Chemical Components from the Stems of Pueraria lobata and Their Tyrosinase Inhibitory Activity

Abubaker M. A. Morgan,정민이,정민혜,양서영,김영호 한국생약학회 2016 Natural Product Sciences Vol.22 No.2

Phytochemical investigation of the stems of Pueraria lobata (Wild) Ohwi (Leguminosae), led to the isolation of eighteen known compounds: β-amyrone (1), (+)-pinoresinol (2), (+)-syringaresinol (3) (+)-syringaresinol- O-β-D-glucoside (4), (+)-lariciresinol (5), (−)-tuberosin (6), naringenin (7), liquiritigenin (8), isoliquiritigenin (9) genistein (10), daidzein (11) daidzin (12) daidzein 4',7-diglucoside (13) 2,4,4'-trihydroxy deoxybenzoin (14), S-(+)-1- hydroxy-3-(4-hydroxyphenyl)-1-(4-hydroxy-2-methoxy-phenyl)propan-2-one (15), methyl 2-O-β-D-glucopyranosylbenzoate (16), pyromeconic acid 3-O-β-D-glucopyranoside 6'- (O-4''-hydroxy-3-methoxybenzoate) (17), and allantion (18). The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of those data with previously published results. The effects of isolated compounds on mushroom tyrosinase enzymatic activity were screened. The results indicated that, chloroform extract of P. lobata stems turned out to be having tyrosinase inhibitory effect, and only compounds 5, 8, 9, and 11 showed enzyme inhibitory activity, with IC50 values of 21.49 ± 4.44, 25.24 ± 6.79, 4.85 ± 2.29, and 17.50 ± 1.29 μM, respectively, in comparison with these of positive control, kojic acid (IC50 12.28 ± 2.72 μM). The results suggest that P. lobata stems extract as well as its chemical components may represent as potential candidates for tyrosinase inhibitors.

Phytochemical Constituents from the Aerial Part of Ducrosia ismaelis Asch.

Abubaker M. A. Morgan,Jang Hoon Kim,Hyun Woo Lee,이상현,CHI HWAN LIM,장해동,김영호 한국생약학회 2015 Natural Product Sciences Vol.21 No.1

Phytochemical investigation of the aerial components of Ducrosia ismaelis Asch. led to the isolation of six known compounds, psoralen (1), isopsoralen (2), cnidioside A (3), (-)-syringaresinol-O-b-D-glucopyranoside (4), (E)-plicatin B (5), trilinolein (6). The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of these data with previously published results. The antioxidant, anti-osteoporotic and cardiovascular related activities of the isolated compounds were assessed using oxygen radical absorbance capacity (ORAC), reducing capacity, tartrate-resistant acid phosphatase (TRAP), and soluble epoxide hydrolase (sEH) inhibitory activity assays. Compounds (3-5) showed potent peroxyl radical-scavenging capacities with ORAC values of 11.06 ? 0.39, 7.98 ? 0.10, and 13.99 ? 0.06 Trolox equivalent (TE) at concentrations of 10 mM, respectively. Only compounds 4 and 5 was able to significantly reduce Cu2+ ions, with a reduction value of 9.06 ? 0.32 and 4.61 ? 0.00 mM Trolox Equivalent (TE) at a concentration of 10 mM. Compound 5 at 10 mM exhibited a potent inhibitory effect on osteoclastic TRAP activity with a TRAP value of 86.05 ? 6.55% of the control. Com- pounds 1, 3 and 5 potently inhibited sEH activity with IC50 values of 41.6 4.9, 16.0 1.1, and 49.0 5.7 mM, respectively.

A Numerical Study on Combustion Characteristics in a Syngas-Diesel Dual Fuel Engine

( Abubaker Ahmed ),( Ali Kabbir ),( Changup Kim ),( Yonggyu Lee ),( Seungmook Oh ),( Kiseong Kim ) 한국액체미립화학회 2018 한국액체미립화학회 학술강연회 논문집 Vol.2018 No.-

The objective of this study is to analyze the combustion characteristics of an LSLB(Low calorific Syngas Lean Burn) dual-fuel engine, operated under overly lean conditions of syngas for power plant usages. A comprehensive chemical kinetics and computational fluid dynamics analysis were performed. In the present work, syngas is derived from coal that consists of H₂, CO and a high percentage of N₂ and CO₂, having low calorific value. This syngas is used with the similar amount of diesel to compensate for the excessive lean condition of syngas. The results indicate that most of diesel is burned as premixed combustion mode in dual fuel engine, then flame propagates through the syngas region in the piston bowl and squish zone. The hydrogen content affects little in the squish zone combustion. The effects of several injection parameters on the combustion characteristics were investigated also.

