Toxicity and anti termite activities of the essential oils from Piper sarmentosum

The leaves of Piper sarmentosum were hydro distilled using the modified Clevenger-type apparatus, and an average yield of essential oil of 1.10 % (v/ dry weight) was obtained. The leaf oils were analyzed by GC and GC-MS. A total of 31 components were identified. Spathulenol (21.0 %), myristicin (18.8 %), β-caryophyllene (18.2 %) and (E,E)-farnesol (10.5 %) were the major compounds found in the leaf oil. The leaf oil showed inhibitory activity against the larvae of Artemia salina with LC50 value of 35.2 μg/ mL, and 100 % mortality within two days at 1 % concentration against the subterranean termite (Coptotermes sp.). The crude extract was then subjected to bioassay-guided isolation using silica gel column chromatography, and eluted with hexane containing increasing volumes of ethyl acetate and yielded three pure compounds. Their toxicity and anti termite activities of the three compounds were determined. Compound 2 showed the most potent activity against the larvae of A. salina with LC50 value of 7.5 μg/ mL, while the LC50 values for compound 3 and compound 1 were 17.2 μg/ mL and 22.5 μg/ mL respectively. Compound 3 showed the strongest inhibitory activity against the subterranean termite (Coptotermes sp.) with 100 % mortality after 3 days at 0.1 % concentration followed by compound 2 with the same mortality rate at 0.5 % concentration. Compound 1 showed the weakest inhibitory activity with 80 % mortality after 3 days at 2 % concentration. Based on spectroscopic data and comparison with published information, compound 1 and 2 have been identified as caryophyllene and myristicin respectively. Compound 3 is still being studied in order to elucidate its structure. (author)