Five compounds (syringic acid, tricin, acacetin, syringoside, and diosmetin) were isolated from the aerial parts of wild oats (Avena fatua L.) using chromatography columns of silica gel and Sephadex LH-20. Their chemical structures were identified by means of electrospray ionization and high-resolution mass spectrometry as well as (1)H and (13)C nuclear magnetic resonance spectroscopic analyses. Bioassays showed that the five compounds had significant allelopathic effects on the germination and seedling growth of wheat (Triticum aestivum L.). The five compounds inhibited fresh wheat as well as the shoot and root growth of wheat by approximately 50% at a concentration of 100 mg/kg, except for tricin and syringoside for shoot growth. The results of activity testing indicated that the aerial parts of wild oats had strong allelopathic potential and could cause different degrees of influence on surrounding plants. Moreover, these compounds could be key allelochemicals in wild-oat-infested wheat fields and interfere with wheat growth via allelopathy.
Glutathione S-transferase genes in the epsilon group were reported to function in insecticide resistance. SlGSTE12 was validated to be overexpressed in pyrethroid-and organophosphate-resistant populations of Spodoptera litura compared to a susceptible population. A functional study of heterologously expressed SlGSTE12 showed that K m and V max for 1-chloro-2,4dinitrobenzene (CDNB) conjugating activity were 0.70 ± 0.18 mmol L −1 and 90.6 ± 9.4 nmol mg −1 min −1 , respectively. β-Cypermethrin and cyhalothrin showed much weaker inhibition of SlGSTE12 activity to CDNB conjugation than fenvalerate, chlorpyrifos, and phoxim. Ultrahigh-performance liquid chromatography analysis showed that SlGSTE12 had significant metabolism activity to fenvalerate and phoxim both in vitro and in Escherichia coli, especially to chlorpyrifos, and slight metabolism activity toward cyhalothrin only in vitro. Silencing of SlGSTE12 by RNAi increased the mortality to fenvalerate, cyhalothrin, and chlorpyrifos significantly. SlGSTE12 also had a significant antioxidant ability against cumene hydroperoxide. Our study suggested that SlGSTE12 could metabolize phoxim, fenvalerate, cyhalothrin, and especially chlorpyrifos. SlGSTE12 might also participate in pyrethroid and organophosphate resistance by antioxidant activity.
A rapid, sensitive and selective method for determining phthalanilic acid residue in bean, fruits and vegetables based on a modified quick, easy, cheap, effective, rugged and safe (QuEChERS) extraction procedure was developed by ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS). The samples were extracted by acidified acetonitrile (0.4% (v/v) formic acid) and simultaneous liquid-liquid partitioning formed by adding anhydrous magnesium sulfate (MgSO 4 ) and sodium chloride (NaCl). The extract was then cleaned up by dispersive-SPE using florisil and graphitized carbon black (GCB) as selective sorbent. Parameters including the matrix effect, linearity, precision, accuracy and stability were undertaken. The method showed good linearity in the concentration range of 10-1000 mg L À1 , with correlation coefficients $0.997. Recovery studies were performed at three fortification levels of 10, 100 and 1000 mg kg À1 in soybean, apple, grape, cucumber, tomato and pepper.Further optimization of sample preparation and determination achieved recoveries ranging between 70.1% and 105.3% for the analyte with 0.7-14.9% intra-day relative standard deviations (RSD) and 0.2-8% inter-day RSD at three spiked levels (10, 100 and 1000 mg kg À1 ). The limits of detection (LOD) were below 1 mg kg À1 , and the limits of quantification (LOQ) did not exceed 3 mg kg À1 . The effects of two columns on the separation were also investigated. The method is demonstrated to be convenient and reliable for determination of phthalanilic acid in bean, fruits and vegetables. With the developed method, 60 samples of commercial fruit products (grape, apple), soybean and vegetables (pepper, tomato, cucumber) were analyzed. Phthalanilic acid was not detected in all samples.
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