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.
Pesticides are an important for maintaining a stable crop yield, but many of them are highly toxic and have long-term persistence in the environment. Despite all these efforts, losses due to these pests can annually reach 10–20% (Ferry et al. 2004) and still remain a challenge to be resolved (Zapata et al. 2009).
In recent years, attention has been directed towards using plant extracts to provide alternatives to synthetic insecticides. Plants have evolved many chemical defense mechanisms against insects (Wink 1993). As a result of interactions with insects, plants synthesize a broad range of different chemical compounds called secondary metabolites (Howe and Jander 2008), such as alkaloids, polyphenols, terpenoids, steroids, essential oils, lignans, sugars, and fatty acids, that protect the plants from insect pests (Regnault-Roger et al. 2004; Isman 2006) and are potentially suitable for use in integrated pest management (Schmutterer 1992). The majority of commercially produced botanical insecticides utilize the effects of plant metabolites that show acute or chronic toxicity to insects (Dayan et al. 2009; Pavela et al. 2009). Over 2000 species of plants are known to possess some insecticidal activity, by containing either antifeedant, repellent, or insecticidal compounds that enable the crude plant material, or an extracted active compound, to protect stored products (Klocke 1989; Bouda et al. 2001). Many compounds have been identified from numerous plant species, with the most promising ones for insect control coming from the families Meliaceae, Rutaceae, Annonaceae, Asteraceae, Labiatae, Solanaceae, and Piperaceae (Chaieb et al. 2004; Koul 2005; Chaieb et al. 2007).
Some species of Capparidacea possesses notable biological activities, such as antimicrobial (Mali 2010), anti-diabetic (Yaniv et al. 1987), analgesic, immune modulatory (Mali 2010), anti-inflammatory (Al-Said et al. 1988; Rossi et al. 1988), antioxidant (Germano et al. 2002), genotoxic (Sultan and Çelik 2009), anti-allergic, antihistaminic (Trombetta et al. 2005), antifungal (Ali-Shtayeh and Abu-Ghdeib 1999), antihepatotoxic (Gadgoli and Mishra 1999; Aghel et al. 2007; Mali 2010), and hypolipidemic activity (Eddouks et al. 2005). According to Willis (1966), Cleome (L.) is a large genus, with 150 species in the tropical and subtropical countries of both the Old and New World. The spiderflower, Cleome arabica L. (Brassicales: Capparidaceae), is widespread in North Africa. It has been used as folk medicine in the treatment of scabies and inflammation (Ahmad et al. 1990; Tsichritzis et al. 1993), rheumatic pains (Bouriche and Arnhold 2010), and as an antioxidant (Selloum et al. 1997). Yang and Tang (1988) reviewed plants used for pest insect control and found that there was a strong connection between medicinal and pesticidal plants, suggesting the possibility that C. arabica may also have useful insecticidal activity. Chemical compounds from C. arabica have been isolated from its aerial parts (Bouriche et al. 2003; Selloum et al. 2003; Bouriche and Arnhold 2010;). Some studies on Saudi Arabian Cleome amblyocarpa revealed the presence of 4 new dammarane triterpenes and 2 known compounds, cleocarpanol (Tsichritzis et al. 1993) and cabraleahydroxy lactone (Cascon and Browon 1972). An Egyptian study of this plant under the name C. africana described the presence of cleocarpanol and cabraleahydroxy lactone (Tsichritzis et al. 1993) together with stigma-4-en-3-one, lupeol, taraxasterol, and a membrane derivative (Jente et al. 1990). The leaves of C. arabica contain a number of glucosylated, rhamnosylated flavonols (Bouriche and Arnhold 2010).
The aim of this study was to evaluate the potential activity of the aqueous and organic extracts of T