Chong-Soon Lee

Cytotoxicity and DNA topoisomerase inhibitory activity of constituents isolated from the fruits of Evodia officinalis.

Four alkaloids (1–4), three quinolone alkaloids (5–7), and three flavanoid glucosides (8–10) were isolated from the fruits ofEvodia officinalis Dode, and their structures were determined from chemical and spectral data. Compounds,3, 8, 9 and10 were isolated from this plant for the first time. Of these compounds,1–3 and5–7 exhibited moderate cytotoxicities against cultured human colon carcinoma (HT-29), human breast carcinoma (MCF-7), and human hepatoblastoma (HepG-2). Compound8 showed strong inhibitory effects on DNA topoisomerases I and II (70 and 96% inhibition at a concentration of 20 μM, respectively).

A new stilbene glucoside from the roots ofPolygonum multiflorum Thunb.

One new stillbene glucoside (6), along with five known compounds (1–5), were isolated from the roots ofPolygonum multiflorum Thumb., and their chemical structures established based on physicochemical and spectroscopic data. Of the compounds, compound3 showed DNA topoisomerase I and II inhibitory activities.

Cytotoxic constituents isolated from the fruit bodies of Hypsizigus marmoreus.

The bioactivity-guided fractionation of chloroform extracts of the fruit bodies ofHypsizigus marmoreus led to our isolation of (22E, 24R)-ergosta-7,22-diene-3β,5α,6β-triol (1), ergosterol-3-O-β-D-glucopyranoside (2), 5α,8α-epidioxyergosta-6,22-dien-3β-ol (3), hypsiziprenol A9 (4), hypsiziprenol AA8 (5), hypsiziprenol AA9 (6) and hypsiziprenol BA10 (7). Among these seven isolates, compound2 was identified for the first time from this plant. All compounds (1–7) exhibited moderate cytotoxicity towards cultured human colon carcinoma (HT-29), human breast carcinoma (MCF-7) and human hepatoblastoma (HepG-2) cell lines.

Sequence selectivity of DNA alkylation by adozelesin and carzelesin

Adozelesin and carzelesin are synthetic analogues of the extremely potent antitumor antibiotic CC-1065, which alkylates N3 of adenine in a consensus sequence 5′-(A/T)(A/T)A* (A* is the site of alkylation). We have investigated the DNA sequence selectivity of adozelesin and carzelesin by thermally induced DNA strand cleavage assay using radiolabeled restriction DNA fragments. An analysis of alkylation patterns shows that the consensus sequences for carzelesin and adozelesin have been found to be 5′-(A/T)(A/T)A* and 5′-(A/T)(G/C)(A/T)A*. A new consensus sequence, 5′-(A/T)(A/T)CA*, has been observed to display an additional alkylation site for adozelesin but not for carzelesin. These results indicate that the pattern of sequence selectivity induced by carzelesin is similar but not identical to those induced by adozelesin.

Sequence specificity for DNA interstrand cross-linking induced by anticancer drug chlorambucil

Chlorambucil is known to alkylate primarily N7 of guanine and N3 of adenine to induce DNA monofunctional adducts and interstrand cross-links (ISC). We have investigated the sequence specificity for DNA ISC induced by chlorambucil using duplex oligomers containing a difined cross-linkable sequences 5′-A*TT, 5′-G*TT, or 5′-G*CC in which asterisk indicates the potential cross-linking site and underlined base indicates the potential cross-linking site on the opposite strand. An analysis of 20% denaturing polyacrylamide gel electrophoresis showed that chlorambucil was able to induce DNA ISC in the duplex oligomers containing a sequence 5′-GCC. The formation of DNA ISC was not observed in the duplex oligomers containing sequences 5′-ATT or 5′-GTT. These results indicate that chlorambucil induces guanineguanine DNA ISC but not guanine-adenine or adenine-adenine DNA ISC. In addition, we have tested the ability of chlorambucil to induce DNA ISC within 5′-GNNC or 5′-GC sequences using duplex oligomers containing the sequence 5′-G4G3G2C. The result of DNA strand cleavage assay showed that DNA ISC was formed at the 5′-GGC sequence (an 1,3 cross-link, G1-G3) but not at 5′-GGGC (an 1,4 cross-link, G1-G4) or 5′-GC sequence (an 1,2 cross-link, G1-G2).

Base specificity for DNA interstrand cross-linking induced by anticancer agent bizelesin

Bizelesin is a promising novel anticancer agent which is known to alkylate N3 of adenine to induce DNA interstrand cross-links (ISC) within 5′-TAATTA and 5′-TAAAAAA. We have investigated the base specificity for DNA ISC induced by bizelesin using oligomers containing the cross-linkable sequence 5′-TAATTN, in which “N” was either A, C, G, or T. An analysis of denaturing polyacrylamide gel showed that bizelesin is able to induce DNA ISC in the duplex oligomer containing sequences 5′-TAATTA and 5′-TAATTG. The formation of interstrand cross-linking did not occur in the sequences 5′-TAATTC and 5′-TAATTT. DNA strand cleavage assay to determine the cross-linking site within 5′-TAATTG sequence showed that bizelesin alkylates guanine. These results demonstrate that bizelesin is able to induce DNA ISC at guanine but not at cytosine or thymine. In addition, guanine adducts have been found to be susceptible to DNA strand cleavage by exposure to hot piperidine. The extent of DNA strand cleavage, however, was not 100% efficient in either neutral pH buffer or hot piperidine.