title: Identification and characterization of thiosemicarbazones with antifungal and antitumor effects: cellular iron chelation mediating cytotoxic activity.
abstract: Thiosemicarbazones derived from acetylpyrazines were prepared by condensing an acetylpyrazine or a ring-substituted acetylpyrazine with thiosemicarbazide. Using the same procedure, N, N-dimethylthiosemicarbazones were synthesized from acetylpyrazines and N, N-dimethylthiosemicarbazide. A total of 20 compounds (16 novel) were chemically characterized and then tested for antifungal effects on eight strains of fungi and also for antitumor activity against SK-N-MC neuroepithelioma cells. The most effective compound identified in terms of both antifungal and antitumor activity was N, N-dimethyl-2-(1-pyrazin-2-ylethylidene)hydrazinecarbothioamide (5a). The mechanism of action of this and its related thiosemicarbazones was due, at least in part, to its ability to act as a tridentate ligand that binds metal ions. This was deduced from preparation of the related thiosemicarbazones [acetophenone thiosemicarbazone (6) and acetophenone N, N-dimethylthiosemicarbazone (7)] that do not possess a coordinating ring-N, which plays a vital role in metal ion chelation. Furthermore, 5a and several other thiosemicarbazones that showed high antiproliferative activity were demonstrated to have marked iron (Fe) chelation efficacy. In fact, these agents were highly effective at mobilizing (59)Fe from prelabeled SK-N-MC cells and preventing (59)Fe uptake from the serum Fe transport protein, transferrin. In contrast, compounds 6 and 7 that do not possess a tridentate metal-binding site showed little activity. Further studies examining ascorbate oxidation demonstrated that the Fe complexes of the most effective compounds were redox-inactive. Thus, in contrast to other thiosemicarbazones with potent antiproliferative activity, Fe chelation and mobilization rather than free radical generation played a significant role in the cytotoxic effects of the current ligands.
authors.affiliation: Faculty of Pharmacy in Hradec Kralove, Charles University in Prague, Hradec Kralove, Czech Republic.
authors.forename: Veronika
authors.initials: V
authors.lastname: Opletalová
authors.forename: Danuta S
authors.initials: DS
authors.lastname: Kalinowski
authors.forename: Marcela
authors.initials: M
authors.lastname: Vejsová
authors.forename: Jirí
authors.initials: J
authors.lastname: Kunes
authors.forename: Milan
authors.initials: M
authors.lastname: Pour
authors.forename: Josef
authors.initials: J
authors.lastname: Jampílek
authors.forename: Vladimír
authors.initials: V
authors.lastname: Buchta
authors.forename: Des R
authors.initials: DR
authors.lastname: Richardson
mesh_terms: D020095:Absidia / Q000187:drug effects; D000935:Antifungal Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D000970:Antineoplastic Agents / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D001205:Ascorbic Acid / Q000378:metabolism; D001232:Aspergillus fumigatus / Q000187:drug effects; D002175:Candida / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D006801:Humans; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D008024:Ligands; D008826:Microbial Sensitivity Tests; D015394:Molecular Structure; D010084:Oxidation-Reduction / Q000187:drug effects; D013237:Stereoisomerism; D013882:Thiosemicarbazones / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology* / Q000633:toxicity; D014249:Trichophyton / Q000187:drug effects; D014250:Trichosporon / Q000187:drug effects; D014407:Tumor Cells, Cultured
chemical_list: D000935:Antifungal Agents; D000970:Antineoplastic Agents; D007502:Iron Chelating Agents; D008024:Ligands; D013882:Thiosemicarbazones; D007501:Iron; D001205:Ascorbic Acid