Fe(III) complexes of two anthracyclines, adriamycin and daunorubicin, have been studied. Using potentiometric and spectroscopic measurements, we have shown that adriamycin and daunorubicin form two well-defined species with Fe(III), which can be formulated as respectively Fe(HAd)3 and Fe(HDr)3. In these formulas, HAd and HDr stand for adriamycin and daunorubicin in which the 1,4-dihydroxy-anthraquinone moiety is half-deprotonated. Both complexes are six-membered chelates. The stability constant is beta = (2.5 +/- 0.5) X 10(28) for both complexes. Interaction with DNA has been studied showing that, despite strong coordination to Fe(III), anthracyclines are able to intercalate between DNA bases pairs, releasing the metal. These complexes display antitumor activity against P 388 leukemia that compares with that of the free drug. Fe(HAd)3, unlike adriamycin, does not catalyze the flow of electrons from NADH to molecular oxygen through NADH dehydrogenase. Moreover, it is shown that the triferric adriamycin compound so called "quelamycin" is in fact a mixture of Fe(HAd)3 and polymeric ferric hydroxide.

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The more significant bioactivities of a variety of semicarbazones (anti-protozoa, anticonvulsant) and thiosemicarbazones (antibacterial, antifungal, antitumoral, antiviral) and their metal complexes are reviewed together with proposed mechanisms of action and structure-activity relationships. Clinical or potential pharmacological applications of these versatile compounds are discussed.

Depending on pH and molar ratio, adriamycin forms two well-defined species with Cu(II), which can be formulated Cu(HAd)2 and Cu(Ad). In these formulas, HAd and Ad stand for adriamycin in which the 1,4-dihydroxyanthraquinone moiety is respectively half or totally deprotonated. Both complexes are six-membered chelates. Cu(HAd)2 is a bis chelate of the stacked type that is fully defined at pH 5.8. Cu(Ad) is a long-chain polymer that forms at pH 7.2. Stability constants were obtained by two methods: spectrometric titrations and competing equilibria. They give for the first complex ft = (4.6 ± 1.1) X 1016 and for the second ß = (1.8 • 0.7) X 1012. Resonance Raman spectra indicate coordination through quinone and phenolate oxygens forming nondelocalized chelate rings. In addition, CD data suggest intermolecular hydrogen bonding at high concentrations of adriamycin (>100 µ ) when self-association takes place. Although formation of Cu(HAd)2 brings about self-association at lower concentration of adriamycin (50 µ ), resonance Raman data show disruption of intermolecular hydrogen bonding.

Recebido em 31/7/03; aceito em 24/9/03 SEMICARBAZONES AND THIOSEMICARBAZONES: THEIR WIDE PHARMACOLOGICAL PROFILE AND CLINICAL APPLICATIONS. This article shows that thiosemicarbazones, semicarbazones and their metal complexes can exhibit target selectivity along with a wide pharmacological profile. Complexes of thiosemicarbazones with cytotoxic or antitumoral activity are presented, some of which show activity against cisplatinum-resistant cells. The inhibition mechanism of the enzyme ribonucleoside diphosphate reductase (RDR), involved in DNA syntheses, by α(N)-heterocyclic thiosemicarbazones is discussed. The encouraging results of clinical trials with the RDR inhibitor 3-aminopyridine-2-carboxaldehyde thiosemicarbazone ("Triapine") against rapidly growing tumors are outlined. Examples are also given of thiosemicarbazones with antiviral and antimicrobial activity. The possible applications of semicarbazones as anticonvulsants with low toxicity and good therapeutic index are presented. . Ehrlich foi o fundador da quimioterapia e introduziu as primeiras idéias sobre relações estrutura-atividade e o conceito de índice terapêutico. Fez ainda uso de complexos metálicos, em especial os de arsênio, na preparação de drogas para o tratamento da sífilis 2 . Werner é considerado o pai da Química de Coordenação pelo desenvolvimento de sua teoria para explicar a estrutura e a ligação química nos complexos metálicos.Apesar da grande importância dos trabalhos desses e de outros pesquisadores, a Química Medicinal dedicou-se, durante muitos anos, principalmente ao estudo de compostos orgânicos e produtos naturais. A investigação a respeito do uso de complexos metálicos como fármacos teve início, de modo sistemático, apenas após a descoberta feita pelo físico Barnett Rosemberg, da atividade antitumoral do cis(diaminodicloro)platina(II), o "cisplatina" ou cis-ddp, em 1965 3 . Desde então, uma imensa variedade de complexos metálicos foi e tem sido investigada quanto às suas propriedades terapêuticas. É interessante observar que o primeiro número da revista Metal-Based Drugs apareceu em 1994.Tiossemicarbazonas e semicarbazonas (Figura 1) apresentam um amplo perfil farmacológico e constituem uma importante classe de compostos cujas propriedades têm sido extensivamente estudadas na Química Medicinal e, particularmente, na Química Medicinal Inorgânica, em razão de sua capacidade quelante e do papel da coordenação no seu mecanismo bioquímico de ação. Apesar da ampla versatilidade farmacológica desses compostos como uma classe, especificidades estruturais podem levar à manifestação de atividades específicas. Para os complexos metálicos, em alguns casos é possí-vel modular a atividade através do desenho do ligante ou através da escolha do metal, como veremos adiante.De modo geral pode-se dizer que tiossemicarbazonas e semicarbazonas agem, seja como inibidores de enzimas, através da complexação de metais endógenos ou através de reações de redox, seja através de interações com o ADN e da inibição da síntese do ADN. Além disso, alguns compl...

New imidazole derived thiosemicarbazones and hydrazones were prepared by condensation of 4(5)-imidazole carboxaldehyde, 4-(1H-imidazole-1-yl)benzaldehyde and 4-(1H-imidazole-1-yl)acetophenone with a thiosemicarbazide or hydrazide. All compounds were characterized by quantitative elemental analysis, IR and NMR techniques. Eight structures were determined by single crystal X-ray diffraction. The antifungal activities of the compounds were evaluated. None of the compounds exhibited significant activity against Aspergillus flavus and Candida albicans, while 4(5)-imidazolecarboxaldehyde thiosemicarbazone (ImT) and 4-(1H-imidazole-1-yl)benzaldehyde thiosemicabazone (4ImBzT) were highly and selectively active against Cladosporium cladosporioides. 4(5)-Imidazolecarboxaldehyde benzoyl hydrazone (4(5)ImPh), 4(5)-imidazolecarboxaldehydepara-chlorobenzoyl hydrazone (4(5)ImpClPh), 4(5)-imidazolecarboxaldehyde-paranitrobenzoyl hydrazone (4(5)ImpNO 2 Ph), 4-(imidazole-1-yl)acetophenone-para-chlorobenzoyl hydrazone (4ImAcpClPh) and 4-(imidazole-1-yl)acetophenone-para-nitrobenzoylhydrazone (4ImAcpNO 2 Ph) were highly active against Candida glabrata. 4(5)ImpClPh and 4(5)ImpNO 2 Ph were very effective against C. cladosporioides. In many cases, activity was superior to that of the reference compound nystatin.

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