Low-dimensional compounds containing bioactive ligands. V: Synthesis and characterization of novel anticancer Pd(II) ionic compounds with quinolin-8-ol halogen derivatives

The antibacterial activity and selectivity of bismuth(III) tris(8-hydroxyquinolinates)

The series of bismuth(III) tris(8-hydroxyquinolinates); [Bi(Q")3] (1), [Bi(Q'Cl)3] (2), [Bi(QCl2)3] (3), [Bi(QBr2)3] (4), and [Bi(QI2)3] (5) (where Q"-H = C9H7NO; Q'Cl-H = C9H6NOCl, QCl2-H = C9H5NOCl2; QBr2-H = C9H5NOBr2; and QI2-H = C9H5NOI2) were synthesised, fully characterised, and evaluated for their antibacterial activity towards three Gram-positive bacteria (vancomycin-resistant E. faecalis, S. aureus, methicillin-resistant S. aureus), and four Gram-negative bacteria (A. baumannii, P. aeruginosa, K. pneumoniae, and E. coli) and also their cytotoxicity towards mammalian cells. New crystallographic data on 4 indicates it is dimeric in the solid state through 'Bi2O2' bridging which is consistent with data previously reported for 5. The five complexes (1-5) all exhibited good but variable antibacterial activity and selectivity. Complexes 2 and 5 showed significant activity towards Gram-positive bacteria with MIC (minimum inhibitory concentration) values ranging from 0.78 μM - 3.13 μM and selectivity indices of 6.2 - ≥16.0. For Gram-negative species, complexes 3 and 4 exhibited highly selective activity towards multi-drug resistant strains of A. baumannii with a range of MIC values 0.39-1.56 μM and selectivity indices of 3.14-7.23 respectively. While some of the 8-hydroxyquinolines themselves show reasonable antibacterial activity this is generally enhanced through complexation to bismuth(III).

Russian Doll-like 3d-4f Cluster Wheels with Slow Relaxation of Magnetization

The solvothermal reactions of LnCl3·6H2O and MCl2·6H2O (M = Co, Ni) with 2,2'-diphenol (H2L1) and 5,7-dichloro-8-hydroxyquinoline (HL2) gave three 3d-4f heterometallic wheel-like nano-clusters [Ln7M6(L1)6(L2)6(µ3-OH)6(OCH3)6Cl(CH3CN)6]Cl2·xH2O (Ln = Dy, M = Co, x = 3 for 1; Ln = Dy, M = Ni, x = 0 for 2; Ln = Tb, M = Ni, x = 0 for 3) with similar cluster structure. The innermost Ln(III) ion is encapsulated in a planar Ln6 ring which is further embedded in a chair-conformation M6 ring, constructing a Russian doll-like 3d-4f cluster wheel Ln(III)⸦Ln6⸦M6. 2 and 3 show obvious slow magnetic relaxation behavior with negligible opening of the magnetic hysteresis loop. Such a Russian doll-like 3d-4f cluster wheel with the lanthanide disc isolated by transition metallo-ring is rarely reported.

Insights of metal 8-hydroxylquinolinol complexes as the potential anticancer drugs

8-Hydroxyquinoline and its derivatives, which belong to a well-known class of quinoline based drugs with varied biological activities, have been extensively explored for the treatments of cancer, Alzheimer's disease, neurodegenerative diseases and other life-threatening diseases. In virtue of the existence of bicyclic heterocyclic scaffold, their bidentate chelators can further bind to metal ions via O- and N-donors from 8-hydroxylquinolinol skeletons to yield a variety of metal 8-hydroxylquinolinol complexes appealing as the anticancer drugs with low toxicity, due to their better biological effects and higher anticancer activities than free 8-hydroxylquinolinol ligands and cis-diammine-dichloro-platinum. The present review summarizes the recent developments in the syntheses, crystal structures, and anticancer activities of metal 8-hydroxylquinolinol complexes, attempting to discover a correlation between their structures and anticancer activities, and to provide an evidence for their potential application perspectives. It means to offer the helpful and meaningful guidance for the researchers in the future syntheses of new and highly efficient anticancer metal 8-hydroxylquinolinol complexes based drugs.

