Therapeutic potential of coumarin bearing metal complexes: Where are we headed?

The successfully application of some metallodrugs such as salvarsan, silver sulfadiazine and cisplatin in modern medicine launched the biological investigation of organometallic and metal-organic complexes. The availability and tunability of various ligands including N-heterocycles, phosphines, N-heterocyclic carbenes present an extended research area to chemists. In recent years, the preparation of the metal complexes of bioactive organic compounds is a new strategy. Coumarin derivatives are one of the classes of compounds used for this purpose, and many complexes of coumarin derivatives were prepared for enhanced biological activity, especially anticancer and antimicrobial. In this paper, we discuss the current situation of this topic.

Water Soluble Coumarin Quaternary Ammonium Chlorides: Synthesis and Biological Evaluation.

In the present study, coumarin-bearing three pyridinium and three tetra-alkyl ammonium salts were synthesized. The compounds were fully characterized by 1 H- and 13 C-NMR, LC/MS and IR spectroscopic methods and elemental analyses. The cytotoxic properties of all compounds were tested against human liver cancer (HepG2), human colorectal cancer (Caco-2) and non-cancer mouse fibroblast (L-929) cell lines. Some compounds performed comparable cytotoxicity with standard drug cisplatin. Antibacterial properties of the compounds were tested against Gram-negative Escherichia coli and Gram-positive Bacillus subtilis bacteria, but the compounds did not have any antibacterial effect against both bacteria. Enzyme inhibitory properties of all compounds were tested on the activities of human carbonic anhydrase I and II, and xanthine oxidase. All compounds inhibited both enzymes more effectively than standard drugs, acetazolamide and allopurinol, respectively. The biological evaluation results showed that ionic and water soluble coumarin derivatives are promising structures for further investigations especially on enzyme inhibition field.

Catechol-bearing imidazolium and benzimidazolium chlorides as promising antimicrobial agents.

Catechol-containing imidazolium (four) and benzimidazolium chlorides (eight) were synthesized to evaluate their antimicrobial properties. All the compounds were fully characterized using 1 H and 13 C nuclear magnetic resonance, liquid chromatography-mass spectrometry, infrared spectroscopic methods, and elemental analyses. Antimicrobial activities of the compounds were tested against the bacteria Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, Klebsiella pneumoniae, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Enterococcus faecalis, and the fungal strains Candida albicans and Candida glabrata, and promising results were achieved. The two most important benzyl-substituted benzimidazolium chlorides, 3l and 3k, showed comparable activity to vancomycin against MRSA.

Microwave-assisted synthesis of 1-substituted-1H-benzimidazolium salts: Non-competitive inhibition of human carbonic anhydrase I and II.

A series of 1-substituted-1H-benzimidazolium p-toluenesulfonate salts were synthesized in good yields by the reaction of 1-substituted benzimidazole derivatives and p-toluenesulfonic acid under microwave irradiation. Two iodide salts were synthesized by the anion exchange reaction of the corresponding p-toluenesulfonate salt and NaI. All compounds were characterized by 1 H NMR, 13 C NMR, IR, LC-MS spectroscopic methods, and elemental analyses. The crystal structure of 1-methoxyethyl-1H-benzimidazolium p-toluenesulfonate 2d showed that cation and anion are interconnected by N-H···O and C-H···O hydrogen bonds. All compounds were examined as inhibitor of human carbonic anhydrase (hCA) I and II, and all of them inhibited hCA I and hCA II. Kinetic investigation results revealed that these compounds inhibit hCA I and hCA II in a non-competitive manner. The iodide salts had higher inhibitory activity than their corresponding p-toluenesulfonate salts.

Synthesis, characterization and antimicrobial activities of novel silver(I) complexes with coumarin substituted N-heterocyclic carbene ligands.

