排序方式: 共有32条查询结果,搜索用时 15 毫秒
1.
Pyridinium methanesulfonate (m.p. 185°C) and pyridinium p-toluenesulfonate (m.p. 121°C) were used as catalysts and media for the esterification of carboxylic acids with primary alcohols
to give the corresponding esters selectively in high yields. The high melting points of these pyridinium salts did not prevent
their application as ionic liquid medium for these reactions which were performed at 90°C. 相似文献
2.
Gopal Lamichhane Prakash Raj Pandeya Ramakanta Lamichhane Su-jin Rhee Hari Prasad Devkota Hyun-Ju Jung 《Molecules (Basel, Switzerland)》2022,27(3)
Background: Ponciri Fructus, a crude drug consisting of the dried immature fruits of Poncirus trifoliata (L.) Raf., is a popular folk medicine used for the treatment of allergy and gastrointestinal disorders in Korea and China. In this study, the anti-adipogenic activity of extracts and isolated compounds were evaluated using 3T3-L1 preadipocytes. Methods: Dried immature fruits were extracted and fractionated into n-hexane, ethyl acetate (EtOAc), n-butanol and water-soluble fractions. The ethanol extract and fractions were tested for anti-adipogenic activity in the 3T3-L1 cell line. The active fractions (n-hexane and EtOAc fractions) were further subjected to chromatographic techniques to isolate and identify active compounds. Furthermore, the isolated compounds were evaluated for their anti-adipogenic activity. Results: Altogether, seven compounds, including two flavonoids, one phytosteroid and four coumarin derivatives, were isolated. Ethanol extract, n-hexane fraction, EtOAc fraction and three isolated compounds (phellopterin, oxypeucedanin and poncirin) showed significant anti-adipogenic activity as observed by reduced lipid deposition in differentiated 3T3-L1 cells. Further, oxypeucedanin downregulated the key adipogenic markers, such as peroxisome proliferator-activated receptors proteins γ (PPAR-γ), sterol response element binding proteins-1 (SREBP-1), CCAAT/enhancer binding proteins-α (C/EBP-α), adipocyte-specific lipid binding proteins (FABP-4), adipocyte fatty acid binding proteins (aP2), lipoprotein lipase (LPL) and leptin. Conclusion: This study indicated that the ethanol extract, hexane fraction and ethyl acetate fraction of P. trifoliata fruits possess strong anti-adipogenic activity, containing the active compounds such as phellopterin, oxypeucedanin and poncirin. Further research is recommended to explore their efficacy and safety in animal and clinical models. 相似文献
3.
Sonal M. Patel Uma V. Chudasama Pralhad A. Ganeshpure 《Reaction Kinetics and Catalysis Letters》2002,76(2):317-325
Metal(IV) phosphates of tin, zirconium and titanium in different morphological forms, viz. amorphous, calcined and crystalline, have been used as catalysts for selective cyclodehydration of 1,4-butanediol to tetrahydrofuran. A comparative study of the three catalysts for the above reaction has been carried out to understand the effect of their composition and morphology on the catalytic activity. 相似文献
4.
Mortar methods with dual Lagrange multiplier bases provide a flexible, efficient and optimal way to couple different discretization
schemes or nonmatching triangulations. Here, we generalize the concept of dual Lagrange multiplier bases by relaxing the condition
that the trace space of the approximation space at the slave side with zero boundary condition on the interface and the Lagrange
multiplier space have the same dimension. We provide a new theoretical framework within this relaxed setting, which opens
a new and simpler way to construct dual Lagrange multiplier bases for higher order finite element spaces. As examples, we
consider quadratic and cubic tetrahedral elements and quadratic serendipity hexahedral elements. Numerical results illustrate
the performance of our approach.
This work was supported in part by the Deutsche Forschungsgemeinschaft, SFB 404, C12, the Netherlands Organization for Scientific
Research and by the European Community's Human Potential Programme under contract HPRN-CT-2002-00286. 相似文献
5.
Bishnu P. Lamichhane 《BIT Numerical Mathematics》2014,54(2):469-484
A new non-conforming finite element method is proposed for the approximation of the biharmonic equation with clamped boundary condition. The new formulation is based on a gradient recovery operator. Optimal a priori error estimates are proved for the proposed approach. The approach is also extended to cover a singularly perturbed problem. 相似文献
6.
