Growth-inhibitory effects of coumarin (1,2-benzopyrone) and 7-hydroxycoumarin on human malignant cell lines in vitro

Synthesis and antitumor studies on novel Co(II), Ni(II) and Cu(II) metal complexes of bis(3-acetylcoumarin)thiocarbohydrazone

The synthesis, structure, physico-chemical investigation and biological studies of some metal complexes of thiocarbohydrazone ligands are described. The ligand is obtained by condensation of N,N'-thiocarbohydrazide with 3-acetylcoumarin. The metal complexes of Co(II), Ni(II) and Cu(II) with bis(3-acetylcoumarin)thiocarbohydrazone were synthesized and isolated as solid products and characterized by analytical means as well as by spectral techniques such as FT-IR, (1)H NMR and EPR and UV spectrometry. The ligand acts as bidentate, through NO or NN, neutral in coordinating the M(II) ions. The bonding sites are the azomethine nitrogen, lactone carbonyl oxygen and respective anion counterparts. The metal complexes exhibit either octahedral or distorted octahedral structures. The complexes are found to be soluble in dimethylformamide and dimethylsulphoxide. Molar conductance values in dimethylsulphoxide indicate the non-electrolytic nature of the complexes. The compounds tested in present study have shown promising cytotoxic activity when screened using the in vitro method and at the same time were shown to have good activity when tested using the Ehrlich Ascites Carcinoma model. Preliminary antimicrobial screening shows the promising results against both bacterial and fungal strains.

New diorganotin(IV) derivatives of 7-hydroxycoumarin (umbelliferone) and their adducts with 1,10-phenanthroline

New diorganotin(IV) derivatives of the general formula R2Sn(Umb)2 (where R = n-Bu, n-Oct and Ph; Umb = umbelliferone anion) have been synthesized either by the reaction of R2SnO with umbelliferone under azeotropic removal of water or by the reaction of R2SnCl2 with sodium salt of umbelliferone. Further, the adducts of the general formula R2Sn(Umb)2.phen (where R = n-Bu and n-Oct; phen = 1,10-phenanthroline) have also been synthesized by the interaction of R2Sn(Umb)2 with 1,10-phenanthroline. The bonding and coordination behavior in these derivatives are discussed on the basis of IR and 119Sn Mössbauer spectroscopic studies in solid state. Their coordination behavior in solution is discussed by the multinuclear (1H, 13C and 119Sn) NMR spectral studies. The Mössbauer and IR studies indicate that umbelliferone acts as a monoanionic bidentate ligand in R2Sn(Umb)2 coordinating through O(7) and O(1). A distorted octahedral geometry around tin has been proposed for R2Sn(Umb)2 as well as for R2Sn(Umb)2.phen in solid state. The newly synthesized derivatives have been tested for their anti-inflammatory and cardiovascular activities. The average LD50 value >1000 mg kg(-1) of these compounds indicates their safety margin.

A study of the role of cell cycle events mediating the action of coumarin derivatives in human malignant melanoma cells

6-Nitro-7-hydroxycoumarin (6-NO2-7-OHC) and 3,6,8-trinitro-7-hydroxycoumarin (3,6,8-NO2-7-OHC) have previously been shown to be potent and selective anti-proliferative agents to the human skin cell line, SK-MEL-31. Here, we investigate the reversibility of their cytotoxicity, along with their effects on DNA synthesis and cell cycle events. Comparative studies were carried out using the main metabolite of coumarin in man, 7-hydroxycoumarin (7-OHC). 6-NO2-7-OHC and 3,6,8-NO2-7-OHC, were found to be irreversible cytotoxic agents, unlike 7-OHC. All three derivatives inhibited DNA synthesis, but 7-OHC was only nitro-derivatives which acted in an irreversible manner. Flow cytometric studies demonstrated that both nitro-derivatives caused a dose- and time-dependant S phase accumulation. 7-OHC exerted a similar effect, but appeared to be less potent. Finally, the two nitro-derivatives caused a dose-dependant inhibition of the S phase regulatory protein, cyclin A. Consequently, these and other nitro-derivatives of 7-OHC may represent novel therapeutic agents for the treatment of malignant melanoma as they are capable of selective and irreversible cytotoxicity.

