Sesquiterpene, alkene, and alkane hydrocarbons in virgin olive oils of different varieties and geographical origins

The hydrocarbon fraction of 30 virgin olive oils was analyzed, focusing in particular on the sesquiterpenes. The oil samples were of different geograp hical origins and obtained from different olive varieties. The hydrocarbon fraction was isolated by silica gel column chromatography of the unsaponifi able fraction of the oils. The sesquiterpene hydrocarbons were then fractio nated, on the basis of their degree of unsaturation, by AgNO3 TLC and silic a gel AgNO3 column chromatography. The composition of the sesquiterpenes wa s more complex than previously reported. Among the 31 sesquiterpenes detect ed, 24 have been tentatively identified, by comparison of the linear retent ion indices on two capillary columns of different polarities and mass spect ra with those reported in the literature. The total concentration of the se squiterpenes in the oils analyzed ranged from about 2 to 37 ppm. Among the sesquiterpenes the more abundant were alpha -farnesene, alpha -copaene, ere mophyllene, and alpha -muurolene. The alkenes present in the hydrocarbon fr action were isolated by TLC AgNO3 and characterized by GC-MS of their dimet hyl disulfide derivatives. The series of n-Delta (9)-alkenes from C-22 to C -27, 8-heptadecene, and 6,10-dimethyl-1-undecene were detected. Among the n -alkanes, those with an odd number of carbon atoms predominated in all of t he analyzed oils, the most common being C-23, C-25, C-27, and C-29. The con centration of the n-alkenes ranged from about 0.5 to 2 ppm, whereas for the n-alkanes the range was from 30 to 177 ppm.