Eight new coumarin substituted silver(I) N-heterocyclic carbene (NHC) complexes were synthesized by the interaction of the corresponding imidazolium or benzimidazolium chlorides and Ag2O in dichloromethane at room temperature. Structures of these complexes were established on the basis of elemental analysis, (1)H NMR, (13)C NMR, IR and mass spectroscopic techniques. The antimicrobial activities of carbene precursors and silver NHC complexes were tested against standard strains: Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungi Candida albicans and Candida tropicalis. Results showed that all the compounds inhibited the growth of the all bacteria and fungi strains and some complexes performed good activities against different microorganisms. Among all the compounds, the most lipophilic complex bis[1-(4-methylene-6,8-dimethyl-2H-chromen-2-one)-3-(naphthalene-2-ylmethyl)benzimidazol-2-ylidene]silver(I) dichloro argentate (5e) was found out as the most active one.

Functionalized imidazolium and benzimidazolium salts as paraoxonase 1 inhibitors: Synthesis, characterization and molecular docking studies.

Paraoxonase (PON) is a key enzyme in metabolism of living organisms and decreased activity of PON1 was acknowledged as a risk for atherosclerosis and organophosphate toxicity. The present study describes the synthesis, characterization, PON1 inhibitory properties and molecular docking studies of functionalized imidazolium and benzimidazolium salts (1a-5g). The structures of all compounds were elucidated by IR, NMR, elemental analysis and structures of compounds 2b and 2c were characterized by single-crystal X-ray diffraction. Compound 1c, a coumarin substituted imidazolium salt showed the best inhibitory effect on the activity of PON1 with good IC50 value (6.37 µM). Kinetic investigation was evaluated for this compound and results showed that this compound is competitive inhibitor of PON1 with Ki value of 2.39 µM. Molecular docking studies were also performed for most active compound 1c and one of least active compound 2c in order to determine the probable binding model into active site of PON1 and validation of the experimental results.

In vitro inhibition effect of some coumarin compounds on purified human serum paraoxonase 1 (PON1).

Human serum paraoxonase 1 (PON1; EC 3.1.8.1) is a high-density lipoprotein associated, calcium-dependent enzyme that hydrolyses aromatic esters, organophosphates and lactones and can protect the low-density lipoprotein against oxidation. In this study, in vitro effect of some hydroxy and dihydroxy ionic coumarin derivatives (1-20) on purified PON1 activity was investigated. Among these compounds, derivatives 11-20 are water soluble. In investigated compounds, compounds 6 and 13 were found the most active (IC50 = 35 and 34 µM) for PON1, respectively. The present study has demonstrated that PON1 activity is very highly sensitive to studied coumarin derivatives.

Some coumarins and benzoxazinones as potent paraoxonase 1 inhibitors.

In this study, we aimed to investigate the effect of some coumarin and benzoxazinone derivatives on the activity of human PON1. Human serum paraoxonase 1 was purified from fresh human serum blood by two-step procedures that are ammonium sulfate precipitation (60-80%) and then hydrophobic interaction chromatography (Sepharose 4B, L-tyrosine and 1-napthylamine). The enzyme was purified 232-fold with a final specific activity of 27.1 U/mg. In vitro effects of some previously synthesized ionic coumarin or benzoxazinone derivatives (1-21) on purified PON1 activity were investigated. Compound 14 (1-(2,3,4,5,6)-pentamethylbenzyl-3-(6,8-dimethyl-2H-chromen-2-one-4-yl))benzimidazolium chloride was found out as the strongest inhibitor (IC50 = 7.84 µM) for PON1 among the compounds. Kinetic investigation and molecular docking study were evaluated for one of the most active compounds (compound 12) and obtained data showed that this compound is competitive inhibitor of PON1 and interact with Leu262 and Ser263 in the active site of PON1. Moreover, coumarin derivatives were found out as the more potent inhibitors for PON1 than benzoxazinone derivatives.

Coumarin or benzoxazinone based novel carbonic anhydrase inhibitors: synthesis, molecular docking and anticonvulsant studies.

