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101.
Kamal Ja’afar Muhammad Norazah Basar Satyajit D. Sarker Magaji Garba Mohammed 《Natural product research》2020,34(19):2746-2753
AbstractPhytochemical study was conducted on the leaves of Globimetula braunii which is a hemi parasitic plant belonging to the family Loranthaceae. Extraction was carried out using cold extraction method with increasing polarity of solvents i.e n-hexane, CH2Cl2 and MeOH. The components were separated by chromatographic technique and the structures of the compounds were elucidated by extensive spectroscopic analyses including MS, FTIR, 1D and 2D NMR, HRMS and chemical methods. Six new pentacyclic triterpenoid esters named as globrauneine A (1), globrauneine B (2), globrauneine C (3), globrauneine D (4), globrauneine E (5), and globrauneine F (6), together with six known compounds (7 – 12) were successfully isolated from the leaves of G. braunii growing on Piliostigma thonningii. These results depict a substantial support to the chemotaxonomy of the genus Globimetula. 相似文献
102.
3-Bromo-2-chloro-4-methoxypyridine has been developed as a practical 2,3-pyridyne precursor. The substituted 2,3-pyridyne generated from this precursor by halogen-metal exchange has been found to react regioselectively with 2-methoxyfuran and 2-methylfuran. 相似文献
103.
In this article, we study didactic phenomena identified in integration experiments within our classes, CAS (implemented in calculators). From this study, we show the interest of an instrumental approach to understand the influence of tools on the mathematical approach and on the building of student's knowledge: through a process—instrumental genesis—a calculator becomes a mathematical work tool; this process depends on the tool's constraints and potentialities, on students' knowledge, and on the class' work situations. To analyze the differentiation of instrumental genesis, we then have taken interest in students' behaviour and we propose a method enabling us to constitute a typology of extreme behaviour in environments of symbolic calculators. To take the variety of these genesis into account, the professor needs a particular organization of space and time of the study in the class. We suggest the notion of instrumental orchestration to name this organization. We demonstrate how this notion gives a better definition of the objectives, the configurations and the exploitation modes of different arrangements which aim at constituting coherent instrument systems for each student and for the class. 相似文献
104.
Reversed-phase HPLC analysis of the methanol extract of the seeds of Centaurea montana afforded a flavanone, montanoside (4), six epoxylignans, berchemol (7), berchemol 4′-O-β-d-glucoside (5), pinoresinol (10), pinoresinol 4-O-β-d-glucoside (8), pinoresinol 4,4′-di-O-β-d-glucoside (6), pinoresinol 4-O-apiose-(1→2)-β-d-glucoside (9), two quinic acid derivatives, trans-3-O-p-coumaroylquinic acid (1), cis-3-O-p-coumaroylquinic acid (2), and eight indole alkaloids, tryptamine (3), N-(4-hydroxycinnamoyl)-5-hydroxytryptamine (11), cis-N-(4-hydroxycinnamoyl)-5-hydroxytryptamine (12), centcyamine (16), cis-centcyamine (17), moschamine (13), cis-moschamine (14) and a dimeric indole alkaloid, montamine (15). While the structures of two new compounds, montanoside (4) and montamine (15), were established unequivocally by UV, IR, MS and a series of 1D and 2D NMR analyses, all known compounds were identified by comparison of their spectroscopic data with literature data. The antioxidant properties of these compounds were assessed by the DPPH assay, and their toxicity towards brine shrimps and cytotoxicity against CaCo-2 colon cancer cells were evaluated by the brine shrimp lethality and the MTT cytotoxicity assays, respectively. The novel dimer, montamine (15), showed significant in vitro anticolon cancer activity (IC50=43.9 μM) while that of the monomer, moschamine (13), was of a moderate level (IC50=81.0 μM). 相似文献
105.
