Natural insecticides fromHippocratea excelsa andHippocratea celastroides

Hippocratea excelsa andHippocratea celastroides have therapeutic and insecticide applications in Mexican traditional medicine. The toxicity ofH. excelsa root cortex has been previously demonstrated against the stored grain pest Sitophilus zeamais. To identify the active compounds, several extracts (petroleum ether, CH₂Cl₂, acetone, methanol, and water) and compounds were obtained from the roots, and tested (1% w/w) with a force-feeding assay againstS. zeamais. AllH. excelsa extracts showed high antifeedant activity, and elicited moderate mortality. The triterpenoid pristimerin and a mixture of sesquiterpene evoninoate alkaloids, isolated from the hexane and methanol extracts, respectively, strongly reduced the insect feeding capacity. Other triterpenoids (friedelin, β-sitosterol, canophyllol) isolated from the hexane extract, and the alditol galactitol obtained from the water extract, were innocuous or its activity was not statistically significant. The organic extracts fromH. celastroides only showed moderate antifeedant activity, while the water extract was innocuous. Galactitol was also obtained from this extract.