Moshfiqur Rahman

Celecoxib analogs possessing a N-(4-nitrooxybutyl)piperidin-4-yl or N-(4-nitrooxybutyl)-1,2,3,6-tetrahydropyridin-4-yl nitric oxide donor moiety: Synthesis, biological evaluation and nitric oxide release studies

A new group of hybrid nitric oxide (NO) releasing anti-inflammatory (AI) coxib prodrugs (NO-coxibs) wherein the para-tolyl moiety present in celecoxib was replaced by a N-(4-nitrooxybutyl)piperidyl 15a-b, or N-(4-nitrooxybutyl)-1,2,3,6-tetrahydropyridyl 17a-b, NO-donor moiety was synthesized. All compounds released a low amount of NO upon incubation with phosphate buffered saline (PBS) at pH 7.4 (2.4-5.8% range). In comparison, the percentage NO released was higher (3.1-8.4% range) when these nitrate prodrugs were incubated in the presence of L-cysteine. In vitro COX-1/COX-2 isozyme inhibition studies showed this group of compounds are moderately more potent, and hence selective, inhibitors of the COX-2 relative to the COX-1 enzyme. AI structure-activity relationship data acquired showed that compounds having a MeSO2 COX-2 pharmacophore exhibited superior AI activity compared to analogs having a H2NSO2 substituent. Compounds having a MeSO2 COX-2 pharmacophore in conjunction with a N-(4-nitrooxybutyl)piperidyl (ED50=132.4 mg/kg po), or a N-(4-nitrooxybutyl)-1,2,3,6-tetrahydropyridyl (ED50=118.4 mg/kg po), moiety exhibited an AI potency profile that is similar to aspirin (ED50=128.7 mg/kg po) but lower than ibuprofen (ED50=67.4 mg/kg po).

Kinetic Study and Thermal Decomposition Behavior of Lignite Coal

A thermogravimetric analyzer was employed to investigate the thermal behavior and extract the kinetic parameters of Canadian lignite coal. The pyrolysis experiments were conducted in temperatures ranging from 298 K to 1173 K under inert atmosphere utilizing six different heating rates of 1, 6, 9, 12, 15, and 18 K min−1, respectively. There are different techniques for analyzing the kinetics of solid-state reactions that can generally be classified into two categories: model-fitting and model-free methods. Historically, model-fitting methods are broadly used in solid-state kinetics and show an excellent fit to the experimental data but produce uncertain kinetic parameters especially for nonisothermal conditions. In this work, different model-free techniques such as the Kissinger method and the isoconversional methods of Ozawa, Kissinger-Akahira-Sunose, and Friedman are employed and compared in order to analyze nonisothermal kinetic data and investigate thermal behavior of a lignite coal. Experimental results showed that the activation energy values obtained by the isoconversional methods were in good agreement, but Friedman method was considered to be the best among the model-free methods to evaluate kinetic parameters for solid-state reactions. These results can provide useful information to predict kinetic model of coal pyrolysis and optimization of the process conditions.

Synthesis of 1-(methanesulfonyl- and aminosulfonylphenyl)acetylenes that possess a 2-(N-difluoromethyl-1,2-dihydropyridin-2-one) pharmacophore: Evaluation as dual inhibitors of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity

A hitherto unknown class of linear acetylene regioisomers were designed such that a SO(2)Me or SO(2)NH(2) group was located at the ortho-, meta- or para-position of the acetylene C-1 phenyl ring, and a N-difluoromethyl-1,2-dihydropyridin-2-one moiety was attached via its C-5 position to the C-2 position on an acetylene template (scaffold). All three SO(2)Me regioisomers, and the 4-SO(2)NH(2) analog, were potent inhibitors of 5-lipoxygenase (5-LOX IC(50)=3.2-3.5 microM range) relative to the reference drug caffeic acid (IC(50)=4.0 microM). The SO(2)Me regioisomers exhibited weak cyclooxygenease-1 (COX-1) and -2 (COX-2) inhibitory activity with a modest COX-2 selectivity index. The most potent 3-SO(2)Me, 4-SO(2)Me and 4-SO(2)NH(2) compounds, with respective ED(50) values of 66.1, 68.5 and 86.5 mg/kg po, exhibited comparable oral anti-inflammatory (AI) activity to that of the reference drug ibuprofen (ED(50)=67.4 mg/kg po). The N-difluoromethyl-1,2-dihydropyridin-2-one moiety provides a novel pharmacophore for the design of cyclic hydroxamic mimetics capable of inhibiting 5-LOX for exploitation in the development of 5-LOX inhibitory AI drugs.

A Comparative Study on Lignite Coal Drying by Different Methods

ABSTRACT Abundance of low-rank coal (LRC) and increasing demand for energy provides motivation for upgrading LRC in terms of their high moisture content. Canadian lignite coal (425–1000 µm) was dried at different temperatures using different methods, namely hydrothermal treatment (HT), vacuum drying and hot air drying. These processes resulted in significant reduction (up to 9.65%) in moisture from as-received lignite coal (34%), especially at higher temperatures (300 and 325°C) using HT for 30 minutes. Vacuum drying (70°C) over the period of 7 hours and hot air drying (70°C) for 110 minutes liberated almost the same amount of moisture from the raw coal. Several investigations were conducted on these samples and chars derived from these in conditions similar to a boiler to understand the impact of drying methods. Char samples were prepared by pyrolyzing at 1200°C under inert atmosphere (N2) in a drop tube furnace (DTF). The morphological changes of these char samples were investigated by scanning electron microscopy analysis to see the physiochemical changes that occurred during different treatment processes. Raw and treated coal samples were also analyzed by several analytical techniques including Fourier transform infrared spectroscopy and thermogravimetric analysis (TGA). The present paper also describes the effectiveness of the different processes for upgrading the LRC and how it transforms LRC to a value-added coal that is easily transportable and environmental friendly source of energy.

Effect of initial coal particle size on coal liquefaction conversion

In coal liquefaction process initial coal particle size can be considered as one of the important process parameters. In this work, particles of coal are prepared by pulverisation and separation into different particle size ranges below 45 to 1,000 µm. Since conventional batch autoclave is not suitable for short contact time experiments, as the time required for the autoclave to reach the reaction temperature can be substantial, the liquefaction runs were investigated with a rapid injection reactor designed specifically for investigating the effect of initial particle size on liquefaction conversion. A Canadian coal was examined in a tubular bomb reactor in presence of tetralin at 400°C for a short reaction time (5 min) with pressure of 6 MPa under nitrogen atmosphere. The results indicated that total conversion obtained during the liquefaction changed according to the different particle size, and optimum particle size (150-212 µm) was detected for the liquefaction condition. [Received: November 27, 2014; Accepted: August 22, 2015]