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61.
Muhammad Ashram 《Journal of inclusion phenomena and macrocyclic chemistry》2007,59(3-4):315-321
Two novel chromogenic cone calix[4]dibenzothiacrown ethers 3 and 4 in which nitrophenylazo groups attached at the phenyl ring of dibenzothiacrown unit were described. The extraction properties
of 3 and 4 toward different transition metal ions have been studied using conductometric technique and found to exhibit Cu2+ and Hg2+ selectivity with very high stability constants range from log K
assoc
= 5.19 to log K
assoc
= 8.72. 相似文献
62.
ViqarUddin Ahmad MuhammadAthar Abbasi Muhammad Zubair Naheed Fatima Umar Farooq M.Iqbal Choudhary 《Helvetica chimica acta》2004,87(1):67-72
Phytochemical investigation of Symplocos racemosa resulted in the isolation of two new glycosides, symploracemoside ( 1 ) and symplomoside ( 2 ), which are structurally related to the reported benzoylsalireposide ( 3 ) and salireposide ( 4 ). The structure elucidation of the isolated compounds was based primarily on 1D‐ and 2D‐NMR analysis, including COSY, NOESY, HMQC, and HMBC correlations. These glycosides showed inhibitory activity against snake‐venom phosphodiesterase I. 相似文献
63.
Ali MOGHIMI Mohammad SABER‐TEHRANI Syed WAQIF‐HUSAIN Majid MOHAMMADHOSSEINI 《中国化学》2007,25(12):1859-1865
A novel and selective method for the fast determination of trace amounts of chromium species in water samples has been developed. The procedure is based on the selective formation of chromium diethyldithiocarbamate complexes at different pH in the presence of Mn(II) as an enhancement agent of chromium signals followed by elution with organic eluents and determination by atomic flame absorption spectrometry. The maximum capacity of the employed disks was found to be (396±3) µg and (376±2) µg for Cr(III) and Cr(VI), respectively. The detection limit of the proposed method is 49 and 43 ng·L?1 for Cr(III) and Cr(VI), respectively. The proposed method was successfully applied for determination of chromium species Cr(III) and Cr(VI) in different water samples. 相似文献
64.
Mehmood A Malik A Anis I Khan PM Riaz M Makhmoor T Choudhary MI 《Natural product letters》2002,16(6):371-376
Two new oleanane triterpenes; 2alpha,3alpha,24-trihydroxyolean-12-ene-28,30-dioic acid ([structure: see text]) and 2alpha,3alpha,24,28-tetrahydroxyolean-12-ene ([structure: see text]) have been isolated from the roots of Atropa acuminata. Anti-oxidant p-hydroxyphenethyl trans-ferulate ([structure: see text]), beta-sitosterol-3-O-beta-D-glucopyranoside ([structure: see text]) and oleanolic acid ([structure: see text]) have also been reported for the first time from this species. The structures were determined by spectroscopic studies including 2D-NMR. 相似文献
65.
Excessive exposure of solar ultraviolet (UV) radiation, particularly its UV-B component, to humans causes many adverse effects that include erythema, hyperplasia, hyperpigmentation, immunosuppression, photoaging and skin cancer. In recent years, there is increasing use of botanical agents in skin care products. Pomegranate derived from the tree Punica granatum contains anthocyanins (such as delphinidin, cyanidin and pelargonidin) and hydrolyzable tannins (such as punicalin, pedunculagin, punicalagin, gallagic and ellagic acid esters of glucose) and possesses strong antioxidant and anti-inflammatory properties. Recently, we have shown that pomegranate fruit extract (PFE) possesses antitumor promoting effects in a mouse model of chemical carcinogenesis. To begin to establish the effect of PFE for humans in this study, we determined its effect on UV-B-induced adverse effects in normal human epidermal keratinocytes (NHEK). We first assessed the effect of PFE on UV-B-mediated phosphorylation of mitogen-activated protein kinases (MAPK) pathway in NHEK. Immunoblot analysis demonstrated that the treatment of NHEK with PFE (10-40 microg/mL) for 24 h before UV-B (40 mJ/cm(2)) exposure dose dependently inhibited UV-B-mediated phosphorylation of ERKl/2, JNK1/2 and p38 protein. We also observed that PFE (20 microg/mL) inhibited UV-B-mediated phosphorylation of MAPK in a time-dependent manner. Furthermore, in dose- and time-dependent studies, we evaluated the effect of PFE on UV-B-mediated activation of nuclear factor kappa B (NF-kappaB) pathway. Using Western blot analysis, we found that PFE treatment of NHEK resulted in a dose- and time-dependent inhibition of UV-B-mediated degradation and phosphorylation of IkappaBalpha and activation of IKKalpha. Using immunoblot analysis, enzyme-linked immunosorbent assay and electrophoretic mobility shift assay, we found that PFE treatment to NHEK resulted in a dose- and time-dependent inhibition of UV-B-mediated nuclear translocation and phosphorylation of NF-kappaB/p65 at Ser(536). Taken together, our data shows that PFE protects against the adverse effects of UV-B radiation by inhibiting UV-B-induced modulations of NF-kappaB and MAPK pathways and provides a molecular basis for the photochemopreventive effects of PFE. 相似文献
66.
