Volatile components of two endemic species from the Apuan Alps (Tuscany, Italy) Centaurea aachnoidea and C. montis-borlae. (Asteraceae)

The volatile fractions of Centaurea arachnoidea and C. montis-borlae, two endemic species growing wild on the Apuan Alps (Tuscany, Italy), were isolated by steam distillation from fresh leaves and flowerheads and analyzed by GC/FID and GC/MS. The yield in essential oil ranged from 0.01% to 0.09% of fresh material. A wide variety of volatile compounds was detected in the examined plant species and organs, both in qualitative and quantitative terms. Sesquiterpenes were identified as the major constituents ranging from 18.9% to 73.2% of the total oil. Alcohols (1.6-25.8%), aldehydes (1.5-12.0%), hydrocarbons (1.8-11.9%), acids (0.2-25.4%), esters (0.2-1.3%), monoterpenes (0.7-1.4%), and miscellaneous compounds (0.6-2.6%), were also detected at variable amounts in all different sample tissues. A series of unidentified compounds was also isolated from the two species, both in leaves and flowerheads, accounting for 2.4-6.7% of the total oil. According to MS spectral data, these substances likely belong to the class of polyunsaturated compounds; moreover they appear to be species-specific, as their presence was only detected either in one or in the other Centaurea species