Antifeedant Activity of Essential Oil and Carbazole Derivatives and of Murraya koenigii (L) Spreng Leaves against Spodoptera litura (Fab.)

The essential oil and carbazole alkaloids isolated from fresh leaves of Murraya koenigii (L) were studied for their antifeedant activity against fifth instar larvae of Spodoptera litura. The essential oil had shown antifeedancy more than 50% at 250 μg ml⁻¹ concentration level. The ED₅₀ value for hydrodistilled oil was 130 μg ml⁻¹. Amongst crude extracts, benzene (ED₅₀ = 710 μg ml⁻¹) was found more effective as antifeedant than hexane extract (ED₅₀ 4261 μg mL⁻¹). Antifeedant activity of pure carbazole alkaloids namely koenimbine and koenidine were improved by converting them into corresponding dihydro derivatives through hydrogenation. However, methylation of these two carbazole alkaloids into their corresponding N-methyl derivatives did not have much effect on the antifeedant properties of these compounds.