Computational Analysis of the Effects of Spray Parameters and Piston Shape on Syngas-Diesel Dual-Fuel Engine Combustion Process

Abubaker Ahmed M. M. Ali,Ali Kabbir,김창업,이용규,오승묵,김기성 한국분무공학회 2018 한국액체미립화학회지 Vol.23 No.4

In this study, a 3D CFD analysis method for the combustion process was established for a low calorific value syngasdiesel dual-fuel engine operating under very lean fuel-air mixture condition. Also, the accuracy of computational analysis was evaluated by comparing the experimental results with the computed ones. To simulate the combustion for the dualfuel engine, a new dual-fuel chemical kinetics set was used that was constituted by merging two verified chemical kinetic sets: n-heptane (173 species) for diesel and Gri-mech 3.0 (53 species) for syngas. For dual-fuel mode operations, the early stage of combustion was dominated by the fuel burning inside or near the spray plume. After which, the flame propagated into the syngas in the piston bowl and then proceeded toward the syngas in the squish zone. With the baseline injection system and piston shape, a significant amount of unburned syngas was discharged. To solve this problem, effects of the injection parameters and piston shape on combustion characteristics were analyzed by calculation. The change in injection variables toward increasing the spray plume volume or the penetration length were effective to cause fast burning in the vicinity of TDC by widening the spatial distribution of diesel acting as a seed of auto-ignition. As a result, the unburned syngas fraction was reduced. Changing the piston shape with the shallow depth of the piston bowl and 20% squish area ratio had a significant effect on the combustion pattern and lessened the unburned syngas fraction by half.

NUMERICAL STUDY OF THE COMBUSTION CHARACTERISTICS IN A SYNGAS-DIESEL DUAL-FUEL ENGINE UNDER LEAN CONDITION

Abubaker Ahmed Mohammed Mohammed Ali,Kabbir Ali,Changup Kim,Yonggyu Lee,오승묵,Kiseong Kim 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.5

The aim of this study was to investigate the combustion characteristics of a syngas-diesel dual fuel engine operates in very lean fuel-air mixture conditions. 3D CFD simulation combined with chemical kinetics were used for analysis. The main parameter for this study was the hydrogen content in the syngas. To simulate the combustion for the dual fuel engine, a new dual-fuel chemical kinetics set was used that was constituted by merging the two chemical kinetics sets: n-heptane (173 species), and Gri-mech 3.0 (53 species) for natural gas. The calculation results were in good agreements with the experimental results. Most of the diesel fuel burned as premixed combustion mode. When the hydrogen concentration was high, as in syngas45, most of the syngas in the piston bowl and squish region, except near the cylinder wall, was combusted in the vicinity of TDC; but when hydrogen concentration was low, as in syngas25, flame propagation to the central region of the piston was delayed, which led to an increase of time loss and unburned syngas emission. Due to the strong reverse squish flow, the syngas composition did not affect the flame arrival time at the cylinder wall through the squish area by much.

A New Flavonol Glycoside from the Leaves of Boscia senegalensis

Abubaker M. A. Morgan,김장훈,김상겸,임치환,김영호 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Detailed chemical investigation of Boscia senegalensis (Per) Lam. ex Poir. led to the isolation of one new flavonol glycoside, rhamnocitrin-3-O-β-D-(6''-O-E-feruloyl)-glucopyranoside named bosenegaloside A (1), with seven known compounds, rhamnocitrin-3-O-β-D-(6''-O-E-p-coumaroyl)-glucopyranoside (2), rhamnocitrin- 3-O-β-D-glucopyranoside (3), 3,4,5-trimethoxyphenol-β-D-glucopyrinoside (4), lasianthionoside A (5), 3,7- dimethyl-1-octene-3,6,7-triol-6-O-β-D-glucopyranoside (6), syringin (7), and austroside B (8). The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of these data with previously published results. The inhibitory activity of the isolated compounds on soluble epoxide hydrolase (sEH) was assessed. Compounds 1-3 potently inhibited sEH activity with IC50 values of 12.8 ± 0.5, 18.4 ± 0.2, and 11.3 ± 0.9 μM, respectively.

