Anticancer activity of novel amino acid derivative of palladium complex with phendione ligand against of human colon cancer cell line

The aim of this work is the identification of the structural effect of amino acid-Pd complex on DNA as an intracellular target which was studied using various spectroscopic techniques such as fluorescence, UV-visible and circular dichroism in combination with a molecular docking study. Hence, a novel water-soluble palladium complex, [Pd(phendione)(isopentylglycine)]NO₃, has been synthesized and characterized by spectroscopic method. The anticancer activity of complex was investigated against human colon cancer cell line of HCT116 after 24 h of incubation using MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay. In addition, this complex was interacted with calf thymus DNA (ct-DNA) via positive cooperative interaction. The fluorescence data indicate that Pd complex is intercalated in DNA. These results were confirmed by circular dichroism spectra. The molecular docking results indicate that docking may be an appropriate method for the prediction and confirmation of experimental results. Complementary molecular docking results may be useful for the determination of the binding mechanism of DNA in pharmaceutical and biophysical studies providing new insight into the novel pharmacology and new solutions in the formulation of advanced oral drug delivery systems. Docking and spectroscopic studies show that new water-soluble Pd complex has anticancer activity and it can bind to DNA via intercalation and groove binding.

High cytotoxicity of vanadium(IV) complexes with 1,10-phenanthroline and related ligands is due to decomposition in cell culture medium

Cytotoxic effects of Metvan (cis-[V^IVO(OSO₃)(Me₂phen)₂], where Me₂phen = 4,7-dimethyl-1,10-phenanthroline) and its analogues with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy) ligands in cultured human lung cancer (A549) cells have been re-investigated in conjunction with reactivity of the V(IV) complexes in neutral aerated aqueous solutions and in cell culture medium. All the V(IV) complexes underwent rapid oxidation to the corresponding V(V) species (cis-[V^V(O)₂L₂]⁺), followed by release of free ligands (shown by electrospray mass spectrometry). Decomposition of V(IV) complexes in cell culture medium within minutes at 310 K was confirmed by UV-Vis and EPR spectroscopies. High cytotoxicities (low μM or sub-μM IC₅₀ range in 72 h assays) were observed for the phen and Me₂phen complexes, but they were not different from that of the corresponding free ligands, which confirmed that the original V(IV) complexes played no significant role in the observed biological activities. The cytotoxicities of the ligands were most likely due to their complexation of redox-active essential metal ions, such as Cu(II) and Fe(II), in the medium, and their increased cellular uptake, leading to oxidative stress-related cell death. These results emphasize the need to assess the stability of metal-based drugs under the conditions of biological assays, particularly when biologically active ligands, such as 1,10-phenanthroline and its derivatives, are used. These ligands have high systemic toxicities in vivo and their release in the GI tract and blood makes the complexes unsuitable for use as anti-cancer drugs.

1,10-Phenanthroline-5,6-Dione-Based Compounds Are Effective in Disturbing Crucial Physiological Events of Phialophora verrucosa

Phialophora verrucosa is a dematiaceous fungus able to cause chromoblastomycosis, phaeohyphomycosis and mycetoma. All these fungal diseases are extremely difficult to treat and often refractory to the current therapeutic approaches. Therefore, there is an urgent necessity to develop new antifungal agents to combat these mycoses. In this context, the aim of the present work was to investigate the effect of 1,10-phenanthroline-5,6-dione (phendione) and its metal-based derivatives [Ag(phendione)₂]ClO₄ = ([Ag(phendione)₂]⁺) and [Cu(phendione)₃](ClO₄)₂.4H₂O = ([Cu(phendione)₃]²⁺) on crucial physiological events of P. verrucosa conidial cells. Using the CLSI protocol, we have shown that phendione, [Ag(phendione)₂]⁺ and [Cu(phendione)₃]²⁺ were able to inhibit fungal proliferation, presenting MIC/IC₅₀ values of 12.0/7.0, 4.0/2.4, and 5.0/1.8 μM, respectively. [Cu(phendione)₃]²⁺ had fungicidal action and when combined with amphotericin B, both at sub-MIC (½ × MIC) concentrations, significantly reduced (~40%) the fungal growth. Cell morphology changes inflicted by phendione and its metal-based derivatives was corroborated by scanning electron microscopy, which revealed irreversible ultrastructural changes like surface invaginations, cell disruption and shrinkages. Furthermore, [Cu(phendione)₃]²⁺ and [Ag(phendione)₂]⁺ were able to inhibit metallopeptidase activity secreted by P. verrucosa conidia by approximately 85 and 40%, respectively. Ergosterol content was reduced (~50%) after the treatment of P. verrucosa conidial cells with both phendione and [Ag(phendione)₂]⁺. To different degrees, all of the test compounds were able to disturb the P. verrucosa conidia-into-mycelia transformation. Phendione and its Ag⁺ and Cu²⁺ complexes may represent a promising new group of antimicrobial agents effective at inhibiting P. verrucosa growth and morphogenesis.

