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

The volatile fractions of Centaurea arachnoidea and C. montis-borlae, two endemic species growing wild in 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 of 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 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 in 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 were likely to be polyunsaturated compounds; moreover, they appear to be species-specific, as their presence was only detected in either one or the other Centaurea species.