Antitumor activities of ferrocene compounds

Charge-compensated nido-carborane derivatives in the synthesis of iron(II) bis(dicarbollide) complexes

A series of stable iron(II) bis(dicarbollide) derivatives [8,8'-(RNHC(Et)HN)2-3,3'-Fe(1,2-C2B9H10)2] (R = Pr, R = Ph, (CH2)2OH, (CH2)3OH, (CH2)2NMe2) was prepared starting from FeCl2 or [FeCl2(dppe)] and the corresponding nido-carboranyl amidines [10-RNHC(Et)HN-7,8-C2B9H11]. In a similar way, the reactions of the oxonium derivatives of nido-carborane with FeCl2 in tetrahydrofuran in the presence of t-BuOK lead to the corresponding stable oxonium derivatives iron(II) bis(dicarbollide) [8,8'-(RR'O)2-3,3'-Fe(1,2-C2B9H10)2] (RR' = (CH2)4, (CH2)2O(CH2)2, (CH2)5; R = R' = Et), which can be alternatively prepared by the reaction of the parent iron(II) bis(dicarbollide) with tetrahydrofuran or 1,4-dioxane in the presence of Me2SO4. The cyclic voltammetry studies of the synthesized iron(II) bis(dicarbollide) derivatives revealed that the introduction of amidinium and oxonium substituents leads to a significant increase in the Fe2+/Fe3+ redox potential relative to the parent iron(II) bis(dicarbollide). The redox potentials of the oxonium derivatives are close to the redox potential of ferrocene and somewhat lower than redox potentials of sulfonium and phosphonium derivatives of iron(II) bis(dicarbollide).

Synthesis and ultrasound mediated antibacterial activity of ferrocene-triazole-porphyrin derivative

The [3 + 2]-cycloaddition reaction of various azides with ferrocenylmethylpropargyl ester in the presence of copper (I) salt lead to the formation of ferrocenyl-containing derivatives, including porphyrin, which exhibit pronounced cytotoxicity against Escherichia coli under ultrasound irradiation.

Application of capillary electrophoresis technique for the enantioseparation of bioactive ferrocene-based compounds versus DFT calculated data

Herein, a series of bioactive ferrocene-modified N-heterocycles with alkyl linkers was prepared in good to quantitative yields starting from easy accessible ferrocene alcohols and heterocycles under acidic or neutral (for imidazole) conditions in racemic forms. The analytical resolution of a number of bioactive racemic ferrocene azoles 1-6 (where azole = imidazole, pyrazole, and benzotriazole derivatives) into enantiomers was first carried out by CE using sulfobuthylether-β-CD (captisol) as a chiral selector. The analytical approaches to highly enantiomeric-enriched ferrocene derivatives are based on the formation of their inclusion complexes. The best chiral separation was achieved using zone CE in a quartz capillary. The ACE was used to evaluate the stability constants of captisol complexes with enantiomeric forms of two ferrocene derivatives 1, FcCHMe-imidazole, and 6, FcCHMe-benzotriazole. The optimal conditions for the resolution of the studied (R, S)-ferrocene compounds 1, 2, and 6 were predicted on the basis of the performed quantum chemical calculations and then implemented by the electrophoretic method. A high correlation between density functional theory calculation results and experimental electrophoresis data were obtained. Successful enantioseparation of racemic mixtures is of great importance for the characterization and further applications of drug candidates in enantiopure forms and in the development of clinical treatment. The advantages of the CE procedure make it possible to have important practical value and significance for determining the purity and enantiomeric excess of other ferrocene-containing compounds.

Synthesis and In Vitro Anticancer Activity of 6-Ferrocenylpyrimidin-4(3H)-one Derivatives

AIM AND OBJECTIVE

Some ferrocenyl derivatives are active in vitro and in vivo against cancer. Generally, ferrocenyl derivatives for cancer research have three key components: a ferrocene moiety, a conjugated linker that lowers the oxidation potential and some derivative (peptide, nucleobase and others) that can interact with biomolecules. Since the pyrimidine fragment can easily pass through the membrane into the cells and become involved in metabolism; it appears to be promising. Furthermore, this fragment is an electron-acceptor group, so a spacer can be excluded. Therefore, the synthesis of 6-ferrocenylpyrimidin-4(3H)-one derivatives and the study of their anticancer activity have scientific and practical interest.

METHODS

The syntheses of 6-ferrocenylpyrimidin-4(3H)-one derivatives were performed by the condensation of ethyl 3-ferrocenyl-3-oxopropionate with thiourea or acetamidine or guanidine. The cytotoxicity of four 6- ferrocenylpyrimidin-4(3H)-one derivatives was evaluated by using the MTT assay in vitro against Human breast adenocarcinoma MCF-7 and normal human skin fibroblast HSF cells. The tested derivatives induced a concentration-dependent cytotoxic response in cell lines.

