Action Of Coumarin Research Articles

Coumarin and eugenol ameliorate LPS-induced inflammation in RAW 264.7 cells via modulating the NLRP3 inflammasome pathway

Objective: To investigate the underlying mechanism of anti-inflammatory action of coumarin and eugenol in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. Methods: RAW 264.7 cells were treated with 2.5 μg/mL of LPS, 50 μM of coumarin, and 50 μM eugenol for 24 h. The viability of the cells was assessed using MTT assay. The production of nitric oxide was determined using Griess reagent and DCFH-DA was used to measure the production of reactive oxygen species. The protein expression of NLRP3, IL-1β, NF-κB, and cyclooxygenase 2 was assessed using Western blot analysis. Results: Coumarin and eugenol showed anti-inflammatory effects against LPS-induced inflammatory response by ameliorating the expression of NLRP3 inflammasome and NF-κB, which further led to a subsequent reduction in IL-1β, nitric oxide, and reactive oxygen species. Conclusions: Coumarin and eugenol exert their anti-inflammatory activities by modulating the NLRP3 inflammasome pathway and NF-κB. These compounds may have promising therapeutic applications for the treatment of various inflammatory diseases.

Antiplasmodial activity of coumarins isolated from Polygala boliviensis: in vitro and in silico studies

Polygala boliviensis is found in the Brazilian semiarid region. This specie is little chemically and biologically studied. Polygala spp. have different metabolites, especially coumarins. Studies indicate that coumarins have antimalarial potential, denoting the importance of researching new active compounds from plants, since the resistance of Plasmodium strains to conventional therapy has increased. The present study aimed to evaluate the antiplasmodial activity of auraptene and poligalen against a chloroquine-resistant strain of Plasmodium falciparum. Coumarins were isolated from P. boliviensis by open column chromatography and identified by Nuclear Magnetic Resonance Spectroscopy. A cytotoxicity assay was carried out using MTT test, and the in vitro antiplasmodial activity was evaluated using the W2 strain. The antiplasmodial activity results found were IC50=0.171 ± 0.016 for auraptene and 0.164 ± 0.012 for poligalen; the selectivity indexes were 78.71 and 609.76, respectively. Inverse virtual screening in the BRAMMT database by OCTOPUS 1.2 was applied to coumarins to find potential P. falciparum targets and showed higher affinity energy of auraptene for purine nucleoside phosphorylase (PfPNP) and of poligalen for dihydroorotate dehydrogenase (PfDHODH). Molecular Dynamics studies (MD and MM-GBSA) approach were applied to calculate binding energies against selected P. falciparum targets and showed that all coumarins were stable at the binding site during simulations. Furthermore, energies were favorable for complexation. This is the first report of auraptene in P. boliviensis species and of in vitro antiplasmodial activity of auraptene and poligalen. In silico studies indicated that the mechanism of action of coumarins is the inhibition of PfPNP and PfDHODH. Communicated by Ramaswamy H. Sarma

Изменение физико-химических и культуральных свойств бактерий Azospirillum baldaniorum Sp245 под влиянием некоторых синтетических кумаринов

