Ffx

Concentration

FIGURE 8.10 A simplified process for betalain extraction. (Adapted from Delgado-Vargas et al.17)

separation.84115 In the preparative purification, the use of ion exchange (Table 8.17), followed by column chromatography using Polyamide, Polyclarc-AT, or polyvinylpyrrolidone, Sephadex G-15, and G-25, is recommended. The chromatographic and electrophoretic properties of the isolated compounds can be compared with those of the literature to achieve a tentative identification.116

Today, the method of choice for chromatographic separation of betalains is HPLC; reverse-phase supports with particle sizes between 3 to 10 pm are preferred (Table 8.17).8498 117 It must be pointed out that discrepancies between spectrophotometry and HPLC methods have been observed; differences up to 15% have been reported after extended heat treatment of betalains. Such differences have been attributed to degradation products or interfering substances formed during process-ing.118 Interestingly, it has been shown that betalain quantitation by capillary zone electrophoresis is in close agreement with the HPLC determination.119

c. Characterization

First, it is necessary to differentiate between anthocyanins and betalains. It is clear that if the plant that is the source of pigment has been previously classified, one can differentiate between these two kinds of pigments, as discussed above. Additionally, several chemical tests have been developed to distinguish between anthocyanins and betalains (Table 8.18).8384

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