Changhyun Roh

Korea Atomic Energy Research Institute (KAERI), Daiden, Daejeon, South Korea

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Publications (45)101.8 Total impact

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    Journal of Alloys and Compounds 10/2015; DOI:10.1016/j.jallcom.2015.10.068 · 3.00 Impact Factor
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    ABSTRACT: Radioactive cesium (137Cs) has seriously become a human concern owing to exposure from a nuclear accident release at a nuclear plant. Many efforts have focused at the removal of radioactive cesium and remediation of a contaminated environment. To meet these demands, an effective sorbent based on magnetic composites functionalized with synthetic clay minerals was demonstrated. This sorbent shows a high removal efficiency of contaminated water containing suspended sorbents at a level of 0.5 mg ml−1 [137Cs of 84.68 Becquerel (Bq) gram (g)−1], decontaminated to 0.47 Bq g−1 (99.44 % removal efficiency) with just one treatment. The radioactive cesium is dramatically adsorbed into synthetic clay minerals. Subsequently, a rapid and easy sorbent separation from the radioactive cesium solution occurs after treatment using a magnetic field. Thus, a magnetic sodium-phlogopite sorbent can offer high potential for in situ remediation.
    International journal of Environmental Science and Technology 08/2015; 12(11). DOI:10.1007/s13762-015-0853-7 · 2.19 Impact Factor
  • Changhyun Roh · ChanKyu Kang · Jonathan R. Lloyd ·
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    ABSTRACT: Microbial processes can affect the environmental behavior of priority radionuclides, and understanding these reactions is essential for the safe management of radioactive wastes and can contribute to the remediation of radionuclide-contaminated land. Underlying mechanisms that can control radionuclide solubility in biogeochemical systems can range from biosorption and biomineralization process, through direct (enzymatic) and indirect redox transformations. The mechanisms of enzyme-mediated reduction of problematic actinides, in principal, uranium (U), but including neptunium (Np), plutonium (Pu) and Americium (Am), are described in this review. In addition, the mechanisms by which the fission products technetium (Tc), cesium (Cs), and strontium (Sr) are removed from a solution by microorganisms are also described. The present review discusses the status of these microbiological processes, and the potential for cost-effective and scalable in situ remediation of radioactive waste.
    Korean Journal of Chemical Engineering 07/2015; 32(9). DOI:10.1007/s11814-015-0128-5 · 1.17 Impact Factor
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    ABSTRACT: Radioactive cesium (137 Cs) has inevitably become a human concern due to exposure from nuclear power plants and nuclear accident releases. Many efforts have been focused on removing cesium and the remediation of the contaminated environment. In this study, we elucidated the ability of Prussian blue-coated magnetic nanoparticles to eliminate cesium from radioactive contaminated waste. Thus, the obtained Prussian blue-coated magnetic nanoparticles were then characterized and examined for their physical and radioactive cesium adsorption properties. This Prussian blue-coated magnetic nanoparticle-based cesium magnetic sorbent can offer great potential for use in in situ remediation.
    Nanomaterials 12/2014; 4:894-901. DOI:10.3390/nano4040894 · 2.08 Impact Factor
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    Changhyun Roh ·
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    ABSTRACT: Recently, there has been a great deal of remarkable interest in finding bioactive compounds from nutritional foods to replace synthetic compounds. In particular, ortho-dihydroxyisoflavones and glycitein are of growing scientific interest owing to their attractive biological properties. In this study, 7,8-ortho-dihydroxyisoflavone, 6,7-ortho-dihydroxyisoflavone, 3',4'-ortho-dihydroxyisoflavone and 7,4'-dihydroxy-6-methoxyisoflavone were characterized using microorganism screened from soybean Doenjang. Three ortho-dihydroxyisoflavones and glycitein were structurally elucidated by 1H-NMR and GC-MS analysis. Furthermore, bacterial strains from soybean Doenjang with the capacity of biotransformation were screened. The bacterial strain, identified as Bacillus subtilis Roh-1, was shown to convert daidzein into ortho-dihydroxyisoflavones and glycitein. Thus, this study has, for the first time, demonstrated that a bacterial strain had a substrate specificity for multiple modifications of the bioactive compounds.