Due to the small number of studies on the role of coumarins in associative symbiotic relationships, some aspects of the influence of synthetic coumarins on the physicochemical and cultural properties of Azospirillum baldaniorum Sp245 were studied for the first time. To reveal the role of hydroxylation in position 7 of the fused aromatic ring – 1-(2-oxo-2H-chromen-3-yl)butan-1,3-dione, comparative studies of the effect of the original and hydroxylated coumarins on the culture of a model strain of azospirilla were carried out. The survival of bacteria after the addition of coumarins was studied by counting CFU on an agar medium. The biofilm formation activity of the culture was assessed using crystal violet. The change in the surface of bacteria under the action of coumarins was studied by the electrical polarizability of bacterial cells on an ELUS electrooptical analyzer (EloSystemGbR, Germany). The yield and monosaccharide composition of extracellular glycopolymers were studied using gas-liquid chromatography.For the first time, an increase in the yield of EPS of bacteria during growth in the presence of 1-(7-hydroxy-2-oxo-2Hchromen-3-yl)butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM respectively was observed. It has been established for the first time that the hydroxylated substance has a higher antibacterial activity compared to the unsubstituted one. A decrease in the number of viable cells in planktonic culture and inhibition of biofilm growth were revealed. It has been shown by electro-optical analysis that the presence of coumarins in the cultivation medium in all concentrations studied leads to a change in the electrical polarizability of A. baldaniorum Sp245 cells. The use of electrooptical analysis of cell suspensions using monospecific antibodies obtained against lipopolysaccharides of this strain made it possible to reveal the absence of changes in carbohydrate antigenic determinants on the surface of bacterial cells. This is consistent with the data of the analysis of the composition of extracellular polysaccharides by GLC, during which no differences were found in the qualitative composition and ratio of monosaccharides. An increase in the yield of bacterial EPS during growth in the presence of 1-(7-hydroxy-2-oxo-2H-chromen-3-yl) butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM was shown. The results obtained allow us to consider the changes that have occurred as features of the adaptation of bacteria to the associative conditions of existence.

The Delay of Raphanus raphanistrum subsp. sativus (L.) Domin Seed Germination Induced by Coumarin Is Mediated by a Lower Ability to Sustain the Energetic Metabolism.

In the present study, the mode of action of coumarin using the germination process as a target was investigated. A dose–response curve, built using a range of concentrations from 0 to 800 µM, allowed us to identify a key concentration (400 µM) inhibiting the germination process, reducing its speed without compromising seed development. Successively, short time-course (0–48 h) experiments were carried out to evaluate the biochemical and metabolic processes involved in coumarin-induced germination delay. The results pointed out that coumarin delayed K+, Ca2+, and Mg2+ reabsorption, suggesting a late membrane reorganisation. Similarly, seed respiration was inhibited during the first 24 h but recovered after 48 h. Those results agreed with ATP levels, which followed the same trend. In addition, the untargeted metabolomic analysis allowed to identify, among the pathways significantly impacted by the treatment, amino acids metabolism, the TCA cycle, and the glyoxylate pathway. The results highlighted that coumarin was able to interact with membranes reorganisation, delaying them and reducing the production of ATP, as also supported by pathway analysis and cell respiration. The in vivo 31P-NMR analysis supported the hypothesis that the concentration chosen was able to affect plant metabolism, maintaining, on the other hand, its viability, which is extremely important for studying natural compounds’ mode of action.

Coumarin (2H-1-Benzopyran-2-one) act against planktonic and biofilm forms of Staphylococcus aureus, Klebsiella pneumoniae and Pseudomonas aeruginosa

Introduction: biofilm-related infections caused by Staphylococcus aureus, Klebsi-ella pneumoniae and Pseudomonas aeruginosa are difficult to treat and few effective pharmacological options are currently available for this purpose. In this context, coumarin (2H-1-Benzopyran-2-one) has been reported to have antibacterial and antibiofilm activity, but this potential remains poorly understood. Aim: to investi-gate the action of coumarin on planktonic and biofilm forms of S. aureus, K. pneu-moniae and P. aeruginosa. Results: a minimum inhibitory concentration (MIC) of coumarin ranging from 256 to 1024 μg/mL was observed, with a remarkable ability to inhibit the formation of biofilms and to act on mature biofilms in concentrations close to MIC. Conclusion: coumarin has strong activity against planktonic and biofilm forms on the three species of great relevance in the clinical scenario. These results are interesting to enable a pharmacological alternative for the treatment of these infections.

Allelochemical Activity of Eugenol-Derived Coumarins on Lactuca sativa L.

