Comparative aroma compound analysis of different essential oils of Lippia rugosa from Cameroon using GC/FID, GC/MS and olfactometry

The essential oils of flowers, stems, fresh old, fresh young and dried leaves of Lippia rugosa A.Chev. (syn. L. adoensis F.TW.A., L. nigeriensis Moldenke) from Cameroon were analyzed by GC, GC/MS and olfactometry. The oils were characterized by a high percentage of oxygenated monoterpenes (18.6-93.1%), represented especially by geraniol (0.4-51.5%), linalool (4.6-32.9%), 1,8-cineole (less than 0.1-19.1%), nerol (0.1-18.6%) and geranial (less than 0.1-16.5%). The main monoterpene hydrocarbons were identified as limonene (less than 0.1-37.8%), myrcene (less than 0.1-14.1%), beta-pinene (less than 0.1-6.5%), (Z)-beta-ocimene (not detected-3.3%), gamma-terpinene (less than 0.1-2.3%) and (E)-beta-ocimene (less than 0.1-2.2%). Sesquiterpene derivatives (hydrocarbons and oxygenated) were found in a lower concentration (together 3.3-28.0%), represented mainly by (E)-beta-farnesene (0.3-12.1%), germacrene D (1.2% and 4.2%), beta-caryophyllene (0.8-3.9%) isocaryophyllene oxide (less than 0.1-2.9%) and tau-muurolol (0.1-2.2%).