RESULTS

A study of the cytotoxic activity of 6-ferrocenylpyrimidin-4(3H)-one derivatives by the MTT test has found that all compounds have a dose-dependent toxic effect on the lines of breast cancer cells (MCF-7) and normal human fibroblast cells (HSF). The most pronounced cytotoxic effect is exhibited by 2-methyl-6-ferrocenylpyrimidin- 4(3H)-one (MCF-7, IC50 17 ± 1 µM).

CONCLUSION

The experimental results confirm the importance of investigation and design of ferrocenylpyrimidin- 4(3H)-one derivatives as anticancer agents. Compounds where the pyrimidine derivatives are directly linked to the ferrocene unit rather than via a spacer group also may be of interest for antiproliferative drug design.

Electrochemical characterization and estimation of DNA-binding capacity of a series of novel ferrocene derivatives

The synthesis of a series of methyl 2-alkyl-5-aryl-4-ferrocenoylpyrrolidine-2-carboxylates has been achieved by [3 + 2] dipolar cycloaddition of azomethine ylides to acryloylferrocene. The electrochemical properties of novel products were examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). These techniques revealed the quasi-reversible one-electron oxidation process. The DNA-binding capacity of all the products was also studied using CV and DPV, and significant interactions between synthesized compounds and nucleic acid, mostly of the electrostatic type, were disclosed. DFT calculations and molecular docking tests were carried out to gain a more exhaustive insight into the interactions of the obtained products with nucleic acid. A detailed characterization of the new compounds was performed by IR, NMR and elemental analyses, followed by single-crystal X-ray diffraction experiments for two representatives.

Activation by Oxidation: Ferrocene-Functionalized Ru(II)-Arene Complexes with Anticancer, Antibacterial, and Antioxidant Properties

Organometallic Ru(II)-cymene complexes linked to ferrocene (Fc) via nitrogen heterocycles have been synthesized and studied as cytotoxic agents. These compounds are analogues of Ru(II)-arene piano-stool anticancer complexes such as RAPTA-C. The Ru center was coordinated by pyridine, imidazole, and piperidine with 0-, 1-, or 2-carbon bridges to Fc to give six bimetallic, dinuclear compounds, and the properties of these complexes were compared with their non-Fc-functionalized parent compounds. Crystal structures for five of the compounds, their Ru-cymene parent compounds, and an unusual trinuclear compound were determined. Cyclic voltammetry was used to determine the formal M^III/II potentials of each metal center of the Ru-cymene-Fc complexes, with distinct one-electron waves observed in each case. The Fc-functionalized complexes were found to exhibit good cytotoxicity against HT29 human colon adenocarcinoma cells, whereas the parent compounds were inactive. Similarly, antibacterial activity from the Ru-cymene-Fc compounds was observed against Bacillus subtilis, but not from the unfunctionalized complexes. In both cases, the IC₅₀ values correlated quantitatively with the Fc^+/0 reduction potentials. This is consistent with more facile oxidation to give ferrocenium, and subsequent generation of toxic reactive oxygen species, leading to greater cytotoxicity. The antioxidant properties of the complexes were quantified by a 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. EC₅₀ values indicate that linking of the Ru and Fc centers promotes antioxidant activity.

A strategic approach to the synthesis of ferrocene appended chalcone linked triazole allied organosilatranes: Antibacterial, antifungal, antiparasitic and antioxidant studies

A series of ferrocene appended chalcone allied triazole coupled organosilatranes (FCTSa 7-FCTSa 12) were synthesised with the aim of amalgamating the pharmacological action of the constituting moieties into a single molecular scaffold. All the synthesised silatranes were well characterized by various spectroscopic techniques like IR, ¹H NMR, ¹³C NMR and elemental analysis. Organosilatranes were then evaluated for their biological alacrity against bacterial and fungal strains compared with the standard drugs Rifampicin and Amphotericin B respectively. The ferrocene conjugates were found to be only moderately effective against the tested microbes. However, the organosilatranes conceded excellent efficacy against parasite G. lamblia with FCTSa 11 arraying the leading results. On the other hand against another parasite T. vaginalis, FCTSa 8 has emerged as an outstanding composite. Further, Total Antioxidant Assay (TAA) with 2,2'-azino-bis-3-(ethylbenzothiazoline-6-sulphonic acid) revealed FCTSa 10 to be the best claimant for radical scavenging activity. Along these lines, introducing some different substituents in the synthesised hybrids may act as a useful strategy for increasing the biological profile of the drugs.

