Jianjun Ren

Acaricidal Activities of Wikstroemia chamaedaphne Extracts against Tetranychus urticae and Tetranychus cinnabarinus (Acari: Tetranychidae)

Various extracts of Wikstroemia chamaedaphne were evaluated their acaricidal activities against Tetranychus cinnabarinus (Boisduval) and Tetranychus urticae Koch (Acari: Tetranychidae) in laboratory. According to our study, the Wikstroemia chamaedaphne extracts had significant acaricidal activities against T. cinnabarinus and T. urticae. In this study, the mean LC50 value for T. cinnabarinus and T. urticae were 0.79 mg/mL for methanol extracts of W. chamaedaphne, which were liquid partitioned from the crude methanol extracts using the water bath immersion method. Conventional column chromatography was used to further purify active components from methanol partition extracts. The obtained 7th chromatographic fraction caused a mortality rate of 94.21 % for T. cinnabarinus, 91.52 % for T. urticae, and the 10th chromatographic fraction caused a mortality rate of 85.92 % for T. cinnabarinus, 88.21 % for T. urticae.

Effects of Chloroform Extracts from Kochia scoparia on Protect Enzyme activity of Tetranychus viennensis

There were few reports mentioned changes of protective enzyme activities of Tetranychus viennensis after exposed to pesticides by now. Our previous study had showed that the chloroform extracts of Kochia scoparia had effective acaricidal activity against T. viennensis. Here, the toxicosis symptoms of T. viennensis were detaiedly studied after exposed to the chloroform extracts of K. scoparia KFCE-2. We found that T. viennensis exposed to extract KFCE-2 showed typical toxicosis symptoms including over-excitation, uncoordinatedly moving, turning in circles, limb twitching and egg production decreasing in the contact action bioassay. Afterwards, we measured the potential changes of three protective enzymes [peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT)] of T. viennensis in response to extract KFCE-2. Treatment with extract KFCE-2 enhanced SOD activities during the 24 hr after treatment, while the POD and CAT activity were also enhanced except two periods: the 7th - 11th hr (7th - 14th hr for CAT activity) and the 20th -24th hr after treatment. During these two periods, POD and CAT activity were inhibited. The change of the protective enzyme activities may affect the removal of the toxic oxygen free radical species, which may be one of acaricidal mechanisms of K. scoparia extract KFCE-2 against T. viennensis.

Acaricidal Activity of Methyl Palmitate to T. cinnabarinus

Methyl palmitate, a kind of fatty acid methyl ester, has been found in many plants. Many biological functions of methyl palmitate have been found. Recently we isolated the methyl palmitate from the green walnuts husks and found it has acaricidal activity that had not been reported before. Here, the acaricidal activity of methyl palmitate, industrial methyl palmitate and the mixtures of methyl palmitate and Silwet L-77 were studied respectively. The results showed that the LC 50 of methyl palmitate for female mites was 1.72 mg/ml and 7.73 mg/ml for eggs. The contact toxicity of methyl palmitate on female mites is better than on eggs. Methyl palmitate also has strong repellent effect on the female mites. Then the acaricidal activity of industrial methyl palmitate was studied, and the results showed that both of the mortality and adjusted mortality of Tetranychus cinnabarinus were more than 70% when the concentration of industrial methyl palmitate was 10 mg/ml and 8 mg/ml. In order to improve the acaricidal activity of industrial methyl palmitate, Silwet L-77, a kind of silicone surfactants, was used to mix with industrial methyl palmitate to increase the permeability of industrial methyl palmitate. The female mites were treated with nine kinds of mixture of industrial methyl palmitate and Silwet L-77. The results showed that the best mixture ratio of the industrial methyl palmitate and Silwet L-77 was 8 mg/mltimes200 ppm, 5 mg/mltimes400 ppm and 8 mg/mltimes400 ppm, and all the acaricidal activity of the three mixtures were more than 90%. The mixture ratio could be used in the production of methyl palmitate acaricides.

