Figure 1

Sections of chromatograms resulting from IEC of (a) a physiological standard showing compounds eluting at positions P-Ser, Tau, P-Eta, urea, and Asp, and of juices prepared from (b) white), (c) orange (for arrow see text), and (d) red pulp of Opuntia ficus-indica from Sicily, (e) a complete chromatogram of a commercial juice made from O. ficus-indica in comparison to (f) the physiological standard (BENSON) used for the assignment of peaks in (b) - (e), and (g) IEC of a juice prepared from the orange-yellow pulp of a South African prickly pear (upper trace) superimposed by a subsequently recorded chromatogram of a supplemented physiological standard from SIGMA-ALDRICH (lower trace). Note that the chemical nature of compounds eluting at positions assigned as P-Ser, Tau, P-Eta and urea by the instrument, as well as of non-proteinogenic amino acids in (e) and (g) have not been confirmed by us by independent analytical methods. For acronyms of special amino components in standards (f) and (g) see list of abbreviations.