Insect Anti-Feedant and Growth-Inhibitory Activities of a Limonoid from Seeds of Dalanghita (Citrus reticulata Blanco cv. Ladu) against Larvae of the Asian Corn Borer [Ostrinia furnacalis (Guenee)]

摘要

A limonoid was isolated from seeds of dalanghita (Citrus reticulate Blanco 'Ladu') through microwave-assisted extraction. Insect-antifeedant and growth-inhibitory activities of crude and partially purified extracts were tested against Asian corn borer [Ostrinia fumacalis (Guenee)] larvae using choice and no-choice feeding bioassay. The choice tests showed that feeding deterrence increased as the concentration of the partially purified extracts increased, with observed avoidance of treated diets. In the no-choice tests, significant antifeedant activity was observed, with an EC50 of 7.502 +/- 1.096 mg g(-1). Growth inhibition index, determined through changes in larval weight after 10 d of treatment, was found to have an EC50 of 5.728 +/- 1.285 mg g(-1). Larval durations of the treated O. furnacalis were also shown to be extended. Molting success was scored and results showed that the crude extract was effective in reducing pupal emergence. O. furnacalis treated with the 20 mg g(-1) partially purified extract exhibited greater frequencies of developmental abnormalities, including malformation of the wings, legs and antennae. Chromatographic separation of this extract led to the isolation of a limonoid. Chemical, IR and H-1-NMR spectroscopic analyses suggest that the isolated limonoid could be limonin. This study shows that dalanghita seed contains a bioactive limonoid that can potentially be used in insect pest control.