• Journal of the Korean Wood Science and Technology
• /
• v.33 no.2 s.130
• /
• pp.72-77
• /
• 2005

Streptococcus mutans is known as a strong cariogenic bacterium and produces dental caries. This study was carried out to develop anticariogenic agents from Callistemon citrinus. Crude extracts and thier various solvent fractions of the plant extracts were tested for the antibacterial activity against S. mutans. The anticariogenic activity was evaluated with by paper disc diffusion method and minimal inhibition concentration (MIC). The extract from the fruit and its hexane fraction showed a strong inhibitory effect on the growth of S. mutans and the MICs were 31.2 and $3.9{\mu}g/m{\ell}$, respectively.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.11
• /
• pp.3340-3344
• /
• 2013

The fabrication of polymer field-effect transistors with good electrical properties requires the minimization of molecular defects caused by low molecular weight (MW) fractions of a conjugated polymer. Here we report that the electrical properties of a narrow bandgap conjugated polymer could be dramatically improved as a result of dipping a thin film into a poor solvent. The dipping time in hexanes was controlled to efficiently eliminate the low molecular weight fractions and concomitantly improve the molecular ordering of the conjugated polymer. The correlation between the structural order and the electrical properties was used to optimize the dipping time and investigate the effects of the low MW fraction on the electrical properties of the resulting thin film.

• Archives of Pharmacal Research
• /
• v.16 no.3
• /
• pp.180-185
• /
• 1993

The acid dissociation constants of certain Schiff bases derived from isatin with p-substituted benzoyl hydrazines and somee amino acids of glycine, $\beta$-and $\alpha$-alanine, valine, $\beta$-phenyl-$\alpha$-alanine and anthranilic acid have been detemined potentiometrically at different temperatures in different aquo-organic solvent mixtures (ethnol, dioxane, dimethyl formamide, methanol, acetone and tetrahydrofurance). The pKa values were demonstrated on the light of the different electornic and steric effects of the substituents and the sovlent characteristics. In all the mixed media used, ionization of the compounds decreased by increasing the mole fraction of the organic cosolvent. Theemodynamic parameters $(\Delta{H}^\circ,\;\Delta{G}^\circ,\;\Delta{S}^\circ)$ were evaluated. The structural effects of the investigated compounds on these parameters were reported and discussed.

• YAKHAK HOEJI
• /
• v.58 no.1
• /
• pp.47-52
• /
• 2014

Clematis mandshurica (Ranunculaceae) has traditionally been used as a remedy for antidiuretic, antifungal, rheumatic conditions and alleviate pain. We carried out to evaluate the anti-oxidative effect, anti-inflammatory effect and anti-melanogenic effect of ethanol extract and solvent fractions of Clematis mandshurica. The ethanol extract and the dichloromethane fraction of Clematis mandshurica showed an anti-oxidative effect in DPPH assay, the inhibitory activity of nitric oxide (NO) production in lipopolysaccharide (LPS) activated RAW 264.7 cell, and melanin synthesis and tyrosinase activity of B16F10 melanoma cells. They reduced NO production and melanin content in a dose-dependent manner at concentrations of $2.5{\sim}10{\mu}g/ml$. They also suppressed iNOS and tyrosinase protein and m-RNA expressions dose dependently, assayed by western blot analysis and RT-PCR experiment.

• YAKHAK HOEJI
• /
• v.45 no.5
• /
• pp.484-490
• /
• 2001

Mylabris phalerata(MP) is an insect that has been used for the treatment of cancer in oriental medicine. To evaluate the anticancer activity of Mylabris phalerata, We measured the cytotoxicity of Mylabris phalerata solvent fractions such as MC, EA, BuOH and residual layers on U937, human monocytic leukemia cells. Of those fractions BuOH layer of Mylabris phalerata was the most effective with ID$_{50}$ of 140$\mu\textrm{g}$/ml. It effectively caused DNA fragmentation from the concentration of 50$\mu\textrm{g}$/ml, showed apoptotic nucleus by tenets assay and expressed apototic portion stained by Annexin-V. It also induced the activation of caspase-3 and cleavage of the substrate poly (ADP-ribose) polymerase (PARP). These results suggest BuOH layer of Mylabris phalerata exerts anticancer activity by induction of apoptosis via activation of caspase-3 protease.e.