Among many others, coumarin derivatives are known to show human carbonic anhydrase (hCA) inhibitory activity. Since hCA inhibition is one of the underlying mechanisms that account for the activities of some antiepileptic drugs (AEDs), hCA inhibitors are expected to have anti-seizure properties. There are also several studies reporting compounds with an imidazole and/or benzimidazole moiety which exert these pharmacological properties. In this study, we prepared fifteen novel coumarin-bearing imidazolium and benzimidazolium chloride, nine novel benzoxazinone-bearing imidazolium and benzimidazolium chloride derivatives and evaluated their hCA inhibitory activities and along with fourteen previously synthesized derivatives we scanned their anticonvulsant effects. As all compounds inhibited purified hCA isoforms I and II, some of them also proved protective against Maximal electroshock seizure (MES) and ScMet induced seizures in mice. Molecular docking studies with selected coumarin derivatives have revealed that these compounds bind to the active pocket of the enzyme in a similar fashion to that previously described for coumarin derivatives.

Synthesis, characterization, and tyrosinase inhibitory properties of benzimidazole derivatives.

1-Alkylbenzimidazole and 1,3-dialkyl benzimidazolium salts were synthesized and characterized by the data of IR, 1H NMR, 13C NMR spectra and elemental analyses. These compounds were investigated as tyrosinase inhibitors. Tyrosinase has been purified from banana by affinity chromatography on a Sepharose 4B gel conjugated with L-tyrosine-p-aminobenzoic acid. All the synthesized compounds inhibited the tyrosinase activity. Among the compounds studied, 1,4-di(1H-benzo[d]imidazol-1-yl)butane was found to be the most active tyrosinase inhibitor (IC50 0.31 mM).

Synthesis and carbonic anhydrase inhibitory properties of novel coumarin derivatives.

A newly series of water-soluble 1-alkyl-3-(4-methyl-7, 8-dihydroxy-2H-chromen-2-one) benzimidazolium chloride salts (3a-j) were synthesized and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA) I and II were evaluated. hCA I and II from human erythrocytes were purified by a simple one step procedure by using Sepharose 4B-L-tyrosine-sulphanilamide affinity column. The result showed that all the synthesized compounds were inhibited the CA isoenzymes activity. Among them, 3g and 3j were found to be most active (IC(50) = 22.09 µM and 20.33 µM) for hCA I and hCA II, respectively.

Efficiency enhancement with chloride to iodide ion exchange of benzimidazolium salt as a redox mediator.

The new benzimidazolium derivative (SM-1) salt with ion exchange from the (SM-0) was fabricated and characterized by proton-nuclear magnetic resonance (1H-NMR), carbon-nuclear magnetic resonance (13C-NMR), Fourier-transform infrared spectroscopy (FT-IR), electrospray ionization (EIS-MS), thermal analysis (TG), cyclic voltammetry (CV), and ultraviolet-visible spectroscopy (UV-vis), for electrolytes (liquid or dried) in the DSSC charge transportation mechanism. Also, the influence of ion exchange from chloride to iodine in the synthesized electrolytes, compared to other electrolytes (conventional or commercial), was investigated about DSSC performance efficiency. When using as a liquid electrolyte (SM-1), the power conversion efficiency (ƞ) of the working DSSC device was recorded as 1.980% and it was observed that the performances of DSSCs increased up to 56% when comparing dried electrolyte for SM-1 without conventional redox material (I-/I3 -). In the future, different molecular modifications of this type of benzimidazole derivatives or mixtures with conventional redox couples may further improve the performance of DSSC devices.

Iridium(i) complexes bearing hemilabile coumarin-functionalised N-heterocyclic carbene ligands with application as alkyne hydrosilylation catalysts.

A set of iridium(i) complexes of formula IrCl(κC,η2-IRCouR')(cod) or IrCl(κC, η2-BzIRCouR')(cod) (cod = 1,5-cyclooctadiene; Cou = coumarin; I = imidazolin-2-carbene; BzI = benzimidazolin-2-carbene) have beeen prepared from the corresponding azolium salt and [Ir(µ-OMe)(cod)]2 in THF at room temperature. The crystalline structures of 4b and 5b show a distorted trigonal bipyramidal configuration in the solid state with a coordinated coumarin moiety. In contrast, an equilibrium between this pentacoordinated structure and the related square planar isomer is observed in solution as a consequence of the hemilability of the pyrone ring. Characterization of both species by NMR was achieved at the low and high temperature limits, respectively. In addition, the thermodynamic parameters of the equilibrium, ΔHR and ΔSR, were obtained by VT 1H NMR spectroscopy and fall in the range 22-33 kJ mol-1 and 72-113 J mol-1 K-1, respectively. Carbonylation of IrCl(κC,η2-BzITolCou7,8-Me2)(cod) resulted in the formation of a bis-CO derivative showing no hemilabile behaviour. The newly synthesised complexes efficiently catalyze the hydrosilylation of alkynes at room temperature with a preference for the ß-(Z) vinylsilane isomer.

