Busca de compostos inseticidas: estudo de espécies do gênero Trichilia (Meliaceae)

Abstract

This work describes the results of the search for insecticidal compounds from the Meliaceae family. The samples assayed against fall armyworm Spodoptera frugiperda were the hexane, methanol and hydromethanol extracts of twigs, leaves, seeds, aril and exocarp of T. catigua; twigs, leaves, fruits, seeds, aril and exocarp of T. claussenii and twigs, leaves and fruits of T. elegans. The hexane and methanol extracts of leaves, hexane of twigs and methanol of fruits from T. claussenii showed to possess the higher insecticidal activity against S. frugiperda. Nevertheless, the hexane and methanol extracts of fruits from T. elegans showed the highest rate of larval mortality (100 %). The hydromethanol extract of T. elegans showed moderate insecticidal activity and also showed growth inhibition and antifeedant activities. The active extracts were fractionated and the chemical study led to isolation of 20 compounds, including limonoids, triterpenes, coumarins, steroids and one sesquiterpene. From the hexane extract of leaves from T. claussenii were isolated the steroids β-sitosterol, stigmasterol, campesterol and sitostenone; the triterpenoids α-amyrin, β-amyrin, lupeol, lupenone, in addition to the cycloartane triterpene 24-methylen-26- hydroxycicloartan-3-on and sesquiterpene criptomeridiol. From the methanol extract of leaves of T. claussenii were isolated the steroids 24-methylen-3 β,4 β,22 α- trihydroxy-colesterol and 3- β-O- β-D-glucopyranosilsitosterol. From the methanol extract of fruits from T. elegans were isolated the coumarins 6,7- dimethoxycoumarin, 6-methoxy-7-hydroxycoumarin e 7-hydroxycoumarin. The same coumarins and the steroids were also isolated from the hexane extract of fruits from T. elegans. The limonoids cedrelone and 11 β-methoxycedrelone were isolated from the hexane extract of aril from T. catigua. Limonoids methylangolensate together with the photogedunin epimeric mixture were isolated from the methanol extract of aril from T. catigua. This is first report of the isolation of limonoids from T. catigua. Triterpens isolated from Cedrela fissilis and limonoids isolated from Cipadessa fruticosa (Meliaceae) were tested against S. frugiperda. Among them odoratol showed the best results (insecticidal activity, growth inhibition and antifeedant). Febrifugin A showed the highest rate of mortality of total cycle (at 50 mg kg-1) of 73.3%.