Abstract: Insecticidal activities and active ingredients of Derris fordii var. lucida were studied for the first time. Insecticidal activities and action mode were determined by bioassay. The active ingredients were isolated from the roots by activity-directed fractionation with column chromatography, thin layer chromatography (TLC) and recrystallization, and identified predominantly on the basisof MS and NMR data. The results showed among methanol extracts from various parts of D. fordii var. lucida only that from the roots had insecticidal activity. The methanol extract from the roots of D. fordii var. lucida had toxicity against the 4th instar larva of Aedes albopictus, Aphis gossypii Glover, Aphis craccivora，Myzus persicae, the 2nd instar larva of Herse convolvuli (L.), the neonate larva of Scirpophaga incertulas (Walker), the 2nd instar larva of Pieris rapae (L.) and the adult of Phyllotreta striolata (Fabricius)，with LC₅₀ value 24 h after treatment being 260.3 mg/L, 234.6 mg/L, 141.3 mg/L, 16.4 mg/L, 233.4 mg/L, 20.8 mg/L, 11.7 mg/L and 148.4 mg/L, respectively. The methanol extract from the roots had high contact toxicity and stomach toxicity to the 3rd instar larva of H. convolvuli at 24 h after treatment, with the values being 101.6 mg/L and 234.9 mg/L, respectively. Moreover, the sublethal dosage of the extract had sublethal effect of antifeeding and growth inhibition. Three compounds were isolated from the roots and identified: rotenone,β-sitosterol and 6a, 12a-dehydrodegulin. The two compounds, rotenone and 6a, 12a-dehydrodeguelin, possessed poison effect on the neonate larva of S. incertulas, with the LC₅₀ value at 24 h after treatment being 2.6 mg/L and 5.3 mg/L, respectively. It is so concluded that only the roots of D. fordii var. lucida had insecticidal activities, contact toxicity and stomach toxicity were the important action mode, and rotenone and 6a, 12a-dehydrodeguelin were the main active ingredients in the roots.

Key words: Derris fordii var. lucida, insecticidal activity, active ingredient, rotenone, 6a, 12a-dehydrodeguelin