Myoung-Chong Song

Enzymatic synthesis of salicin glycosides through transglycosylation catalyzed by amylosucrases from Deinococcus geothermalis and Neisseria polysaccharea

Amylosucrase (ASase, EC 2.4.1.4) is a member of family 13 of the glycoside hydrolases that catalyze the synthesis of an alpha-(1-->4)-linked glucan polymer from sucrose instead of an expensive activated sugar, such as ADP- or UDP-glucose. Transglycosylation reactions mediated by the ASases of Deinococcus geothermalis (DGAS) and Neisseria polysaccharea (NPAS) were applied to the synthesis of salicin glycosides with sucrose serving as the glucopyranosyl donor and salicin as the acceptor molecule. Two salicin glycoside transfer products were detected by TLC and HPLC analyses. The synthesis of salicin glycosides was very efficient with NPAS with a yield of over 90%. In contrast, DGAS specifically synthesized only one salicin transglycosylation product. The transglycosylation products were identified as alpha-d-glucopyranosyl-(1-->4)-salicin (glucosyl salicin) and alpha-D-glucopyranosyl-(1-->4)-alpha-D-glucopyranosyl-(1-->4)-salicin (maltosyl salicin) by NMR analysis. The ratio between donor and acceptor had a significant effect on the type of product that resulted from the transglycosylation reaction. With more acceptors present in the reaction, more glucosyl salicin and less maltosyl salicin were synthesized.

Lignans from the fruits of cornus kousa burg. and their cytotoxic effects on human cancer cell lines

The fruits of Cornus kousa Burg. were extracted with 80% aqueous MeOH, and the concentrated extract partitioned with EtOAc, n-BuOH and H2O. Six lignans were isolated from the EtOAc fraction through repeated silica gel, ODS and Sephadex LH-20 column chromatographies. From the physico-chemical data, including NMR, MS and IR, the chemical structures of the compounds were determined to be (+)-pinoresinol (1), (-)-balanophonin (2), (+)-laricresinol (3), erythro-guaiacylglycerol-β-coniferyl aldehyde ether (4), threo-guaiacylglycerol-β-coniferyl aldehyde ether (5) and dihydrodehydrodiconiferyl alcohol (6), which were isolated for the first time from this plant. Most of these compounds showed cytotoxicity against human colon carcinoma (HCT-116) and human hepatocellular carcinoma (HepG2) cell lines in vitro, with IC50 values ranging from 19.1 to 71.3 μg/mL.

Cytotoxic and ACAT-inhibitory sesquiterpene lactones from the root ofIxeris dentata formaalbiflora

Ixeris dentata formaalbiflora was extracted with 80% aqueous MeOH, and the concentrated extract was partitioned with EtOAc,n-BuOH and H2O. Eight sesquiterpenes were isolated through repeated silica gel and octadecyl silica gel (C18, ODS) column chromatography of the EtOAc andn-BuOH fractions. Physicochemical analysis using NMR, MS and IR revealed the chemical structures of the sesquiterpenes, which were zaluzanin (1), 9a-hydroxyguaian-4(15), 10(14), 11(13)-triene-6, 12-olide (2), 3β-O-β-D-glucopyranosyl-8β-hydroxyguaian-4(15), 10(14)-diene-6,12-olide (3), 3-O-β-D-glucopyranosyl-8β-hydroxyguauan-10(14)-ene-6,12-olide (4), ixerinM (5), glucozaluzanin C (6), crepiside I (7), and ixerin D (8). This is the first time that these sesquiterpene lactones have been isolated from this plant. Compounds1, 2 and7 revealed relatively high cytotoxicities on human colon carcinoma cell and lung adenocarcinoma cell, while compounds5 and7 showed acyl-CoA: cholesterol acyltransferase (ACAT) inhibitory activity.

Heterocyclic compounds from Chrysanthemum coronarium L. and their inhibitory activity on hACAT-1, hACAT-2, and LDL-oxidation

The aerial parts of Chrysanthemum coronarium L. were extracted with MeOH, and the concentrated extract was partitioned using EtOAc, n-BuOH, and H2O, successively. Repeated column chromatography of the EtOAc and n-BuOH fractions gave a new heterocycle, 5,5′-dibuthoxy-2,2′-bifuran (1) along with five known compounds: methyl trans-ferulate (2), prunasin (3), sambunigrin (4), pterolactam (5), and adenosine (6), which were identified by several spectroscopic methods including NMR and MS. This paper is the first report on the isolation of these compounds from C. coronarium L. The IC50 values of compound 1 for human Acyl-CoA:cholesterol acyltransferase (hACAT)-1 and hACAT-2 were 0.16 mM and 0.19 mM, respectively. Compound 2 inhibited low-density lipoprotein (LDL) oxidation with an IC50 value of 7.7 μM.

Antioxidant and antiatherogenic activity ofcis-hinokiresinol fromTrapa pseudoincisa

Abstractcis-Hinokiresinol, also known as (+)-nyasol, was isolated for the first time from an aquatic herbaceous plant,Trapa pseudoincisa NAKAI, via silica gel and octadecyl silica gel column chromatographies. The chemical structure was determined via analyses of the spectroscopic data, including NMR, MS and IR. cis-Hinokiresinol was also found to exhibit antioxidant and antiatherogenic activities. The IC50 values for the scavenging activities of cis-hinokiresinol on ABTS cation and superoxide anion radicals were 45.6 and 40.5 μM, respectively. The IC50 values for the inhibitory effects on Lp-PLA2, hACAT1, hACAT2 and LDL-oxidation were 284.7, 280.6, 398.9 and 5.6 μM, respectively.

A new lignan glycoside from the rhizomes of Imperata cylindrica

A new lignan glycoside, 6-acetyl-1-[1,3-(4,4′-dihydroxy-3,3′-dimethoxy-β-truxinyl)-β-d-fructofuranosyl]-α-d-glucopyranoside (1), named impecyloside, was isolated from the rhizomes of Imperata cylindrica. The structure of the compound was determined by spectroscopic data including FABMS, UV, IR, 1H NMR and 13C NMR (DEPT) and 2D NMR (COSY, HSQC, HMBC).

Screening and isolation of a natural dopamine D1 receptor antagonist using cell-based assays.

To develop a cell-based assay to screen for human dopamine D(1) receptor agonists or antagonists from medicinal plant extracts, a stable Chinese hamster ovary (CHO) cell line (CHO-D1R) expressing the human dopamine D(1) receptor was established using an expression vector containing a scaffold attachment region (SAR) element. CHO-D1R cells showed specific binding to [(3)H]-SCH23390 with high affinity (K(d)=1.47+/-0.17 nM) and dose-dependent responses for the dopamine-mediated stimulation of cAMP concentrations (EC(50)=20.6+/-1.44 nM). The screening of medicinal plant extracts using cell-based cAMP assays revealed that an extract of Gleditsia sinensis Lam., which is known to be rich in saponin, had strong antagonist activity for the D(1) receptor. From the activity-guided fractionation and chemical structural analysis of the G. sinensis extract, a compound called gleditsioside F was isolated and was identified to have antagonist activity for the D(1) receptor. Gleditsioside F showed very effective D(1) antagonist activity by inhibiting ligand binding to the D(1) receptor as well as by inhibiting dopamine-mediated increases in cAMP concentration.