Enantioselective analysis of secondary alcohols and their esters in purple and yellow passion fruits.
The enantiomeric compositions of the acetates, butanoates, hexanoates, and octanoates of the secondary alcohols 2-pentanol, 2-heptanol, and 2-nonanol were determined in yellow (Passiflora edulis f. flavicarpa) and purple (Passiflora edulis Sims) passion fruits. The compounds were isolated by means of simultaneous distillation-extraction. Enantiodifferentiation was performed via multidimensional gas chromatography using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-beta-cyclodextrin as chiral stationary phase. The series of homologous 2-alkyl esters, which are typical constituents of purple passion fruits, were shown to be present as nearly optically pure (R)-enantiomers. The proportions of the (S)-enantiomers varied in different batches and were dependent on the alcohol moieties of the esters. For minor amounts of esters detected in yellow fruits, the (R)-enantiomers were also dominating. However, the enantiomeric excesses were significantly lower than in the purple variety. Enantioselective analysis of the free alcohols revealed that 2-heptanol exhibited opposite configurations in purple and yellow passion fruits. A similar phenomenon was observed for 2-pentanol, which was present in the yellow fruits as a nearly racemic mixture. Data determined in extracts obtained by other techniques (liquid-liquid extraction, vacuum headspace technique) showed that the isolation procedure had no significant impact on the enantiomeric ratios.
Strohalm
Hedwig
H
Lehrstuhl für Allgemeine Lebensmitteltechnologie, Technische Universität München, Am Forum 2, D-85350 Freising-Weihenstephan, Germany.
Dregus
Márta
M
Wahl
Astrid
A
Engel
Karl-Heinz
KH
D004952:Esters / Q000032:analysis / Q000737:chemistry*; D005233:Fatty Alcohols / Q000032:analysis / Q000737:chemistry*; D005638:Fruit / Q000737:chemistry*; D019850:Heptanol / Q000032:analysis / Q000737:chemistry*; D029598:Passiflora / Q000737:chemistry*; D000439:Pentanols / Q000032:analysis / Q000737:chemistry*; D013237:Stereoisomerism
D004952:Esters; D005233:Fatty Alcohols; D000439:Pentanols; C526153:2-nonanol; D019850:Heptanol