Mario A. Bianchet Ying H. Pan Leighanne A. Brammer Basta Harry Saavedra Evan P. Lloyd Pankaj Kumar Rohini Mattoo Craig A. Townsend Gyanu Lamichhane 《BMC biochemistry》2017,18(1):8
Background
The carbapenem subclass of β-lactams is among the most potent antibiotics available today. Emerging evidence shows that, unlike other subclasses of β-lactams, carbapenems bind to and inhibit non-classical transpeptidases (L,D-transpeptidases) that generate 3 → 3 linkages in bacterial peptidoglycan. The carbapenems biapenem and tebipenem exhibit therapeutically valuable potencies against Mycobacterium tuberculosis (Mtb).Results
Here, we report the X-ray crystal structures of Mtb L,D-transpeptidase-2 (LdtMt2) complexed with biapenem or tebipenem. Despite significant variations in carbapenem sulfur side chains, biapenem and tebipenem ultimately form an identical adduct that docks to the outer cavity of LdtMt2. We propose that this common adduct is an enzyme catalyzed decomposition of the carbapenem adduct by a mechanism similar to S-conjugate elimination by β-lyases.Conclusion
The results presented here demonstrate biapenem and tebipenem bind to the outer cavity of LdtMt2, covalently inactivate the enzyme, and subsequently degrade via an S-conjugate elimination mechanism. We discuss structure based drug design based on the findings and propose that the S-conjugate elimination can be leveraged to design novel agents to deliver and locally release antimicrobial factors to act synergistically with the carbapenem carrier.7.
Production of the fibrinolytic enzyme was carried out using 2.5-L glass fermentor, culture of thermophilic Streptomyces sp., and glucose yeast extract peptone medium of pH 8.0. Five successive batches were carried out under controlled fermentation conditions viz., agitation 140 rpm, aeration 0.5 vvm, 55 °C, and 18 h. The total protein extracellularly produced in the cell-free broth was ~300-500 mg/L. The enzyme belongs to serine endopeptidase type. Studies on the fibrin degradation indicate that the enzyme degrades the fibrin into small molecular weight products as seen from HPLC profile. Phase-contrast microscopic structure of fibrin showed that enzyme cleaves the fibrin filaments. The ex vivo activity of the actinokinase was compared with 500 IU of urokinase and 350 IU of streptokinase. The ex vivo clot lysis was found to be faster as compared to the commercial available enzymes. 相似文献
8.
9.
Virupaxappa H. Arali Vidyanand K. Revankar Vinayak B. Mahale Pralhad J. Kulkarni 《Transition Metal Chemistry》1994,19(1):57-60
Summary Complexes of stoichiometries M(Acbim)2X2·nH2O and M(Bzbim)2X2·nH2O (M = Co, Ni or Cu; Acbim = 2-acetylbenzimidazole, Bzbim = 2-benzoylbenzimidazole; X = Cl, Br, NO3 or ClO4; n = 0, 1 or 2) have been prepared and characterised by spectroscopic and physicochemical methods. The ligands coordinate through carbonyl oxygen and tertiary nitrogen. 相似文献
10.
Gopal L. Tembe Pralhad A. Ganeshpure Sheo Satish 《Reaction Kinetics and Catalysis Letters》1998,63(2):385-389
Oxidation of cyclohexane bytert-butyl hydroperoxide was carried out in acetonitrile solution at room temperature in the presence of manganese(II) β-diketonate
complexes, Mn(acac)2, Mn(acac)2.2H2O, Mn(ba)2.H2O, Mn(dbm)2 and Mn(dbm)2.2H2O (where acacH=acetylacetone, baH=benzoylacetone and dbmH=dibenzoyl-methane). Cyclohexanol and cyclohexanone were obtained
as the products. Oxidation ofcis-cyclooctene gave the corresponding epoxide together with two minor byproducts in the presence of Mn(acac)2.2H2O and Mn(dbm)2.2H2O. A mechanistic pathway predominantly involving autoxidation is proposed.
IPCL communication No. 322 相似文献