Influence of Drying and Extraction Methods on Yield and Chemical Composition of the Essential Oil of Eucalyptus sargentii

Many parameters affect essential oil yield and chemical composition of aromatic plants. For obtaining the highest quantity and quality of essential oil, it is necessary to know the proper methods of drying and distillation. The aim of this research was to investigate the influence of drying and extraction methods on the yield and chemical composition of the essential oil of Eucalyptus sargentii. The fresh leaves of Eucalyptus sargentii, cultivated in Kashan (central region of Iran), were collected in the middle of spring and dried by five different drying sun-drying, shade-drying, and oven-drying at 30, 40 and 50°C. The essential oils of every treatment were obtained by hydro-distillation in three replication. In addition, the essential oil of shade-dried sample was obtained by two other distillation methods, namely, water- and steam-distillation and direct steam-distillation. The oils were analyzed by capillary GC and GC-MS. Statistical analysis showed significant difference between oil yield (w/w) of the shade-dried sample (3.39%) compared to oven-dried at 40°C (2.92%), sun-dried (2.66%), oven-dried at 30°C (2.59%) and oven-dried at 50°C (2.30%). The oil content of the shade-dried sample obtained by hydro-distillation (3.39%) was higher than those of the water and steam distillation (2.89%) and steam distillation (1.35%). Twenty-three components were identified in the oil of E. sargentii in the different drying methods, including 1,8-cineole (57.9-65.8%) and α-pinene (11.3-28.3%) as main components. Twenty-four compounds were characterized in the oils of different distillation methods, including 1,8-cineole (61.2-66.6%) and α-pinene (19.7-28.3%) as the major compounds. Among the different drying methods, shade-dried samples produced the highest oil yield and 1,8-cineole content, while in different distillation methods, hydro-distillation produced the highest oil yield, but the highest percentage of 1,8-cineole was obtained by water and steam distillation.