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Semi-synthesis of red beet betacyanin ethyl-esters by esterification

Tuwalska D., Starzak K., Szot D., Wybraniec S., Winterhalter P., Jerz G.

Challenges of Modern Technology

2014

Vol. 5, no. 3

27--31

Red beet pigments recovered from Beta vulgaris L. (Chenopodiaceae), mainly consist of purple betacyanins, such as 15R/15S-betanin. Currently,this pigment class is intensively investigated in respect of stability in food systems. Quite popular is the use of red beet extracts in dairy products such as yoghurts, and ice-creams. So far, there are no issues of toxicity using these natural pigments in food – so they seem to be a very good alternative to replace synthetic dyes which had been frequently discussed for negative side-effects to human health. Betacyanins, the glycosidation products of betanidin are very polar and therefore water soluble pigments, which are biosynthetically derived from condensation of cyclo-DOPA and betalamic acid. The significant polarity of betacyanins requires the use of ion-pair reagents such as trifluoro-acetic acid (TFA) or other homologue fluorinated additives under standard separation conditions on larger scale in spiral coil countercurrent chromatography (spCCC). In our synthetic experiment, the polarity of the natural betacyanins was reduced. This omitted the use of toxic per-fluoro ion-pair reagents. The three carboxylic groups of the betanin pigment backbone were the target functional groups of the derivatisation. In semi-synthesis, fortified red beet pigment extract was esterified with water-free ethanolic hydrogen chloride solution. The reaction was carried out at ambient temperature (7 days) to yield a mixture of betacyanin mono-, di- and tri-ethyl-esters, and their epimeric forms, as well as the respective betanidin-ethyl-esters. The time course of the reaction mixture was monitored by analytical C18-HPLC with ESI-DAD-MS/MS detection. The detected molecular weights of the pigments confirmed the presence of expected products. To the best of our knowledge, the presence of betalains containing ethyl-ester groups in biological samples have not been studied before.

Spiral-coil countercurrent chromatographic separation of betanin and betanidin ethyl-esters monitored by continuous ESI-MS/MS injection and LC-ESI-MS/MS

Tuwalska D., Szot D., Wybraniec S., Winterhalter P., Jerz G.

Challenges of Modern Technology

2013

Vol. 4, no. 4

21--25

Betalains present in Beta vulgaris L. (Chenopodiaceae) have a high potential as natural pigments for food applications. They have been used as a substitute of synthetic dyes in processing of gelatine, strawberry yogurts, ice creams, fruits cocktails, candies and biscuits. The stability of betalains is strongly influenced by numerous factors – sugar content, and impact of light, oxygen, water activity, pH and temperature. A mixture of betacyanin mono-, di- and tri-ethyl-esters was separated by a large-volume spiral-coil countercurrent chromatography (spCCC) prototype which yielded fractions continuously off-line injected to anÂ ESI-MS/MS device. This method yielded a reconstituted pigment profile and finally enabled the MS-target-guided isolation procedure for the whole spCCC-experiment. The individual fractions were analyzed by LC/ESI-MS/MS. Betanin and betanidin mono-, di- and tri-ethyl-esters as well as other decarboxylated derivatives were detected in the chromatograms. The ethyl-esters of betanin were only partially fractionated, but clearly fractionated from the ethyl-esters of betanidin which will be of great value for biological evaluations.