Identification of Insecticidal Constituents from the Essential Oil from the Aerial Parts Stachys riederi var. japonica

The essential oil ofStachys riederivar.japonica(Family: Lamiaceae) was extracted by hydrodistillation and determined by GC and GC-MS. A total of 40 components were identified, representing 96.01% of the total oil composition. The major compounds in the essential oil were acetanisole (15.43%), anisole (9.43%), 1,8-cineole (8.07%), geraniol (7.89%), eugenol (4.54%), caryophyllene oxide (4.47%), caryophyllene (4.21%) and linalool (4.07%). Five active constituents (acetanisole, anisole, 1,8-cineole, eugenol and geraniol) were identified by bioactivity-directed fractionation. The essential oil possessed fumigant toxicity against maize weevils (Sitophilus zeamais) and booklice (Liposcelis bostrychophila), with LC50values of 15.0 mg/L and 0.7 mg/L, respectively. Eugenol and anisole exhibited stronger fumigant toxicity than the oil against booklice. 1,8-Cineole showed stronger toxicity, and anisole as well as eugenol exhibited the same level of fumigant toxicity as the essential oil against maize weevils. The essential oil also exhibited contact toxicity againstS. zeamaisadults andL. bostrychophila, with LC50values of 21.8 µg/adult and 287.0 µg/cm2, respectively. The results indicated that the essential oil ofS. riederivar.japonicaand its isolates show potential as fumigants, and for their contact toxicity against grain storage insects.Keywords:Stachys riederivar.japonica;Sitophilus zeamais;Liposcelis bostrychophila;fumigant;contact toxicity;essential oil