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Thiazacridine and imidazacridine derivatives have shown promising results as tumors suppressors in some cancer cell lines. For a better understanding of the mechanism of action of these compounds, binding studies of 5-acridin-9-ylmethylidene-3-amino-2-thioxo-thiazolidin-4-one, 5-acridin-9-ylmethylidene-2-thioxo-thiazolidin-4-one, 5-acridin-9-ylmethylidene-2-thioxo-imidazolidin-4-one and 3-acridin-9-ylmethyl-thiazolidin-2,4-dione with calf thymus DNA (ctDNA) by electronic absorption and fluorescence spectroscopy and circular dichroism spectroscopy were performed. The binding constants ranged from 1.46 × 104 to 6.01 × 104 M−1. UV-Vis, fluorescence and circular dichroism measurements indicated that the compounds interact effectively with ctDNA, both by intercalation or external binding. They demonstrated inhibitory activities to human topoisomerase I, except for 5-acridin-9-ylmethylidene-2-thioxo-1,3-thiazolidin-4-one. These results provide insight into the DNA binding mechanism of imidazacridines and thiazacridines.

Thiazacridine and imidazacridine derivatives have shown promising results as tumors suppressors in some cancer cell lines. For a better understanding of the mechanism of action of these compounds, binding studies of 5-acridin-9-ylmethylidene-3-amino-2- thioxo-thiazolidin-4-one, 5-acridin-9-ylmethylidene-2-thioxo-thiazolidin-4-one, 5-acridin- 9-ylmethylidene-2-thioxo-imidazolidin-4-one and 3-acridin-9-ylmethyl-thiazolidin-2,4-dione with calf thymus DNA (ctDNA) by electronic absorption and fluorescence spectroscopy and circular dichroism spectroscopy were performed. The binding constants ranged from1.46 × 104 to 6.01 × 104 M-1. UV-Vis, fluorescence and circular dichroism measurements indicated that the compounds interact effectively with ctDNA, both by intercalation or external binding. They demonstrated inhibitory activities to human topoisomerase I, except for 5-acridin-9-ylmethylidene-2-thioxo-1,3-thiazolidin-4-one. These results provide insight into the DNA binding mechanism of imidazacridines and thiazacridines. [ABSTRACT FROM AUTHOR]

Acridine derivatives represent a well-known class of anticancer agents that generally interfere with DNA synthesis and inhibit topoisomerase II. A series of eight new 3-acridin-9-ylmethyl-thiazolidine-2,4-dione and 3-acridin-9-ylmethyl-5-arylidene-thiazolidine-2,4-dione derivatives were synthesized. All the compounds were evaluated for their cell antiproliferation activity with the 3-(4,5-dimethyl-2-thiozolyl)-2,5-diphenyl-2 H-tetrazolium bromide, MTT assay. The antiproliferative effects of the synthesized compounds were tested against several tumoral cell lines, namely SF-295 (central nervous system), HCT-8 (colon carcinoma), and MDA-MB-435 (melanoma) cells using doxorubicin as a positive control. Among the synthesized compounds, 3-acridin-9-ylmethyl-5-acridin-9-ylmethylene-thiazolidine-2,4-dione, 3-acridin-9-ylmethyl-5-(4-methoxy-benzylidene)-thiazolidine-2,4-dione, and 3-acridin-9-ylmethyl-5-(4-bromo-benzylidene)-thiazolidine-2,4-dione exhibited the most potent anticancer activity against the HCT-8 and MDA-MB-435 cell lines. After a detailed analysis of the structure of the thiazacridine molecules, we revealed the main possible interactions using the compound 3-acridin-9-ylmethyl-5-acridin-9-ylmethylene-thiazolidine-2,4-dione as an example. The benefits of these compounds, regardless of the pharmacological target are the presence of two aromatic rings (pi systems), significant planarity (intercalating ability) and the presence of three hydrogen-bond acceptors, two of which are stronger (oxygen atoms) than the other (sulfur atom). [ABSTRACT FROM AUTHOR]

Abstract: Thiazacridine derivatives (ATZD) are a novel class of cytotoxic agents that combine an acridine and thiazolidine nucleus. In this study, the cytotoxic action of four ATZD were tested in human colon carcinoma HCT-8 cells: (5Z)-5-acridin-9-ylmethylene-3-(4-methylbenzyl)-thiazolidine-2,4-dione — AC-4; (5ZE)-5-acridin-9-ylmethylene-3-(4-bromo-benzyl)-thiazolidine-2,4-dione — AC-7; (5Z)-5-(acridin-9-ylmethylene)-3-(4-chloro-benzyl)-1,3-thiazolidine-2,4-dione — AC-10; and (5ZE)-5-(acridin-9-ylmethylene)-3-(4-fluoro-benzyl)-1,3-thiazolidine-2,4-dione — AC-23. All of the ATZD tested reduced the proliferation of HCT-8 cells in a concentration- and time-dependent manner. There were significant increases in internucleosomal DNA fragmentation without affecting membrane integrity. For morphological analyses, hematoxylin–eosin and acridine orange/ethidium bromide were used to stain HCT-8 cells treated with ATZD, which presented the typical hallmarks of apoptosis. ATZD also induced mitochondrial depolarisation and phosphatidylserine exposure and increased the activation of caspases 3/7 in HCT-8 cells, suggesting that this apoptotic cell death was caspase-dependent. In an assay using Saccharomyces cerevisiae mutants with defects in DNA topoisomerases 1 and 3, the ATZD showed enhanced activity, suggesting an interaction between ATZD and DNA topoisomerase enzyme activity. In addition, ATZD inhibited DNA topoisomerase I action in a cell-free system. Interestingly, these ATZD did not cause genotoxicity or inhibit the telomerase activity in human lymphocyte cultures at the experimental levels tested. In conclusion, the ATZD inhibited the DNA topoisomerase I activity and induced tumour cell death through apoptotic pathways. [Copyright &y& Elsevier]