Acaricidal Activities of Root Extracts of Tateges erecta against Tetranychus viennensis

The acaricidal activities of root extracts from the of Tateges erecta against T. viennensis were determined under illumination and non-illumination conditions. Furthermore, the effects of chloroform extract on several enzymes activities of T. viennensis were also evaluated. According to the F-test statistical analysis, the chloroform extract had acaricidal activities against T. viennensis under non-illumination condition, but petroleum ether, and methanol extracts had no significant acaricidal activities. Furthermore, the extracts of T. erecta had photo-activated insecticidal activity, and the mean lethal concentrations (LC50) of chloroform, petroleum ether, and methanol extracts were respectively 5.8mg/mL, 3.5 mg/mL and 8.4mg/mL under illumination condition. The enzymatic activity assay suggested that the protease activities in T. viennensis were obviously inhibited by the extracts, while the activity of glutathione-s-transferase was activated under non-illumination condition, but significantly inhibited under illumination condition. The activities of esterase isozymes in T. viennensis were not significantly influenced under non-illumination condition, but were significantly inhibited under illumination condition.

The Acaricidal Mechanism of Stellera chamaejasme Extracts against Tetranychus vienneusis

Previous reports showed that the root extracts of Stellera Chamaejasme L had acaricidal activity against Tetranychus vienneusis Zacher. However, the acaricidal mechanism of the root extracts from Stellera Chamaejasme L against Tetranychus vienneusisis not clear. Here, the effects of the root extracts from Stellera Chamaejasme L. on the activities of three enzymes of mites: protease, glutathiona s-transferase (GSTs) and esterase isozyme, were detailedly studied. Our results showed that the activities of protease, GSTs and esterase isozyme in treated mites were induced by the root extracts from S. chamaejasme in the systemic toxicity bioassay compare with those of the control. The effects of the root extracts from S. chamaejasme on the activities of some important metabolism enzymes of T. vienneusis may help to elucidate the acaricidal mechanism of the root extracts from Stellera Chamaejasme L against Tetranychus vienneusis.

Antifeedant Activities of the Methanol Extracts of Stellera chamejasme against Plutella xylostella

Few studies reported the antifeedant activity of Stellera chamejasme extracts against larvae of Plutella xylostella. Here, laboratory choice and no-choice test feeding studies were conducted to assess the antifeedant activity of methanol extracts of S. chamejasme against larvae of P. xylostella. S. chamejasme Extracts caused severe feeding deterrence by 2nd or 3rd instars larvae of P. xylostella in a concentration-dependent manner, which were observed both in laboratory choice and no choice test feeding studies. Within 24 h, 93.8% feeding deterrence were achieved in 2nd or 3rd instars larvae of P. xylostella using Stellera chamejasme extracts in choice test, while 86.5 % got in no-choice test. In choice test, the AFC50 values (24 h) by 2nd or 3rd instars larvae were 41.6 mg/L for the extracts of S. chamejasme, while 569.3 mg/L got in no-choice test. S. chamejasme may be a potential source of antifeedants that can be used for P. xylostella control.

A New Report on Acaricidal Activities of Wikstroemia chamedaphne Extracts against Tetranychus viennensis (Acari: Tetranychidae)

Few studies mentioned acaricidal activity of Wikstroemia chamedaphne against Tetranychus viennensis. Here, we reported that W. chamedaphne had strongly acaricidal activity against T. viennensis. A method for purification of miticidal components from W. chamedaphne was developed as follows: Step 1, methanol immersion at room temperature; Step 2, liquid-liquid partition using petroleum ether; Step 3, conventional column chromatography and thin layer chromatography. The efficiency of various extraction techniques was also compared using extraction rate and mortality rate as its index of evaluation. Two fractions, named WCME-7 and WCME-11, were got from W. chamedaphne. WCME-7 had a LC50 value of 0.14 mg/mL for female adults T. viennensis, and 0.09 mg/mL for WCME-11. Furthermore, the effects of various extracts of W. chamedaphne on female adults, eggs and nymphae in every stage of mites were further studied. Nymphae were most sensitive to W. chamedaphne extracts, female adults were in the second place, and eggs were the least. Briefly, W. chamedaphne is a potential source of botanic acaricide against T. viennensis.

