Bioactive compounds from ipil-ipil (Leucaena leucocephala) seeds were isolated using solvent extraction and silica gel column chromatography. Antifeedant activities of the crude ethanolic extract, chromatographic fractions and crystalline isolate were tested on third instar larvae of the common cutworm (Spodoptera litura). Dual choice assay using 10 μg cm-2 applied on both adaxial and abaxial parts of castor (Ricinus communis) leaves showed that the crystalline isolate had the highest activity, with percentage relative feeding inhibition of 79.93 ± 1.00%. The very high melting point, together with data from chemical and spectroscopic analyses, suggest that the isolate is a saponin-containing complex with molar mass of 662 g mol^-1 in the major component.