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Wang Y.,Northwest University, China | Hu Z.,Northwest University, China | Hu Z.,Key Laboratory of Botanical Pesticide R and D in Shaanxi Province | Wu W.,Northwest University, China | Wu W.,Key Laboratory of Botanical Pesticide R and D in Shaanxi Province

Bacillus thuringiensis (Bt) Cry toxins from the Cry1A family demonstrate significantly different toxicities against members of the family Noctuidae for unknown reasons. In this study, membrane potential was measured and analyzed in freshly isolated midgut samples from Mythimna separata and Agrotis ipsilon larvae under oral administration and in vitro incubation with Bt toxin Cry1Ab to elucidate the mechanism of action for further control of these pests. Bioassay results showed that the larvae of M. separata achieved a LD50 of 258.84 ng/larva at 24 h after ingestion; M. separata larvae were at least eightfold more sensitive than A. ipsilon larvae to Cry1Ab. Force-feeding showed that the observed midgut apical-membrane potential (Vam) of M. separata larvae was significantly depolarized from —82.9 ± 6.6 mV to —19.9 ± 7.2 mV at 8 h after ingestion of 1 μg activated Cry1Ab, whereas no obvious changes were detected in A. ipsilon larvae with dosage of 5 μg Cry1Ab. The activated Cry1Ab caused a distinct concentration-dependent depolarization of the apical membrane; Vam was reduced by 50% after 14.7 ± 0.2, 9.8 ± 0.4, and 7.6 ± 0.6 min of treatment with 1, 5, and 10 µg/mL Cry1Ab, respectively. Cry1Ab showed a minimal effect on A. ipsilon larvae even at 20 µg/mL, and Vam decreased by 26.3% ± 2.3% after 15 min. The concentrations of Cry1Ab displayed no significant effect on the basolateral side of the epithelium. The Vam of A. ipsilon (—33.19 ± 6.29 mV, n = 51) was only half that of M. separata (—80.94 ± 6.95 mV, n = 75). The different degrees of sensitivity to Cry1Ab were speculatively associated with various habits, as well as the diverse physiological or biochemical characteristics of the midgut cell membranes. © 2015 by the authors; licensee MDPI, Basel, Switzerland. Source

Li J.,Northwest University, China | Zhao X.,Northwest University, China | Li L.,Northwest University, China | Yuan Z.,Northwest University, China | And 4 more authors.

Thirty novel steroidal pyrazole derivatives were designed and synthesized via a highly efficient route from pregnenolone (1) as starting material. The key intermediates 3a-c were obtained under Vilsmeier conditions, and the subsequent hydrolysis, acetylation or Borch reduction afforded thirty target compounds. These compounds were mainly characterized by 1H NMR, 13C NMR, DEPT135°. The structure of compound 3a was also confirmed by X-ray single crystal diffraction. The cytotoxicity of these compounds was evaluated by the SRB method against four cancer cell lines, including A549, Hela, MCF-7 and HepG2, and the results indicated that compounds 5a, 6a, 7a and 8a exhibited significant cytotoxicity with IC50 values ranging from 0.91 to 5.44 μM. Most importantly, compound 5a exhibited excellent cytotoxicity against A549 with an IC50 value of 0.91 μM. On the basis of our research the structure-activity relationships (SAR) of these compounds were discussed. This work provides some important hints for further structural modification of steroids towards developing novel and highly effective anticancer drugs. © 2015 Published by Elsevier Inc. Source

Zhao X.,Northwest University, China | Xi X.,Northwest University, China | Hu Z.,Northwest University, China | Wu W.,Key Laboratory of Botanical Pesticide R and D in Shaanxi Province | And 2 more authors.
Journal of Agricultural and Food Chemistry

The discovery of novel leads and new mechanisms of action is of vital significance to the development of pesticides. To explore lead compounds for botanical insecticides, 77 β-dihydroagarofuran derivatives were designed and synthesized. Their structures were mainly confirmed by 1H NMR, 13C NMR, DEPT-135°, IR, MS, and HRMS. Their insecticidal activity was evaluated against the third-instar larvae of Mythimna separata Walker, and the results indicated that, of these derivatives, eight exhibited more promising insecticidal activity than the positive control, celangulin-V. Particularly, compounds 5.7, 6.6, and 6.7 showed LD50 values of 37.9, 85.1, and 21.1 μg/g, respectively, which were much lower than that of celangulin-V (327.6 μg/g). These results illustrated that β-dihydroagarofuran ketal derivatives can be promising lead compounds for developing novel mechanism-based and highly effective botanical insecticides. Moreover, some newly discovered structure-activity relationships are discussed, which may provide some important guidance for insecticide development. © 2016 American Chemical Society. Source

Lu L.,Northwest University, China | Qi Z.,Northwest University, China | Qi Z.,Key Laboratory of Botanical Pesticide R and D in Shaanxi Province | Li Q.,Northwest University, China | And 2 more authors.

A series of insecticidal dihydroagarofuran sesquiterpene polyesters were isolated from the root bark of Chinese bittersweet (Celastrus angulatus Max). A previous study indicated that these compounds affect the digestive system of insects, and aminopeptidase N3 and V-ATPase have been identified as the most putative target proteins by affinity chromatography. In this study, the correlation between the affinity of the compounds to subunit H and the insecticidal activity or inhibitory effect on the activity of V-ATPase was analyzed to validate the target protein. Results indicated that the subunit H of V-ATPase was the target protein of the insecticidal compounds. In addition, the possible mechanism of action of the compounds was discussed. The results provide new ideas for developing pesticides acting on V-ATPase of insects. © 2016 by the authors; licensee MDPI, Basel, Switzerland. Source

Feng M.,Key Laboratory of Botanical Pesticide R and D in Shaanxi Province | Feng M.,Northwest University, China | He Z.,Key Laboratory of Botanical Pesticide R and D in Shaanxi Province | Wang Y.,Northwest University, China | And 6 more authors.

Periplocosides, which are insecticidal compounds isolated from the root bark of Periploca sepium Bunge, can affect the digestive system of insects. However, the mechanism though which periplocosides induces a series of symptoms remains unknown. In this study, affinity chromatography was conducted by coupling periplocoside E-semi-succinic acid ester with epoxy amino hexyl (EAH) sepharose 4B. Sodium dodecyl sulfonate-polyacrylamide gelelectrophoresis (SDS-PAGE) was performed to analyze the fraction eluted by periplocoside E. Eight binding proteins (luciferin 4-monooxygenase, aminopeptidase N, aminopeptidase N3, nicotinamide adenine dinucleotide health (NADH) dehydrogenase subunit 5, phosphatidylinositol 3-phosphate 3-phosphatase myotubularin, actin, uncharacterized family 31 glucosidase KIAA1161, and 2OG-Fe(2) oxygenase superfamily protein) were obtained and identified through liquid chromatography/quadrupole-time of flight-mass spectrometry (LC/Q-TOF-MS) analysis of the midgut epithelium cells of Mythimna separata larvae. Aminopeptidase N and N3 are potential putative targets of periplocosides. This study establishes the foundation for further research on the mechanism of action and target localization of periplocosides in agricultural pests. © 2016 by the authors; licensee MDPI, Basel, Switzerland. Source

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