    12/2014; 4(4):1093-1101. DOI:10.3390/biom4041093
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    Changhyun Roh · ChanKyu Kang ·
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    ABSTRACT: Microbial biotransformation is a great model system to produce drugs and biologically active compounds. In this study, we elucidated the fermentation and production of an anti-cancer agent from a microbial process for regiospecific hydroxylation of resveratrol. Among the strains examined, a potent strain showed high regiospecific hydroxylation activity to produce piceatannol. In a 5 L (w/v 3 L) jar fermentation, this wild type Streptomyces sp. in the batch system produced 205 mg of piceatannol (i.e., 60% yields) from 342 mg of resveratrol in 20 h. Using the product, an in vitro anti-cancer study was performed against a human cancer cell line (HeLa). It showed that the biotransformed piceatannol possessed a significant anticancer activity. This result demonstrates that a biotransformation screening method might be of therapeutic interest with respect to the identification of anti-cancer drugs.
    Molecules 10/2014; 19(10):16684-16692. DOI:10.3390/molecules191016684 · 2.42 Impact Factor
  • Changhyun Roh · Se Jy Lee · S. M. Nasir Uddin · Jin Kyu Kim · ChanKyu Kang ·
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    ABSTRACT: Obesity is the fifth leading cause of death globally. At least 2.8 million adults die each year as a result of being overweight. Therefore, the development of an efficient lipid inhibitor for the biological effects of obesity is highly needed. The discovery of bioactive compounds from food is one possible way to control obesity and to prevent or reduce the risks of various obesity-related diseases. In this study, we found that 7,3′,4′-trihydroxyisoflavone from Korean soybean paste has remarkable anti-obesity activity in vitro and in vivo. Treatment with 7,3′,4′-trihydroxyisoflavone significantly reduced the adipose tissue weight to 1.6/100 g of body weight in high-fat mice. In addition, in 7,3′,4′-trihydroxyisoflavone-treated mice, a significant reduction in the serum triglyceride and T-cholesterol was observed at 29 and 37 %, respectively. These results support the hypothesis that 7,3′,4′-trihydroxyisoflavone is expected to create a therapeutic interest in its use for the treatment of obesity.
    European Food Research and Technology 04/2014; 240(4):865-869. DOI:10.1007/s00217-014-2390-x · 1.56 Impact Factor
  • Chankyu Kang · Robert W Ashurst · Jae-Jin Shim · Yun Suk Huh · Changhyun Roh ·
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    ABSTRACT: Here, we present a simple method for controlling the density of Au nanoparticles (Au NPs) on a modified silicon substrate, by destabilizing the colloidal Au NPs with 3-mercaptopropyltrimethoxylsilane (3-MPTMS) for microelectromechanical-system-based applications to reduce tribological issues. A silicon surface was pretreated with a 3-MPTMS solution, immediately after which thiolated Au NPs were added to it, resulting in their uniform deposition on the silicon substrate. Without any material property change of the colloidal Au NPs, we observed the formation of large clusters Au NPs on the modified silicon surface. Analysis by scanning electron microscopy with energy dispersive X-ray spectroscopy indicated that the addition of 3-MPTMS resulted in an alternation of the chemical characteristics of the solution. Atomic force microscopy imaging supported the notion that silicon surface modification is the most important factor on tribological properties of materials along with ligand-modified Au NPs. The density of Au NPs on a silicon surface was significantly dependent on several factors, including the concentration of colloidal Au NPs, deposition time, and concentration of 3-MPTMS solution, while temperature range which was used throughout experiment was determined to have no significant effect. A relatively high density of Au NPs forms on the silicon surface as the concentrations of Au NPs and 3-MPTMS are increased. In addition, the maximum deposition of Au NPs on silicon wafer was observed at 3 h, while the effects of temperature variation were minimal.
