ESSENTIAL OIL COMPOSITION OF SOME CENTAUREA SP. (ASTERACEAE) FROM DIFFERENT ITALIAN ISLANDS

The volatile constituents of leaves and flower heads of several Centaurea spcies from different islands of Ligurian and Tyrrhenian Sea were investigated for the first time. C. veneris (Sommier) Bég. from Palmaria Island (Ligurian Sea),C. gymnocarpa Moris & De Not. from Capraia Island, C. aetaliae (Somm.) Bég. and C. ilvensis (Sommier) Arrigoni from Elba Island (Northern Tyrrhenian Sea); C. aeolica Lojac. subsp. aeolica from Lipari, Aeolian Islands, C. busambarensis Guss., C. panormitana Lojac. subsp. ucriae (Lacaita) Greuter, C. panormitana Lojac. subsp. umbrosa (Fiori) Greuter, C. panormitana Lojac. subsp. todaroi (Lacaita) Greuter, C. panormitana Lojac. subsp. seguenzae (Lacaita) Greuter from different localities in Sicilia (southern Tyrrhenian Sea), were collected at flowering stage. All samples were extracted by steam distillation to obtain the volatile fraction with a yield ranging from 0.02-0.13% in leaves and 0.01-0.09% in flower heads (weight/fresh weight basis), respectively. The oils were then analyzed by GC/FID and GC/MS methods and more than 100 compounds belonging to several chemical classes were identified and quantified in all the samples. Sesquiterpenes represent the most abundant class of compounds (22.35-61.67% and 35.16-57.51% of the total volatiles in leaves and flower heads, respectively) of which germacrene D was the dominant constituent (10.03-42.65% and 7.33-30.32% in leaves and flower heads, respectively). Aldehydes, hydrocarbons, ketones, monoterpenes, alcohols, acids, esters and miscellaneous compounds were also identified and quantified in different amount in the volatile oils from all the examined plant organs. Other compounds were also detected and they appear to be species-specific, as their presence was only detected in either one or the other Centaurea species