GC-MS characterisation and chemometric differentiation of volatile fractions from inflorescences of selected Echinacea and Rudbeckia species

Volatile fractions obtained by hydrodistillation from inflorescences of Echinacea purpurea, E. paradoxa, Rudbeckia fulgida, R. hirta and R. laciniata cultivated in Estonia were analysed by GC-MS. In total, 104 compounds were identified and semi-quantified. The highest yields were recorded for E. purpurea (0.62%) and R. hirta (0.53%). The volatile profiles showed clear interspecific differentiation. E. purpurea was characterised by a predominance of monoterpene hydrocarbons (notably o-cymene, α-pinene and camphene), whereas Rudbeckia species were dominated by sesquiterpene hydrocarbons, particularly germacrene D and eremophilene. E. paradoxa exhibited a distinct profile enriched in oxygenated sesquiterpenes, including (E)-α-bergamotene and α-cadinol. PCA and HCA consistently separated the taxa studied by their volatile composition and showed high within-species similarity. To the best of our knowledge, this is the first report on the volatile composition of E. paradoxa inflorescences. The results highlight pronounced chemical differentiation among the examined taxa and support the use of volatile constituents as auxiliary chemotaxonomic markers within the tribe Heliantheae.