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201.
Uvarani C Chandraprakash K Sankaran M Ata A Mohan PS 《Natural product research》2012,26(13):1265-1270
Antioxidant activity-guided fractionations of chloroform extract of Swertia minor yielded five known tetraoxygenated xanthones (1-5), of which compound 3 was isolated for the first time from plant sources. Compounds 1-5 were identified with the aid of extensive NMR spectroscopic studies. A relationship between the structural features of 1-5 and their antioxidant activity was also determined. Among these bioactive isolates (1-5), compound 4 exhibited strong scavenging effect in DPPH (IC(50)?=?10.31?μg?mL(-1)), FRAP (8536.32?±?34.1?Mmol Fe (II)?g(-1)) and metal chelating (17.2?±?0.88?mg?EDTA?g(-1)) assays. Compound 5 was potently active in secondary antioxidant assay (i.e. binding to metal ions strongly); however, its primary antioxidant capacity was found to be feeble. 相似文献
202.
A simple technique for the collection of an extraction solvent lighter than water after dispersive liquid–liquid microextraction combined with high‐performance liquid chromatography with ultraviolet detection was developed for the determination of four paraben preservatives in aqueous samples. After the extraction procedure, low‐density organic solvent together with some little aqueous phase was separated by using a disposable glass Pasteur pipette. Next, the flow of the aqueous phase was stopped by successive dipping the capillary tip of the pipette into anhydrous Na2SO4. The upper organic layer was then removed simply with a microsyringe and injected into the high‐performance liquid chromatography system. Experimental parameters that affect the extraction efficiency were investigated and optimized. Under optimal extraction conditions, the extraction recoveries ranged from 25 to 86%. Good linearity with coefficients with the square of correlation coefficients ranging from 0.9984 to 0.9998 was observed in the concentration range of 0.001–0.5 μg/mL. The relative standard deviations ranged from 4.1 to 9.3% (n = 5) for all compounds. The limits of detection ranged from 0.021 to 0.046 ng/mL. The method was successfully applied for the determination of parabens in tap water and fruit juice samples and good recoveries (61–108%) were achieved for spiked samples. 相似文献
203.
Syed Ahmad Tirmizi Feroza Hamid Wattoo Muhammad Hamid Sarwar Wattoo Saadia Sarwar Allah Nawaz Memon Allah Bux Ghangro 《Arabian Journal of Chemistry》2012,5(3):309-314
Cimetidine, a histamine H2-receptor, has a structure which enables it to act as a chelating agent. The formation of nickel(II) complex with cimetidine has been studied spectrophotometrically at an absorption maximum of 622 nm at different temperatures. The data show that nickel(II) and cimetidine combine in the molar ratio of 1:2. The stability constants of the complex were calculated to be 1.40–2.4 × 108 by continuous variation method and 1.24–2.4 × 108 by mole ratio method at 25 and 40 °C, respectively. The immediately formed complex shows stability with respect to time and temperature. 相似文献
204.
Assamoi Allah Antoine Destain Jacqueline Philippe Thonart 《Applied biochemistry and biotechnology》2010,160(1):50-62
There is an increasing interest for the organic residues from various sectors of agriculture and industries over the past
few decades. Their application in the field of fermentation technology has resulted in the production of bulk chemicals and
value-added products such as amino acid, enzymes, mushroom, organic acids, single-cell protein, biologically active secondary
metabolites, etc. (Ramachandran et al., Bioresource Technology 98:2000–2009, 2007). In this work, the production of extracellular xylanase by the fungus Penicillium canescens was investigated in solid-state fermentation using five agro-industrial substrates (soya oil cake, soya meal, wheat bran,
whole wheat bran, and pulp beet). The best substrate was the soya oil cake. In order to optimize the production, the most
effective cultivation conditions were investigated in Erlenmeyer flasks and in plastic bags with 5 and 100 g of soya oil cake,
respectively. The initial moisture content, initial pH, and temperature of the culture affected the xylanase synthesis. The
optimal fermentation medium was composed by soya oil cake crushed to 5 mm supplemented with 3% and 4% (w/w) of casein peptone and Na2HPO4.2H2O. After 7 days of incubation at 30 °C and under 80% of initial moisture, a xylanase production level of 18,895 ± 778 U/g
(Erlenmeyer flasks) and 9,300 ± 589 U/g (plastic bags) was reached. The partially purified enzyme recovered by ammonium sulfate
fractionation was completely stable at freezing and refrigeration temperatures up to 6 months and reasonably stable at room
temperature for more than 3 months. 相似文献
205.
Amen Allah Hajem Basma Trojette Ahmed Driss Tahar Jouini 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(7):793-794
The title compound, N,N,N′,N′‐tetramethylethylenediammonium diaqua(arsenate)(hydrogen arsenate)dizinc(II), (C6H18N2)0.5[Zn2(AsO4)(HAsO4)(H2O)2], is a new zincoarsenate obtained by hydrothermal synthesis. The structure consists of infinite two‐dimensional anionic layers alternating with planes containing centrosymmetric organic diprotonated template N,N,N′,N′‐tetramethylethylenediammonium cations, [H3NC6H12NH3]2+. The latter are interconnected to the framework through hydrogen bonds. 相似文献
206.
The Mössbauer effect technique has been employed for the study of magnetic properties of spinel series Ni1?xCuxMnyFe2?yO4 with 0.0≤x≤1.0, and y=0.6. The substitution of Mn3+ and Cu2+ ions results in a slight decrease of the hyperfine field at B‐ as well as A‐sites. The area ratio of Fe3+ ions at the A‐ and B‐site at 77 K indicates that Cu2+, Ni2+ and Mn3+ ions occupy the octahedral sites in an evidence for complete inverse spinel in this system. The temperature dependence of the hyperfine parameters has been studied for composition with x=0.5 where Nèel point TN and Debye temperature θD are found to be 650 and 679 K, respectively. The temperature dependence of the sublattice magnetization σ(T) obeys a one‐third‐power law in the range 0.5N<0.99. 相似文献
207.