Chemical composition and toxicity against Sitophilus zeamais and Tribolium castaneum of the essential oil of Murraya exotica aerial parts

In our screening program for new agrochemicals from Chinese medicinal herbs, Murraya exotica was found to possess insecticidal activity against the maize weevil, Sitophilus zeamais and red flour beetle, Tribolium castaneum. The essential oil of aerial parts of M. exotica was obtained by hydrodistillation and investigated by GC and GC-MS. The main components of M. exotica essential oil were spathulenol (17.7%), alpha-pinene (13.3%), caryophyllene oxide (8.6%), and alpha-caryophyllene (7.3%). Essential oil of M. exotica possessed fumigant toxicity against S. zeamais and T. castaneum adults with LC(50) values of 8.29 and 6.84 mg/L, respectively. The essential oils also show contact toxicity against S. zeamais and T. castaneum adults with LD(50) values of 11.41 and 20.94 microg/adult, respectively.