Seasonal Influence on the Essential Oil Compositions of Eucalyptus urophylla S. T. Blake and E-grandis W. Hill ex Maiden from Brazilian Cerrado

Essential oils from leaves of Eucalyptus grandis and E. urophylla collected in two seasons of Brazilaian Cerrado were investigated by GC and GC/MS. 1,8-Cineole, alpha-pinene, alpha-terpinyl acetate, and p-cymene were the main constituents. The results were submitted to Principal Components and Clusters Analysis which enabled four groups of oils to be distinguished with regard to specimens and harvest seasons: clusters I and II with only E. graudis samples collected in the cold and dry winter and the hot and humid summer, which were characterized by a high percentage of isoleptospermone (9.6% and 13.2%), alpha-pinene (12.2% and 24.7%), p-cymene (20.5% and 14.5%), and alpha-terpineol (14.3% and 4.9%), respectively; clusters III and IV only associated with E. urophylla samples collected in summer and winter with 1,8-cineole (36.6% and 44.7%) and alpha-terpinyl acetate (7.0% and 11.7%) rich oils. Canonical discriminant analysis showed that it is possible to accurately predict 96% well-classification in the original clusters using alpha-pinene, 1,8-cineole, alpha-terpineol, and isoleptospermone as predictor variables.