    Bioprocess and Biosystems Engineering 03/2014; 37(10). DOI:10.1007/s00449-014-1175-8 · 2.00 Impact Factor
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    ABSTRACT: Highly branched fatty acids are of particular interest as they have polyketide-like structures with several chiral centers and regioselective fictionalization of such substances would offer convenient routes to new important pharmaceutical compounds. A novel biocatalyst from Bacillus cereus was cloned and expressed in Escherichia coli BL21 using pET expression system. It can be easily expressed in Escherichia coli with a high yield. The expressed recombinant enzyme was purified by Ni-NTA affinity chromatography and characterized. We elucidated that this enzyme catalyzes the oxidation of alkanoic acids (C8 to C17) and unsaturated fatty acids (C18). Substrate binding study showed the tightest binding fatty acid was myristic acid (C14), yielding a Kd value of 7.88 µM. This biocatalyst showed the activity of saturated fatty acids of shorter (C8,C10), which could not be observed from other enzyme.
    Biocatalysis and Agricultural Biotechnology 03/2014; 3(4). DOI:10.1016/j.bcab.2014.03.006
  • ChanKyu Kang · ChangHyun Roh · Ruel A. Overfelt ·
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    ABSTRACT: Pressure-driven flows through optically transparent polydimethylsiloxane (PDMS) microfluidic channels using a syringe pump are common in many experimental applications. However, because of small changes, the pressure-induced deformations due to soft materials and shapes and patterns in the microchannels, which generate untargeted flow velocity and pressure drop, have been easily ignored. In this paper, we present a simple experimental investigation with circular-shaped, periodically arranged objects of three different characteristic dimensions, as well as various channel heights ranging from 15 μm to 200 μm. The resultant CCD images and pressure data were used to determine the extent of the start-up transients and evaluate the establishment of quasi-steady flow conditions. Channel deformation, measured by fluorescence intensity difference, was severe in shallow microchannels that had characteristically large obstacles. In addition, PDMS microchannel bulging effects in shallow microchannels exerted a greater deleterious effect on (ΔP/Δx)QS values than upon VQS for the experiments using a volumetrically controlled syringe pump. The discrepancy between experimental and theoretical (ΔP/Δx) increased with decreasing microchannel height. This means that the severe PDMS bulging observed in shallow microchannels using a syringe pump can generate large deviations from the desired experimental result. As a result, the slope of Darcy friction factors plotted against the Reynolds number indicates that the slope was strongly dependent on microfluidic channel height and the degree of PDMS bulging. The microfluidic channel with the greatest height exhibited the smallest bulging effect and was shown to be in relatively good agreement with predicted values, while the slope became much steeper than −1 as channel heights decreased.
    RSC Advances 01/2014; 4(7):3102. DOI:10.1039/c3ra46708b · 3.84 Impact Factor
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    ABSTRACT: Development of microbial and enzymatic platforms for the production of pharmaceuticals and other industrial chemicals is an important area of research. Flavonoid and isoflavonoid oxidation is of potential importance in the synthesis of active antioxidants for biological activity in human. Especially, ortho-dihydroxyisoflavones (7,8,4′-trihydroxyisoflavone, 6,7,4′-trihdyroxyisoflavone and 7,3′,4′-trihydroxyisoflavone) are a growing scientific interest to enhance their health-related quality in human. The roles of biocatalysts from microorganisms which are called as treasure islands for natural products of medicine and antibiotics are not well understood. Thus, substrate specificity study on enzymes may give a solution for elucidation their roles. In this study, it was elucidated an enzyme had substrate specificity for regiospecific multiple hydroxylation to 7,8,4′-trihydroxyisoflavone, 6,7,4′-trihdyroxyisoflavone and 7,3′,4′-trihydroxyisoflavone. We demonstrated here that the biotransformation of daidzein can be significantly improved by modulating the monooxygenase and redox partner. The studies presented here provide the basis for future strain optimization to improve ortho-dihydroxyisoflavones production.