• Journal of the Korean Ceramic Society
• /
• v.50 no.4
• /
• pp.294-300
• /
• 2013

The effect of chemical treatments of porous silicon in organic solvents on its nanostructural and optical features was investigated. When the porous Si was dipped in the organic solvent with various PH values, the morphological, chemical, and structural properties of the porous silicon was sensitively affected by the chemical conditions of the solvents. The size of silicon nanocrystallites in the porous silicon decreased from 5.4 to 3.1 nm with increasing pH values from 1 to 14. After the samples were dipped in the organic solvents, the Si-O-H bonding intensity was increased while that of Si-H bonding decreased. Photoluminescence peaks shifted to a shorter wavelength region in the range of 583 to 735 nm as the pH value increased. PL intensity was affected by the size as well as the volume fraction of the nanocrystalline silicon in the porous silicon.

• Bulletin of the Korean Chemical Society
• /
• v.16 no.1
• /
• pp.42-47
• /
• 1995

Interpolymer complex formation between basic polypeptide poly(L-proline) Form Ⅱ (PLP(Ⅱ)) and acidic polypeptides poly(L-glutamic acid) (PLGA) and poly(L-aspartic acid)(PLAA) has been studied in water-methanol (1:2 v/v) mixed-solvent by viscometry, potentiometry, light scattering and circular dichroism (CD) measurements. It has been found that polymer complexes between PLP(Ⅱ) and PLGA (or PLAA) are formed via hydrogen bonding with a stoichiometric ratio of PLP(Ⅱ)/PLGA (or PLAA)=1:2 (in unit mole ratio) and that PLP(Ⅱ) forms polymer complex more favorably with PLGA than with PLAA. In addition, the minimum (for pH 5.0) and the maximum (for pH 3.2) in reduced viscosity of dilute PLP(Ⅱ)-PLGA mixed solutions are observed at 0.67 unit mole fraction of PLGA (i.e., [PLP(Ⅱ)]/[PLGA]=1/2). These findings could be explained in terms of molecular structure (or conformation) of the complementary polymers associated with the complex formation.

• Proceedings of the PSK Conference
• /
• 2003.04a
• /
• pp.259.2-259.2
• /
• 2003

This study was carried out to isolate and to identify the compounds and to find out antioxidants from the leaf of Distylium racemosum which belongs to Hamamelidaceae family. To isolate compounds, leaf of this plant were extracted with 50％ Acetone and then crude extracts was partitioned with hexane. ether and ethyl acetate (EtOAc) successively. After partitioned, EtOAc fraction was subjected to column chromatography with various solvent systems in silica gel and/or Sephadex LH-20. (omitted)

• Proceedings of the PSK Conference
• /
• 2002.10a
• /
• pp.300.1-300.1
• /
• 2002

From 4 fractions as n-hexane (yield. 0.09%), EtOAc (0.48%). BuOH (3, 0%) and H2O (5.17%) fraction from MeOH extract (11, 64%) of powdered Gastrodia elata Rhizoma (GER) for the activity-guided separation on anti-inflammatory action. some biological active agents were isolated by column chromatography (column. silica gel: elution solvent. CHCl3 : MeOH) according to the method of Junko Hayashi et. al. and Heihachiro Taguchi et. al. Compound I, II, III, IV, V as phenolic derivatives were isolated in the EtOAc and BuOH fractions. (omitted)

• Journal of the Korean Wood Science and Technology
• /
• v.31 no.3
• /
• pp.30-34
• /
• 2003

This study was carried out to investigate the constituents of Platycarya strobilacea (Juglandaceae) wood. To isolate compounds, wood was extracted with ethanol (EtOH) and then partitioned with petroleum ether, diethyl ether (Et₂O) and ethyl acetate (EtOAc) successively. After partitioned, diethyl ether fraction was subjected to column chromatography with various solvent system in silica gel and/or Sephadex LH-20. Structures were elucidated by spectroscopic methods including MS, ¹H, ¹³C and 2D-NMR experiments. Three compounds were isolated from the wood and identified as kaempferol 3-O-𝛼-L-rhamnopyranoside (afzelin, I), quercetin 3-O-𝛼-L-rhamnopyranoside (quercitrin, II), myricetin 3-O-𝛼-L-rhamnopyranoside (myricitrin, III).