| Phytolacca americana L., as a kind of medicinal plant, its medical usage has been studied extensively and deeply. The researches of it for agricultural purposes have also been reported for a long time, such as the Pokeweed Antivirus Protein (PAPs) which separated from the P. americana can inhibit the reflection of many plant viruses. The solvent extracts of it also possess the insecticidal activity against Attagenus minutus Olivie, Callosobruchus maculates, Epilachna varivesti, Yponomeutidae evonymellus L. et al. Its antibacterial properties against plant pathogens, such as Penicilliam digitatum, Bacillus megaterium, Rhizotonia cerealis were also proved. Meanwhile, the acaricidal activity of the P. americana against Tetranychus cinnabarinus was little reported so far.This paper studied the acaricidal property of the whole plant of P. americana, the purpose is to screen out the best bioactive plant part, and identify its mode actions against Tetranychus cinnabarinus. Then isolate the bioactive components and study different mode actions of the active compound, which could lay the foundation for the agricultural usage of P. americana.1The acaricidal activity of the whole plant of P. americana against T. cinnabarinusThe P. americana leaves, stems and roots were extracted with petroleum ether, acetone and methanol, these9solvent extracts from different organs of P.americana were tested for their contact acaricidal activities against female carmine spider mite. The acetone extract of the root with95.72%mortalities at2.5mg/mL was more active than the acetone extracts of leaves and stems and compared with other solvent extracts from other organs after48h of treatment, and its LC50value was2.1637mg/mL.2The action modes of the acetone extract of P. americana roots against T. cinnabarinusThe acetone extract obtained from P. americana root were investigated for contact acaricidal, repellent, systemic and oviposition deterrent properties against carmine spider mite. The treatment concentrations were1.20,2.16and3.91mg/mL. At the concentration of2.16mg/mL, the corrected mortalities of P. americana acetone root extract were69.85%and68.42%after treatment of48h, respectively. The corrected mortalities were89.04%and80.81%after treatment of72h, respectively. Meanwhile, the P. americana acetone root extract showed highly repellent activity against each mite stage of T. cinnabarinus. After treatment of72h, the repellent activitues against larvae and nymphs of carmine spider mites all remained more than96%. The repellent activity against adults of T. cinnabarinus was reduced as the increasing of the treated time. The repellent property was the highest after treated for12h, which were up to grade Ⅲ; then dropped into grade Ⅱ after treated for84h.Furthermore, the P. americana acetone root extract showed highly oviposition deterrent property against female adults of T. cinnabarinus. The activities were all more than70%after treated for96h. Nevertheless, the systemic toxicity of the acetone root extract was not significant, only the treatment of3.91mg/mL reached72.87%after treated for72h, while, the activities of the other two concentration treatments were all less than51%.3The Bioguided fractionation and identification of active substances from Phytolacca americana L.The acetone root extract was fractionated using a silica gel column; after thin-layer chromatography, the concentrated extract was separated into15groups and further tests of their acaricidal activities were conducted. The ninth fraction was found to possess the highest acaricidal activity. The corrected mortalities of the fraction9against adult mites were60.84and95.75%in12h and24h after treatment, respectively. However, its extract rate was just2.2%. In order to save the extract time and increase the extract rates, the acaricidal activity of different ultrasonic wave extracts from Phytolacca americana L. root against Tetranychus cinnabarinus was tested. Two ultrasonic wave extracts (n-butarol and ethyl acetate as solvents) of Phytolacca americana L. acetone extract and residues after extracting were investigated for acaricidal activities against Tetranychus cinnabarinus. Results indicated that the n-butarol extract exhibited the highest acaricidal activity among all treatments. The corrected mortalities of n-butarol extract was97.43%after48h of treatment at2.5mg/mL. The n-butarol extract was further separated by the silica gel column and monitored by thin-layer chromatography (TLC) with UV detection, and after bioassay. The11th fraction showed highest acaricidal activity with LC50of0.9323mg/mL after48h of treatment. Its extract rate was up to15.02%, which was13%higher than the before.Using crystal chromatography at room temperature, we obtained white amorphous powder. After recrystallization, a white amorphous crystal was finally received, which was named as anti-mite crystal (AMC). Phytochemical analysis of the white crystal S revealed the presence of saponins and saccharides. Relatively high amounts of triterpenoid saponins were detected through LC/MS determination in the ninth group. After comparisons with library spectra, esculentoside P (molecular weight is680) was detected in large amounts in the ninth fraction, whereas other components have to be studied further.4Action modes of the anti-mite crystal (AMC) against T. cinnabarinusThis part evaluated the potential acaricidal activity of the anti-mite crystal (AMC) against T. cinnabarinus in the laboratory condition, including the contact, repellent, systemic, ovicidal and oviposition inhibition activities. For the contacted bioassay, only the treatment of1mg/mL showed some activity against larvae and nymphs of carmine spider mites, which were73.74%and88.39%after treatment of72h, the other concentration treatments were relatively low, which were no more than40%. For the repellent bioassay, the activity was reduced over time, the repellent activity was the highest at the treatment of12h which were up to grade Ⅲ and Ⅳ, and then went down. The oviposition inhibitory activity of the anti-mite crystal (AMC) presented a decreasing-increasing trend. The treatments of0.5,1and2mg/mL showed the highest inhibitory activity at the treatment of48h, went down at72h, and then increased again at96h. the inhibitory activity of4mg/mL treatment increased in time-dependent manner, which could reach up to86.89%after72h of treatment. Otherwise, the0.25mg/mL treatment did not show any significant bioactivity.Moreover, the anti-mite crystal (AMC) represented a slightly systemic toxicity and ovicidal activity. Just the treatments of2mg/mL and4.0mg/mL have showed a certain systemic toxicity and ovicidal activity against T. cinnabarinus, the other low concentrations did not exhibit any activities which mentioned above. |
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