In vitro evaluation of apoptotic effect of bis(acetylacetonato-k2 O,O')(1,10-phenanthroline-k2 N,N')Zn(II) complex

Phenanthroline derivatives have been reported as potential bioactive compounds because of their ability to interact with DNA. To evaluate the antiproliferative effect of bis(acetylacetonate-k² O,O)(1,10-phenanthroline-k² N,N)Zn(II) or Zn(acac)₂ (phen) complex, the compound was obtained in a simple manner and further characterized to determine crystal structure, thermal behavior, morphology, and spectroscopic properties. The structure of the complex was confirmed by X-ray single structure as well as by 1H and 13C nuclear magnetic resonance (NMR) in dmso-d6 (dimethyl sulfoxide) solution and in the solid state by 13C CP/MAS. Although preparation of this compound has been described previously, there are no reports on its biological activity; here, we assessed its antiproliferative effect on fibroblasts, A253, FaDu, Cal-27, RH-30, RD, U-373, C6, A-549, MDA-MB-231, and MCF-7 cancer cell lines at different doses (50-100 and 150 μg/ml). The cell viability was determined by MTT assay and high activity was observed for the most of the cell lines, and TUNEL results showed the induction of apoptosis.

Anti-Pseudomonas aeruginosa activity of 1,10-phenanthroline-based drugs against both planktonic- and biofilm-growing cells

OBJECTIVES

The beneficial antimicrobial properties of 1,10-phenanthroline (phen)-based drugs, together with the imperative need to develop new chemotherapeutic options for prevention/treatment of infections caused by MDR Gram-negative bacteria, led us to evaluate the effects of phen, 1,10-phenanthroline-5,6-dione (phendione), [Ag(phendione)2]ClO4 and [Cu(phendione)3](ClO4)2·4H2O on planktonic- and biofilm-growing Pseudomonas aeruginosa.

METHODS

Thirty-two non-duplicated Brazilian clinical isolates of P. aeruginosa with distinct genetic backgrounds were used in all experiments. The effect of test compounds on planktonic bacterial proliferation was determined as recommended by CLSI protocol. The effect on biofilm formation was evaluated by crystal violet incorporation (biomass determination) and XTT (viability assay). Mature biofilm disorganization was evidenced by staining with crystal violet.

RESULTS

Phen-based compounds presented anti-P. aeruginosa activity, but with different potencies concerning the geometric mean MIC: [Cu(phendione)3](2+) (7.76 μM) > [Ag(phendione)2](+) (14.05 μM) > phendione (31.15 μM) > phen (579.28 μM). MICs of each compound were similar irrespective of whether the P. aeruginosa isolates were susceptible or resistant to classical antimicrobials (ceftazidime, meropenem and imipenem). The pretreatment of bacteria with phen, phendione and phendione's metal derivatives at 0.5 × MIC value inhibited biofilm formation, particularly the use of [Cu(phendione)3](2+) and [Ag(phendione)2](+), which significantly reduced both biomass (48% and 44%, respectively) and viability (78% and 77%, respectively). The compounds studied also disrupted mature biofilm in a dose-dependent manner, especially [Ag(phendione)2](+) and [Cu(phendione)3](2+) (IC50, 9.39 and 10.16 μM, respectively).

