Identification of Insecticidal Constituents of the Essential Oil of Curcuma wenyujin Rhizomes Active against Liposcelis bostrychophila Badonnel

The aim of this research was to determine the chemical composition and insecticidal activity of the essential oil of Curcuma wenyujin Y.H. Chen et C. Ling rhizomes against the booklouse Liposcelis bostrychophila Badonnel and to isolate any insecticidal constituents from the essential oil. The essential oil of C. wenyujin rhizomes was obtained by hydrodistillation and analyzed by GC-MS. A total of 43 components of the essential oil were identified and the principal compounds in the essential oil were 1,8-cineole (15.26%), camphor (10.12%), germacrone (6.86%), β-elemene (6.33%), curzerene (6.70%), and β-elemenone (5.23%). followed by curzerenone (4.52%), curdione (4.45%) and linalool (4.43%). Based on bioactivity-guided fractionation, the two main active constituents were isolated from the essential oil and identified as 1,8-cineole and camphor. The essential oil of C. wenyujin rhizomes exhibited contact toxicity against L. bostrychophila with an LD(50) value of 208.85 µg/cm(2). Camphor (LD(50) = 207.26 µg/cm(2)) exhibited stronger contact toxicity than 1,8-cineole (LD(50) = 1048.75 µg/cm(2)) against booklouse. The essential oil of C. wenyujin (LC(50) = 2.76 mg/L air) also possessed fumigant toxicity against L. bostrychophila, while the two constituents, camphor and 1,8-cineole had LC(50) values of 1.03 mg/L air and 1.13 mg/L air, respectively. The results indicate that the essential oil of C. wenyujin rhizomes and its constituent compounds have potential for development as natural insecticides or fumigants for control of insects in stored grains.