ABSTRACT. A methanol extract of Piper longum fruit was found to be active against mosquito larvae of
Culex pipiens pallens at l0 pglml after 24 h. A piperidine alkaloid, pipernonaline, was found to be responsible
for this activity, with the 24-h rnedian lethal dose (LDr) value for this compound being 0.21 mg/liter. The LDro
value of pipernonaline was not much higher than those for the 3 organophosphorous insecticides malathion,
chlorpyrifos-methyl, and pirimiphos-methyl, used for comparative purpose in this study. Structural elucidation
of pipernonaline was by means of mass spectrometry ('H and r3C nuclear magnetic resonance imaging).