Phytochemical studies on the leaves of Ailanthus altissima (Simaroubaceae) have not been reported... more Phytochemical studies on the leaves of Ailanthus altissima (Simaroubaceae) have not been reported previously. Thus, the authors isolated and identified secondary metabolites from A. altissima. Dried and powdered leaves were extracted with 80% aqueous methanol, and the concentrated extract was successively partitioned with ethyl acetate, n-butanol, and water. Four flavonoids were isolated from the ethyl acetate fraction through repeated silica gel and octadecyl silica gel column chromatography. Spectroscopic data including NMR, MS, and IR allowed for identification of the chemical structures as quercetin (1), afzelin (2), quercitrin (3), and isoquercitrin (4). This is the first report of the isolation of these compounds from A. altissima. The four isolated flavonoids 1-4 as well as solvent fractions (ethyl acetate, n-butanol, and water), were evaluated for DPPH radical scavenging activity.
International journal of molecular sciences, Jan 13, 2014
Three minor ginsenosides, namely, ginsenoside Rh6 (1), vina-ginsenoside R4 (2) and vina-ginsenosi... more Three minor ginsenosides, namely, ginsenoside Rh6 (1), vina-ginsenoside R4 (2) and vina-ginsenoside R13 (3), were isolated from the leaves of hydroponic Panax ginseng. The chemical structures were determined based on spectroscopic methods, including fast atom bombardment mass spectroscopy (FAB-MS), 1D-nuclear magnetic resonance (NMR), 2D-NMR, and, infrared (IR) spectroscopy. The melanogenic inhibitory activity of compounds 1, 2 and 3 was 23.9%, 27.8% and 35.2%, respectively, at a concentration of 80 µM. Likewise, the three compounds showed inhibitory activity on body pigmentation on a zebrafish model, which is commonly used as a model for biomedical or cosmetic research. These results from in vitro and in vivo systems suggest that the three aforementioned compounds isolated from Panax ginseng may have potential as new skin whitening compounds.
We investigated the optimum flow channel design for direct methanol fuel cells (DMFCs). Especiall... more We investigated the optimum flow channel design for direct methanol fuel cells (DMFCs). Especially, we explored the effect of the pressure drop across the inlet and outlet on the performance of the DMFCs with various flow channel designs. In DMFC systems, the optimization of such parameters are critical to minimize the power usage by the auxiliary devices, such as fuel pump and blowers. In this paper, we present how the pressure drop control may determine the optimal driving point of the DMFC stack. Also, we show how the optimal fuel utilization ratio may be achieved, without degrading the performance of DMFC stacks. Overall, we discuss how the flow channel design affects the selection of the balance of plant (BOP) components, the design of the DMFC system, and the efficiency of the entire system.
ABSTRACT In order to identify secondary metabolites, the root of Brassica rapa was extracted with... more ABSTRACT In order to identify secondary metabolites, the root of Brassica rapa was extracted with 80% aqueous MeOH, and the concentrated extract was partitioned with EtOAc, n-BuOH and . From the EtOAc and n-BuOH fractions, four secondary metabolites were isolated through the repeated silica gel and octadecyl silica gel (ODS) column chromatographies. From the result of spectroscopic data including NMR and MS, the chemical structures of the compounds were determined as 4-(methoxymethyl)phenol (1), -methoxy-2,5-furandimethanol (2), phenyl--D-glucopyranoside (3), and 2-phenylethyl--D-glucopyranoside (4). They were isolated for the first time from Brassica rapa.
ABSTRACT Nepalese sumac (Rhus parviflora) is a wild edible fruit used for the treatment of variou... more ABSTRACT Nepalese sumac (Rhus parviflora) is a wild edible fruit used for the treatment of various ailments including neurological complications and stomach disorders in the traditional medicinal system of south Asia (Ayurveda). Four flavonoids were isolated from ethyl acetate (EtOAc) fraction of Nepalese sumac fruits and their chemical structures were determined on the basis of NMR, fast atom bombardment mass spectrometry (FAB/MS), and IR. The efficiency of isolated compounds in attenuating glutamateinduced cell death in an immortalized mouse hippocampal cell line (HT-22) and inhibition of cycline dependent kinase 5 (Cdk5) were investigated. Among the compounds, flavanols, fustin (1) and taxifolin (2), an aurone, aureusidin (3), and a biflavonoid, agathisflavone (4) were found to have protective effect against glutamate induced oxidative injury in HT22 cells. Aureusidin (3), a Cdk5/p25 inhibitor (IC50 3.5 μM), was the most potent neuroprotector with an EC50 value of 11.90 μM.
Chrysoeriol-7-O-β-d-glucopyranoside (1), luteolin-7-O-β-d-glucopyranoside (2), quercetin-3-O-β-d-... more Chrysoeriol-7-O-β-d-glucopyranoside (1), luteolin-7-O-β-d-glucopyranoside (2), quercetin-3-O-β-d-glucopyranoside (3), quercetin-3-O-β-d-galactopyranoside (4), and quercetin-3-O-α-l-rhamnopyranoside (5) were isolated for the first time from the fruits of Rhus parviflora. The chemical structures of the compounds were determined using nuclear magnetic resonance, fast atom bombardment mass spectrometry, and infrared spectroscopy. Compound 4 (hyperin) inhibited cyclin dependent kinases (CDK2 and CDK5) in vitro with IC50 values of 21.02 and 10.28 μM, respectively.
