New trans -β-bergamotene derivatives in the root and the flower essential oils of Cyanthillium cinereum (L.) H. Rob. from Côte d'Ivoire.

Root and flower essential oils of Cyanthillium cinereum (L.) H. Rob. (Synonym Vernonia cinerea (L.) Less.) (Asteraceae) collected in Southern Côte d'Ivoire was investigated using a combination of chromatographic and spectroscopic techniques. The root oil composition was dominated by trans -β-bergamotene (20.7%), β-elemene (19.0%), cyperene (10.6%), germacrene A (7.1%) and β-pinene (3.8%), whereas γ-humulene (31.0%), ( E )-β-caryophyllene (17.0%), trans -β-bergamotene (7.7%), β-pinene (7.5%) and ( E )-β-farnesene (6.0%) were the major components of flower oil. Two new compounds bearing the trans -β-bergamotene framework were identified: trans -β-bergamotenone and ( E )- trans -β-bergamotenol.