Coumarins are widely distributed substances in plant species that promote phytotoxic effects, allowing them to be exploited as herbicides less harmful to the environment, since many invasive species have demonstrated resistance to commercially available products. The derived coumarins used in this study had not been tested in plant models and their effect on plants was unknown. The objective of this study was to evaluate the phytotoxic action of these coumarins in bioassays with Lactuca sativa L., in order to select the most responsive substance whose toxicity was best elucidated by chromosomal complement and enzymatic antioxidant metabolism studies. From the phytotoxicity assays, coumarin 8-methoxy-2-oxo-6-(prop-2-en-1-yl)-2H-chromene-3-carboxylic acid (A1), reported here for the first time, was selected as the most responsive and caused a reduction in the following parameters: number of normal seedlings, fresh biomass, root length and shoot length. Subsequent studies demonstrated that this coumarin is cytogenotoxic due to damage caused to the cell cycle and the occurrence of chromosomal abnormalities. However, it did not interfere with antioxidant enzyme activity and did not cause lipid peroxidation. The changes caused by coumarin A1 described herein can contribute to better understanding the allelochemical actions of coumarins and the potential use of these substances in the production of natural herbicides.

Coumarin enhances nitrate uptake in maize roots through modulation of plasma membrane H+ -ATPase activity.

Coumarin is one of the simplest plant secondary metabolites, widely distributed in the plant kingdom, affecting root form and function, including anatomy, morphology and nutrient uptake. Although, some plant responses to coumarin have been described, comprehensive knowledge of the physiological and molecular mechanisms is lacking. Maize seedlings exposed to different coumarin concentrations, alone or in combination with 200μm nitrate (NO3- ), were analysed, through a physiological and molecular approach, to elucidate action of coumarin on net NO3- uptake rate (NNUR). In detail, the time course of NNUR, plasma membrane (PM) H+ -ATPase activity, proton pumping and related gene expression (ZmNPF6.3, ZmNRT2.1, ZmNAR2.1, ZmHA3 and ZmHA4) were evaluated. Coumarin alone did not affect nitrate uptake, PM H+ -ATPase activity or transcript levels of ZmNRT2.1 and ZmHA3. In contrast, coumarin alone increased ZmNPF6.3, ZmNAR2.1 and ZmHA4 expression in response to abiotic stress. When coumarin and NO3- were concurrently added to the nutrient solution, a significant increase in the NNUR, PM H+ -ATPase activity, together with ZmNAR2.1:ZmNRT2.1 and ZmHA4 expression was observed, suggesting that coumarin affected the inducible component of the high affinity transport system (iHATS), and this effect appeared to be mediated by nitrate. Moreover, results with vanadate, an inhibitor of the PM H+ -ATPase, suggested that this enzyme could be the main target of coumarin. Surprisingly, coumarin did not affect PM H+ -ATPase activity by direct contact with plasma membrane vesicles isolated from maize roots, indicating its possible elicitor role in gene transcription.

New Insights into the Antibacterial Activity of Hydroxycoumarins against Ralstonia solanacearum.

Coumarins are important plant-derived natural products with wide-ranging bioactivities and extensive applications. In this study, we evaluated for the first time the antibacterial activity and mechanisms of action of coumarins against the phytopathogen Ralstonia solanacearum, and investigated the effect of functional group substitution. We first tested the antibacterial activity of 18 plant-derived coumarins with different substitution patterns, and found that daphnetin, esculetin, xanthotol, and umbelliferone significantly inhibited the growth of R. solanacearum. Daphnetin showed the strongest antibacterial activity, followed by esculetin and umbelliferone, with MICs of 64, 192, and 256 mg/L, respectively, better than the archetypal coumarin with 384 mg/L. We further demonstrated that the hydroxylation of coumarins at the C-6, C-7 or C-8 position significantly enhanced the antibacterial activity against R. solanacearum. Transmission electron microscope (TEM) and fluorescence microscopy images showed that hydroxycoumarins may interact with the pathogen by mechanically destroying the cell membrane and inhibiting biofilm formation. The antibiofilm effect of hydroxycoumarins may relate to the repression of flagellar genes fliA and flhC. These physiological changes in R. solanacearum caused by hydroxycoumarins can provide information for integral pathogen control. The present findings demonstrated that hydroxycoumarins have superior antibacterial activity against the phytopathogen R. solanacearum, and thus have the potential to be applied for controlling plant bacterial wilt.

