Continual misidentification of 5-oxolinalool as 2-methylnon-2-en-4-one in essential oils

ABSTRACT When employing GC and GC-MS, constituents of essential oils are most frequently identified by comparing retention indices and mass spectra with those reported in the literature or analytical libraries. While this allows for a rapid analysis, incorrect data can lead to a constituent being repeatedly misidentified. This was demonstrated in this work for 5-oxolinalool (6-hydroxy-2,6-dimethylocta-2,7-dien-4-one), an oxygenated monoterpene that was often erroneously identified as 2-methylnon-2-en-4-one. After encountering an unknown constituent of the essential oil of Sambucus nigra L. (Viburnaceae) flowers, we sought to acquire relevant analytical data on both compounds. Even though their mass spectra were rather similar (with 2-methylnon-2-en-4-one missing the peak at m/z 71), their retention indices were found to be significantly different. It follows that a revision of all prior identifications of 2-methylnon-2-en-4-one as an essential-oil constituent is needed.