Screening and mass-spectral confirmation of betalains in cactus pears

The presence of betalain pigments in fruits of Opuntia stricta, Opuntia undulates and Opuntia ficus-indica has been studied. Cultivars of deep red-purple colour, with high betacyanin content, were choosen for this investigation. The total betacyanin content was estimated spectrophotometrically (E-1cm(1%)=1120) and the results obtained indicated a higher betacyanin content in O. stricta (70 mg . 100 g(-1) fresh fruit), than in O. undulates and O. ficus-indica (14-19 mg . 100 g(-1) fresh fruit). Individual pigment analysis by HPLC with photodiode array detection revealed substantial differences between these species. In cactus pears from O. stricta only betanin and isobetanin were detected. However, in cactus pears from O. undulates and O. ficus-indica the predominant pigments were betanin and indicaxanthin, with very low levels of isobetanin. The identity of all these pigments was confirmed by mass-spectral analysis. The presence of neobetanin was not detected in fruits of any of the three species considered.