Antiplatelet and anticoagulation therapyEdited by AlbertFerro & David E.Garcia. Published by Springer, New York. 2013. 247 pp, £27.99. ISBN 978-1-4471-4296-6; ISBN 978-1-4471-4297-3 (eBook)

As a clinician, I found that the book edited by Albert Ferro and David A. Garcia provided not only all the updated information necessary to guide therapeutic options but also a deep and comprehensive insight into the mechanisms of the action of antiplatelet and anticoagulant drugs along with an open discussion on the main controversy in the field of antithrombotic therapy. All these points have been addressed in five chapters by recognized experts in their field, with an updated, thorough and extremely detailed analysis of the available evidence. The book is timely, because we have new therapeutic opportunities with novel antiplatelet and anticoagulation agents that promise improvements in efficacy and tolerability; promises and also uncertainties, when these drugs are used on a large scale in the real world. In addition, we still have unanswered questions concerning the efficacy and safety of drugs such as coumarins, heparins, aspirin and the ADP receptor P2Y12 inhibitors thienopyridines, drugs that have for decades been the only therapeutic options. The book opens with an overview of the mechanisms of platelet activation and its modulation, followed by a comprehensive description of kinetics, mechanisms of action and proofs of efficacy of current and novel inhibitors of platelet function. The so-called resistance to the antiplatelet activity of aspirin and P2Y12 inhibitors is dissected in the second chapter, with an open-minded view of the present scientific discussion. Variable activity, as assessed in platelet functional tests, has been advocated as evidence for failure in treatment and cause of an excess in cardiovascular events. Differences in bioavailability, which may be due to genetic polymorphysms in metabolizing enzymes, are a likely explanation. However, whether genetic testing or the analysis of platelet function is necessary for monitoring prior to during treatment has yet to be proved. The chapter dedicated to anticoagulant agents mirrors in its structure that on antiplatelet drugs, containing an exhaustive description of the kinetics and mechanisms of the action of coumarins, heparins and the new direct thrombin and Factor Xa inhibitors, accompanied by data concerning appropriate doses and evidence of efficacy in the clinical setting. The strength of new anticoagulant agents is pointed out, because they have more predictable pharmacokinetics and direct inhibitory effects on critical steps in the coagulation cascade. At the same time, issues such as dosing in patients with renal failure, the need for monitoring and optimization of the antihrombotic activity vs. the risk of haemorrhage are clearly discussed. The second part of the book contains the two chapters dedicated to antithrombotic prevention and therapy in cardiovascular and thromboembolic diseases. The description of the recommended prevention and treatment for acute coronary syndrome and stroke is synthetic, but extremely accurate. The same can be said for the chapter dedicated to deep vein thrombosis, pulmonary embolism and atrial fibrillation. The dilemmas that we face concerning the criteria for risk assessment in individual patients, appropriate choice and combination of antithrombotic agents, duration and intensity of treatment, as well as monitoring and safety issues are carefully and convincingly discussed, with a rational interpretation of the information derived from clinical trials and updated guidelines. The book is written in clear language, and the reader is also aided by a large number of figures, tables and diagrams summarizing all the major notions. It is intended as a reference guide to be used by cardiovascular professionals in daily clinical practice, but can be seen also as a systematic essay that allows the reader to be guided, step by step, to a thorough comprehension of clinical pharmacology of antithrombotic agents and their use in the treatment of cardiovascular and thromboembolic diseases.