    Biocatalysis and Agricultural Biotechnology 10/2013; 2(4):403–408. DOI:10.1016/j.bcab.2013.09.004
  • Chankyu Kang · Ruel A Overfelt · Changhyun Roh ·
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    ABSTRACT: Understanding the mechanical properties of optically transparent polydimethylsiloxane (PDMS) microchannels was essential to the design of polymer-based microdevices. In this experiment, PDMS microchannels were filled with a 100 μM solution of rhodamine 6G dye at very low Reynolds numbers (∼10(-3)). The deformation of PDMS microchannels created by pressure-driven flow was investigated by fluorescence microscopy and quantified the deformation by the linear relationship between dye layer thickness and intensity. A line scan across the channel determined the microchannel deformation at several channel positions. Scaling analysis widely used to justify PDMS bulging approximation was allowed when the applied flow rate was as high as 2.0 μl/min. The three physical parameters (i.e., flow rate, PDMS wall thickness, and mixing ratio) and the design parameter (i.e., channel aspect ratio = channel height/channel width) were considered as critical parameters and provided the different features of pressure distributions within polymer-based microchannel devices. The investigations of the four parameters performed on flexible materials were carried out by comparison of experiment and finite element method (FEM) results. The measured Young's modulus from PDMS tensile test specimens at various circumstances provided reliable results for the finite element method. A thin channel wall, less cross-linker, high flow rate, and low aspect ratio microchannel were inclined to have a significant PDMS bulging. Among them, various mixing ratios related to material property and aspect ratios were one of the significant factors to determine PDMS bulging properties. The measured deformations were larger than the numerical simulation but were within corresponding values predicted by the finite element method in most cases.
    Biomicrofluidics 09/2013; 7(5):54102. DOI:10.1063/1.4819918 · 3.36 Impact Factor
  • Changhyun Roh · Rolf D Schmid ·
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    ABSTRACT: Although the use of lipases as biocatalysts has frequently been proposed, it is yet scarcely being implemented in industrial processes. This is mainly due to the difficulties associated with the discovery and engineering of new enzymes and the lack of versatile screening methods. In this study, we screened the available strategy from a metagenomic pool for the organic solvent-tolerant lipase with enhanced performance for industrial processes. A novel lipase was identified through functional screening from a metagenomic library of activated sludge in an Escherichia coli system. The gene encoding the lipase from the metagenomic pool, metalip1, was sequenced and cloned by PCR. Metalip1 encoding a polypeptide of 316 amino acids had typical residues essential for lipase such as pentapeptide (GXSXGG) and catalytic triad sequences (Ser160, Asp260, and His291). The deduced amino acid sequence of metalip1 showed high similarity to a putative lipase from Pseudomonas sp. CL-61 (80 %, ABC25547). Metalip1 was expressed in E. coli BL21 (DE3) with a his-tag and purified using a Ni-NTA chelating column and characterized. This enzyme showed high expression level and solubility in the heterologous E. coli host. This enzyme was active over broad organic solvents. Among organic solvents examined, dimethyl formamide was the best organic solvent for metalip1. We showed that function-based strategy is an effective method for fishing out an organic solvent-tolerant lipase from the metagenomic library. Also, it revealed high catalytic turnover rates, which make them a very interesting candidate for industrial application.
    Applied biochemistry and biotechnology 09/2013; 171(7). DOI:10.1007/s12010-013-0464-z · 1.74 Impact Factor
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    ABSTRACT: The roles of cytochrome P450 monooxygenases (CYPs) from Streptomyces spp. which are called the "treasure islands" for natural products for medicine and antibiotics are not well understood. Substrate specificity studies on CYPs may give a solution for elucidation of their roles. Based on homology sequence information, the CYP105D7 of a soluble cytochrome P450 known as heme protein from Streptomyces avermitilis MA4680 was expressed using the T7 promoter of the bacterial expression vector pET24ma, over-expressed in Escherichia coli system and characterized. An engineered whole cell system for daidzein hydroxylation was constructed using an exogenous electron transport system from ferredoxin reductase (PdR) and ferredoxin (Pdx). Also, an in vitro reaction study showed the purified CYP105D7 enzyme, using NADH-dependent-reducing equivalents of a redox partner from Pseudomonas putida, hydroxylated daidzein at the 3' position of the B ring to produce 7,3,'4' trihydroxyisoflavone. The hydroxylated position was confirmed by GC-MS analysis. The turnover number of the enzyme was 0.69 μmol 7,3,'4'-trihydroxyisoflavone produced per μmol P450 per min. This enzyme CYP105D7 represents a novel type of 3'-hydroxylase for daidzein hydroxylation. A P450 inhibitor such as coumarin significantly (ca.98%) inhibited the daidzein hydroxylation activity.
