Development of a protocol for the semi‐synthesis and purification of betaxanthins

Abstract

A method for the analytical and semi-preparative chromatographic purification of betaxanthins is described together with an improved procedure for the semi-synthesis of these compounds from betalamic acid. Standard conditions for obtaining preparative amounts of betaxanthins free of the precursor amino acids are provided. Following this procedure, 14 pure betaxanthins were obtained with yields of up to 100%. A simple reversed-phase HPLC protocol for pigment identification and quantification is also provided. Calibration for betaxanthins is reported for the first time using the synthesised and purified pigments as standards. Structures were confirmed by UV-vis spectroscopy, HPLC retention times and electrospray ionization mass spectrometry. Betaxanthins can be obtained pure, and in sufficient amounts for further studies, which opens up new perspectives in the research and applications of these pigments.

Structural implications on color, fluorescence, and antiradical activity in betalains

“…The rest of betalains were obtained as immonium condensation products of betalamic acid with the following amines: ethylamine, propylamine, 2-phenylethylamine, N-methyl-ethanamine, N-methyl-N-propylamine, pyrrolidine, aniline, N-methylaniline, N-ethyl-aniline, indoline, (S)-phenylalanine, and (S)-indoline-2-carboxylic acid. Semi-synthesis was carried out following a previously described method (Wyler et al 1965;Gandía-Herrero et al 2006). In short, betanin puriWed from red beet was used as starting material.…”

“…The application of an improved procedure for the semi-synthesis and puriWcation of betaxanthins (Gandía-Herrero et al 2006) based on the SchiV base synthesis (Wyler et al 1965) allowed us to work with both natural and previously unconsidered pigments. A relevant series of structurally related pigments was obtained in order to clarify the role of diVerent structural features in betalain properties.…”

Characterization of recombinant Beta vulgaris 4,5-DOPA-extradiol-dioxygenase active in the biosynthesis of betalains

“…The diastereoisomeric methionine-derived betaxanthin was obtained as an immonium condensation product of the enzyme-produced betalamic acid with the (S)-form of methionine (obtained from Sigma), following a previously described methodology (Wyler et al 1965;Gandía-Herrero et al 2006). Briefly, a Schiff condensation reaction was performed between the aldehyde group of betalamic acid and the amine group of the amino acid to form the imine.…”

Estudo do mecanismo de ação antirradicalar de betalaínas

“…A abordagem mais comum para a semissíntese de betalaínas é a hidrólise alcalina de betanina de beterraba na presença de excesso de amina, seguida de reacoplamento pela adição de ácido. [41] Esta abordagem produz, obviamente, uma mistura entre a betalaína desejada e betanina, a última fruto do reacoplamento entre o ácido betalâmico e ciclo-DOPA 5-Oglicosilada, a menos que um grande excesso de amina seja usado. Alguns autores preferem hidrolisar a betanina em meio aquoso alcalino e extrair o ácido betalâmico resultante com AcOEt.…”