Antinociceptive Profiles and Mechanisms of Orally Administered Coumarin in Mice

In the present study, the antinociceptive profiles of coumarin were examined in ICR mice. Coumarin administered orally (from 1 to 10 mg/kg) showed an antinociceptive effect in a dose-dependent manner as measured in the acetic acid-induced writhing test. Duration of antinociceptive action of coumarin maintained at least for 60 min. But, the cumulative response time of nociceptive behaviors induced by a subcutaneous (s.c.) formalin injection, intrathecal (i.t.) substance P (0.7 µg) or glutamate (20 µg) injection was not affected by coumarin. In addition, intracerebroventricular (i.c.v.) or intrathecal (i.t.) administration with coumarin (10-40 µg) attenuated acetic acid-induced writhing response in a dose dependent manner. Intraperitoneal (i.p.) pretreatment with naloxone (an opioid receptor antagonist) attenuated antinociceptive effect induced by coumarin in the writhing test. Furthermore, i.c.v. or i.t. pretreatment with naloxone (5 µg) reversed the decreased acetic acid-induced writhing response. However, methysergide (a 5-HT serotonergic receptor antagonist) or yohimbine (an α2-adrenergic receptor antagonist) did not affect antinociception induced by coumarin in the writhing test. Our results suggest that coumarin exerts a selective antinociceptive property in the acetic acid-induced visceral-derived pain model. Furthermore, the antinociceptive effect of coumarin may be mediated by activation of central opioid receptors, but not serotonergic and adrenergic receptors.

Class action of oral coumarins in the treatment of a patient with chronic spontaneous urticaria and delayed-pressure urticaria

Chronic spontaneous urticaria is a common condition, with a lifetime prevalence of 0.5-1.0%. It has a significant effect on quality of life, comparable to having triple-vessel coronary artery disease. Warfarin and nicoumalone are synthetic derivatives of the plant toxin coumarin. We report the first case of successful response to both warfarin and nicoumalone in the same patient, thereby demonstrating a class action of synthetic coumarins in the disease. Complete response with both coumarins occurred once an INR above 2.0 was achieved, and was maintained during a 12-month follow-up. The mechanism of action of coumarins on urticaria is not known, but may be related to decrease in thrombin production or to interference of activation of other inflammatory proteins produced during the coagulation process. Side-effects of anticoagulation can be catastrophic, and coumarin treatment currently remains reserved for restricted severe recalcitrant cases only.

Mechanism of Action of Coumarin against Candida albicans by SEM/TEM Analysis

The aim of this study was to identify the antifungal activity of coumarin isolated from Ageratum conyzoides L. leaves and to observe its influence on Candida albicans cells by scanning electron microscope (SEM) and transmission electron microscope (TEM). Antifungal activity testing with the disk diffusion method showed coumarin was active toward pathogenic fungus Candida albicans with an MIC value of coumarin of 125 g mL -1 . The results show that this compound damaged the cell by pores formation on the cell wall. Death of cells occurred due to leakage and necrosis of cytoplasmic content.

The Structure and Pharmacological Functions of Coumarins and Their Derivatives

Coumarins are of many different structures. They constitute an important class of pharmacological agents possessing a range of different physiological activities including anti-cancer, anti-oxidant, anti- inflammation, anti-HIV, anti-coagulant, anti-bacterial, analgesic and comparative immune-modulation. Recently, coumarins have attracted intense research interest. Of great interest is the possibility that this class of molecules could be a source of drugs for the therapy of several diseases. These include recent insights into inhibiting cell proliferation by interfering with mitotic spindle microtubule function, decrease Matrix Metalloproteinase (MMP) activity, block the cell cycle in the S or G2/M phases to interfere with processes of cell division, suppress O2(-) generation in leukocytes, inhibit different protein kinases, modulate the signalings, induce carcinogen-detoxifying enzymes glutathione S-transferases (GSTs) and/or NAD(P)H quinine oxidoreductase (NQO1), suppress the phosphorylation of Akt/PKB as a mechanism inhibiting inflammation, progress in structure modification to increase in anti-fungal action, to broaden against bacteria spectrum, to enhance inhibiting activities of nitric oxide synthase (NOS) and cyclooxygenase (COX), to strengthen anti-oxidant activity and to exhibite a much higher cytotoxicity against human umbilical vein endothelial cell (HUVEC). With fewer non-hemorrhagic side effects than the indanedione derivatives, they can be applied as an oral anticoagulant commonly for preventing venous thromboembolism following orthopedic surgery, recurrent myocardial infarction and the treatment of systemic embolism in atrial fibrillation, together with the significant advances in the basis of drug action. It is therefore useful to build up some correlations with the data available in order to better explore the molecular and cellular mechanism of coumarin action in the treatment of diseases. This review will focus on recent advances in molecular and cellular mechanisms of coumarin action involved with the relationship between structure and activity.