    Molecules 03/2013; 18(3):3028-40. DOI:10.3390/molecules18033028 · 2.42 Impact Factor
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    Changhyun Roh · Uhee Jung ·
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    ABSTRACT: Obesity is a global health problem. It is also known to be a risk factor for the development of metabolic disorders, type 2 diabetes, systemic hypertension, cardiovascular disease, dyslipidemia, and atherosclerosis. In this study, we screened crude extracts from 400 plants to test their anti-obesity activity using porcine pancreatic lipase assay (PPL; triacylglycerol lipase, EC in vitro activity. Among the 400 plants species examined, 44 extracts from plants, showed high anti-lipase activity using 2,4-dinitrophenylbutyrate as a substrate in porcine pancreatic lipase assay. Furthermore, 44 plant extracts were investigated for their inhibition of lipid accumulation in 3T3-L1 cells. Among these 44 extracts examined, crude extracts from 4 natural plant species were active. Salicis Radicis Cortex had the highest fat inhibitory activity, whereas Rubi Fructus, Corni Fructus, and Geranium nepalense exhibited fat inhibitory capacity higher than 30% at 100 μg/mL in 3T3-L1 adipocytes, suggesting anti-obesity activity. These results suggest that four potent plant extracts might be of therapeutic interest with respect to the treatment of obesity.
    International Journal of Molecular Sciences 12/2012; 13(2):1710-9. DOI:10.3390/ijms13021710 · 2.86 Impact Factor
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    Changhyun Roh · Min-Kyoung Park · Hee-June Shin · Uhee Jung · Jin-Kyu Kim ·
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    ABSTRACT: Obesity is a global health problem. It is also known to be a risk factor for the development of metabolic disorders, type 2 diabetes, systemic hypertension, cardiovascular disease, dyslipidemia, and atherosclerosis. In this study, we elucidated that Buddleja officinalis Maximowicz extract significantly inhibited lipid accumulation during 3T3-L1 adipocyte differentiation. Furthermore, Buddleja officinalis Maximowicz extract reduced the body weight gain induced through feeding a high-fat diet to C57BL/6 mice. The treatment of Buddleja officinalis Maximowicz extract significantly reduced the adipose tissue weight to 2.7/100 g of body weight in high-fat mice. When their adipose tissue morphology was investigated for histochemical staining, the distribution of cell size in the high-fat diet groups was hypertrophied compared with those from Buddleja officinalis Maximowicz extract-treated mice. In addition, in Buddleja officinalis Maximowicz extract-treated mice, a significant reduction of serum triglyceride and T-cholesterol was observed at to 21% and 17%, respectively. The discovery of bioactive compounds from diet or dietary supplementation is one of possible ways to control obesity and to prevent or reduce the risks of various obesity-related diseases. These results support that Buddleja officinalis Maximowicz extract is expected to create the therapeutic interest with respect to the treatment of obesity.
    Molecules 12/2012; 17(7):8687-95. DOI:10.3390/molecules17078687 · 2.42 Impact Factor
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    Min-Kyoung Park · Seolhwa Kim · Uhee Jung · Insub Kim · Jin Kyu Kim · Changhyun Roh ·
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    ABSTRACT: Ionizing radiation has become an inevitable health concern emanating from natural sources like space travel and from artificial sources like medical therapies. In general, exposure to ionizing radiation such as γ-rays is one of the methods currently used to stress specific model systems. In this study, we elucidated the long-term effect of acute and fractionated irradiation on DCX-positive cells in hippocampal neurogenesis. Groups of two-month-old C57BL/6 female mice were exposed to whole-body irradiation at acute dose (5 Gy) or fractional doses (1 Gy × 5 times and 0.5 Gy × 10 times). Six months after exposure to γ-irradiation, the hippocampus was analyzed. Doublecortin (DCX) immunohistochemistry was used to measure changes of neurogenesis in the subgranular zone (SGZ) of the hippocampal dentate gyrus (DG). The number of DCX-positive cells was significantly decreased in all acute and fractionally irradiation groups. The long-term changes in DCX-positive cells triggered by radiation exposure showed a very different pattern to the short-term changes which tended to return to the control level in previous studies. Furthermore, the number of DCX-positive cells was relatively lower in the acute irradiation group than the fractional irradiation groups (approximately 3.6-fold), suggesting the biological change on hippocampal neurogenesis was more susceptible to being damaged by acute than fractional irradiation. These results suggest that the exposure to γ-irradiation as a long-term effect can trigger biological responses resulting in the inhibition of hippocampal neurogenesis.
