A Potential Visible-Light NO Releaser: Synthesis, Reactivity and Vasodilator Properties

Abstract

The cis-[Ru(bpy) 2 (4-bzpy)(NO)](PF 6 ) 3 complex was prepared (4-bzpy = 4-benzoylpyridine), and characterized by UV-visible, infrared and nuclear magnetic resonance (NMR) spectroscopies and electrochemical techniques. The reaction with cysteine was preliminarily investigated, aiming to shed light on the potential biological mechanism for NO or HNO release mediated by thiols. Furthermore, photochemical behavior of cis-[Ru(bpy) 2 (4-bzpy)(NO)](PF 6 ) 3 was studied, where it was observed NO release upon ultraviolet, blue and green light irradiations. This latter long wavelength showed still good efficiency, which has not been reported for this type of complex. This feature is very important for a potential application in phototherapy. Additionally, vasorelaxant activity was investigated in rat-isolated aorta. This compound exhibited a greater maximum efficacy than sodium nitroprusside (SNP) as a blood vessel relaxant. Nevertheless, the EC 50 for SNP (13.3 nmol L ). Altogether, these results suggest this complex is a promising NO donor agent deserving further biological studies.

When NO. Is not Enough: Chemical Systems, Advances and Challenges in the Development of NO. and HNO Donors for Old and Current Medical Issues

“…The most accepted mechanistic proposal for these processes follows the one illustrated by Franco and collaborators (Scheme 16). [120a,123,127] This mechanism describes the reaction of a nitrosyl complexes of Ru II and thiol‐based compound, which following quite similar steps as proposed in Scheme 14. A metal system [Ru(L) x (NO)] n+ (L is a ligand and x varies from 1 to 5) when attacked by an RS − group produces a first intermediate [Ru(L) x (N(O)SR)] (n−1)+ .…”

“…On the other hand, [Ru(L) x (N(O)SR)] (n−1)+ in reaction with an excess of RS − can produce a second adduct [Ru(L) x (N(O)(SR) 2 )] (n−2)+ , a precursor of the [Ru(L) x HNO] (n−1)+ complex. This latter species has been proposed as the donor of HNO (Scheme 16B) [120a,123,127] …”

“…Several metal complexes have been investigated as NO . releasing phototherapeutic agents [120a,b,132] . Metal complexes are versatile in terms of design and reactivity modulation, which have raised interest in their use as model photosensitizers [133] .…”

“…In general, it is admitted that the incidence of irradiation (UV‐Vis) in a metallo‐nitrosyl compound induces formation of an excited state, in which π* anti‐bonding orbitals of the nitrosyl ligand are electronically populated, leading to a decrease in the bond order between the metallic center and NO . , promoting the release of this ligand [120a,b,132b,134] . However, this mechanism was never unambiguously established.…”

SÍNTESE E CARACTERIZAÇÃO DE NITROSIL COMPLEXOS COM AÇÃO ANTIBACTERIANA FRENTE A Pseudomonas aeruginosa

“…Com base nesses resultados, constata-se um comportamento similar entre os dois compostos estudados neste trabalho com sistemas relatados na literatura. 70,71 Atividade antibacteriana frente a Pseudomonas aeruginosa A atividade antibacteriana do nitrosilo complexo foi testada frente à bactéria de cepa gram-negativa Pseudomonas aeruginosa ATCC -9027 (Figura 6). Desse modo, foi observado que o complexo 1 (Concentração Inibitória Mínima (CIM) = 121,5 mmol L -1 ) é capaz de inibir o crescimento das bactérias Pseudomonas aeruginosa (ATCC -9027) numa concentração bem menor que o complexo 2 (CIM > 500 mmol L -1 ).…”