Ceanothane and oleanane-type triterpenes from Talguenea quinquenervia have insecticidal activity against Cydia pomonella, Tenebrio molitor and Drosophila melanogaster

Many secondary metabolites from plants are constitutive and/or induced chemical defenses that play a role in protection against phytopathogenic attack. Talguenea quinquenervia (Rhamnaceae) is a notorious weed that possesses several medicinal applications such as American taxa of Rhamnaceae species are toxic to insects, fungi and several bacteria strains. These effects have been associated with the presence of alkaloids, phenolics and terpenes. A methanolic extract from the roots afforded 9 triterpenes belonging to lupane, oleanane, ursane, sterol and ceanothane groups. Our results indicate that these compounds are involved in interference of sclerotization and moulting. They showed selective effects on pre-emergence metabolism of selected insects including lepidoptera and diptera, but not to coleoptera. The results were fully comparable to known natural insect growth inhibitors such as azadirachtin, gedunin and Cedrela extract and have a possible role as natural insecticidal agents. To the best our knowledge, this is the first report of the isolation of ceanothane-type triterpenes from this plant species. The level of activity achieved by the assayed compounds indicated inhibition in a concentration dependent manner with LD50 values between 41 and 17 μg/mL.