    Molecules 12/2012; 17(8):9462-8. DOI:10.3390/molecules17089462 · 2.42 Impact Factor
  • Changhyun Roh · Min-Kyoung Park · Hee-June Shin · Insub Kim · Jin Kyu Kim · Uhee Jung ·

    12/2012; 2(4):204-210. DOI:10.3390/agriculture2030204
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    Changhyun Roh ·
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    ABSTRACT: Globally, over hundreds of million people are infected with the hepatitis C virus: the global rate of death as a direct result of the hepatitis C virus has increased remarkably. For this reason, the development of efficient drug treatments for the biological effects of the hepatitis C virus is highly necessary. We have previously shown that quantum dots (QDs)-conjugated RNA oligonucleotide can recognize the hepatitis C virus NS3 protein specifically and sensitively. In this study, we elucidated that this biochip can analyze inhibitors to the hepatitis C virus NS3 protein using a nanoparticle-based RNA oligonucleotide. Among the polyphenolic compounds examined, 7,8,4'-trihydroxyisoflavone and 6,7,4'-trihydroxyisoflavone demonstrated a remarkable inhibition activity on the hepatitis C virus NS3 protein. Both 7,8,4'-trihydroxyisoflavone and 6,7,4'-trihydroxyisoflavone attenuated the binding affinity in a concentrated manner as evidenced by QDs conjugated RNA oligonucleotide. At a concentration of 0.01 μg·mL-1, 7,8,4'-trihydroxyisoflavone and 6,7,4'-trihydroxyisoflavone showed more than a 30% inhibition activity of a nanoparticle-based RNA oligonucleotide biochip system.
    12/2012; 2(4):427-32. DOI:10.3390/bios2040427
  • Changhyun Roh · Uhee Jung · Sung-Kee Jo ·
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    ABSTRACT: Globally, one in three of the World's adults are overweight and one in 10 is obese. By 2015, World Health Organization (WHO) estimates the number of chubby adults will balloon to 2.3 billion--Equal to the combined populations of China, Europe and the United States. The discovery of bioactive compounds from herbs is one possible way to control obesity and to prevent or reduce the risks of developing various obesity-related diseases. In this study, we screened anti-obesity agents such as methyl gallate from the herbal composition known as HemoHIM that actively inhibits lipid formation as evidenced by Oil Red O staining and triglyceride (TG) contents in 3T3-L1 adipocytes, suggesting their use as an anti-obesity agent. Furthermore, the amount of glycerol released from cells into the medium had increased by treatment of methyl gallate in a concentration-dependent manner. The present study suggests that a promising anti-obesity agent like methyl gallate might be of therapeutic interest for the treatment of obesity.
    Molecules 12/2012; 17(4):3630-8. DOI:10.3390/molecules17043630 · 2.42 Impact Factor

Publication Stats

272 Citations
101.80 Total Impact Points


  • 2010-2014
    • Korea Atomic Energy Research Institute (KAERI)
      • Radiation Research Division for Biotechnology
      Daiden, Daejeon, South Korea
  • 2012
    • Auburn University
      • Department of Mechanical Engineering
      AUO, Alabama, United States
  • 2007-2010
    • Seoul National University
      • • Department of Chemical and Biological Engineering
      • • Institute of Molecular Biology and Genetics
      Sŏul, Seoul, South Korea
  • 2005-2008
    • Universität Stuttgart
      • Institute of Technical Biochemistry
      Stuttgart, Baden-Württemberg, Germany