α-Linalool - a marker compound of forged/synthetic sweet basil (Ocimum basilicum L.) essential oils

BACKGROUND Ocimum basilicum L. (sweet basil) is known to occur as several chemotypes or cultivars that differ in their essential oil composition. The surprising discovery of 3,7-dimethylocta-1,7-dien-3-ol, the rare isomer of the well-known monoterpene alcohol -linalool (3,7-dimethylocta-1,6-dien-3-ol), in samples of Serbian basil oil provoked an investigation of the origin of -linalool in these samples. Three scenarios were considered, namely (a) the existence of a new natural chemotype, (b) an artefactual formation during the isolation procedure and (c) the case of a synthetic/forged oil. RESULTS Noteworthy amounts (15.1-16.9%) of pure -linalool were isolated from a commercial sample of basil oil, and detailed spectral analyses (MS, IR, H-1 and C-13 NMR) unequivocally confirmed its identity. The analysis by GC and GC/MS of an additional 20 samples of different O. basilicum oils commercially available on the Serbian market or isolated from plant material cultivated in Serbia resulted in the identification of 149 compounds. The obtained compositional data were compared using multivariate statistical analysis to reveal the possible existence of a new basil chemotype. CONCLUSION The results of the chemical and statistical analyses give more pro arguments for the synthetic/forged oil hypothesis and suggest that -linalool could be used as a marker compound of such O. basilicum oils. (c) 2013 Society of Chemical Industry