Betalamic acid

The latter point to the natural occurrence of betaxanthins derived from a-ami-noadipic acid, asparagine, leucine, and valine. Some of these pigments were prepared from betalamic acid and the corresponding amino acids 71). 

Betalamic acid (3) is an essential structural element of all natural betacyanins and betaxanthins. It had been suggested as an intermediate in the amino exchange reaction between dilferent members of this group 72,80) before its natural occurrence was established by Mabry and co-workers 81,82). in a chem-otaxonomic investigation, Reznik 83) demonstrated the wide distribution of 3 in plants of the order CaryophyHales (Table I). Compound 3 can also be obtained by mild base-catalyzed hydrolysis of betaxanthins 42,84). In contrast to the be- 

On treatment of 3 with semicarbazide a crystalline semicarbazone is formed (55), and the reaction with aniline yields a salmon-pink Schiflf base 06 nm) (81). The formation of betalains by reaction of 3 with amino acids and amines is discussed in Section VIII,C. 

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COLORANTS FORFOOD,DRUGS,COSPffiTICS AND PffiDICALDEVICES] (Vol 6) Betalamic acid [18766-66-0]... 

Rj = H, R2 = COOH) and isobetanidine (96, R2 = H, Rj = COOH). Furthermore, it would appear that all betacyanins or betaxanthins may simply be imine derivatives (with the appropriate amino acid) of betalamic acid (97). 

Von Elbe, J.H., Stability of betalaines as food colors, Food TechnoL, 29, 42, 1975. Kimler, L. et al., Betalamic acid, a new naturally occurring pigment, J. Chem. Soc./Chem. Commun., 21, 1329, 1971. 

Betalains are N-heterocyclic water-soluble pigments deposited in vacuoles. Their common precursor is betalamic acid consisting of a 1,7-diazaheptamethin system, an extended Jt-electron system exhibiting a canary yellow color. Betalamic acid may condense with cyc/o-dopa to yield betanidin, the common precursor aglycon of the red betacyanins. Betanidin in turn may be glycosylated and/or acylated, yielding 29... 

The yellow analogues, the betaxanthins, are composed of betalamic acid with amino acids or amines, respectively, amounting to 26 structures known to occur naturally. " Structures unambiguously assigned by NMR spectroscopy usually carry trivial names derived from the plant material from which they have been first isolated. The substitution patterns of betalyanins and betaxanthins hitherto reported together with their particular plant sources are listed in Table 4.4.1 and 4.4.2, respectively. 

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. ... 

For betaxanthins, partial synthesis is quite common and presents a viable tool for identification by co-injection experiments. - Starting from a red beet extract or semi-purified betanin-isobetanin blend, alkaline hydrolysis by addition of 32% ammonia is initiated. Spectrophotometric monitoring at 424 nm allows the release of betalamic acid to be followed. Betaxanthins are obtained through the addition of the respective amino acid or amine in at least 20-fold molar excess followed by careful evaporation. Since the starting material most often consists of a racemic betacyanin mixture, the resulting betaxanthin will also consist of two stereoisomers that may not easily be separated by HPLC. ... 

The feasibility of partial synthesis has been demonstrated in the course of structural confirmation of a great number of betaxanthins. Due to incomplete hydrolyses, residual betanin and isobetanin may also accompany the respective target betaxanthin. Most importantly, the purification of betalamic acid does not appear to be possible because it exhibits both amino and aldehyde functions (Stintzing, unpublished observations), resulting in self-condensation. Therefore, data by Barth and co-workers reporting NMR data on purified betalamic acid should be carefully interpreted. ... 

Investigations relying on HPLC coupled to a UV-Vis detector should be set at 470 to 475 nm for betaxanthins and 535 to 540 nm for betacyanins. Gradient elution is commonly preferred to achieve complete separation. If a diode array detector is available, common monitoring wavelengths are 280 nm for colorless phenolics, 406 nm for betalamic acid, 470 nm for betaxanthins, and 536 nm for betacyanins. 

As a rule, indicaxanthin and portulacaxanthin I exhibit the highest absorption maxima. The lowest are usually represented by amine addncts of betalamic acid such as miraxanthin The absolute values will also be affected by the... 

Betalains consist of two groups of pigments of similar structure, the yellow compounds classed as betaxanthins and the purple as betacyanins [14]. Both groups contain a betalamic acid residue coupled to an amine or an amino acid to form an iminium salt. Whereas the amino components of the betaxanthins vary considerably. 

Based on genetic studies (cross-breeding) with Portulaca grandma, Trezzini and Zryd (1990) postulated that only three loci are responsible for betalain biosynthesis. While two loci control the bios)mthesis of q/do-Dopa and betalamic acid, the third controls the transport of betalamic acid into the vacuole. They proposed that the formation of betanidin (condensation of cydo-Dopa with betalamic acid) proceeds in the cytoplasm and the formation of betaxan-thins (condensation of betalamic acid with an amino acid/amine) takes place spontaneously in the plant vacuole (Trezzini, 1990). 

Fischer, N. and Dreiding, A.S. (1972) Biosynthesis of betalaines. On the cleavage of the aromatic ring during the enzymatic transformation of dopa into betalamic acid. Helv. Chim. Acta, 55, 649-58. 

Mueller, L.A., Hinz, U. and Zryd, J.-P. (1997a) The formation of betalamic acid and muscafiavin by recombinant Dopa-dioxygenase from Amanita. Phytochemistry, 44, 567-69. 

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). 

Detailed studies on the stability of betanin in aqueous solutions have shown that the pigment is hydrolyzed on heating to betalamic acid (3) and cyclodo-pa-5-O-glucoside 53). The latter compound has been obtained on a preparative scale by base exchange of betanin with proline in the presence of dilute aqueous ammonia 43). 

Most of the betaxanthins could not be obtained in crystalline form. As with the betacyanins, epimerization at C-11 of the betalamic acid moiety may lead to the formation of iso compounds (29). The complete stereochemistry of the betaxanthins has not been determined in many cases. It can be assumed, however, that the natural compounds are derived from L-amino acids and (5)-betalamic acid (3). Thus, the betalamic acid dimethyl ester obtained from betaxanthins of the fly agaric is always dextrorotatory, which proves its (5) configuration (77). 

Betaxanthins are immediately recognized by their characteristic absorption spectra, which show a maximum at 475 nm. On alkaline or acid hydrolysis, they yield the corresponding amino acids. In a more recent approach (77) the betaxanthins were cleaved with 0.6 N aqueous ammonia to yield betalamic acid (3) and the corresponding amino acids. Compound 3 was then extracted with organic solvents and characterized as its dimethyl ester. Unknown amino acids were identified by GC-MS of their A -trifluoroacetyl methyl ester derivatives. 

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