The bioassay-guided fractionation of the n-hexane extracts from the roots of Lonchocarpus pentaphyllus led to the isolation of four known rotenoids: milletone (1), milletosine (2), degueline (3) and tephrosine (4). These compounds were isolated using chromatographic techniques and their chemical structures were assigned by 1D, 2D-NMR spectrometry and EIMS, IR, UV spectra. Their activity against Aedes aegypti is reported and its structure-activity relationship in the A. salina bioassay is discussed.