Assessment the Contact Toxicity of Methyl Palmitate on the Carmine Spider Mite

Our previous studies showed that methyl palmitate had the acaricidal activity to T. viennensis. However, the mechanism of action of methyl palmitate on T. viennensis is unknown. Here, the toxicosis symptoms of T. viennensis exposed to methyl palmitate were studied to preliminarily uncover the acaricidal mechanism of methyl palmitate. Methyl palmitate caused dose-dependent mortality of T. viennensis in our studies. A moderate dose of methyl palmitate (5 mg/mL) initially elicited excite, and early oviposit without spinning. After a few hours, limb twitching was observed, and this was followed by a stage of depressed activity in about 5 hours. Subsequently, the mites developed a condition, which had the outward appearance of exosmosis on the back of the mites during the 15 th -20 th hr, and reduced eggs production. The mites eventually died in a few hours. Some typical neurotoxin symptoms such as excitement and convulsions were observed on the mites exposed to methyl palmitate. Methyl palmitate might be a type of neurotoxin. Compared to other neurotoxic insecticide, poisoning with methyl palmitate is slow in mites. Furthermore, the effects caused at sub cellular level by methyl palmitate were evaluated by transmission electron microscopy. Serious damage in ultra structure was observed at a concentration of methyl palmitate (5 mg/mL). Autolysis of membranous structure was observed, especially in mitochondria, which may imply a novel action of methyl palmitate.

Structure Identification of an Acaricidal Active Ingredient From Green Walnuts Husks (Juglans regia)

Most plants could produce bioactive substances including alkaloids, flavonoids, terpenes and relative materials, which are poisonous or have antifeedant effect to herbivorous animals, including some insects. Some well-known pesticides originated from plant bioactive substances have been successfully identified and used, for example, the azadirachtin from neem, nicotine from tobacco, rotenone and deguelin from derris, and pyrethrin from pyrethrum. Its necessary to extract, separate and identify single compounds from plants with biological activity in order to use them directly on crop protection, or to use them as model to synthesize new pesticides without pollution. The green walnut husks contain many kinds of bioactive compounds. By now more than 16 kinds of important components have been found, including tannin, walnuts quinone (juglune), nuts Glycoside (juglanin), alpha-hydride quinone walnuts (alpha-Hydrojuglone) and beta-hydride quinone walnuts (beta-Hydrojuglone), naphthalene Qian (naphthazarin), gallic acid, walnuts drunk alkaloids (C 10 H 8 O 3 ), 1, 4-naphthoquinone and some pigments. We have found that the petroleum-ether extracts of walnut have strong acaricidal activity, but the major compounds of the extracts and the structures of the compounds are unclear. Here we isolated one bioactive fraction G 7 from the green walnut husks which have better acaricidal activity and identified the structure of the compound. The fraction was found to be a signal compound by two-dimensional thin-layer chromatography and High Performance Liquid Chromatography (HPLC), and the HPLC analysis also showed the absorbance peak at 222 nm wavelength of G 7 was the same as that of methyl palmitate reported by Moshitzky and the molecular weight of G 7 was identified by mass spectrometry, and the result showed the G 7 have the same M W as methyl palmitate. Furthermore the molecular structure was analyzed with the nuclear magnetic resonance spectroscopy and the infrared spectrum. It was found that G 7 had the same molecular formula as methyl palmitate C 17 H 34 O 2 . Then, G 7 was compared with methyl palmitate through thin-layer chromatography and HPLC, and it was found that G 7 had the same Rt value 0.6 on TLC and the same absorbance peak at 222 nm wavelength in HPLC as methyl palmitate. So the G 7 fraction was confirmed to be the methyl palmitate.

Preliminary Study on the Acaricidal Mechanism of Methyl Palmitate to Tetranychus cinnabarinus

Methyl palmitate has showed acaricidal activity to Tetranychus cinnabarinus in our previous studies. However, the acaricidal mechanism of methyl palmitate to T. cinnabarinus is unknown. It was presumed that methyl palmitate may play its acaricidal activity to T. cinnabarinus by interfering the biological function of muscarinic receptors. In our studies, the most important muscarinic receptor subtypes M 1 , M 2 and M 3 were detected in the methyl palmitate treated T. cinnabarinus by immunoblotting method. Subsequently, the two-dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis (2D SDS-PAGE) method was used to analyze the change of the protein expression patterns in T. cinnabarinus in response to methyl palmitate treatment to preliminarily discuss its action mechanism. About 19 protein spots with approximately 2-fold increased density, about 31 protein spots with approximately 2- fold reduced density, about 14 disappeared protein spots, and about 13 novel protein spots were detected in the 2D SDS-PAGE gels of the methyl palmitate treated T. cinnabarinus compared to the control. Methyl palmitate may play its acaricidal activity on T. cinnabarinus by affecting muscarinic receptors related signal transduction, and changing the protein expression patterns in T. cinnabarinus.