Decaleside: a new class of natural insecticide targeting tarsal gustatory sites.

Natural sources for novel insecticide molecules
hold promise in view of their eco-friendly nature, selectivity,
and mammalian safety. Recent progress in understanding the
biology of insect olfaction and taste offers new strategies for
developing selective pest control agents.We have isolated two
natural insecticidal molecules from edible roots of Decalepis
hamiltonii named Decalesides I and II, which are novel trisaccharides,
highly toxic to household insect pests and storedproduct
insects. We have experimentally shown that insecticidal
activity requires contact with tarsi on the legs but is not
toxic orally. The insecticidal activity of molecules is lost by
hydrolysis, and various sugars modify toxic response, showing
that the insecticidal activity is via gustatory sites on the
tarsi. Selective toxicity to insects by virtue of their gustatory
site of action and the mammalian safety of the new insecticides
is inherent in their chemical structure with 1-4 or 1-1 α
linkage that is easily hydrolyzed by digestive enzymes of
mammals. Decalesides represent a new chemical class of
natural insecticides with a unique mode of action targeting
tarsal chemosensory/gustatory system of insects.