Chemical composition of essential oils and hydrosols of three Eucalyptus species from Senegal: Eucalyptus alba Renv, Eucalyptus camaldulensis Dehnh and Eucalyptus tereticornis Hook

The leaves of three eucalyptus species Eucalyptus Alba, Eucalyptus camaldulensis and ucalyptus tereticornis were collected in Kaolack (Senegal) and were extracted by steam distillation after 3, 7, 14 and 21 days of drying. The volatile components of aqueous distillates (hydrosols) were obtained by liquid–liquid extraction using n-hexane. The different extracts were analyzed by gas chromatography coupled to a flame ionization detector (GC-FID) and by gas chromatography coupled to a mass spectrometer (GC-MS). Essential oils yields obtained range from 0.3 to 1.6%. E. camaldulensis had the higher yield. Forty four compounds were characterized in E. camaldulensis essential oils. These lasts were dominated by 1.8-cineole (47.54 to 52.47%), limonene (16.5 to 19.1%), α-pinene (7.3 to 11.2%) and p-cymene (6.0 to 8.8%). Fifty compounds were identified in E. Alba oils with 1.8-cineole (36.0-38.3%) α-pinene (19.0-26.4%), limonene (5.7- 8.3%), trans-pinocarveol (3.5 -5.0%) β-pinene (1.9 to 4.6%) as major compounds. In E. tereticornis oils, fifty two compounds were identified. Their composition were dominated by p-cymene (42.49 to 48.51%) followed by 1.8-cineole (21.3- 24.5%), limonene (4.8- 5.9%) and α-pinene (1.9 to 6.7%). The analyzed hydrosols were composed by oxygenated molecules whose major part was found in oils. As essential oils, all corresponding hydrosols hade high rate of 1.8-cineole. E. alba hydrosol contains mainly 1.8-cineole (39.1%), trans-pinocarveol (19.3%), pinocarvone (6.8%). E. camaldulensis hydrosol was dominated by 1.8-cineole (52.6%), α-terpineol (6.6%), cis-p-mentha-1-(7)-8-dien-2ol (5.1%). The major compounds of E. tereticornis hydrolat were: 1.8-cineole (30.7%), α-terpineol (8.8%), trans-pinocarveol (7.6%), carvacrol (7.0%). The results showed that although 1.8-cineole was the main component of the hydrosols of all eucalyptus species, but its relative content was higher in E. camaldulensis.« WBI-Sénégal n°2: Production d’huiles essentielles à partir de plantes locales : expérimentation, adaptation et diffusion de technologies