Mosquito larvicidal activity of Piper longum fruit-derived materials against the fourth-instar larvae of Aedes aegypti was examined. A crude methanol extract of P. longum fruits was found to be active against the larvae, and the hexane fraction of the methanol extract showed a strong larvicidal activity of 100% mortality. The biologically active component of P. longum fruits was characterized as pipernonaline by spectroscopic analyses. The LC(50) value of pipernonaline was 0.25 mg/L. The toxicity of pipernonaline is comparable to that of pirimiphos-methyl as a mosquito larvicide. In tests with available components derived from P. longum, no activity was observed with piperettine, piperine, or piperlongumine.

The insecticidal activities of compounds derived from the rhizomes of Acorus gramineus against four agricultural insect pests were examined using direct contact application method. The biologically active constituents of A. gramineus rhizomes were characterized as the phenylpropenes, cis-and trans-asarones by spectroscopic analyses. Potencies varied according to insect species, compound, and dose. In a test with female adults of Nilaparvata lugens, cis-asarone caused 100, 83, and 40% mortality at 1,000, 500, and 250 ppm, respectively, whereas 67% mortality was achieved at 1,000 ppm of trans-asarone. Against 3rd instar larvae of Plutella xylostella, cis-asarone gave 83 and 50% mortality at 1,000 and 500 ppm, respectively, whereas trans-asarone at 1,000 ppm showed 30% mortality. Against female adults of Myzus persicae and 3rd instar larvae of Spodoptera litura, cis-and trans-asarones both were almost ineffective at 2,000 ppm. The A. gramineus rhizome-derived materials merit further study as potential insect-control agents or as lead compounds against N. lugens and P. xylostella.

No abstract