Structural investigations on betacyanin pigments by LC NMR and 2D NMR spectroscopy

Publication Type

Journal contribution (peer reviewed)

Authors

Stintzing, F. C.; Conrad, J.; Klaiber, I.; Beifuss, U.; Carle, R.

Year of publication

2004

Published in

Phytochemistry

Band/Volume

65/4

DOI

10.1016/j.phytochem.2003.10.029

Page (from - to)

415-422

Keywords

Betacyanin, Betain, Hylocereus polyrhizus, Isobetanin, LC-NMR

Four betacyanin pigments were analysed by LC NMR and subjected to extensive NMR characterisation after isolation. Previously, low pH values were applied for NMR investigations of betalains resulting in rapid degradation of the purified substances thus preventing extensive NMR studies. Consequently, up to now only one single ¹³C NMR spectrum of a betalain pigment, namely that of neobetanin (= 14,15-dehydrobetanin), was available. Because of its suficient stability under highly acidic conditions otherwise detrimental for betacyanins, this pigment remained an exemption. Since betalains are most stable in the pH range of 5-7, a new solvent system has been developed allowing improved data acquisition through improved pigment stability at near neutral pH. Thus, not only ¹H, but for the .rst time also partial ¹³C data of betanin, isobetanin, phyllocactin and hylocerenin isolated from red-purple pitaya [Hylocereus polyrhizus (Weber) Britton & Rose, Cactaceae] could be indirectly obtained by gHSQC- and gHMQC-NMR experiments.