Synthesis, spectroscopic investigation, and DFT study of N,N'-disubstituted ferrocene-based thiourea complexes as potent anticancer agents

In the present work, the synthesis, characterization (FT-IR, multinuclear (¹H and ¹³C) NMR, AAS, Raman, and elemental analyses), DNA binding (cyclic voltammetry, UV-Vis spectroscopy), and in vitro biological screening of nine new ferrocene-incorporated thioureas (A1-A9) are reported. Furthermore, the single-crystal X-ray structure of compound A8 was also determined. The ferrocene-based N,N'-disubstituted thioureas were derived by allowing the ferrocenyl anilines to react with freshly prepared isothiocyanates under a N₂ atmosphere in dry acetone. The DNA binding studies performed by cyclic voltammetry and UV-Vis spectroscopy produced results that are in close agreement with one another for the binding constants (K) and an electrostatic mode of interaction was observed. The DFT/B3LYP method was used to determine the charge distribution and HOMO/LUMO energies of the optimized structure. The DFT calculated HOMO and LUMO energies correlate well with the experimentally determined redox potential values. The synthesized ferrocenyl thioureas exhibited good scavenging activity against the 1,1-diphenyl-2-picrylhydrazyl radical (DPPH). These complexes were also scanned for their in vitro cytotoxic activity against MCF-7 carcinoma cells, and also towards the non-cancerous cell line MCF-10A. The results showed modest cytotoxicity against the subjected cancer cell line compared with a standard chemotherapeutic drug (cisplatin). However, these ferrocenyl derivatives have fewer toxic effects in normal cells.

Recent advances in iron complexes as potential anticancer agents

The iron complexes discussed in this review highlight their promising future as anticancer agents.

Induction of Cytotoxicity in Pyridine Analogues of the Anti-metastatic Ru(III) Complex NAMI-A by Ferrocene Functionalization

A series of novel ferrocene (Fc) functionalized Ru(III) complexes was synthesized and characterized. These compounds are derivatives of the anti-metastatic Ru(III) complex imidazolium [trans-RuCl4(1H-imidazole) (DMSO-S)] (NAMI-A) and are derived from its pyridine analogue (NAMI-Pyr), with direct coupling of Fc to pyridine at the 4 or 3 positions, or at the 4 position via a two-carbon linker, which is either unsaturated (vinyl) or saturated (ethyl). Electron paramagnetic resonance (EPR) and UV-vis spectroscopic studies of the ligand exchange processes of the compounds in phosphate buffered saline (PBS) report similar solution behavior to NAMI-Pyr. However, the complex with Fc substitution at the 3 position of the coordinated pyridine shows greater solution stability, through resistance to the formation of oligomeric species. Further EPR studies of the complexes with human serum albumin (hsA) indicate that the Fc groups enhance noncoordinate interactions with the protein and help to inhibit the formation of protein-coordinated species, suggesting the potential for enhanced bioavailability. Cyclic voltammetry measurements demonstrate that the Fc groups modestly reduce the reduction potential of the Ru(III) center as compared to NAMI-Pyr, while the reduction potentials of the Fc moieties of the four compounds vary by 217 mV, with the longer linkers giving significantly lower values of E1/2. EPR spectra of the compounds with 2-carbon linkers show the formation of a high-spin Fe(III) species (S = 5/2) in PBS with a distinctive signal at g = 4.3, demonstrating oxidation of the Fe(II) ferrocene center and likely reflecting degradation products. Density functional theory calculations and paramagnetic (1)H NMR describe delocalization of spin density onto the ligands and indicate that the vinyl linker could be a potential pathway for electron transfer between the Ru and Fe centers. In the case of the ethyl linker, electron transfer is suggested to occur via an indirect mechanism enabled by the greater flexibility of the ligand. In vitro assays with the SW480 cell line reveal cytotoxicity induced by the ruthenium ferrocenylpyridine complexes that is at least an order of magnitude higher than the unfunctionalized complex, NAMI-Pyr. Furthermore, migration studies with LNCaP cells reveal that Fc functionalization does not reduce the ability of the compounds to inhibit cell motility. Overall, these studies demonstrate that NAMI-A-type compounds can be functionalized with redox-active ligands to produce both cytotoxic and anti-metastatic activity.

Facile synthesis and characterization of bio-organometallic compounds and their biological activity contour against human pathogens

We have reported the synthesis of novel di & trisubstituted pyrroles and their biological activity.

Anti-cancer palladium complexes: a focus on PdX2L2, palladacycles and related complexes

Much success has been achieved with platinum-based chemotherapeutic agents, i.e. through interactions with DNA. The long-term application of Pt complexes is thwarted by issues, leading scientists to examine other metals such as palladium which could exhibit complementary modes of action (given emphasis wherever known). Over the last 10 years several research groups have focused on the application of an eclectic array of palladium complexes (of the type PdX2L2, palladacycles and related structures) as potential anti-cancer agents. This review therefore provides readers with an up to date account of the advances that have taken place over the past several decades.