Investigation of intracellular signalling events mediating the mechanism of action of 7-hydroxycoumarin and 6-nitro-7-hdroxycoumarin in human renal cells

Previously, 7-hydroxycoumarin (7-OHC) and 6-nitro-7-hydroxycoumarin (6-NO2-7-OHC) have been shown to be potent and selective anti-proliferative agents to the human renal cell carcinoma (RCC) cell line, A-498. Their effect on mitogen-activated protein kinases (MAPK's) was investigated. 6-NO2-7-OHC was shown to alter the phosphorylation status of ERK1/ERK2, p38 and SAPK, while 7-OHC activated ERK1/ERK2 but had no effect on p38 and SAPK. Also, 7-OHC inhibited topoisomerase II mediated relaxation of DNA, while neither compound was a substrate for P-glycoprotein (P-gp) mediated multi-drug resistance (MDR). Therefore, 6-NO2-7-OHC, rather than 7-OHC, modulated signalling events associated with cellular differentiation and apoptosis, suggesting its mechanism of action may be the promotion of cellular maturation and/or death. Consequently, 6-NO2-7-OHC may represent a novel therapeutic agent for the treatment of RCC's.

Apoptosis and cell cycle disturbances induced by coumarin and 7-hydroxycoumarin on human lung carcinoma cell lines

Coumarin and 7-hydroxycoumarin have anti-tumour actions in vitro and in vivo. There are no previous reports on the cytostatic and apoptotic actions of coumarin and 7-hydroxycoumarin in non-small cell lung carcinoma (NSCLC) cell lines. Here we report on: (1) the inhibition of cell proliferation, (2) the phase in which cell cycle arrest occurs, and (3) the induction of apoptosis. Inhibition of cell proliferation was determined by 3H-thymidine incorporation. The effects on cell cycle phases were determined at 100 microg/ml of coumarin or 7-hydroxycoumarin using propidium iodide and flow cytometry. Higher concentrations were used to study apoptosis, detected by: (1) morphological cell changes, (2) subG1 peak detection and (3) Annexin-V assay. Peripheral blood mononuclear cells (PBMC) stimulated with phytohemagglutinin were used as controls. The actions of these compounds depended on drug concentrations and on histological cell type. Coumarin and 7-hydroxycoumarin inhibited cell growth by inducing cell cycle arrest in the G1 phase in all the lung carcinoma cell lines. Apoptosis required large concentrations of the coumarin compounds and was observed in adenocarcinomas. Apoptosis was not associated with intra-nucleosomal DNA fragmentation. Apoptosis was not observed in squamous lung carcinoma cell lines, but an increase in G1 cell cycle arrest was detected. In PBMC, only large concentrations of the coumarin compounds elicited a cystostatic action. Coumarins in combination with other anti-neoplastic drugs might increase the effectiveness of NSCLC treatments.

Biologically active alkylated coumarins from Kayea assamica

Four coumarin derivatives, theraphins A (1), B (2), C (3), and D (4), along with three known xanthones, 2-hydroxyxanthone, 1,7-dihydroxyxanthone, and 5-hydroxy-1-methoxyxanthone, were isolated from the bark of Kayea assamica (Clusiaceae) native to Myanmar. Their structures were determined using spectroscopic and chemical techniques. The absolute configuration of 1 was established by the modified Mosher ester method. Theraphins A (1), B (2), and C (3) exhibited good cytotoxicity against Col2, KB, and LNCaP human cancer cell lines. Theraphin D (4) showed mild activity only against the KB cell line. The coumarins also exhibited mild antimalarial activities.

In vitro cytotoxic potential and mechanism of action of selected coumarins, using human renal cell lines

This study determined the selective cytotoxicity of eight coumarin compounds to human renal carcinoma cells, relative to non-carcinoma proximal tubular cells. Selectivity cytotoxicity was observed following exposure to 6-nitro-7-hydroxycoumarin (6-NO(2)-7-OHC) and 7,8-dihydroxycoumarin (7,8-OHC). 6-NO(2)-7-OHC induced cytotoxicity was irreversible in both cell lines, unlike 7,8-OHC, which was reversible in the carcinoma cells only. Mobility shift and BrdU incorporation assays showed that both compounds did not intercalate DNA but had a concentration-dependent inhibitory effect on its synthesis. All coumarins studied were found to be non-mutagenic using the standard Ames test. These results would suggest that 6-NO(2)-7-OHC and 7,8-OHC might have a therapeutic role to play in the treatment of renal cell carcinoma.

Decrease of cyclin D1 in the human lung adenocarcinoma cell line A-427 by 7-hydroxycoumarin

