3-HYDROXY-RETRO-ALPHA-IONOL - A NATURAL PRECURSOR OF ISOMERIC EDULANS IN PURPLE PASSION-FRUIT (PASSIFLORA-EDULIS-SIMS)

In a polar extract obtained from purple passion fruit (Passiflora edulis Sims) juice, capillary gas chromatography (HRGC), and coupled HRGC techniques, i.e., on-line mass spectrometry (HRGC-MS) and Fourier transform infrared spectroscopy (HRGC-FTIR), revealed for the first time the presence of 3-hydroxy-retro-alpha-ionol. The identification was verified by comparison of HRGC, HRGC-MS, and HRGC-FTIR data of the new natural product with those of an authentic reference compound synthesized from the known C-13 keto alcohol, 3-oxo-alpha-ionol. Degradation studies carried out with 3-hydroxy-retro-alpha-ionol showed the easy formation of isomeric edulans under acidic conditions. Possible mechanisms for the formation of the odor active edulans, key flavour components of purple passion fruit juice, are discussed.