Summary Thin layers of stannic arsenate have been used to study the chromatographic behaviour of 57 metal ions in different mixed solvents. Au3+, Hg2+, UO
2
2+
, Be2+ and Al3+ and others can be easily separated from numerous metal ions. Fast quaternary, ternary and binary separations have been also achieved. Important separations are discussed. The effect of pH, duration of heating of ionexchanger plates and layer thickness on the Rf values has been studied and discussed. It is shown that Lederer's equation is also obeyed by thin layers of stannic arsenate, if instead of concentration of Na+ ion its activity is taken into consideration. 相似文献
67.
Amination of 4-nitrophenol, umbelliferone and 4-methylumbelliferone gave the corresponding oxyamines 1-3. These oxyamines react with aldehydes and ketones to form oximes. In the case of aliphatic aldehydes and electron-poor aromatic aldehydes, the oximes undergo base-catalyzed fragmentation in aqueous buffer in the presence of bovine serum albumin to give the parent phenols, which is the acyclic analog of Kemp's elimination reaction of 5-nitrobenzisoxazole 28. The process can be used as a spectrophotometric assay for formaldehyde under aqueous neutral conditions. 相似文献
68.
A validated kinetic spectrophotometric method has been developed for the determination of losartan potassium in pure and dosage forms. The method is based on oxidation of the losartan potassium with alkaline potassium permanganate at room temperature (25 ± 1 °C). The reaction is followed spectrophotometrically by measuring the increase in absorbance with time at 603 nm, and the initial rate, fixed time (at 12.0 min) and equilibrium time (at 90.0 min) methods are adopted for constructing the calibration graphs. All the calibration graphs are linear in the concentration range of 7.5–60.0 μg mL?1 and the calibration data resulted in the linear regression equations of n? = ?6.422 × 10?7 + 1.173 × 10?5 C, A =3.30 × 10?4 + 5.28 × 10?3 C and A = ?2.09 × 10?2 + 1.05 × 10?1 C for initial‐rate, fixed time and equilibrium time methods, respectively. The limits of detection for initial rate, fixed time and equilibrium time methods are 0.71, 0.21 and 0.19 μg mL?1, respectively. The activation parameters such as Ea, ΔH?, ΔS?, and ΔG? are also determined for the reaction and found to be 87.34 KJ mol?1, 84.86 KJ mol?1, 50.96 JK?1 mol?1 and ?15.10 KJ mol?1, respectively. The variables are optimized and the proposed methods are validated as per ICH guidelines. The method has been applied successfully to the estimation of losartan potassium in commercial tablets. The performance of the proposed methods was judged by calculating paired t‐ and F‐ values. The analytical results of the proposed methods when compared with those of the reference method show no significant difference in accuracy and precision and have acceptable bias. 相似文献
69.
Muhammad Zafrullah 《manuscripta mathematica》1975,17(1):55-66
Let R be a commutative integral domain. An element x of R is calledrigid if for all r,s dividing x; r divides s or s divides r. In our terminology, R issemirigid if each non zero non unit of R is a finite product of rigid elements. We show that semirigid GCD domains have a type of unique factorization, and are a known generalization of Krull domains. 相似文献
70.
The central idea of this paper is to construct a new mechanism for the solution of Abel’s type singular integral equations that is to say the two-step Laplace decomposition algorithm. The two-step Laplace decomposition algorithm (TSLDA) is an innovative adjustment in the Laplace decomposition algorithm (LDA) and makes the calculation much simpler. In this piece of writing, we merge the Laplace transform and decomposition method and present a novel move toward solving Abel’s singular integral equations. 相似文献