ENANTIOMERIC COMPOSITION OF THE PRINCIPAL COMPONENTS OF THE OIL OF MELALEUCA-ALTERNIFOLIA

The concentrations and enantiomeric purity of the major monoterpene constituents in a number of Melaleuca alternifolia (tea tree) oils have been determined by enantioselective gas chromatography. Consistent enantiomeric ratios of 65:35 (+:-) for terpinen-4-ol and 76:24 (+:-) for alpha-terpineol were observed for the range of oils analyzed. Attempts to validate these ratios in the intact oil by H-1 NMR together with chiral lanthanide shift reagents have not yet been successful. H-1 NMR was, however, successful in confirming the enantiomeric purity determined by gas chromatography of standard terpinen-4-ol [79:21 (+:-)] and alpha-terpineol [35:65 (+:-)] samples. Under the correct conditions, a single analysis on a beta-cyclodextrin column enable's the determination of the quality of the oil as set forth by the Australian standard and provides additional enantiomeric evidence of the authenticity of the oil.