Hoon Huh

Trimeric Cinchona alkaloid phase-transfer catalyst: α,α′,α′′-tris[O(9)-allylcinchonidinium]mesitylene tribromide

A trimeric Cinchona alkaloid ammonium salt, α,α′,α′′-tris[O(9)-allylcinchonidinium]mesitylene tribromide has been prepared as a novel phase-transfer catalyst. The catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using the trimer catalyst showed high enantioselectivity (90–97% ee).

Inhibition of HIV-1 reverse transcriptase and HIV-1 integrase and antiviral activity of Korean seaweed extracts

Forty-seven species of marine macroalgae from the coast of Korea havebeen screened for the presence of inhibitory compounds against humanimmunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) and HIV-1integrase (IN). One of 4 Chlorophyta, 8 of 17 Phaeophyta and 6 of 26 Rhodophytashowed inhibitory activity against HIV-1 reverse transcriptase. Five species(Ecklonia cava, Ishige okamurae,Sargassum confusum, Sargassumhemiphyllum, Sargassum ringgoldianum) belongingto Phaeophyta showed to inhibit the 3′-processing activity of HIV-1integrase. In cell-based assays, the methanol extracts ofBossiella sp. and Chondriacrassicaulis inhibited cytopathogenecity of HIV-1 at a concentrationbelow that cytotoxic for MT4 cells.

Immunomodulating activity of a polysaccharide isolated from mori cortex radicis

The immunomodulating activity of a polysaccharide isolated fromMorus alba (PMA) root bark was examined in murine splenic lymphocytes. PMA enhanced proliferation of splenic lymphocytes in a synergistic manner in the presence of mitogens. However, PMA suppressed primary IgM antibody production, from B cells, which was activated with lipopolysaccharide, a polyclonal activator, or immunized with a T-cell dependent antigen sheep red blood cells. Our observations showed that the immunomodulating activity of PMA increased lymphocyte proliferation and that PMA decreased antibody production from B cells, which was distinct from those of other plant-originated polysaccharides.

HIV integrase inhibitory activity ofAgastache rugosa

We have been screening anti-HIV integrase compounds from Korean medicinal plants by using anin vitro assay system which is mainly composed of recombinant human immunodeficency virus type 1 integrase and radiolabeled oligonucleotides. From the above screening, the aqueous methanolic extract of the roots ofAgastache rugosa exhibited a significant activity. Bioactivity-guided chromatographic fractionation of the methanolic extract resulted in the isolation of rosmarinic acid. The structure of the compound was determined by spectroscopic data and by the comparison with the reported values. The IC50 of the rosmarinic acid was approximately 10 μ/ml against HIV integrase.

An antiviral furanoquinone from Paulownia tomentosa Steud.

A methanol extract of the stem bark of Paulownia tomentosa showed antiviral activity against poliovirus types 1 and 3. Sequential liquid–liquid extraction with n‐hexane, chloroform and water, and a silicagel column chromatography resulted in the purification of a compound. The compound was identified as methyl‐5‐hydroxy‐dinaphthol[1,2–2′,3′]furan‐7,12‐dione‐6‐carboxylate on the basis of spectroscopic data. The component caused a significant reduction of viral cytopathic effect when it was subjected to a standard antiviral assay by using HeLa cells. The EC50 of the compound against poliovirus type 1 strain Brunhilde, and type 3 strain Leon were 0.3 µg/mL and 0.6 µg/mL, respectively. Copyright

Purification and characterization of Moran 20K fromMorus alba

A new glycoprotein was purified from the aqueous methanolic extract of the root bark ofMorus alba which has been used as a component of antidiabetic remedy in Oriental Medicine. SDS-PAGE result shows that the molecular weight of the glycoprotein was approximately 20 kDa. This new glycoprotein was named as Moran 20K. The protein lowered blood glucose level in streptozotocin-induced hyperglycemic mice model and it also increased the glucose transport in cultured epididymis fat cells. The amino acid composition of the protein was analyzed, and the protein contained above 20% serine and cysteine such as insulin. The actual molecular weight of the protein was determined as 21,858 Da by MALDI-TOF mass spectroscopy.

Antihepatotoxic zeaxanthins from the fruits ofLycium chinense

A CHCl3: MeOH extract of the fruit ofLycium chinense Mill. (Solanaceae) was found to afford significant protection against carbon tetrachloride-induced toxicity in primary cultures of rat hepatocytes. Subsequent activity-guided fractionation resulted in the isolation of zeaxanthin and zeaxanthin dipalmitate as antihepatotoxic components. Incubation of injured hepatocytes with zeaxanthin dipalmitate reduced the levels of glutamic pyruvic transaminase (GPT) and sorbitol dehydrogenase (SDH) released from damaged cells to 60.5% and 76.3% of those released from untreated controls, respectively. Zeaxanthin also reduced the levels of GPT and SDH to 68.5% and 61.3% of the levels of those released from the untreated control. The results confirm the hepatoprotective activities of zeaxanthins. Antihepatotoxic activities of zeaxanthins are comparable to that of silybin.

Synthesis and application of dimeric Cinchonaalkaloid phase-transfer catalysts:α,α′-bis[O(9)-allylcinchonidinium]-o,m, or p-xylene dibromide

A dimeric Cinchona alkaloid ammonium salt, α,α′-bis[O(9)-allylcinchonidinium]-m-x ylene dibromide 4, has been developed as a new efficient phase-transfer catalyst; the catalytic enantioselective alkylation of N-(diphenylmethylene)glycine tert-butyl ester using 4 provided 7 in a high enantiomeric excess (90–99% ee).

Production of a hepatoprotective cerebroside from suspension cultures of Lycium chinense

Abstract Suspension cultures derived from Lycium chinense Miller seedlings produced significant amounts of a hepatoprotective cerebroside. Callus was induced from the stem of aseptic seedlings of L. chinense and maintained on MS solid media supplemented with 1.0 ppm 2,4-D and 0.1 ppm kinetin. Suspension cultures were established, and the cells were grown in the same liquid media in the dark. Lyophilized cells were extracted with a combined reagent of chloroform and methanol (2:1, v/v). An aqueous suspension of the evaporated cell extract was partitioned with chloroform, and the chloroform layer was subjected to silicic acid column chromatography followed by semi-preparative reverse phase C8 high pressure liquid chromatography. The purified compound showed hepatoprotective activity comparable to that shown by silymarin, and the structure was identified as 1-O-(β-d-glucopyranosyl)-(2S,3R,4E,8Z)-2-N-2′-hydroxy-(palmitoyl)-4,8-sphingadiene on the basis of spectral data. The content of the compound in cultured cell was tenfold higher than that of the fruit of L. chinense. The biosynthesis of the compound in cultured cell systems appears to parallel cell growth.

Ginkgolide B production in cultured cells derived from Ginkgo biloba L. leaves

Callus cultures and cell suspension cultures derived from Ginkgo biloba L. leaves produced ginkgolidc B. In cell suspension cultures, the production reached a maximum by the 13th day of subculture and followed by a sharp decrease. The medium of Murashige and Skoog induced the highest ginkgolide B content in cultures while the medium of Schenk and Hildebrandt promoted cell growth. For the maximal production of ginkgolide B, cells were cultured in Murashige and Skoog medium modified to contain 1.0 mg/l of α-naphthaleneacetic acid, 0.1 mg/1 of kinetin, 30 g/1 sucrose and 1.25 mM potassium phosphate with a molar ratio of ammonium to nitrate ions of 1 ∶ 3.