Study On Biological Activity Of The Extract Of Pharbitis Purpurea Seeds Against Tetranychus Cinnabarinus

Pharbitis purpurea seeds was investigated for its acarocidal activity against Tetranychus cinnabarinus,a serious pest of many crops including fruit trees in china.Action mechanism of effective substance of P. purpurea seeds against T.cinnabarinus was also investigated.(1)The acaricidic activities of herbal extracts were measured in laboratory by Slide-dip method.The results showed that 24 hours after treatment,the acaricidic activities of 10 herbal extracts were high, with corrected mortality over 90%.The contact toxicities of these 10 herbal extracts against T. cinnabarinus were also tested and the LC₅₀ value of the 10 herbal extracts,ranging from low to high, with P.purpurea petroleum ether extract at 0.6979±0.0598mg/ml,followed by Strychnos nux-vomica petroleum ether extract at 0.7670±0.0554 mg/ml,Xanthium sibiricum petroleum ether extract at 1.1239±0.0615mg/ml,Xanthium sibiricum methanol extract at 1.3417±0.0773mg/ml,Strychnos nux-vomica methanol extract at 1.3492±0.0738mg/ml,Stemona japnicaapetroleum ether extract at 1.3679±0.0810mg/ml,Sargentodoxa cuueata,petroleum ether extract at 1.4863±0.0921mg/ml, Osmuncla japonica chloroform extract at 1.6347±0.1060mg/ml,Dictammus dasycarpus chloroform extract at 1.7185±0.1003mg/ml and Osmuncla japonica methanol extract at 1.8201±0.0934mg/ml.(2)The extracts of P.purpurea seeds investigated for their biological activity against T.cinnabarinus. Slide-dip and Leaf-residue methods were used to measure biological activity.Liquid-liquid distribution and the silica gel column were used to separate and purify active matter.The results indicated that bioactivity(touch kill,oviposit inhibition,repellency)of petroleum ether extract of P.purpurea seeds was the highest with the adjusted mortalities of female mite and egg were 93.7%and 77.3%, Oviposition inhibition and repellency rate were 82.51%and 94.54%respectively at the concentration of 2 mg/ml.LC₅₀ is 0.6979mg/ml and 1.3037mg/ml.The petroleum ether extract of P.purpurea seeds was then separated and purified.The bioactivity of petroleum ether purified extracts of P.purpurea seeds was the highest with the adjusted mortalities of female mite and egg were 96.2%and 82.1%,LC₅₀ is 0.5042 mg/ml and 1.1016mg/ml.The silica gel column was used to separate and purify active constitutes of the crude purified extracts of petroleum ether.A total of 12 bands were seen by TLC analysis.The isolation fraction 8 appeared a strong acarocidal activity against T.cinnabarinus,the adjusted mortalities of female mite was 96.4%respectively at the concentration of 2 mg/ml.The isolation fraction 8 had strongly acaricidal activities against adult and egg of T.cinnabarinus,the LC₅₀ value were 0.4477mg/ml and 1.1971mg/ml,the LC₉₀ value were 2.2321mg/ml and 2.9152mg/ml.(3) Action mechanism of isolation fraction 8 of petroleum ether extract of.purpurea seeds against T. cinnabarinus was investigated.The toxicosis symptom of T.cinnabarinus were measured by Leaf-residue,and several kinds of important enzymes in T.cinnabarinus treated with isolation fraction 8 were tested.The ultrastructure of T.cinnabarinus treated by isolation fraction 8 was observed through transmission electron microscope(TEM).The results showed that the activities of glutathione-S-transferase in T.cinnabarinus were strongly induced,but the activities of acetylcholinease, monoamine oxidase and Ca²⁺-ATPase were restrained after treating with isolation fraction 8.The result suggested that isolation fraction 8 of P.purpurea seeds was effective against T.cinnabarinus,which may be the cause the transmit block of nerve in mites.Observation tinder TEM revealed that cuticle, muscular filament,nuclear membrane,mitochondria and endoplasmic reticulum were ruptured. The result from the experiment indicated that the discovery had a good developing prospect for making full use of P.purpurea seeds as new resources of botanical acaricide.