Albumin as a prospective carrier of the nitrosyl iron complex with thiourea and thiosulfate ligands under aerobic conditions

Structure, properties, and decomposition in biological systems of a new nitrosyl iron complex with 2-methoxythiophenolyls, promising for the treatment of cardiovascular diseases

A new promising binuclear tetranitrosyl iron complex with 2-methoxythiophenolyl of the composition [Fe2(C7H7OS)2(NO)4] (complex 1), which acts on the therapeutic targets of cardiovascular diseases, guanylate and adenylate cyclase, has been synthesized. X-ray diffraction data show the presence of two isoforms of complex 1; according to quantum chemical calculations, the structure of only the trans isomer is stable in solutions. The processes of transformation of complex 1 in DMSO, in aqueous solutions, as well as in the presence of bovine serum albumin, reduced glutathione, and mucin were studied. DMSO promotes the decomposition of the original complex 1 into mononuclear products. In biological systems, the mechanisms of decomposition of the complex 1 differ from aqueous solutions. In albumin solution, a gradual formation of a high-molecular-weight dinitrosyl complex is observed, obtained by coordinating the [Fe(NO)2]+ fragment with the amino acid groups of the protein. In the presence of mucin, an EPR signal from stable mononitrosyl products is observed. The introduction of glutathione into the system of the complex 1 leads to the replacement of one initial thioligand with glutathione. In the model systems under study, a more efficient and prolonged generation of NO groups is observed compared to a buffer solution. The obtained data on the influence of the environment on the properties of the complex 1 in combination with a study of their effect on enzymes allow us to recommend it for further study as a potential drug with vasodilator, antianginal, and hypotensive properties.

Effects of Nitrosyl Iron Complexes with Thiol, Phosphate, and Thiosulfate Ligands on Hemoglobin

Nitrosyl iron complexes are remarkably multifactorial pharmacological agents. These compounds have been proven to be particularly effective in treating cardiovascular and oncological diseases. We evaluated and compared the antioxidant activity of tetranitrosyl iron complexes (TNICs) with thiosulfate ligands and dinitrosyl iron complexes (DNICs) with glutathione (DNIC-GS) or phosphate (DNIC-PO4-) ligands in hemoglobin-containing systems. The studied effects included the production of free radical intermediates during hemoglobin (Hb) oxidation by tert-butyl hydroperoxide, oxidative modification of Hb, and antioxidant properties of nitrosyl iron complexes. Measuring luminol chemiluminescence revealed that the antioxidant effect of TNICs was higher compared to DNIC-PO4-. DNIC-GS either did not exhibit antioxidant activity or exerted prooxidant effects at certain concentrations, which might have resulted from thiyl radical formation. TNICs and DNIC-PO4- efficiently protected the Hb heme group from decomposition by organic hydroperoxides. DNIC-GS did not exert any protective effects on the heme group; however, it abolished oxoferrylHb generation. TNICs inhibited the formation of Hb multimeric forms more efficiently than DNICs. Thus, TNICs had more pronounced antioxidant activity than DNICs in Hb-containing systems.

A nitrosyl iron complex with 3.4-dichlorothiophenolyl ligands: synthesis, structures and its reactions with targets - carriers of nitrogen oxide (NO) in vivo

In this work, a new binuclear nitrosyl complex with 3.4-dichlorothiophenolyl ligands [Fe₂(SC₆H₃Cl₂)₂(NO)₄] has been synthesized. Nitrosyl iron complexes (NICs) are systems for the storage and delivery of NO in the body. There is a dynamic equilibrium between dinitrosyl iron units bound to low molecular weight ligands and high molecular weight (protein) ligands in vivo. From this point of view, the transformation of the studied complex in DMSO and buffer, as well as in biological systems, has been analyzed. In DMSO, it decomposes into mononuclear NICs, which quickly decay in buffer solutions with NO release. The high molecular weight product is formed as a result of the binding of the complex to bovine serum albumin (the Stern-Volmer constant is 2.1 × 10⁵ M^-1). In this case, the complex becomes a prolonged NO-donor. Such a long-term effect has been observed for the first time. Similarly, in a system with oxyhemoglobin, NO generation is slower; the UV-vis spectra show a gradual formation of methemoglobin. On the other hand, reduced glutathione has little effect on the NO-donor properties of the complex despite the fact that ligand substitution is observed in the system and a binuclear product is formed. Mucin binds the complex, and the decomposition mechanism is different from that for buffer solutions. Thus, these proteins and glutathione are able to participate in the transformation of the complex and modulate its properties as a potential drug.