The influence of oxidative damage on viscosity of seminal fluid in infertile men.

Increased oxidative damage has been suggested to play an important role in the viscosity changes of blood. However, changes in levels of oxidative damage products in semen and their relationship to seminal fluid viscosity are unknown. The aim of our study was to investigate whether oxidative damage was associated with seminal plasma viscosity in infertile subjects. The levels of malondialdehyde, and protein carbonyls were measured in sperm and seminal plasma from 102 individuals, including 60 infertile patients. Seminal fluid viscosity and semen viscosity were studied by use of capillary viscometer and glass pipettes, respectively. Significantly higher levels of oxidative stress and damage markers were found in subfertile subjects compared with the control subjects. The seminal fluid viscosities of patients were found to be significantly higher, although all of the control and patient subjects had normal viscoelasticity when semen samples were assessed according to World Health Organization guidelines. From Pearson correlation analysis, there were significant positive correlations between seminal fluid viscosity and seminal malondialdehyde and carbonyl levels in infertile males (r = .676, P < .01; r = .276, P < .05, respectively). Our results suggest that increased oxidative damage might be a factor for hyperviscosity of seminal plasma in infertile males.

Increased oxidative damage of sperm and seminal plasma in men with idiopathic infertility is higher in patients with glutathione S-transferase Mu-1 null genotype.

AIM: To examine whether a relationship exists between glutathione S-transferase Mu-1 (GSTM1) gene polymorphism and the susceptibility of sperm and seminal plasma from patients with idiopathic infertility to oxidative stress. METHODS: Fifty-two men with idiopathic infertility and 60 healthy fertile men were recruited to this study. GSTM1 gene polymorphism was determined by polymerase chain reaction (PCR) and both the infertile and control individuals were divided into GSTM1 null and GSTM1 positive groups according to their GSTM1 gene structure. We compared reactive oxygen species (ROS) generation, malondialdehyde (MDA), protein carbonyls and glutathione (GSH) concentrations, and glutathione S-transferase (GST) activity in seminal plasma and spermatozoa from infertile patients and controls with respect to GSTM1 genotype. RESULTS: Significantly higher levels of oxidative stress and damage markers were found in idiopathic infertile men with the GSTM1 null genotype compared with those with the GSTM1 positive genotype. There was no significant difference in genotype distribution for the GSTM1 variant between the idiopathic infertile subjects and fertile subjects. Patients with the GSTM1 null genotype also had lower sperm concentrations than those with GSTM1 positive genotype. CONCLUSION: Our results suggest that the susceptibility of sperm and seminal plasma to oxidative stress is significantly greater in idiopathic infertile men with the GSTM1 null genotype compared with those possessing the gene. Therefore, in patients with idiopathic infertility, GSTM1 polymorphism might be an important source of variation in susceptibility of spermatozoa to oxidative damage.

High levels of cadmium and lead in seminal fluid and blood of smoking men are associated with high oxidative stress and damage in infertile subjects.