Phytochemical studies on the leaves of Ailanthus altissima (Simaroubaceae) have not been reported... more Phytochemical studies on the leaves of Ailanthus altissima (Simaroubaceae) have not been reported previously. Thus, the authors isolated and identified secondary metabolites from A. altissima. Dried and powdered leaves were extracted with 80% aqueous methanol, and the concentrated extract was successively partitioned with ethyl acetate, n-butanol, and water. Four flavonoids were isolated from the ethyl acetate fraction through repeated silica gel and octadecyl silica gel column chromatography. Spectroscopic data including NMR, MS, and IR allowed for identification of the chemical structures as quercetin (1), afzelin (2), quercitrin (3), and isoquercitrin (4). This is the first report of the isolation of these compounds from A. altissima. The four isolated flavonoids 1-4 as well as solvent fractions (ethyl acetate, n-butanol, and water), were evaluated for DPPH radical scavenging activity.
International journal of molecular sciences, Jan 13, 2014
Three minor ginsenosides, namely, ginsenoside Rh6 (1), vina-ginsenoside R4 (2) and vina-ginsenosi... more Three minor ginsenosides, namely, ginsenoside Rh6 (1), vina-ginsenoside R4 (2) and vina-ginsenoside R13 (3), were isolated from the leaves of hydroponic Panax ginseng. The chemical structures were determined based on spectroscopic methods, including fast atom bombardment mass spectroscopy (FAB-MS), 1D-nuclear magnetic resonance (NMR), 2D-NMR, and, infrared (IR) spectroscopy. The melanogenic inhibitory activity of compounds 1, 2 and 3 was 23.9%, 27.8% and 35.2%, respectively, at a concentration of 80 µM. Likewise, the three compounds showed inhibitory activity on body pigmentation on a zebrafish model, which is commonly used as a model for biomedical or cosmetic research. These results from in vitro and in vivo systems suggest that the three aforementioned compounds isolated from Panax ginseng may have potential as new skin whitening compounds.
We investigated the optimum flow channel design for direct methanol fuel cells (DMFCs). Especiall... more We investigated the optimum flow channel design for direct methanol fuel cells (DMFCs). Especially, we explored the effect of the pressure drop across the inlet and outlet on the performance of the DMFCs with various flow channel designs. In DMFC systems, the optimization of such parameters are critical to minimize the power usage by the auxiliary devices, such as fuel pump and blowers. In this paper, we present how the pressure drop control may determine the optimal driving point of the DMFC stack. Also, we show how the optimal fuel utilization ratio may be achieved, without degrading the performance of DMFC stacks. Overall, we discuss how the flow channel design affects the selection of the balance of plant (BOP) components, the design of the DMFC system, and the efficiency of the entire system.
ABSTRACT In order to identify secondary metabolites, the root of Brassica rapa was extracted with... more ABSTRACT In order to identify secondary metabolites, the root of Brassica rapa was extracted with 80% aqueous MeOH, and the concentrated extract was partitioned with EtOAc, n-BuOH and . From the EtOAc and n-BuOH fractions, four secondary metabolites were isolated through the repeated silica gel and octadecyl silica gel (ODS) column chromatographies. From the result of spectroscopic data including NMR and MS, the chemical structures of the compounds were determined as 4-(methoxymethyl)phenol (1), -methoxy-2,5-furandimethanol (2), phenyl--D-glucopyranoside (3), and 2-phenylethyl--D-glucopyranoside (4). They were isolated for the first time from Brassica rapa.
ABSTRACT Nepalese sumac (Rhus parviflora) is a wild edible fruit used for the treatment of variou... more ABSTRACT Nepalese sumac (Rhus parviflora) is a wild edible fruit used for the treatment of various ailments including neurological complications and stomach disorders in the traditional medicinal system of south Asia (Ayurveda). Four flavonoids were isolated from ethyl acetate (EtOAc) fraction of Nepalese sumac fruits and their chemical structures were determined on the basis of NMR, fast atom bombardment mass spectrometry (FAB/MS), and IR. The efficiency of isolated compounds in attenuating glutamateinduced cell death in an immortalized mouse hippocampal cell line (HT-22) and inhibition of cycline dependent kinase 5 (Cdk5) were investigated. Among the compounds, flavanols, fustin (1) and taxifolin (2), an aurone, aureusidin (3), and a biflavonoid, agathisflavone (4) were found to have protective effect against glutamate induced oxidative injury in HT22 cells. Aureusidin (3), a Cdk5/p25 inhibitor (IC50 3.5 μM), was the most potent neuroprotector with an EC50 value of 11.90 μM.
Chrysoeriol-7-O-β-d-glucopyranoside (1), luteolin-7-O-β-d-glucopyranoside (2), quercetin-3-O-β-d-... more Chrysoeriol-7-O-β-d-glucopyranoside (1), luteolin-7-O-β-d-glucopyranoside (2), quercetin-3-O-β-d-glucopyranoside (3), quercetin-3-O-β-d-galactopyranoside (4), and quercetin-3-O-α-l-rhamnopyranoside (5) were isolated for the first time from the fruits of Rhus parviflora. The chemical structures of the compounds were determined using nuclear magnetic resonance, fast atom bombardment mass spectrometry, and infrared spectroscopy. Compound 4 (hyperin) inhibited cyclin dependent kinases (CDK2 and CDK5) in vitro with IC50 values of 21.02 and 10.28 μM, respectively.
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Papers by Dae-young Lee