Oleg S. Radchenko

Evaluation of cancer-preventive activity and structure-activity relationships of 3-demethylubiquinone Q2, isolated from the ascidian Aplidium glabrum, and its synthetic analogs.

Purpose3-Demethylubiquinone Q2 (1) was isolated from the ascidian Aplidium glabrum. The cancer-preventive properties and the structure–activity relationship for 3-demethylubiquinone Q2 (1) and 12 of its synthetic analogs (3–14) are reported.MethodsCompounds 3–14, having one or several di- or triprenyl substitutions and quinone moieties with methoxyls in different positions, were synthesized. The cancer-preventive properties of compounds 1 and 3–14 were tested in JB6 Cl41 mouse skin cells, using a variety of assessments, including the methanethiosulfonate (MTS) assay, flow cytometry, and soft agar assay. Statistical nonparametric methods were used to confirm statistical significance.ResultsAll quinones tested were shown to inhibit JB6 Cl41 cell transformation, to induce apoptosis, AP-1, and NF-κB activity, and to inhibit p53 activity. The most promising effects were indicated for compounds containing two isoprene units in a side chain and a methoxyl group at the para-position to a polyprenyl substitution.ConclusionsQuinones 1 and 3–14 demonstrated cancer-preventive activity in JB6 Cl41 cells, which may be attributed to the induction of p53-independent apoptosis. These activities depended on the length of side chains and on the positions of the methoxyl groups in the quinone part of the molecule.

A simple and practical approach to the synthesis of the marine sponge pigment fascaplysin and related compounds

Fascaplysin 1, an antimicrobial and cytotoxic red pigment of the marine sponge Fascaplys-inopsis sp., has been synthesized in five steps from tryptamine 2 in 44% overall yield. The key steps in the synthesis are: (a) dehydrogenation of the dihydro-β-carboline intermediate 4 simultaneously with its benzylic oxidation on treatment with MnO2 and (b) the thermal cyclization of the resulting β-carboline 7 into a quaternary salt 8. Similarly, indoloisoquinolines 15 and 16, the tetracyclic analogues of 1, were prepared in six steps from α-amino ketone 9 in 59 and 55% overall yields, respectively.

Marine Alkaloid Polycarpine and Its Synthetic Derivative Dimethylpolycarpine Induce Apoptosis in JB6 Cells Through p53- and Caspase 3-Dependent Pathways

No HeadingPurpose.Polycarpine from ascidian Polycarpa aurata was previously found to be active against different human tumor cells. In this study, we investigated the antitumor mechanisms of polycarpine and its synthetic derivative, desmethoxyethoxy-polycarpine (dimethylpolycarpine), through the induction of apoptosis. This new knowledge regarding the proapoptotic action of polycarpine and dimethylpolycarpine should lead to a better understanding of their effects and development of a new class of anticancer drugs.Methods.Apoptosis was clearly observed by flow cytometry and Western blotting using an antibody against cleaved caspase-3 as an apoptotic marker.Results.Polycarpines differentially activated p38 kinase, JNKs, and ERKs in JB6 Cl 41 cells. The polycarpines-induced apoptosis was decreased in cells expressing a dominant-negative mutant of JNK. Both compounds stimulated p53-dependent transcriptional activity and phosphorylation. Induction of p53-phosphorylation at serine 15 was suppressed in JNK1 and JNK2 knockout cells. Furthermore, polycarpines were unable to induce apoptosis in p53-deficient MEFs in contrast to a strong induction of apoptosis in wild type MEFs, suggesting that p53 is involved in apoptosis induced by polycarpines. The p53 phosphorylation in turn was mediated by activated JNKs.Conclusions.These results indicate that all three MAPK signaling pathways are involved in the response of JB6 cells to treatment with polycarpines. Evidence also supports a proapoptotic role of the JNKs signaling pathway in vivo and clearly indicates that JNKs are required for phosphorylation of c-Jun, activation of p53, and subsequent apoptosis induced by polycarpines.

