Seasonal Variation in Volatile Oil of Eucalyptus Species in Iran

Abstract

The seeds of three Eucalyptus species (origin: Australia) named E. porosa, E. leucoxylon var. rosea, and E. camaldulensis var. obtusa were cultivated in the years 1993–1994 in two research stations (Shushtar and Dezful) in Khuzistan province (in the southwestern regions of Iran). These species have good adaptability with the climatic condition of this area (dry and warm weather). The leaves of these species were collected in the middle of four seasons (spring, summer, autumn, and winter) to determine the best harvesting time for obtaining the highest oil yield and 1,8-cineole content. After drying the plant materials in shade, their essential oils were obtained by hydro-distillation. The oils were analyzed by capillary gas chromatography using flame ionization and mass spectrometric detection. Analysis of variance showed harvesting time had significant effect on the oil yields of these Eucalyptus species. Thirty-eight components were identified in the oils of Eucalyptus porosa with 1,8-cineole (41.1%–59.5%) as the main constituent. The highest percentage of 1,8-cineole was found in both samples in spring. Thirty-three compounds were characterized in the oil of Eucalyptus leucoxylon with 1,8-cineole (42.1%–89.8%) as the main constituent. The highest percentage of 1,8-cineole was found in autumn for the shushtar sample (71.9%) and in winter for Dezful sample (89.8%). Thirty-eight compounds were identified in the oil of Eucalyptus camaldulensis var. obtusae with 1,8-cineole (29.1%–71.1%) as the main constituent. The highest percentage of 1,8-cineole was found in autumn for the shushtar sample (59.0%) and in winter for Dezful sample (71.1%). The results showed that for obtaining the 1,8-cineole rich oil from E. porosa leaves, the best harvesting time is spring, whereas for E. leucoxylon and E. camaldulensis var. obtusa, autumn and winter are the best times in shushtar and Dezful, respectively.