Chemical composition, insecticidal and in vitro anthelmintic activities of Ruta chalepensis (Rutaceae) essential oil

Abstract

Antipathogenic properties of plants’ essential oils have been investigated to substitute for drugs hence overcome drug resistance. This study investigated the insecticidal and antigastrointestinal parasite effects of fresh leaves and flower essential oils of Ruta chalepensis.Determination of chemical composition revealed that leaves and flowers essential oils samples were dominated by ketone particularly 2-undecanone derivative accounting for 85.94 and 89.89% of leaves and flowers oils, respectively.The insecticidal activity of both leaves and flowers essential oils was assessed in terms of larvicidal effect appreciated by contact against third and fourth instars larvae of Orgyia trigotephras and was compared with a standard commercial chemical insecticide Delta-metrine “Decis”. Mean time of mortality (MMT) of third instar larvae obtained after treatment with a concentration of 0.5% of flower oil was 1.40min, higher than, for leaf oil (MMT=1.27min; p<0.001). Mean time of mortality of the fourth instar larvae, obtained after treatment with flower oil at the same concentration was 42.53min, higher than, that for leaf oil (MMT=20.68min; p<0.001). The MMT of the two instars larvae were shorter compared with the MMT of larvae treated with Decis (p<0.001) while, ethanol induced no toxic effect on larvae.In vitro anthelmintic effects against Haemonchus contortus from sheep were ascertained by egg hatching and worm motility inhibitions compared with a reference drug albendazole. At all tested concentrations (0.125, 0.25, 0.5 and 1mg/mL), both essential oils showed ovicidal activity. Leaves essential oil (inhibitory concentration (IC50)=0.145mg/mL) showed higher inhibitory effects on egg hatching than flowers essential oil (IC50=0.398mg/mL). After 6h and 8h of exposure, the flowers essential oil at 1mg/mL induced 33.3 and 87.5% inhibition motility, respectively. At the same concentration and exposure times, essential oil from leaves induced 29.1 and 75% inhibition motility respectively. Results highlight that 2-undecanone may be a potential antipathogenic constituent.The overall findings of the current study indicated that R. chalepensis essential oil has a potential insecticidal and anthelmintic benefit and further in vitro and in vivo trials against different species and stages are required to make use of this plant for the control of insect pests and gastrointestinal nematode parasites.