Luminescent PhotoCORMs: Enabling/Disabling CO Delivery upon Blue Light Irradiation

Exploring a series of multifunctional Mn(I) tricarbonyls as prospective agents against trypanosomatid parasites: a comparative study with the Re(I) analogues

Diseases caused by trypanosomatid parasites are among the most pressing neglected illnesses. Chagas disease, caused by Trypanosoma cruzi, and visceral Leishmaniasis, caused by Leishmania infantum, have a severe health impact in developing countries. Searching for prospective metal-based drugs against these diseases, five multifunctional fac-[Mn(CO)3(CTZ)(NN)](PF6) compounds, including four new derivatives, were synthesized and thoroughly characterized, featuring NN polypyridyl derivatives and Clotrimazole (CTZ) as bioactive ligands. The biological behavior was compared with that previously reported for the Re analogues. Mn compounds showed EC50 values in the low micromolar range against the infective trypomastigote form of Trypanosoma cruzi and the promastigote form of Leishmania infantum and moderate selectivity indexes. While their potency against T. cruzi was comparable to the Re analogues, their selectivity was lower. Key physicochemical properties relevant to drug development were assessed: Mn(I) compounds showed lower stability in relevant tested media compared with their Re(I) counterparts and higher lipophilicity than the free ligands and the Re analogues. To gain insight into the potential mechanisms of action, the interaction with DNA and the effects on ergosterol biosynthesis in T. cruzi and L. infantum were investigated. Minimal DNA association (<1%) and moderate interaction with this target discarded DNA binding as the primary mechanism of action. In contrast, inhibition of lanosterol 14-α-demethylase (CYP51), key enzyme involved in the parasites' ergosterol biosynthetic pathway, was experimentally confirmed. Metallomic study revealed an uptake by T. cruzi of the most promising compound, fac-[Mn(CO)3(CTZ)(tmp)](PF6), more than twice that of the Re(I) analogue and preferential association to soluble proteins. Proteomic analysis of T. cruzi epimastigotes treated with the Mn(I) and Re(I) analogues showed no change in CYP51 abundance, suggesting that reduced ergosterol levels may arise from post-translational modifications of the enzyme. Raman confocal microscopy allowed us to detect effects of the most promising Mn compound in treated T. cruzi. Furthermore, the photoinduced CO release properties of both Mn and Re analogues were examined, searching for an additional and yet non-studied potential mechanism of action of metal-tricarbonyls in these trypanosomatid parasites. Collectively, the results highlight the potential of Mn(I) tricarbonyls as promising candidates for further drug development.

Aminoquinoline-based Re(I) tricarbonyl complexes: Insights into their antiproliferative activity and mechanisms of action

In an effort to develop new potent anticancer agents, two Schiff base rhenium(I) tricarbonyl complexes, containing the ubiquitous aminoquinoline scaffold, were synthesized. Both aminoquinoline ligands and Re(I) complexes showed adequate stability over a 48-h incubation period. Furthermore, the cytotoxic activity of the precursor ligands and rhenium(I) complexes were evaluated against the hormone-dependent MCF-7 and hormone-independent triple negative MDA-MB-231 breast cancer cell lines. Inclusion of the [Re(CO)3Cl]+ entity significantly enhanced the cytotoxicity of the aminoquinoline Schiff base ligands against the tested cancer cell lines. Remarkably, the incorporation of the Schiff-base iminoquinolyl entity notably enhanced the cytotoxic activity of the Re(I) complexes, in comparison with the iminopyridyl entity. Notably, the quinolyl-substituted complex showed up to three-fold higher activity than cisplatin against breast cancer cell lines, underpinning the significance of the quinoline pharmacophore in rational drug design. In addition, the most active Re(I) complex showed better selectivity towards the breast cancer cells over non-tumorigenic FG-0 cells. Western blotting revealed that the complexes increased levels of γH2AX, a key DNA damage response protein. Moreover, apoptosis was confirmed in both cell lines due to the detection of cleaved PARP. The complexes show favourable binding affinities towards both calf thymus DNA (CT-DNA), and bovine serum albumin (BSA), and the order of their interactions align with their cytotoxic effects. The in silico molecular simulations of the complexes were also performed with CT-DNA and BSA targets.

Spectroscopical and Molecular Studies of Four Manganese(I) PhotoCORMs with Bioinspired Ligands Containing Non-Coordinated Phenol Groups

Carbonyl compounds are widely explored in medicinal inorganic chemistry and have drawn attention due to their signaling functions in homeostasis. Carbon-monoxide-releasing molecules (CORMs) were developed with the purpose of keeping the CO inactive until its release in the intracellular environment, considering its biological relevance. However, for therapeutic applications, the mechanisms of photorelease and which electronic and structural variations influence its rates must be fully understood. In this work, four ligands containing a pyridine, a secondary amine, and a phenolic group with different substituents were used to prepare new Mn(I) carbonyl compounds. Structural and physicochemical characterization of these complexes was carried out and confirmed the proposed structures. X-ray diffractometry structures obtained for the four organometallic compounds revealed that the substituents in the phenolic ring promote only negligible distortions in their geometry. Furthermore, UV-Vis and IR kinetics showed the direct dependence of the electron-withdrawing or donating ability of the substituent group, indicating an influence of the phenol ring on the CO release mechanism. These differences in properties were also supported by theoretical studies at the DFT, TD-DFT, and bonding situation analyses (EDA-NOCV). Two methods were used to determine the CO release constants (k_CO,old and k_CO,new), where Mn-HbpaBr (1) had the greatest k_CO by both methods (K_co,old = 2.36 × 10^-3 s^-1 and k_CO,new = 2.37 × 10^-3 s^-1). Carbon monoxide release was also evaluated using the myoglobin assay, indicating the release of 1.248 to 1.827 carbon monoxides upon light irradiation.

Ruthenium Half-Sandwich Type Complexes with Bidentate Monosaccharide Ligands Show Antineoplastic Activity in Ovarian Cancer Cell Models through Reactive Oxygen Species Production

Ruthenium complexes are developed as substitutes for platinum complexes to be used in the chemotherapy of hematological and gynecological malignancies, such as ovarian cancer. We synthesized and screened 14 ruthenium half-sandwich complexes with bidentate monosaccharide ligands in ovarian cancer cell models. Four complexes were cytostatic, but not cytotoxic on A2780 and ID8 cells. The IC₅₀ values were in the low micromolar range (the best being 0.87 µM) and were similar to or lower than those of the clinically available platinum complexes. The active complexes were cytostatic in cell models of glioblastoma, breast cancer, and pancreatic adenocarcinoma, while they were not cytostatic on non-transformed human skin fibroblasts. The bioactive ruthenium complexes showed cooperative binding to yet unidentified cellular target(s), and their activity was dependent on reactive oxygen species production. Large hydrophobic protective groups on the hydroxyl groups of the sugar moiety were needed for biological activity. The cytostatic activity of the ruthenium complexes was dependent on reactive species production. Rucaparib, a PARP inhibitor, potentiated the effects of ruthenium complexes.