A New Flavonol Glycoside from the Leaves of Boscia senegalensis

Morgan, Abubaker M.A.,Kim, Jang Hoon,Kim, Sang Kyum,Lim, Chi-Hwan,Kim, Young Ho Korean Chemical Society 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Detailed chemical investigation of Boscia senegalensis (Per) Lam. ex Poir. led to the isolation of one new flavonol glycoside, rhamnocitrin-3-O-${\beta}$-$\small{D}$-(6"-O-E-feruloyl)-glucopyranoside named bosenegaloside A (1), with seven known compounds, rhamnocitrin-3-O-${\beta}$-$\small{D}$-(6"-O-E-p-coumaroyl)-glucopyranoside (2), rhamnocitrin-3-O-${\beta}$-$\small{D}$-glucopyranoside (3), 3,4,5-trimethoxyphenol-${\beta}$-$\small{D}$-glucopyrinoside (4), lasianthionoside A (5), 3,7-dimethyl-1-octene-3,6,7-triol-6-O-${\beta}$-$\small{D}$-glucopyranoside (6), syringin (7), and austroside B (8). The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of these data with previously published results. The inhibitory activity of the isolated compounds on soluble epoxide hydrolase (sEH) was assessed. Compounds 1-3 potently inhibited sEH activity with $IC_{50}$ values of $12.8{\pm}0.5$, $18.4{\pm}0.2$, and $11.3{\pm}0.9{\mu}M$, respectively.

Pentacyclic triterpenes from the stem bark of <i>Combretum hartmannianum</i> Schweinf

Morgan, Abubaker M.A.,Mohamed, Azmey E.,Saophea, Chhon,Park, Sang Un,Kim, Young Ho Elsevier 2018 Biochemical systematics and ecology Vol.77 No.-

<P><B>Abstract</B></P> <P>Chemical investigation of the stem bark of <I>Combretum hartmannianum</I> Schweinf (Combretaceae) led to the isolation and identification of nine compounds with pentacyclic triterpene skeletons. These were identified as three ursane-type triterpenes, ursolic acid (<B>1</B>), pomolic acid (<B>2</B>), and corosolic acid (<B>3</B>); one oleanane-type triterpene, arjunic acid (<B>4</B>); and five oleanane-type triterpene glucosides, arjunglucoside I (<B>5</B>), trachelosperoside E-1 (<B>6</B>), combreglucoside (<B>7</B>), chebuloside II (<B>8</B>), and 2α,3β,6β,19α-tetrahydroxyoleanolic acid 28-<I>O</I>-β-<SMALL>D</SMALL>-glucopyranoside (<B>9</B>). The chemical structures of these compounds were elucidated from spectroscopic data and by comparison of these data with previously published results. This is the first report of triterpene compounds from a species of <I>C. hartmannianum</I> and the first report of compounds <B>2</B> and <B>9</B> from a member of the Combretaceae family.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This study is the first comprehensive chemical investigation of <I>Combretum hartmannianum</I> Schweinf. </LI> <LI> Nine compounds were reported first herein as isolates from <I>C. hartmannianum</I>, and compounds 2 and 9 are reported for the first time from Combretaceae family. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Optimization Design and Fabrication of Polymer Micro needle by Hot Embossing Method

Samir Sghayer Abubaker,Yajun Zhang 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.4

This paper presents the design, fabrication and testing of a solid polymer microneedle. Mechanical behavior of the microneedle was simulated by ANSYS via the results of suffered and strength calculations. The results shows, that the maximum stresses of polymer MNs is far less than 3.183 MPa, which is the allowable pressure needed. Taguchi method was used help in data analysis and prediction of optimum parameter settings, a series of experiments were conducted to verify the impact of embossing temperature, embossing pressure, and embossing time on the microneedle’s quality. According to the result from the Taguchi experiment, S/N ratio is calculated to find the best combination settings for microneedle’s height. The highest value of S/N ratio (54.403) for product height is determined as optimal initial parameter settings, achieved by 130 °C, 11 MPa and 150 s for PMMA microneedle with optimized size of 550 µm height, 250 µm base diameter and 50 µm tip diameter. Embossing temperature and embossing pressure are the significant parameters in the experiment. The proposed method was verified by a set of experiments, the force for insertion as well as the modes of mechanical failure were examined.

A Uniquely Finned Tube Heat Exchanger Design of a Condenser for Heavy-Duty Air Conditioning Systems

Ahmad M. Abubaker,Yousef S. H. Najjar,Adnan Darwish Ahmad 대한설비공학회 2020 International Journal Of Air-Conditioning and Refr Vol.28 No.1

This study introduces the design of a novel condenser for air conditioning systems. Enhancement of performance of the system was manifested by increasing the coefficient of performance (COP), decreasing the pressure drop and the power consumed by the refrigerant compressor and the cooling water pump. The design consists of an adiabatic double-pipe heat exchanger with longitudinal rectangular fins. This model can enhance heat transfer coefficient and expose more area per unit length. This novel design supersedes other conventional condenser designs by 4.7% higher COP, 8.2% lower water pressure drop, 4.68% lower compressor power. Two refrigerants have been examined in the study; R-134a which is used in commercial and industrial chillers and R-1234ze which has low global warming potential.