Kwang Sik Im

Topoisomerase i inhibitors from theStreptomyces sp. strain KM86-9B isolated from a marine sponge

The crude extract ofStreptomyces sp. strain KM86-9B, isolated from a marine sponge, displayed significant inhibition on topoisomerase I activity. Investigation of the causative components by bioactivity-directed fractionation resulted in the isolation of a series of iso- and anteiso-fatty acids.

Jacaranone and related compounds from the fresh fruits of Ternstroemia japonica and their antioxidative activity.

Jacaranone and related compounds (1–3) were isolated, along with three triterpenes (4–6), from the fresh fruits ofTernstroemia japonica. The compounds were identified as jacaranone (1), 3-hydroxy-2,3-dihydrojacaranone (2), 3-methoxy-2,3-dihydrojacaranone (3), 3-O-acetyloleanolic acid (4), 3-O-acetylursolic acid (5), and ursolic acid (6). Jacaranone and its derivatives were isolated for the first time from Theaceae. Of the isolated compounds, compound3 is a new compound. Jacaranone (1) exhibited weak antioxidative effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical.

A triterpene glucosyl ester from the roots ofRubus crataegifolius

Along with five known triterpene glycosides, a new triterpene glucosyl ester, named crataegioside, was isolated from the roots ofRubus crataegifolius Bunge. The structure was established as ilexosapogenin A 28-O-ß-D-glucopyranosyl ester by chemical and spectroscopic methods.

Cytotoxic constituents ofSaussurea lappa

The crude extract ofSaussurea lappa displayed significant lethality to brine shrimp larvae. Investigation of the causative components by bioactivity-directed fractionation resulted in the isolation of three C17-polyene alcohols. Based on various nmr spectral data, these compounds were idenfitied as shikokiols which had been previously isolated fromCirsium nipponicum and/orCentaurea aegyptica. These C17-polyene alcohols exhibited moderate cytotoxicities against the human tumor cell lines, A549, SK-OV-3, SK-MEL-2, XF498, and HCT15.

A modified alkaline hydrolysis of total ginsenosides yielding genuine aglycones and prosapogenols

To improve the yield of genuine aglycones from glycosides, the conditions of alkaline hydrolysis were investigated, and a modified method was established. The modified method employed pyridine as an aprotic solvent. To complete the hydrolysis and obtain 20(S)-protopanaxadiol (1) and 20(S)-protopanaxatriol (2), which are the genuine aglycones of ginsenosides, total ginsenosides were refluxed with sodium methoxide in pyridine. Addition of methanol, a protic polar solvent to the reaction mixture, led partial hydrolysis yielding a mixture of the genuine prosapogenols. Of the prosapogenols compound3 and6 characteristically possessed D-glucopyranosyl moiety attached at the sterically hindered C-20 hydroxyl group.3 and6 were not obtained by other hydrolysis methods except by the soil bacterial hydrolysis.

Activity of crude extract ofRubus crataegifolius roots as a potent apoptosis inducer and DNA topoisomerase I inhibitor

The effects of methanol extract ofRubus crategifolius roots and its solvent fractions were investigated on the proliferation of MCF-7 human breast carcinoma cells. The methanol extract inhibited the proliferation of MCF-7 cells in a concentration dependent manner. Moreover, their methanol soluble (W-M) fraction had the greatest inhibitory effect on the growth of MCF-7 cells. To evaluate whether the W-M fraction affects on the cell cycle of MCF-7 cells, cells treated with this fraction were analyzed with flow cytometry. The W-M fraction increased G0/G1 phase after 24 h-treatment and induced apoptosis after 48 h-treatment. The hallmark of apoptosis, DNA fragmentation, also appeared by W-M fraction after 48 h-treatment. Furthermore the methanol extract and its W-M fraction inhibited the activity of the topoisomerase I enzyme in the relaxation assay. From these results, their W-M fraction as well as methanol extract ofR. crategifolius roots are necessary for further studies as a potent inhibitor of the growth of cancer cells.

A scanning calorimetric study of the effect of clover saponin on liposomal phospholipid membrane

The effect of clover saponin on the phase transition of liposomal lipid bilayers of dimyristoyl phosphatidylcholine was investigated with differential scanning calorimetry. The thermograms of the liposomal bilayers incorporated with the clover saponin were obtained, and the enthalpy changes and the sizes of cooperative unit of the transition were calculated. The results showed that incorporation of the clover saponin into the liposomal bilayers effectively reduced the transition temperature at which the transition from solid state to liquid-crystalline state occurs, and broadened the thermogram peaks. It also reduced the size of cooperative unit of the transition. These results indicate that the clover saponin might have significant effect on the fluidity of biological membranes.