Studies on essential oils, part 33: Chemical and insecticidal investigations on leaf oil of Coleus amboinicus Lour

Abstract

Chemical investigations of the leaf essential oil of Coleus amboinicus by GC and GC-MS techniques indicated the presence of six components, accounting for 97% of the total oil. The major component was thymol (94.3%), followed by carvacrol (1.2%), 1,8-cineole (0.8%), p-cymene (0.3%), spathulenol (0.2%), terpinen-4-ol (0.2%) and an unidentified component (1.4%). The oil was insecticidal to white termites (Odontotermes obesus Rhamb.) with 100% mortality at a dose of 2.5 × 10-2 mg/cm3 for 5 h exposure. This oil was also more active than the synthetic insecticides, Thiodan and Primoban-20, against termites, although it was ineffective against Tribolium castaneum, a stored product pest. Copyright © 2002 John Wiley & Sons, Ltd.