Chung Sub Kim

Bioactive Lignans from the Trunk of Abies holophylla

Six new lignans (1-6) were isolated from the trunk of Abies holophylla MAXIM, together with 11 known lignans (7-17). The structures of 1-7 were elucidated by spectroscopic methods, acid hydrolysis, and use of the modified Moshers method. The effects of the isolates on nerve growth factor induction in a C6 rat glioma cell line were evaluated. Compounds 6, 7, and 13 showed significant induction of nerve growth factor secretion at concentrations of 10 μM. Compounds 1, 5, 6, and 16 showed moderate inhibitory effects on nitric oxide production in lipopolysaccharide-activated BV-2 cells (IC50 28.5-36.4 μM).

Chemical constituents from the roots of Cynanchum paniculatum and their cytotoxic activity

Two new steroidal saponins, cynanside A (1) and B (2) were isolated together with three known compounds (3-5) from the roots of Cynanchum paniculatum (Bunge) Kitag. The structures of 1 and 2 were elucidated on the basis of spectroscopic analyses, including extensive 2D NMR and acid hydrolysis. We evaluated the cytotoxicity of isolates (1-5) against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines in vitro using the SRB bioassay. Compounds 1 and 2 showed selective cytotoxicity against SK-MEL-2 cells with IC50 values of 26.55 and 17.36μM, respectively.

Diterpenes from the Trunk of Abies holophylla and Their Potential Neuroprotective and Anti-inflammatory Activities

Eleven new abietane-type diterpenes, holophyllins D-N (1-11), and 17 known analogues (12-28), were isolated from a MeOH extract of the trunk of Abies holophylla. The chemical structures of 1-11 were determined through spectroscopic data analysis, including NMR ((1)H and (13)C NMR, DEPT, (1)H-(1)H COSY, HMQC, HMBC, and NOESY) and HRFABMS methods. All isolated compounds (1-28) were evaluated for their cytotoxicity against four human tumor cell lines (A549, SK-OV-3, SK-MEL-2, and HCT-116), for their potential neuroprotective effects through induction of nerve growth factor in C6 glioma cells, and for their effects on nitric oxide levels in lipopolysaccharide-stimulated murine microglia BV2 cells.

A new monoacylglycerol from the fruiting bodies of Gymnopilus spectabilis

Bioassay-guided fractionation and chemical investigation of the MeOH extract of the wild mushroom Gymnopilus spectabilis resulted in the isolation of a new monoacylglycerol, together with five known compounds. The structure of the new compound (2′S) −1-O-(6,6-dimethoxyhexanol)-glycerol was elucidated on the basis of 1D and 2D NMR (1H and 13C NMR, 1H-1H COSY, HMQC and HMBC) spectroscopic data as well as chemical reactions. The known compounds were identified by comparison of their spectroscopic and physical data with the reported values. The metabolites were evaluated for their anti-proliferative activities against four human tumour cell lines (A549, SK-OV-3, SK-MEL-2 and HCT-15) and for their inhibitory effects on nitric oxide production in lipopolysaccharide (LPS)-activated murine microglial cells.

Lignan Glycosides from the Twigs of Chaenomeles sinensis and Their Biological Activities

Phytochemical investigation of the twigs of Chaenomeles sinensis led to the isolation and identification of six new lignan glycosides, chaenomiside A-F (1-6), along with five known ones (7-11). Their chemical structures were determined by spectroscopic methods, including NMR, MS, ECD, and GC/MS analyses. All the isolated compounds (1-11) were tested for their inhibitory effects on nitric oxide (NO) production in lipopolysaccharide-activated murine microglial cells and the secretion of nerve growth factor (NGF) in a C6 rat glioma cell line. Compound 6 significantly reduced NO levels in the murine microglia BV2 cells with an IC50 value of 21.3 μM, and compounds 1, 3, and 6 were potent stimulants of NGF release with stimulation levels of 151.74 ± 6.77%, 144.31 ± 7.49%, and 167.61 ± 18.5%, respectively.

Cytotoxic and anti-inflammatory disulfide compounds from the fruiting bodies of Boletus pseudocalopus.

Cytotoxic and anti-inflammatory disulfide compounds from the fruiting bodies of Boletus pseudocalopus

Five New Oxylipins from Chaenomeles sinensis

In the course of our continuing search for bioactive constituents of Korean medicinal plants, we isolated five new oxylipins, chaenomic acid A–E (1–5), and six known ones (6–11) from the twigs of Chaenomeles sinensis. The structures of the new compounds (1–5) were determined by spectroscopic methods, including 1D and 2D NMR (1H and 13C NMR, 1H–1H COSY, HMQC, HMBC, and NOESY), olefin cross-metathesis, and LC/MS analysis. The known compounds (6–11) were identified by comparison of their spectroscopic data and specific optical rotation with the reported data. The isolated compounds (1–11) were tested for their inhibitory effects on nitric oxide production in lipopolysaccharide-activated murine microglial cells and for their cytotoxic activities against four human cancer cell lines (A549, SK-OV-3, A498, and HCT-15).

Cytotoxic steroids from the trunk of Berberis koreana.

A new steroid, itesmol 3-O-palmitate (1), along with two known steroids were isolated from the trunk of Berberis koreana. The structure of 1 was determined on the basis of spectroscopic analyses involving 2D NMR and chemical reactions. Compound 1 exhibited potential antiproliferative activity against A549, SK-OV-3, SK-MEL-2, and HCT-15 cell lines (respective IC50 values of 7.41, 9.20, 4.53, and 12.91 μM).

Phenolic Compounds from the Leaves of Stewartia pseudocamellia Maxim. and their Whitening Activities.

The half-dried leaves of Stewartia. pseudocamellia were extracted with hot water (SPE) and partitioned with n-hexane (SPEH), dichloromethane (SPED), and ethyl acetate (SPEE) successively. SPE and SPEE showed significant inhibitory effects against melanogenesis and tyrosinase activities. By bioassay-guided isolation, ten phenolic compounds were isolated by column chromatography from SPEE. The whitening effect of the isolated compounds from SPEE were tested for the inhibitory activities against melanogenesis using B16 melanoma cells, in vitro inhibition of tyrosinase, and L-3,4-dihydorxy-indole-2-carboxylic acid (L-DOPA) auto-oxidation assay. A cytotoxic activity assay was done to examine the cellular toxicity in Raw 264.7 macrophage cells. Of the compounds isolated, gallic acid and quercetin revealed significant inhibitory activities against melanogenesis compared to arbutin. In particular, quercetin exhibited similar inhibitory activities against tyrosinase and L-DOPA oxidation without cytotoxicity. These results suggested that SPE could be used as a potential source of natural skin-whitening material in cosmetics as well as in food products.

Identification of new quinic acid derivatives as histone deacetylase inhibitors by fluorescence-based cellular assay.

A fluorescence-based cellular assay system was established to identify potential epigenetic modulator ligands. This assay method is to detect the de-repression of an EGFP reporter in cancer cells by the treatment of HDAC (histone deacetylase) or DNMT (DNA methyltransferase) inhibitor. Using this system, we conducted a preliminary screening of in-house natural product library containing extracts and pure compounds, and identified several active compounds. Among them, novel quinic acid derivatives were recognized as excellent HDAC inhibitors by both enzymatic and cell-based HDAC assays.