Lutfun Nahar Hesham R. El-Seedi Shaden A. M. Khalifa Majid Mohammadhosseini Satyajit D. Sarker 《Molecules (Basel, Switzerland)》2021,26(16)
Ruta L. is a typical genus of the citrus family, Rutaceae Juss. and comprises ca. 40 different species, mainly distributed in the Mediterranean region. Ruta species have long been used in traditional medicines as an abortifacient and emmenagogue and for the treatment of lung diseases and microbial infections. The genus Ruta is rich in essential oils, which predominantly contain aliphatic ketones, e.g., 2-undecanone and 2-nonanone, but lack any significant amounts of terpenes. Three Ruta species, Ruta chalepensis L., Ruta graveolens L., and Ruta montana L., have been extensively studied for the composition of their essential oils and several bioactivities, revealing their potential medicinal and agrochemical applications. This review provides a systematic evaluation and critical appraisal of publications available in the literature on the composition and bioactivities of the essential oils obtained from Ruta species and includes a brief outlook of the potential applications of nanotechnology and chitosan-based products of Ruta essential oils. 相似文献
106.
Srimanta Guin Pravas Dolui Xinglong Zhang Satyadip Paul Vikas Kumar Singh Sukumar Pradhan Hediyala B. Chandrashekar S. S. Anjana Robert S. Paton Debabrata Maiti 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(17):5689-5694
Directed C?H functionalization has been realized as a complementary tool to the traditional approaches for a straightforward access of non‐proteinogenic amino acids; albeit such a process is restricted mostly up to the γ‐position. In the present work, we demonstrate the diverse (hetero)arylation of amino acids and analogous aliphatic amines selectively at the remote δ‐position by tuning the reactivity controlled by ligands. An organopalladium δ‐C(sp3)?H activated intermediate has been isolated and crystallographically characterized. Mechanistic investigations carried out experimentally in conjunction with computational studies shed light on the difference in the mechanistic picture depending on the substrate structure. 相似文献
107.
Satyajit Roy Hillol Khatua Sandip Kumar Das Buddhadeb Chattopadhyay 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(33):11561-11565
A unique concept for the intermolecular denitrogenative annulation of 1,2,3,4‐tetrazoles and alkynes was discovered by using a catalytic amount of Fe(TPP)Cl and Zn dust. The reaction precludes the traditional, more favored click reaction between an organic azide and alkynes, and instead proceeds by an unprecedented metalloradical activation. The method is anticipated to advance access to the construction of important basic nitrogen heterocycles, which will in turn enable discoveries of new drug candidates. 相似文献
108.
Any idempotent element e of an (associative) algebra T defines an algebra with unit e. We show that the morphism which compares their Hochschild cohomology algebras is a Gerstenhaber algebras morphism. Moreover, this morphism factorizes through the cohomological algebras of many triangular algebras. To cite this article: B. Bendiffalah, D. Guin, C. R. Acad. Sci. Paris, Ser. I 342 (2006). 相似文献
109.
Sarika Bhide V. M. Datar Satyajit Jena S. D. Kalmani N. K. Mondal G. K. Padmashree B. Satyanarayana R. R. Shinde P. Verma 《Pramana》2007,69(6):1015-1023
We are currently developing and studying the performance of glass RPC prototypes, under the INO detector R&D programme. While
we were successful in building and characterising a large number of chambers using local glass, these have met with severe
aging problems after a few months of continuous operation. We have then built a couple of RPCs using a Japanese glass. We
report in this paper on our long term stability tests of these RPCs. We also present some of our recent results on tracking
of cosmic ray muons in a stack of glass RPCs.
India-based Neutrino Observatory Collaboration 相似文献
110.
Experiments are performed to investigate the effects of oxidation upon coal liquefaction in a combined pre-oxidation-liquefaction process. It is found that the air-oxidation of coal preceding liquefaction is generally detrimental to liquefaction yields for both cases with or without presence of hydrogen gas in the dissolution step, and could be highly harmful to the processes which rely solely upon hydrogen donor solvents such as 1,2,3,4-tetrahydronaphthalene. The analyses of oxidized and unoxidized coals show a significant decrease in hydrogen but increase in oxygen contents of the coal with oxidation. These factors together with the possible formation of oxygen-coal bonds and the increase in —OH and/or —COOH groups in the oxidized coal are thought to account for the decreasing conversion of oxidized coal when it is subjected to liquefaction. 相似文献