Insecticiadal Activities And Active Compounds Of The Extracts From Tephrosia Purpurea Seeds

Insecticidal activities and active compounds of the extracts from the seeds of T. purpurea were studied. This research evaluated the insecticidal activities of the essential oils from T. purpurea leaves, T. purpurea barks and T. purpurea seeds against R. dominica, the repellent, contact, fumigant and population inhibition toxicity of the three kinds of essential oils to R. dominica were determined. The insecticidal toxicity of the extracts from the seeds of T. purpurea were determined against the third instar nymph of S. furcifera and C. lividipennis adult. The active compounds were isolated from the seeds of T. purpurea by the bioassay-guided test with column chromatography, thin layer chromatography (TLC) and recrystallization, and identified predominantly on the basis of MS and NMR data. Therefore, this research is aimed at providing the basis for further exploring and utilizing T. purpurea as botanical insecticides.The results were as following:1. The essential oils from the leaves, barks and seeds of T. purpurea got high repellent, contact, fumigant and population inhibition toxicity against R. dominica. At the dosage of 0.5μg/cm2, the repellent rates of the three kinds of essential oils against the adult of R. dominica at 48 hours after treatment were 82.3%,90.7% and 94.3%, respectively. The three kinds of essential oils had exhibited contact toxicity against the 5-day old larvae of R. dominica at 24 hours after treatment, with the value of LD50 being 25.0,27.9 and 27.8μg/insect, respectively. The fumigant activity of the three kinds of essential oils on the adult was examined at 48 hours after treatment.The mortalities of the adult ranged from 56.2% to 57.4% at the concentration of 20.0 mg/L, and there had been no significant difference (P>5%) among the oils. At the dosage of 200 mg essential oils per 100 g paddy, the current population inhibition rate of the three kinds of essential oils against R. dominica were 45.7%,55.9% and 76.7%, respectively, and essential oils of the seeds got the maximal population inhibition activity. The above-mentioned results suggested that essential oils from T. purpurea, especially the essential oils of seeds have good activities against R. dominica, would be explored and utilizied as botanical insecticides for control on R. dominica.2. The methanol extracts from T. purpurea seeds got high insecticidal toxicity against S. furcifera, while got low insecticidal toxicity against C. lividipennis. But C. lividipennis after exposure to the extracts, the surviving time was shorten and the predatory capacity was declined, significantly. The extracts had insecticidal activity against the C. lividipennis adults and the third instar nymphs of S. furcifera at 48 hours after treatment, with the value of LC50 being 298.8 and 16.3 mg/L, respectively. At the dosage of 10.0 mg/L, The surviving period and function response to S. furcifera of C. lividipennis after exposure to the extracts were studied, the function response model had belonged to Holling-II type. After exposure to the extracts, the parameters of model had changes, the predatory capacity of C. lividipennis was enhanced at 1 day after treatment, and then greadually declined at 2 and 3 days after treatment; the surviving time of C. lividipennis was significantly shorten from 21.3 d to 13.3 d. Thus the extracts to C. lividipennis is not safe.3. Ten compounds had been isolated and identified from T. purpurea seeds, they were two coumarins (6-methoxycoumarin and pachyrrhizine) and eight flavoids [(-)-edunol,12-acetyelliptinol,4'-hydroxyemoroidocarpan, rotenone, obovatin, pongachin, 12α-hydroxyrotenone and 2-hydroxyrotenone]. At the dosage of 500 mg/L, five compounds (4'-hydroxyemoroidocarpan,2-hydroxyrotenone,12-acetyelliptinol, rotenone and 12a-hydroxyrotenone) had possessed insecticidal activity against the fourth instar larvae of A. albopictus. Three compounds (rotenone,4'-hydroxyemoroidocarpan and 12a-hydroxyrotenone) had exhibited insecticidal activity against the third larvae of P. xyloslella. All the compounds except obovatin had exhibited insecticidal activity against the adult of M. persicae. It was the first time to isolated the eight compounds [4'-hydroxyemoroidocarpan,2-hydroxyrotenone,6-methoxycoumarin, pachyrrhizine, (-)-edunol, obovatin, pongachin and 12-acetyelliptinol] from this plant seeds.