Betalain pigments

Wasserman, B.P, Eiberger, L.L., and Guilfoy, M.P., Effect of hydrogen peroxide and phenolic compounds on horseradish peroxidase-catalyzed decolorization of betalain pigments, J. Food Sci., 49, 536, 557, 1984. 

Dhillon, A.S. and Maurer, A.J., Evaluation of betalain pigments as colorants in turkey summer sausages, Poultry Sci., 54, 1272, 1975. 

Proline, however, is the predominant amino acid and most interestingly, its betalamic acid adduct indicaxanthin is the major betalain pigment in cactus pear. Proline functions as an osmolyte, accumulating in water- and heat-stressed plant tissues, and in comparison to other amino acids, it exhibits an extraordinarily high solubility of 1623 mg/L water at 25°C. ... 

Two main groups can be discerned (1) endogenous factors such as plant enzymes like polyphenoloxidase, peroxidase, and P-glucosidase and (2) conditions prevailing in the extraction medium will decide the fates of betalain pigments among which temperature, oxygen, and pH are considered the most important conditions. 

Tesoriere, L. et al.. Distribution of betalain pigments in red blood cells after consumption of caems pear fruits and increased resistance of the cells to ex vivo-induced oxidative hemolysis in humans, J. Agric. Food Chem., 53, 1266, 2005. 

Fernandez-Lopez JA and Almela L. 2001. Application of high performance liquid chromatography to the characterization of the betalain pigments in prickly pear fruits. J Chromatogr 913 415 120. 

Betalain pigments have been tested on rodents by feeding 50mg/kg pure betanin, 2000 ppm betanine in the diet and several other conditions.11 No carcinogenic or other toxic effects were observed and the authors concluded that red beet extracts were safe as food colorants. 

RP-HPLC has been applied for the determination of betalain pigments in various plants too. The researches were motivated by the commercial importance of betalain pigments as natural food colourants. An RP-HPLC method was developed for the measurement of betalain pigments in prickly pear (Opuntia ficus-indica) fruits. 

Fig. 2.151. Left HPLC chromatograms of betalain pigments from reddish purple prickly pear fruits. Right HPLC chromatograms of betalain pigments from yellow purple prickly pear fruits. Peaks 1 = indicaxanthin 2 = betanin. Reprinted with permission from J. A. Femandez-Lopez et al. [324].

Some potential interfering materials are other red pigments FD C Red No. 40, FD C Red No. 3, cochineal, and beet powder (betalain pigments). The presence of alternative colorants may be suspected if the /wis-max at pH 1.0 is high (550 nm, more typical of betalain pigments), or if a bright red coloration is found at pH 4.5 (potential presence of artificial dyes). 

Goldman, I.L., Eagen, K.A., Breitbach, D.N., and Gabelman, W.H. 1996. Simultaneous selection is effective in increasing betalain pigment concentration but not total dissolved solids in red beets (Beta vulgaris L.). J. Am. Soc. Hort. Sci. 121 23-26. 

The documented use of betalain pigments as food colorants dates back at least one century, when inferior red wines were colored with betalain-containing juices (e.g., red beet juice). This common practice was, however, soon prohibited, and the application of betalain colorants was widely replaced by artificial dyes, which displayed better stability, at a lower price, and with higher purity. But in recent years the interest in natural food colorants has been renewed, mainly because of consumers concerns about the safety of some artificial colorants, which may be hazardous to human health (234). As a result, the number of permitted artificial dyes has been markedly reduced, and new efforts had to be made to develop natural food colorants (235). However, current legislation restricts the application of betalain colorants to concentrates or powders (E 162) obtained from aqueous extracts of beets (211). 

The first preparative fractionation of betalaine pigments by means of ion-pair high-speed conntercurrent chromatography utilized a solvent system composed of trifluoroacetic acid at low concentration as the IPR that considerably improved affinity of polar betacyanins and betaxanthins to the organic stationary phase of the biphasic solvent mixture [19],... 

In 1971, Dopp et al. (8) reported the unexpected finding that the pigments of the fly agaric belong to the betalains. Later, muscaflavin (4) an isomer of betalamic acid (3), was discovered as a new type of betalain pigment, and it was shown that 4 occurs in the form of amino acid derivatives in the brightly colored fruit-bodies of Hygrocybe species (9). 

With the enormous progress in the development of spectroscopic techniques and methods for separation achieved in the 1980s, a renaissance in the study of betalains appears timely. Recent studies on betalain pigments clearly demonstrate the new possibilities offered by FAB MS, high-field NMR, and HPLC (10). 

The first total synthesis of betalains was announced in 1975 by Hermann and Dreiding (11), and it was later considerably improved by the same group. An independent synthetic approach to betalain pigments was developed by Buchi and co-workers (12). The enzymatic synthesis of betalains has not yet been investigated. Also, the physiological aspects of their formation are still poorly understood, despite the fact that numerous investigations have been carried out, for example, on their photoregulation and hormonal control (73). Betalains have recently received much attention by the food industry as the red to violet beta-... 

The first separations of individual betacyanins were carried out by paper chromatography (55). The observation that betacyanins migrate on paper electrophoresis at pH 2 to 7 toward the anode was used for analyses of the betalain pigments from red beet (36,37) and other plants (38). This method was subsequently applied by two groups (3,4) for the isolation of crystalline betanin from a crude pigment preparation from red beet (39). 

Most of the betalain pigments described in the 1960s have not been characterized by mass or NMR spectra. With FAB MS now at hand, the molecular ions of underivatized betalains can be easily determined, and the sensitivity of high-field NMR spectrometers allows the complete structural assignment, even of small samples. For the structural determination of oligosaccharide moieties, modem two-dimensional (2D) NMR techniques are now the method of choice. 

Scheme 11. Possible biosynthetic routes leading from dopa to the betalain pigments of toadstools.

The striking red colour of the fly agaric Amanita muscaria arises from the presence of betalain pigments. These pigments, which are also responsible for the red colour of beetroots, are formed by the condensation of the amino group of various amino acids with the aldehyde of betalamic acid (7.33). This add and... 

Biosynthesis of Betalain Pigments via Qxidative Cleavage of Dopa 616... 

Figure 37 Biosynthesis of betalain pigments via oxidative cleavage of dopa.

In addition, the synthesis of nor-anatoxin-or and -a from cocaine was published. As a new development, betalamic acid, the major building block of the betalaine pigments, was prepared as its dimethyl ester (19) from N-benzyl-norteloidinone (16) via the major intermediates (17) and (18), as shown in Scheme 1. 

In the superorder Caryophyllidae (or Centrospermae), only the families Caryophyllaceae and Molluginaceae possess anthocyanins. In die other families of the superorder, anthocyanins appear to have been replaced by alkaloidal be-talain pigments. These compounds have nearly identical specti-al properties to those of anthocyanins and also serve in pollination and fruit and seed dispersal. This phenomenon will be discussed more fully under betalain pigments see Chapter 37). 

Betalain pigments in plants often were confused with an-thocyanins until a number of investigators in the late 19th century recognized that betacyanins contain nitrogen. However, purification of these pigments was difficult and, despite study by many well-known chemists, betalains were not fully characterized until 1963 (Wyler et al., 1963). The be-taxanthin, indicaxanthin (51), was characterized a year later (Fig. 37.14) (Piatelli et al, 1964). 

---