Mechanism of action of coumarin and silver(I)–coumarin complexes against the pathogenic yeast Candida albicans

The anti-fungal activity and mode of action of a range of silver(I)–coumarin complexes was examined. The most potent silver(I)–coumarin complexes, namely 7-hydroxycoumarin-3-carboxylatosilver(I), 6-hydroxycoumarin-3-carboxylatosilver(I) and 4-oxy-3-nitrocoumarinbis(1,10-phenanthroline)silver(I), had MIC 80 values of between 69.1 and 4.6 μM against the pathogenic yeast Candida albicans. These compounds also reduced respiration, lowered the ergosterol content of cells and increased the trans-membrane leakage of amino acids. A number of the complexes disrupted cytochrome synthesis in the cell and induced the appearance of morphological features consistent with cell death by apoptosis. These compounds appear to act by disrupting the synthesis of cytochromes which directly affects the cell’s ability to respire. A reduction in respiration leads to a depletion in ergosterol biosynthesis and a consequent disruption of the integrity of the cell membrane. Disruption of cytochrome biosynthesis may induce the onset of apoptosis which has been shown previously to be triggered by alteration in the location of cytochrome c. Silver(I)–coumarin complexes demonstrate good anti-fungal activity and manifest a mode of action distinct to that of the conventional azole and polyene drugs thus raising the possibility of their use when resistance to conventional drug has emerged or in combination with such drugs.

The future prospects of pharmacogenetics in oral anticoagulation therapy

Coumarins are the mainstay of oral anticoagulation for the treatment and prophylaxis of thromboembolic disorders. They have a narrow therapeutic index and regular monitoring is therefore required to avoid serious adverse effects. There is wide interindividual variability in dosage requirements, which makes anticoagulation response unpredictable. Current dosing titrations are haphazard and inconvenient and poor initial control leads to morbidity, and occasional mortality, because of bleeding and further thromboembolism. Recent discoveries have helped to characterize the factors that contribute to the interindividual variability in responses to coumarins. Patient and environmental factors that affect anticoagulation response to coumarins include age, body size, dietary vitamin K status, concurrent disease and drug interactions. More recently, single nucleotide polymorphisms in the 2C9 isoform of cytochrome P450 (CYP2C9) and vitamin K epoxide reductase (VKOR) have been shown to make significant contributions to the variability in coumarin dosage requirements. Polymorphisms in other genes that mediate the actions of coumarins may also contribute to this variability. Racial and cultural differences influence dosage requirements, which can be explained, at least in part, by genetic and dietary factors. Incorporation of genetic and environmental factors could help in the prediction of more individualized loading and maintenance doses for safer anticoagulation therapy.

The Interaction of Drugs with DNA Gyrase: A Model for the Molecular Basis of Quinolone Action

DNA gyrase supercoils DNA in bacteria. The fact that it is essential in all bacteria and absent from eukaryotes makes it an ideal drug target. We discuss the action of coumarin and quinolone drugs on gyrase. In the case of coumarins, the drugs are known to be competitive inhibitors of the gyrase ATPase reaction. From a combination of structural and biochemical studies, the molecular details of the gyrase-coumarin complex are well established. In the case of quinolones, the drugs are thought to act by stabilising a cleavage complex between gyrase and DNA that arrests polymerases in vivo. The exact nature of the gyrase-quinolone-DNA complex is not known; we propose a model for this complex based on structural and biochemical data.

Studies on the cytostatic and cytotoxic effects and mode of action of 8-nitro-7-hydroxycoumarin.

