g). Except for melocactin being the most abundant betacyanin (34.8–38.8%) in the analyzed species, a presence of its malonylated derivative, mammillarinin (15.2–19.9%), as well as more hydrophobic feruloyled and sinapoyled melocactins was confirmed by additional co-chromatographic experiments with authentic reference betacyanins. The acyl migration isomers of the malonylated betacyanins as well as a presence of 5′′- O - E -sinapoyl-2′- O -apiosyl-betanin (2.3–3.0%) found frequently in light-stressed cacti was also acknowledged.