Sterol fractions in hazelnut and virgin olive oils and 4,4"-dimethylsterols as possible markers for detection of adulteration of virgin olive oil

Reports on the methylsterol fractions of hazelnut oils are scarce. The objectives of this study were to characterize methylsterols in hazelnut and virgin olive oils and to study the possibility of detection of adulteration of virgin olive oils. In hazelnut oils, 4-desmethylsterols were present in higher proportions (86 to 91%) than in virgin olive oils where this fraction was ca.50% of the total sterol. In the 4-monomethylsterol fraction, citrostadienol was the major component in both kinds of oils followed by cycloeucalenol and obtusifoliol in virgin olive oils, and obtusifoliol in hazelnut oils. 24-Methylenecycloartanol was predominant in both kinds of oils in the 4,4'-dimethylsterols. For the first time, delta-amyrin was tentatively identified by comparing published mass spectral data in the analyzed samples of both kinds of oils. An unknown compound X (containing a lupane skeleton) and lupeol were detected only in the 4,4'-dimethylsterols fraction of hazelnut oils at a level of 2-8 and 6-10%, respectively. GC-MS analysis showed that adulteration of virgin olive oil by hazelnut oil Could be detected at a level less than 4% by using these two compounds as possible potential markers.