We measured the levels of malondialdehyde (MDA), protein carbonyls, glutathione S-transferase (GST) and reducte glutathione (GSH) in seminal plasma and spermatozoa from 95 subjects including 50 infertile patients to evaluate the association between oxidative stress and damage and the components of the anti-oxidant defenses in seminal plasma and spermatozoa of infertile subjects and concentrations of cadmium (Cd) and lead (Pb) in the blood and seminal plasma because of tobacco smoke exposure. The reactive oxygen species (ROS) in spermatozoa were also evaluated by luminol (5-amino-2,3-dihydro-1,4-phthalazinedione)-enhanced chemiluminescence assay. The sperm count, motility, and morphology in the smokers infertile group were found to be lower than those in the fertile male group and nonsmokers infertile group (p < 0.001). Concentrations of Cd, Pb, MDA, protein carbonyls, and ROS levels in the smokers infertile group were significantly higher than those in the fertile male and nonsmokers infertile male groups (p < 0.001). However, GSH levels and GST activities were decreased in the smokers infertile male group than those in the fertile male and nonsmokers infertile male groups (p < 0.001). The results indicate that smoking could affect semen quality and oxidative lipid and protein damage in human spermatozoa. From Pearson correlation analysis, positive correlations were demonstrated between the seminal plasma Cd and seminal plasma protein carbonyls and between seminal plasma Pb and spermatozoa ROS levels in smokers of the subfertile group, while there was a significant positive correlation between blood Cd and ROS levels in smokers of the fertile group. There was also a significant negative correlation of the Cd level of the blood and GSH levels of the sperm and seminal plasma. These findings suggest that cigarette smoking enhances the levels of Cd and Pb in seminal plasma and blood and the extent of oxidative damage associated with a decrease in components of the anti-oxidant defenses in the sperm of infertile males.

Assessment of the continence status and patients' satisfaction after retropubic radical prostatectomy: a questionnaire based study.

OBJECTIVE: The aim of this study was to assess the continence status and patients' satisfaction after retropubic radical prostatectomy by a self-administered questionnaire composed of 12 questions. MATERIALS AND METHODS: In total, 143 patients who underwent RRP operation at our department from 1992 to 2000 with a minimum 6 months of follow-up were assessed. Seventy two patients participated in the study. The continence status was classified as follows; patients who did not leak were considered as "continent", those who had leakage that occurred less frequent than or equal to once a day were regarded as "socially continent", and those who had more than once a day leakage were regarded as "incontinent". The correlation between urinary leakage, patients' satisfaction and pre-operative, peri-operative and post-operative factors were investigated. Univariate and multivariate analyses were done using Fisher's exact, chi-square, Student's-t and logistic regression tests. RESULTS: The mean age of patients at surgery was 63.9 years (49-76) with a follow-up period of 37.1 months (6-97). Of these patients, 44% were continent, 48% were socially continent, 8% were incontinent. A total of 64 of 72 patients (89%) were satisfied with their final continence status, and 63 (87%) patients accepted to undergo the same surgery again if it is indicated. Pre-, peri- and post-operative factors did not influence the urinary leakage rates. Patients with nocturnal leakage, urgency, decreased urinary flow and patients who use pad (-s) were significantly less satisfied on univariate analysis, while only nocturnal leakage had a significant impact on patients' satisfaction on multivariate analysis. CONCLUSION: Urinary leakage and patients' satisfaction rates after RRP were 56% and 89%, respectively. None of the factors could predict the post-operative continence status. When evaluating the patients' satisfaction, only nocturnal leakage was found to have an adverse affect on multivariate analyses.

Ureteroscopy and holmium laser lithotripsy in pregnancy: stents must be used postoperatively.

PURPOSE: To present our experience with ureteroscopy and holmium laser lithotripsy in pregnant patients and discuss the need for stents postoperatively. PATIENTS AND METHODS: A retrospective analysis was performed on seven consecutive pregnant patients presenting with renal colic necessitating intervention between 1997 and 2003. One patient presented during the first, five in the second, and one in the third trimester. Abdominal ultrasonography was the primary diagnostic test. If the stone could not be seen with a rigid ureteroscope, flexible ureteroscopy (f-URS) was performed. Stones were fragmented with a holmium laser, and large fragments were taken out. Ureteral stents were placed routinely in all but the first two patients. RESULTS: The ureteral stones could be seen with ultrasonography in three patients. In four patients, holmium lasertripsy could be done by the rigid ureteroscope. In the remaining patients, f-URS was performed, and two upper-system stones were fragmented. Six patients were rendered stone free. In one patient, both collectingsystem dilation and right perirenal liquid accumulation were present by ultrasonography, but no stones could be detected. Ureteral-stent insertion reduced postoperative pain and analgesic use in the whole group. CONCLUSIONS: When conservative therapy fails in the pregnant patient with a ureteral stone, ureteroscopy and holmium lasertripsy should be considered. Routine insertion of ureteral stents with pull-out strings for at least 72 hours will reduce the pain and analgesic use postoperatively.