Synthesis of polycarpine, a cytotoxic sulfur-containing alkaloid from the ascidian Polycarpa aurata, and related compounds

Polycarpine 1, a highly cytotoxic marine natural product, has been synthesized in three steps from p-methoxyphenacyl bromide 4 in 57% overall yield. The key reaction for construction of the symmetrically substituted disulfide linkage of polycarpine is the treatment of 2-amino-4-(4-methoxyphenyl)-1-methylimidazole 17 with S2Cl2 in acetic acid. In a similar way ten related compounds, including three thiazole analogues, have been prepared. Most of them exhibit high cytotoxic activities against an array of human cancer cell lines.

The anticancer activity of 3- and 10-bromofascaplysins is mediated by caspase-8, -9, -3-dependent apoptosis.

3- and 10-Bromofascaplysins was previously found to possess cytotoxic activity. In this study, we investigated their cancer preventive and proapoptotic properties. These effects were tested on mouse skin epidermal JB6 P(+) Cl41 cell line, its stable transfectants, and human tumor HL-60, THP-1, SNU-C4, SK-MEL-28, DLD-1, MDA-MB-231, and HeLa cells using a variety of assessments, including a cell viability (MTS) assay, flow cytometry, anchorage-independent soft agar assay, luciferase assay, mitochondrial permeability assay, and Western blotting. 3- and 10-Bromofascaplysins were effective at submicromolar concentrations as the anticancer agents, which exerted their action, at least in part, through the induction of caspase-8, -9, -3-dependent apoptosis.

The Cytotoxic and Antitumor Activities of the Imidazole Alkaloid Polycarpin from the Ascidian Polycarpa aurataand Its Synthetic Analogues

Effective cytostatics and selective inhibitors of the key biochemical processes that are isolated from marine invertebrates are more and more widely used in modern cell biology and medicine [1–5]. It is not surprising that, in solving one of the main problems of modern clinical oncology—the problem of multiple resistance of tumors to drugs—the researchers are counting on the natural compounds from marine hydrobionts whose action is directed to new cell targets. A special attention is paid to marine alkaloids. It will suffice to mention two new antitumor preparations from marine invertebrates: ecteinascidin-743, a tetrahydroisoquinoline alkaloid from the ascidian Ecteinascidia turbinata [1, 5]; and ascididemin, a pentacyclic pyridoacridine alkaloid from the ascidian Cystodytes dellechiajei and a number of ascidians of the genus Didemnum [4], which have already passed the main stages of clinical trials in Europe and the United States. The mechanisms of action of these alkaloids on the tumor cells differ from the mechanisms known for antitumor genotoxic preparations. This may account for the high effectiveness of ecteinascidin and ascididemin against tumors with multiple resistance to drugs, which opens up new fields of successful use of other marine natural compounds as chemotherapeutic drugs of a new generation.

Chemical properties of marine terpenoids. 1. Some reactions of (6S,10R)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5,5]undec-2-en-4-one, a sesquiterpenoid from the sea hare Aplysia dactylomela

The structures of products obtained by reductive debromination and CF3COOH- and KOH-induced transformations of natural chamigrane-type sesquiterpenoid (6S,10R)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5,5]undec-2-en-4-one (dactylone) isolated from the sea hare Aplysia dactylomela were analyzed. The absolute configurations of the reaction products were established by CD spectra taking into account the configuration of the starting dactylone.

1,4-Conjugate addition of 2-hydroxynaphthazarins to acyclic and cyclic α,β-unsaturated ketones. Prototropic ring-chain tautomerism of the adducts

TsOH-Catalyzed reactions of 6,7-disubstituted 2-hydroxynaphthazarins and acyclic or cyclic α,β-enones afforded the corresponding Michael-type adducts, viz., 3-substituted naphthazarins in 17–78% yields. 1H and 13C NMR and IR spectroscopy showed that the adducts with cyclohexenone and methyl vinyl ketone exist in CDCl3 solutions as mixtures of open-chain and cyclic tautomers, whereas the adducts with cyclopentenones exist only as the open-chain forms.