Effect of pesticide 1-[6-chloro-3-methyl-pyridyl-8-nitro-7-methyl-1 2 3 5 6 7-hexahydro imidazo (1,2a)]-pyridine when responding to a wheat plant's antioxidant defense system.

The purpose of this research was to establish an analytical method for analysing the 1-[6-chloro-3-methyl-pyridyl-8-nitro-7-methyl-1 2 3 5 6 7-hexahydro imidazo-(1,2a)]-pyridine (IPP) residue levels and to evaluate the difference in plant growth and its physical condition. A high performance liquid chromatography connected to a diode array detector (HPLC-DAD) was also employed. The results showed that the content of protein and water soluble carbohydrate (WSC) treated by IPP were initially higher with a significant delayed decrease. The biomarker response showed, even at a lower dose rate, exposure to the IPP caused stress effects and modified the activity of superoxide dismutase (SOD), guaiacol peroxidase (POD), catalase (CAT) and polyphenol oxidase (PPO). Different patterns of biomarker responses were observed by an increase in SOD and malondialdehyde (MDA), and differential effects for antioxidant enzymes with a decrease in CAT, POD and PPO. The conclusions show that this profile of biomarker variation could represent a useful method to characterise exposure to IPP in a wheat plant.

Multi-residue method for determination of seven neonicotinoid insecticides in grains using dispersive solid-phase extraction and dispersive liquid-liquid micro-extraction by high performance liquid chromatography.

A method using dispersive solid-phase extraction and dispersive liquid-liquid micro-extraction cleanup followed by high performance liquid chromatography (HPLC) has been established for determination of seven neonicotinoid insecticides residues in grains including brown rice, maize, millet and oat. Based on an appraisal of the characteristics of HPLC, validation experiments were conducted for seven neonicotinoid insecticides. In the method, dispersive solid-phase extraction was carried out using PSA and bonded C18 coupled with graphitised carbon black with acetonitrile as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R(2) ≥ 0.99. At the low, medium and high three fortification levels of 0.05-0.8 mg kg(-1), recoveries fell within 76-123%. The relative standard deviation was between 0.9% and 12.6% for seven neonicotinoid pesticides. Low limits of detection (0.002-0.005 mg kg(-1)) and quantification (0.007-0.018 mg kg(-1)) were readily achieved with this method for all tested pesticides.

Multiresidue method for determination of 88 pesticides in berry fruits using solid-phase extraction and gas chromatography-mass spectrometry: Determination of 88 pesticides in berries using SPE and GC-MS.

A method using solid phase extraction (SPE) cleanup followed by gas chromatography-mass spectrometry (GC-MS) has been established for quantitative determination of 88 pesticide residues in berry fruits including raspberry, strawberry, blueberry and grape. Based on an appraisal of the characteristics of GC-MS, validation experiments were conducted for 88 pesticides. In the method, solid-phase extraction was carried out using Envi-Carb cartridge coupled with NH(2)-LC cartridge with acetonitrile-toluene (3:1, v/v) as the eluted solvent. In the linear range of each pesticide, the correlation coefficient was R(2)⩾0.99. At the low, medium and high three fortification levels of 0.05-0.5mgkg(-1), recoveries fell within 63-137%. The relative standard deviation was between 1% and 19% for all 88 pesticides. Low limits of detection (0.006-0.05mgkg(-1)) and quantification (0.02-0.15mgkg(-1)) were readily achieved with this method for all tested pesticides.

A new pregnane glycoside from Dioscorea collettii var. hypoglauca.

During further bioactivity-guided fractionation, a new pregnane glycoside, hypoglaucin G (1), and a known compound, pregna-5, 16-dien-3beta-ol-20-one 3-O-alpha-L-rhamnopyranosyl-(1-->2)- [alpha-L-rhamnopyranosyl-(1-->4)] -beta-D-glucopyranoside (2), were isolated from the EtOH extract of Dioscorea collettii var. hypoglauca rhizomes, which induced morphological deformation of Pyricularia oryzae mycelia with minimum morphological deformation concentration values of 135 microM and 236 microM, respectively. The structure of 1 was established as 16beta-(4'-methyl-5'-O-beta-D-glucopyranosyl- pentanoxyl)-pre gn-5-en-3 beta-ol-20-one 3-O-alpha-L- rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->4)]-beta-D- glucopyranoside on the basis of chemical evidence and spectral analysis, especially by 2D NMR techniques.