A derivative of coumarin, 8-nitro-7-hydroxycoumarin (8-NO2-7-OHC), was synthesised, purified and characterised. The cytostatic and cytotoxic nature of this compound was determined using both human and animal cell lines grown in vitro for 96 h in the presence of drug (0-500 microM, equivalent to 0-104 microg/ml). 8-NO2-7-OHC was shown to be cytotoxic to three cell lines, but cytostatic to all cell lines tested. With K562 and HL-60 cells, cell death was found to occur by apoptosis. This cytotoxic effect was found to be irreversible, with cell death continuing to occur following a 96 h recovery period. The cytostatic effects were found to be irreversible in four of the five cell lines tested. 8-NO2-7-OHC demonstrated its cytostatic effects within 24 or 48 h, while its cytotoxic effects appeared more gradually. The IC50 of 8-NO2-7-OHC was 475-880 microM, depending on the cell line tested. It was shown to exert its cytostatic effect through an alteration of cell cycle. It also inhibited DNA synthesis. The toxicity of 8-NO2-7-OHC does not appear to be mediated through the multi-drug resistance (MDR) protein since it caused significant cytostatic and cytotoxic effects to CHrC5 cells, which have an increased expression of this protein. This compound was shown to be non-mutagenic in a standard Ames test, both with or without a mammalian enzyme activation system. The applications and mode of actions of coumarins are discussed.

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

Coumarin (1,2-benzopyrone) is a natural substance that has shown antitumor activity in vivo. The major human metabolite of coumarin, 7-hydroxycoumarin (7-HC), is the active form of the drug. While the exact mechanism(s) of action of coumarin is unknown, it has been shown previously that this drug possesses immunomodulatory activity in vitro and in vivo. The present investigations examined the direct (non-immunological) antitumor effects of coumarin and 7-HC in vitro. Both coumarin and 7-HC were found to be growth-inhibitory (cytostatic) for the following human malignant cell lines: A549, ACHN, Caki-2, Dakiki, HS-Sultan, H727, HCT-15, HL-60, K562, LNCaP, PC-3, Du 145 COLO-232, MCF-7 and RP-1788. The growth inhibition was dependent on dose and time and was reversible upon removal of cells from medium containing the drug. Coumarin and 7-HC inhibited [3H]thymidine, [3H]uridine and [3H]leucine incorporation. In a similar fashion, coumarin and 7-HC inhibited the intracellular production of prostate-specific antigen by LNCaP cells. Coumarin and 7-HC stimulated apoptosis in HL-60 cells but not in other cell lines tested. It is concluded that coumarin and 7-HC have direct antitumor (cytostatic) activity as well as immunomodulatory activity. Further information is needed in order to determine which activities are responsible for antitumor activity in vivo.

Mode of action of coumarin in immune cells

In order to characterize further the mode of action of coumarin, binding studies were undertaken using human monocytes and radioactively labelled drug. Since coumarin is only a small compound and we wanted to exclude possible artefacts due to variations in size or conformation, the drug was produced by synthesis in the presence of radioactive 14C. Adding increasing amounts of a mixture of labelled and unlabelled drug to monocytes resulted in saturating conditions only at rather high concentrations. Performing Scatchard analysis demonstrated that binding sites for coumarin appeared to be present in relatively high numbers (7.5 x 10(8)/cell) but their affinity was rather low (K alpha approximately 2 x 10(2) M-1). Inhibition studies with 7-hydroxycoumarin revealed that an approximately four times higher molar concentration of the derivative was necessary to cause 50% displacement of coumarin from its binding site. These results indicate that binding of the drug to cells is characterized by high-capacity but low-affinity conditions. This would be compatible with the hypothesis that coumarin interacts with ubiquitous intracellular receptor proteins able to interact with aromatic hydrocarbons, which might form the basis for enzyme induction, and leads to the effects observed in vitro and in vivo.

Oral Anticoagulant Drugs

The vitamin K-antagonist drugs were reviewed in the Journal in the early 1970s.1 , 2 Since then, there has been considerable progress in research at both a basic and an applied level. The mode of action of coumarins has been clarified; their role in the management of thromboembolic disorders has been more clearly defined; a system has been developed to standardize the measurement of their anticoagulant effect3; and their safety has been improved for a number of indications without compromising efficacy, through the use of a lower degree of anticoagulation than formerly in North America.4 Warfarin (a 4-hydroxycoumarin compound) is the . . .