Coumarin in vivo has antitumor activity in various types of cancer. In vitro, coumarin and 7-hydroxycoumarin, its major biotransformation product in humans, inhibit the proliferation of several human tumor cell lines. The molecular mechanisms of these effects are unknown. To gain information about these mechanisms, we studied the effects of coumarin and 7-hydroxycoumarin in the human lung adenocarcinoma cell line A-427 on the inhibition of: (i) cell proliferation; (ii) cell cycle progression; and (iii) expression of cyclins D1, E and A. The inhibitory concentrations 50 (IC(50)) of both compounds were estimated by cytostatic assays of tetrazolium (MTT) reduction. The effects on cell cycle progression were assayed with propidium iodide and BrdU using DNA histograms and multiparametric flow cytometry. The percentages of cells expressing cyclins D1, E, and A were estimated by means of bivariate flow cytometry using propidium iodide, and FITC-conjugated monoclonal antibodies for each cyclin. The IC(50) (+/-S.E.M. n=3) of 7-hydroxycoumarin and coumarin at 72 h exposure, were 100+/-4.8 and 257+/-8.8 microg/ml, respectively. 7-Hydroxycoumarin at the concentration of 160 microg/ml (1 mM), inhibited the G(1)/S transition of the cell cycle, an action consistent with the cytostatic effect. No significant decreases of cyclins E and A were observed. In contrast, cyclin D1 significantly decreased, which appears to indicate an action of 7-hydroxycoumarin in early events of phase G(1). However, messenger RNA of cyclin D1, assayed by RT-PCR, did not change. This suggests a posttranscriptional effect. The effects of coumarin were not significant. Cyclin D1 is overexpressed in many types of cancer, and its inhibition has been proposed as a pharmacological and therapeutic target for novel antitumor agents. Knowledge of the decrease of cyclin D1 by 7-hydroxycoumarin may lead to its use in cancer therapy, as well as to the development of more active compounds.

Study of the in vitro cytotoxic potential of natural and synthetic coumarin derivatives using human normal and neoplastic skin cell lines

A selection of natural and synthetic coumarin compounds, including the hydroxylated and nitrated derivatives, were assessed for their cytotoxic potential using the microculture 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay for cellular viability. For the first time this study utilized both human skin malignant melanocytes (SK-MEL-31) and normal human skin fibroblastic cells (HS613.SK), allowing identification of those coumarin derivatives that are selectively toxic. Coumarin was found to exhibit comparatively low toxicity in both cell types, while 7-hydroxycoumarin (7-OHC) and coumarin had similar activity in SK-MEL-31 cells. The entire series of hydroxylated coumarins were considerably more toxic in HS613.SK than in SK-MEL-31 cells. Novel synthetic nitrated coumarins, 6-nitro-7-hydroxycoumarin (6-NO2-7-OHC) and 3,6,8-nitro-7-hydroxycoumarin (3,6,8-NO2-7-OHC), were shown to be significantly more toxic to SK-MEL-31 than HS613.SK cells. In the malignant melanocyte skin cell line (SK-MEL-31) the cytotoxic effects of these nitro-derivatives were shown to be dose and time dependent. Therefore, the cytotoxic potential of coumarins appears to be highly dependent on the nature and position of the functional group. In addition, nitration of 7-OHC produced compounds that were cytotoxic to malignant melanocytes, suggesting that these nitro-derivatives may have a chemotherapeutic role in the future.

Suppression of the proliferation and migration of oncogenic ras-dependent cell lines, cultured in a three-dimensional collagen matrix, by flavonoid-structured molecules

The effects of 7-hydroxycoumarin, genistein and quercetin on two ras-oncogene-driven tumour cells (rat breast adenocarcinoma and human bladder carcinoma) were investigated using cellular (proliferation and migration) and molecular targets (p21ras GTPase activity and intracellular amount of p21ras protein). All three compounds inhibited the growth of both cell lines. Genistein was the most effective substance. Furthermore, 7-hydroxycoumarin and genistein affected the motile machinery of both cell lines because major fractions of the cells were slowed down or stopped locomotion. The phorbol ester, phorbol 12-myristate 13-acetate (PMA), a well-known tumour promoter, increased the locomotion behaviour of the cells; the time of migration, the velocity and the distance of migration increased under the control of PMA. 7-Hydroxycoumarin decreased the relative amount of intracellular p21ras, and concomitantly a PMA-induced decrease of p21ras GTPase activity could be partially antagonized by 7-hydroxycoumarin. Because of the low toxicity and the mode of action evaluated, it is likely that the best role for these substances may be adjuvant therapy of some malignancies following surgery. Profiles directed to migration and proliferation inhibition make these drugs exceptional candidates for chemopreventive strategies in tumours diagnosed as having increased ras oncogene levels.

An updated review of the clinical development of coumarin (1,2-benzopyrone) and 7-hydroxycoumarin

Several authors have demonstrated that coumarin (1,2-benzopyrone) in combination with cimetidine can produce objective antitumor responses in some patients with advanced renal cell carcinoma. The purpose of this report is to review the clinical development of coumarin, with or without cimetidine, with special reference to renal cell carcinoma (RCC). Previously unpublished data concerning the survival of a population of patients with RCC, who were treated on a phase I trial of coumarin and cimetidine, are presented. The rationale and study design of an active randomized, double-blinded, placebo-controlled trial of coumarin for RCC are discussed. A progress report is given for an ongoing phase I trial of oral 7-hydroxycoumarin, the major human metabolite of coumarin.