CONCLUSIONS

Coordination of phendione to Ag(+) and Cu(2+) represents a new promising group of anti-infective agents, which revealed a potent anti-P. aeruginosa action against both planktonic- and biofilm-growing cells.

Novel copper(II) complexes as new promising antitumour agents. A crystal structure of [Cu(1,10-phenanthroline-5,6-dione)2(OH2)(OClO3)](ClO4)

The cytotoxic properties of copper(II) complexes with 1,10-phenanthroline (phen) can be modified by substitution in the phen backbone. For this purpose, Cu(II) complexes with phen, 1,10-phenanthrolin-5,6-dione (phendione) and 1,10-phenanthrolin-5,6-diol (phendiol) have been synthesised and characterised. The crystal structure of [Cu(phendione)2(OH2)(OClO3)](ClO4) is discussed. The complex formation equilibria between Cu(II) and phen or phendione were studied by potentiometric measurements at 25 and 37°C in 0.1 M ionic strength (NaCl). The antitumour activity of the compounds has been tested in vitro against a panel of tumour (DU-145, HEP-G2, SK-MES-1, CCRF-CEM, CCRF-SB) and normal (CRL-7065) human cell lines. The studied compounds generally present an antiproliferative effect greater than that of cisplatin. The phen and phendione ligands present a similar antiproliferative effect against all the tested cells. Phendiol presents an antiproliferative effect 1.3 to 18 times greater than that of phen or phendione for leukemic, lung, prostatic and fibroblast cells, while it presents less activity towards hepatic cells. Complexes with two ligands are more cytotoxic towards all the tested cell lines than complexes with one ligand and are generally more cytotoxic than the ligand alone. Complexes [Cu(phendiol)2(OH2)](ClO4)2 and [Cu(phendione)2(OH2)(OClO3)](ClO4) appear to be the most active compounds for the treatment of SK-MES-1 and HEP-G2 cells, respectively, being at least 18 times more cytotoxic than cisplatin. The studied Cu(II) complexes are characterised by a strong DNA affinity and were found to interact with DNA mainly by groove binding or electrostatic interactions. The complexes appear to act on cells with a mechanism different from that of cisplatin.

Re(I) tricarbonyl complex of 1,10-phenanthroline-5,6-dione: DNA binding, cytotoxicity, anti-inflammatory and anti-coagulant effects towards platelet activating factor

The complex fac-[Re(CO)3(phendione)Cl] (1) (where phendione=1,10-phenanthroline-5,6-dione) has been synthesized and fully characterized by UV-visible, FTIR, and NMR techniques. The DNA binding properties of 1 are investigated by UV-spectrophotometric (melting curves), covalent binding assay, CV (cyclic voltammetry), circular dichroism (CD) and viscosity measurements. Experimental data indicate that 1 fits into the major groove without disrupting the helical structure of the B-DNA in contrast to the free phendione which intercalates within the base pairs of DNA. Upon irradiation, complex 1 promotes the cleavage of plasmid pBR322 DNA from supercoiled form I to nicked form II via a proton coupled electron transfer mechanism. This comes as a result of experimental data in anaerobic/aerobic conditions and in the presence of DMSO. The biological activities of 1 and its precursors [Re(CO)5Cl] and phendione are tested towards a series of cancerous cell lines as glioblastoma (T98G), prostate cancer (PC3) and breast cancer (MCF-7) as well as platelet activating factor (PAF)-aggregation. Moreover, all the aforementioned compounds are tested for their ability to modulate PAF-basic metabolic enzyme activities in preparations of rabbit leukolytes. The in vitro experiments indicate that phendione has a better antitumor effect than cisplatin whereas [Re(CO)5Cl] is a better PAF inhibitor than both the phendione ligand and 1. Moreover, for the first time it is indicated that [Re(CO)5Cl], with a IC50 of 17nM is comparable to the widely used PAF receptor antagonists, BN52021 and WEB2170 with IC50 of 30 and 20nM, respectively, whereas 1 affects PAF-catabolism.