Mosquito larvicidal activity of pipernonaline, a piperidine alkaloid derived from long pepper, Piper longum

Abstract

A methanol extract of Piper longum fruit was found to be active against mosquito larvae of Culex pipiens pallens at 10 microg/ml after 24 h. A piperidine alkaloid, pipernonaline, was found to be responsible for this activity, with the 24-h median lethal dose (LD50) value for this compound being 0.21 mg/liter. The LD50 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 (1H and 13C nuclear magnetic resonance imaging).