Detection and enantiomeric distribution of 2‐hydroxy‐5‐methyl‐3‐hexanone and 3‐hydroxy‐5‐methyl‐2‐hexanone in commercial eucalyptus honey

2-Hydroxy-5-methyl-3-hexanone and 3-hydroxy-5-methyl-2-hexanone have been reported as biomarkers for eucalyptus honey. The extracts of eight types of commercial eucalyptus honey products from Australia, Italy and Spain were analysed to detect the presence and the enantiomeric distribution of these two markers using GC-MS and chiral GC-MS. The racemic and optically active standards were synthesized by oxidation or asymmetric oxidation of the corresponding silyl enol ethers. Four honey samples were found to contain these two compounds. 2-Hydroxy-5-methyl-3-hexanone and 3-hydroxy-5-methyl-2-hexanone were present in these eucalyptus samples in enantiomer-enriched form with the (S)-configuration as the major configuration in most cases. The ee values range from 7.2% to 44.4%. Copyright © 2013 John Wiley & Sons, Ltd.