Low-Dimensional Compounds Containing Bioactive Ligands. Part XIX: Crystal Structures and Biological Properties of Copper Complexes with Halogen and Nitro Derivatives of 8-Hydroxyquinoline

Six new copper(II) complexes were prepared: [Cu(ClBrQ)2] (1a, 1b), [Cu(ClBrQ)2]·1/2 diox (2) (diox = 1,4-dioxane), [Cu(BrQ)2] (3), [Cu(dNQ)2] (4), [Cu(dNQ)2(DMF)2] (5) and [Cu(ClNQ)2] (6), where HClBrQ is 5-chloro-7-bromo-8-hydroxyquinoline, HBrQ is 7-bromo-8-hydroxyquinoline, HClNQ is 5-chloro-7-nitro-8-hydroxyquinoline and HdNQ is 5,7-dinitro-8-hydroxyquinoline. Prepared compounds were characterised by infrared spectroscopy, elemental analysis and by X-ray structural analysis. Structural analysis revealed that all complexes are molecular. Square planar coordination of copper atoms in [Cu(XQ)2] (XQ = ClBrQ (1a, 1b), BrQ (3) and ClNQ (6)) and tetragonal bipyramidal coordination in [Cu(dNQ)2(DMF)2] (5) complexes were observed. In these four complexes, bidentate chelate coordination of XQ ligands via oxygen and nitrogen atoms was found. Hydrogen bonds stabilizing the structure were observed in [Cu(dNQ)2(DMF)2] (5) and [Cu(ClNQ)2] (6), no other nonbonding interactions were noticed in all five structures. The stability of the complexes in DMSO and DMSO/water was evaluated by UV-Vis spectroscopy. Cytotoxic activity of the complexes and ligands was tested against MCF-7, MDA-MB-231, HCT116, CaCo2, HeLa, A549 and Jurkat cancer cell lines. The selectivity of the complexes was verified on a noncancerous Cos-7 cell line. Antiproliferative activity of the prepared complexes was very low in comparison with cisplatin, except complex 3; however, its activity was not selective and was similar to the activity of its ligand HBrQ. Antibacterial potential was observed only with ligand HClNQ. Radical scavenging experiments revealed relatively high antioxidant activity of complex 3 against ABTS radical.

Low-dimensional compounds containing bioactive ligands. Part XVII: Synthesis, structural, spectral and biological properties of hybrid organic-inorganic complexes based on [PdCl4]2- with derivatives of 8-hydroxyquinolinium

In this study, four hybrid organic-inorganic compounds (8-H₂Q)₂[PdCl₄] (1), (H₂ClQ)₂[PdCl₄] (2), (H₂NQ)₂[PdCl₄] (3) and (H₂MeQ)₂[PdCl₄]·2H₂O (4) (where 8-H₂Q = 8-hydroxyquinolinium, H₂ClQ = 5-chloro-8-hydroxyquinolinium, H₂NQ = 5-nitro-8-hydroxyquinolinium and H₂MeQ = 2-methyl-8-hydroxyquinolinium) were synthesized through organic cation modulation. Single-crystal X-ray structure analysis of compounds 1 and 3 indicates that their structures are planar and consist of [PdCl₄]^2- anions and 8-H₂Q or H₂NQ cations, respectively. Both ionic components are held together through ionic interactions and hydrogen bonds forming infinite chains linked through π-π interactions to form 2D structures. Furthermore, NMR spectroscopy, UV-Vis spectroscopy, elemental analysis, and FT-IR spectroscopy were used to explore the synthesized compounds. The DNA interaction, antimicrobial activity, antiproliferative activity, and radical scavenging effect of the compounds were evaluated. The hybrid compounds and their free ligands can interact with the calf thymus DNA via an intercalation mode involving the insertion of the aromatic chromophore between the base pairs of DNA; compound 1 has the highest binding affinity. Moreover, they have high antimicrobial efficacy against the tested 14 strains of microorganisms with minimum inhibitory concentration values ranging from <1.95 to 250 μg/mL. The antiproliferative activity of the compounds was investigated against three different cancer cell lines, and their selectivity was verified on mesenchymal stem cells. Compounds 1 and 2 displayed selective and high cytotoxicity against human lung and breast cancer cells and showed moderate cytotoxicity against colon cancer cells. Accordingly, they might be auspicious candidates for future pharmacological investigations in lung and breast cancer research.

Promising Anticancer Activity of [Bis(1,8-quinolato)palladium (II)] Alone and in Combination

Due to similar coordination chemistry of palladium and platinum, a large number of palladium compounds as well have been investigated for their anticancer activity. In the present study, we describe synthesis, characterization, and anticancer activity of palladium complex [Bis(1,8-quinolato)palladium (II)], coded as NH3 against seven different cancer cell lines. NH3 is found to have higher antitumor activity than cisplatin against both parent ovarian A2780 cell line and cisplatin-resistant cell lines. Also, NH3 has the lower IC₅₀ value in HT-29 colorectal cancer cell line. The higher antitumor activity of NH3 is due to the presence of bulky 8-Hydroxyquinoline ligand, thus reducing its reactivity. Proteomic study has identified significantly expressed proteins which have been validated through bioinformatics. NH3 has been found to be less toxic than cisplatin at 2.5 mg/kg and 5 mg/kg dosages on mice models. Binary combinations of NH3 with curcumin and epigallocatechin gallate (EGCG) have demonstrated dose and sequence-dependent synergism in ovarian and colorectal cancer models. All of the preclinical studies indicate promising therapeutic potential of NH3 [Bis(1,8-quinolato)palladium (II)] as an anticancer drug.

