Afef Ladhari

Effect of the Extracts of the Spiderflower, Cleome arabica, on Feeding and Survival of Larvae of the Cotton Leafworm, Spodoptera littoralis

Abstract Aqueous and organic (hexane, chloroform, and methanol) extracts of siliquae, stems and leaves, and seeds of Cleome arabica L. (Brassicales: Capparidaceae) were evaluated in the laboratory for their antifeeding and insecticidal effect on larvae of the cotton leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera, Noctuidae), using a leaf dipping bioassay with castor bean, Ricinus communis L. (Malpighiales: Euphorbiaceae), leaf discs. The polar extracts caused significant mortality. At the highest dose, C. arabica extracts exhibited significant antifeeding and phagostimulating activities against S. littoralis larvae. Under no-choice conditions, the methanol extract of siliquae was the most active, and the antifeedant index calculated over 24 hr for 3rd instar larvae varied significantly from 16 to 37%. Using nutritional indices, it was established that there was a significant decrease in growth rate concomitant with a reduction in consumption. These results suggest the presence of anti-feeding and/or toxic substances in the extracts that may be useful in developing bio-insecticides based on C. arabica extracts for use in integrated pest management of leafworm and other agricultural pests.

A NEW DAMMARANE TRITERPENE FROM Cleome arabica

A new dammarane triterpene was isolated from the seed extracts of Cleome arabica L. found growing in Tunisia. The structure of this novel phytoconstituent was elucidated by extensive spectroscopic techniques, including UV, IR, 1D, and 2D NMR and ESI-MS and HR-ESI-MS experiments.