A study of the larvicidal activity of two Croton species from northeastern Brazil against Aedes aegypti

The essential oils of Croton heliotropiifolius Kunth (Euphorbiaceae) and Croton pulegiodorus Baill. were selected for larvicidal evaluation against Aedes aegypti L. (Diptera: Culicidae) and studied qualitatively and quantitatively by GC and GC-MS. Sixty-one compounds representing 92.03% (C. heliotropiifolius) and 85.68% (C. pulegiodorus) of the essential oils, respectively, have been identified. The major components of C. heliotropiifolius essential oil were identified as β-caryophyllene (35.82%), bicyclogermacrene (19.98%), and germacrene-D (11.85%). The major components in C. pulegiodorus essential oil were identified as β-caryophyllene (20.96%), bicyclogermacrene (16.89%), germacrene-D (10.55%), τ-cadinol (4.56%), and β-copaen-4-α-ol (4.35%). The essential oil of C. pulegiodorus (LC₅₀ 159 ppm) was more effective against Ae. aegypti than that of C. heliotropiifolius (LC₅₀ 544 ppm). In order to verify whether the major compound of both essential oils is the active principle responsible for the larvicidal activity, β-caryophyllene was purchased and its larvicidal potential was further evaluated. However, β-caryophyllene (LC₅₀ 1038 ppm) showed weak larvicidal potency. Results of larvicidal evaluation suggest the existence of a synergistic effect of minor components in the essential oils.