Etude de l’activité insecticide des extraits des feuilles de Ruta graveolens récolté de région de Ghardaïa

Abstract

The damage caused by insects to cereal and legume stocks has been the subject of numerous studies in Africa. The main aim of this work is to find natural substances with an insecticidal effect against the bean pest Bruchus rufimanus, using extracts from the leaves of the Ruta graveolens plant (Rutaceae) from the Zelfana - Ghardaïa region as an alternative to synthetic pesticides that pollute the environment. The plant leaves were extracted by maceration with two solvents: ethyl acetate and ethanol. Qualitative analysis using phytochemical screening determined the presence of several chemical compounds, in particular flavonoids, tannins, steroids and alkaloids. The study of the insecticidal activity of R. graveolens extracts showed a very strong toxic effect on Bruchus rufimanus adults with contact treatment, particularly for the ethyl acetate extract. This efficacy is represented by calculated toxicological parameters, namely LD 50 , LD 90 , TL 50 and TL 90 . The sensitivity of adults was variable and even higher with increasing extract concentrations and exposure time. Fractionation of ethyl acetate extract using chromatographic methods (column and thin layer chromatography) yielded six fractions, which confirmed the toxicity of the various compounds in the leaves of this plant. The bioactive substances contained in the R. graveolens extract fractions were identified using high-performance liquid chromatography (HPLC) which allows to detect the presence of: Chlorogenic acid, Tannic acid, Quercetin, Adonitol, Gallic acid, Coumaric acid, Caffeic acid, Ascorbic acid. In the context of biological control, the application of this insecticidal product could be very effective against pests and for the protection of legume stocks.