Platinum, palladium, gold and ruthenium complexes as anticancer agents: Current clinical uses, cytotoxicity studies and future perspectives

Metallodrugs offer potential for unique mechanism of drug action based on the choice of the metal, its oxidation state, the types and number of coordinated ligands and the coordination geometry. This review illustrates notable recent progress in the field of medicinal bioinorganic chemistry as many new approaches to the design of innovative metal-based anticancer drugs are emerging. Current research addressing the problems associated with platinum drugs has focused on other metal-based therapeutics that have different modes of action and on prodrug and targeting strategies in an effort to diminish the side-effects of cisplatin chemotherapy. Examples of metal compounds and chelating agents currently in clinical use, clinical trials or preclinical development are highlighted.

PdII and PtII complexes with a thio-aza macrocycle ligand containing an intercalating fragment: Structural and antitumor activity studies

Two new Pt^II and Pd^II complexes of formula [LMCl₂] (M=Pt, Pd) were synthesized and characterized both in solution and solid state. They were obtained using the thio-aza macrocycle 9,18-dimethyl-12,17dithia-9,18,27,28-tetraaaza-29-oxatetracyclo[24.2.1.0^2,7.0^20,25]enneicosa-2,4,6,20,22,24,26,28¹-octaene (L) containing the 2,5-diphenyl [1, 3, 4]oxadiazole as intercalating fragment. M^II is coordinated in cis-position by the two S atoms of L. The two crystal structures of [LPtCl₂] and [LPdCl₂] complexes showed that the M^II ion is located outside the macrocyclic cavity. The square planar coordination sphere is fulfilled by two chloride anions in a cisplatin-like arrangement with the chloride leaving groups exposed to the environment. The biological activity of both [LPtCl₂] and [LPdCl₂], monitored towards a leukemic cellular model (U937), is coherent with their ability to interfere, at different levels, with the DNA structure.

A water-soluble Pd(ii) complex with a terpyridine ligand: experimental and molecular modeling studies of the interaction with DNA and BSA; and in vitro cytotoxicity investigations against five human cancer cell lines

[Pd(4-OHPh-tpy)Cl]Cl was prepared. The complex interacts with DNA via a combination of covalent, intercalation, and hydrogen bonding interactions.

Low-dimensional compounds containing bioactive ligands. Part VI: Synthesis, structures, in vitro DNA binding, antimicrobial and anticancer properties of first row transition metal complexes with 5-chloro-quinolin-8-ol

A series of new 3d metal complexes with 5-chloro-quinolin-8-ol (ClQ), [Mn(ClQ)2] (1), [Fe(ClQ)3] (2), [Co(ClQ)2(H2O)2] (3), [Ni(ClQ)2(H2O)2] (4), [Cu(ClQ)2] (5), [Zn(ClQ)2(H2O)2] (6), [Mn(ClQ)3]·DMF (7) and [Co(ClQ)3]·DMF·(EtOH)0.35 (8) (DMF=N,N-dimethylformamide), has been synthesized and characterized by elemental analysis, IR spectroscopy and TG-DTA thermal analysis. X-ray structure analysis of 7 and 8 revealed that these molecular complexes contain three chelate ClQ molecules coordinated to the central atoms in a deformed octahedral geometry and free space between the complex units is filled by solvated DMF and ethanol molecules. Antimicrobial activity of 1-6 was tested by determining the minimum inhibitory concentration and minimum microbicidal concentration against 12 strains of bacteria and 5 strains of fungi. The intensity of antimicrobial action varies depending on the group of microorganism and can be sorted: 1>ClQ>6>3/4>2>5. Complexes 1-6 exhibit high cytotoxic activity against MDA-MB, HCT-116 and A549 cancer cell lines. Among them, complex 2 is significantly more cytotoxic against MDA-MB cells than cisplatin at all tested concentrations and is not cytotoxic against control mesenchymal stem cells indicating that this complex seems to be a good candidate for future pharmacological evaluation. Interaction of 1-6 with DNA was investigated using UV-VIS spectroscopy, fluorescence spectroscopy and agarose gel electrophoresis. The binding studies indicate that 1-6 can interact with CT-DNA through intercalation; complex 2 has the highest binding affinity. Moreover, complexes 1-6 inhibit the catalytic activity of topoisomerase I.

Cytotoxicity, DNA binding and cell apoptosis induction of a zinc(ii) complex of HBrQ

A zinc(ii) complex of HBrQ showed higher in vitro antitumor activity. It induced cell apoptosis in BEL-7404 cells via G₂ phase arrest, led to mitochondria dysfunction and activation of caspase cascade. The central zinc(ii) should play a key role to enhance the antitumor effect