Chemical Composition and Insecticidal Activity of the Essential Oil ofCyperus rotundusRhizomes AgainstLiposcelis bostrychophila(Psocoptera: Liposcelididae)

During our screening program for new agrochemicals from the local wild plants and Chinese medicinal herbs, the essential oil of Cyperus rotundus rhizomes was found to possess strong insecticidal activities against the booklice, Liposcelis bostrychophila Badonnel. Essential oil of C. rotundus rhizomes was obtained by hydrodistillation and analyzed by Gas chromatography-Mass spectrometry. A total of 35 components of the essential oil of C. rotundus were identified. The main components of the essential oil were α-cyperone (29.38%), cyperene (13.97%), caryophyllene oxide (6.71%) and β-selinene (6.47%). Bioactivities-directed chromatographic separation on repeated silica gel columns led to the isolation of two compounds: cyperene and α-cyperone. α-Cyperone exhibited pronounced contact toxicity against L. bostrychophila (LC50 = 41.32 μg/cm2) and was more toxic than cyperene (LC50= 50.08 μg/cm2) while the essential oil acting against the booklice showed an LC50 value of 102.11 μg/cm2. These results suggest that the essential oil of C. rotundus rhizome and the two isolated constituent compounds may be used in grain storage to combat insect pests.