Cactus pear (Opuntia ficus indica) flavour constituents—chiral evaluation (MDGC–MS) and isotope ratio (HRGC–IRMS) analysis



Among the volatiles isolated by solvent extraction from cactus pear fruit (Opuntia ficus indica) and identified by HRGC–MS, selected chiral and achiral constituents were characterized by enantiodifferentiation and 13C/12C isotope ratio analysis, using multidimensional gas chromatography–mass spectrometry (MDGC–MS) and on-line gas chromatography–combustion isotope ratio mass spectrometry (HRGC-C-IRMS), respectively. While the enantiodistributions determined for methyl 2-methylbutanoate (98 : 2%, S : R), methyl 3-hydroxybutanoate (73 : 27%, R : S), 1-phenyl-ethanol (74 : 26%, R : S), linalool (68 : 32%, R : S), γ-nonalactone (65 : 35%, S : R), γ-deca-lactone (79 : 21%, R : S) and γ-dodecalactone (>99% R) can be discussed in relation to data previously provided for these compounds from various plant origins, the δ13C values of −22.0‰, −21.8‰, −19.1‰ and −20.9‰, measured for 1-hexanol, E-2-hexenol, E-2-nonenol and E,Z-2,6-nonadienol, respectively, are clear-cut indicators for their origin from plants with Crassulaceae acid metabolism (CAM), and thus may helpful for authenticity evaluations. Copyright © 2001 John Wiley & Sons, Ltd.