Impact of Cu and Fe concentrations on oxidative damage in male infertility.

Oxidative stress in the reproductive system is thought to have an effect on the fertilizing ability of sperm. The purpose of this study was to assess the interaction of iron (Fe) and copper (Cu) ions in suspected subfertile and fertile male groups and to find out the relationships of the semen parameters (sperm count, motility, and abnormal morphology), glutathione, malondialdehyde, and reactive oxygen species with these variables. Semen and blood obtained from 60 subfertile men and from 40 fertile volunteers were examined. The sperm count and motility in the subfertile male group were found lower than those in fertile male group (p < 0.001). Cu levels in serum and seminal plasma in the subfertile male group were significantly higher than those in the fertile male group (p < 0.001 and p < 0.05, respectively). There was also a significant increase in the Fe level of seminal plasma in the subfertile male group (p < 0.001). However, there was no significant difference in the Fe level of serum in the subfertile male group. In conclusion, these findings suggest that Cu and Fe might be mediators of the effects of oxidative damage and play an essential role in spermatogenesis and male infertility; the determination of Fe and Cu levels in serum and seminal plasma during infertility investigation is recommended.

Changes of nitric oxide synthase-containing nerve fibers and parameters for oxidative stress after unilateral cavernous nerve resection or manuplation in rat penis.

After pelvic surgeries such as radical prostatectomy, two major complications--urinary incontinence and erectile dysfunction (ED) may occur. Etiologies for ED are multiple pathologic mediators/systems. Oxidative stress, which is known to be induced after surgical trauma, could be a cause of ED. The purposes of in this study are to investigate the effect of unilateral manipulation/ dissection and resection of the cavernous nerve (neurotomy) to NOS (nitric oxide synthase)-containing nerve fibers and pressure after electro stimulation in rat corpus cavernosum, and to determine whether these procedures would produce oxidative stress within rat cavernous tissue 3 weeks and 6 months after the operation. Male rats were divided into 5 groups. Rats in groups 1 and 2 underwent unilateral cavernous nerve manipulation and sacrificed 3 weeks and 6 months after the operation, respectively. Rats in groups 3 and 4 underwent unilateral neurotomy of a 5-mm. segment of the cavernous nerve, and they were sacrificed 3 weeks and 6 months after nerve ablation, respectively. Group 5 rats were control animals for biochemical analysis. Intracavernous pressure following electro stimulation reduced is significantly 3 weeks after unilateral resection, as compared to that of the manipulated nerve (P < 0.05), and it recovered 6 months after neurotomy. The recovery was also confirmed by NADPH (nicotinamide adenine dinucleotide phosphate) diaphorase staining in neurotomy groups. Lipid peroxidation, which is an indicater of oxidative stress, was determined by measuring thiobarbituric acid reacting substance (TBARS) levels and superoxide dismutase (SOD) activity. These markers indicated that unilateral cavernous nerve manipulation or resection produced oxidative stress within rat corpus cavernosum. Oxidative stress was more prominent 3 weeks after unilateral neurotomy (P < 0.05). Also, compared to the control animal group, oxidative stress was observed three weeks after manipulation of unilateral cavernous nerve (P < 0.05). Resection of the cavernous nerve caused more prominent oxidative stress than in the manipulation group. This study suggested, that unilateral cavernous neurotomy caused a decrease of intra cavernous pressure and NOS fibers in rat corpus cavernosum, and they recovered 6 months after neurotomy. Our data also provided evidence that neurotomy and manipulation of the cavernous nerve caused oxidative stress in rat corpus cavernosum and that oxidative stress was more prominent in the nerve resection group.