Variability in Essential Oil Composition of Croton Species with Occurrence in the Eastern Brazilian Amazon

The air-dried aerial parts of Croton campestris, C. chaetocalyx, C. eriocladus, and C. glandulosus, with occurrence in the Eastern Brazilian Amazon, yielded essential oils, and their volatile constituents were analyzed by GC and GC-MS. Sesquiterpenes, both hydrocarbons and oxygenated, were the most highly represented classes in the oils: the former ranging from 55.3% to 85.1%, and the latter varying from 7.2% to 33.2%. The oils were separated into two groups using hierarchical cluster analysis whose main constituents were β-caryophyllene, germacrene D, γ-elemene, β-elemene, α-humulene and δ-elemene (Group A, C. campestris and C. eriocladus); and spathulenol, bicyclogermacrene, δ-elemene, germacrene D, β-caryophyllene and δ-cadinene (Group B, C. chaetocalyx and C. glandulosus). Percentage of sesquiterpene hydrocarbons was higher in Group A (83-85%) than in Group B (55-63%). However, regarding the oxygenated sesquiterpenes, it was reversed, being bigger in Group B (28-33%) than in Group A (7-8%). Percentage of similarity in Group A was 92% and in Group B it was 86%. These chemotaxonomic results showed a significant contribution for the better botanical knowledge of these four Croton species occurring in North Brazil.