Chemical composition and antitermitic activity against Coptotermes formosanus Shiraki of Cryptomeria japonica leaf essential oil

Cryptomeria japonica D. Don, called 'sugi' in Japanese, is an abundant and renewable potential resource of valuable natural products that may serve as natural biocides in Taiwan. Hydrodistillation (HD) and steam distillation (SD) were used for extracting the essential oils from C. japonica leaves in this study. The chemical constituents of the two leaf essential oils were identified by GC/MS analysis, and their antitermitic activities were evaluated. The results from the antitermitic tests against Coptotermes formosanus Shiraki showed that the leaf essential oils extracted by HD and SD had excellent antitermitic activities, with LD(50) values of 1.57 and 1.72 mg/g after 7 d of testing, respectively. Comparison of the chemical composition of the two leaf essential oils revealed that oxygenated diterpenes (kaur-16-ene) and oxygenated sesquiterpenes (β-elemol) were the dominant constituents. In addition, 13 constituents isolated from the C. japonica leaf essential oils were tested individually against C. formosanus. Among these constituents, β-elemol and α-terpineol achieved 100% termite mortality at the dosage of 1 mg/g after 7 d of testing. These results demonstrated that both C. japonica leaf essential oils as well as β-elemol and α-terpineol possessed commendable antitermitic activity.