Chemical composition and acaricidal activity of essential oils from two species of the genus Bauhinia that occur in the Cerrado biome in Brazil

Essential oils from the leaves of Bauhinia rufa and B. dumosa collected from the Cerrado biome in central Brazil were obtained by hydrodistillation and analyzed using GC and GC/MS. Both oils had a predominance of sesquiterpenes (B. rufa: 95.3 +/- 0.5%; B. dumosa: 97.2 +/- 1.1%). beta-Caryophyllene (15.8 +/- 0.5%), epi-alpha-cadinol (12.8 +/- 0.4%), gamma-muurolene (12.2 +/- 0.4%) and alpha-cadinol (10.0 +/- 0.5%) were identified as the major constituents of the B. rufa oil, whereas germacrene B (37.6 +/- 1.2%) and (E)-nerolidol (29.1 +/- 0.6%) were the major constituents of the B. dumosa oil. Both oils were toxic to Tetranychus urticae by fumigation (B. rufa: LC50 = 2.76 mu L/L of air; B. dumosa: LC50 = 0.97 mu L/L of air) and residual contact (B. rufa: LC50 = 30.46 mu L/mL; B. dumosa: LC50 = 16.44 mu L/mL). The results of the two-choice method revealed that the oils affect the behavior of the mite, interfering in its feeding and egg-laying preferences.