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PubMed2005

Antioxidant and cytotoxic isoprenylated coumarins from Mammea americana.

Antioxidant-guided fractionation of Mammea americana L. seeds resulted in the identification of three new isoprenylated coumarins, mammea B/BA hydroxycyclo F (1), mammea E/BC (2), and mammea E/BD (3). In addition, twelve known isoprenylated coumarins, mammea A/AA (4), mammea A/AA cyclo D (5), mammea A/AA cyclo F (6), mammea A/AC cyclo D (7), mammea A/AD cyclo D (8), mammea B/BA (9), mammea B/BA cyclo F (10), mammea B/BB (11), mammea B/BC (12), mammea B/BD (13), mammea E/BA (14), and mammea E/BB (15), as well as two known flavanols, (+)-catechin (16) and (-)-epicatechin (17) were identified. The fifteen isoprenylated coumarins were screened for their cytotoxicity in the SW-480, HT-29, and HCT-116 human colon cancer cell lines and antioxidant capacities in the DPPH (1,1-diphenyl-2-picrylhydrazyl) free-radical assay. Compounds 1 - 15 exhibited significant cytotoxic activities in the SW-480, HT-29, and HCT-116 human colon cancer cell lines (IC50 ranges 13.9 - 88.1, 11.2 - 85.3, and 10.7 - 76.7 microM, in the three cell lines, respectively) at concentrations comparable to 5-fluorouracil (IC50 = 53.0, 46.1, and 45.1 microM), a drug frequently used for human colon cancer treatment. Compounds 2 - 4, 9, and 11 - 15 displayed high antioxidant activity in the DPPH assay (IC50 range 86 - 135 microM), compounds 1, 5 - 8, and 10, however, had no antioxidant activity (IC50 > 200 microg/mL) in the DPPH assay. The results of these assays were used to study the structure-activity relationships for this class of compounds. In the SW-480 cell line, the three new coumarins, 1 - 3, also exhibited dose-dependent increases in sub-diploid cells by flow cytometry, indicating that they induce apoptosis.

Antineoplastic Agents, Phytogenic↗
PubMed2002

Species differences in coumarin metabolism: a molecular modelling evaluation of CYP2A interactions.

1. An account of the differences in coumarin metabolism between several mammalian species, including man, is reported. 2. The metabolism of coumarin via 7-hydroxylation in the human (CYP2A6) and mouse (CYP2A5) enzymes is explained in terms of molecular modelling of the active site interactions, whereas the rat orthologue (CYP2A1) exhibits 3,4-epoxidation of coumarin, which is also consistent with the modelled interaction between enzyme and substrate. 3. In addition, quantitative structure-activity relationships (QSARs) for coumarin 7-hydroxylation in wild-type and mutant CYP2A5 show the importance of amino acid residue properties for substrate binding, whereas QSARs for CYP2A6 substrates indicate the importance of hydrogen bonding and lipophilicity for favourable interactions with the enzyme.

Amino Acid Sequence↗
PubMed2006

Coumarins from Coriaria nepalensis.

Two new coumarins (1) and (2), along with seven known coumarins 3-9, were isolated from the leaves and stems of Coriarianepalensis Wall. The two new compounds were established as 7-hydroxy-6-methoxy-3,8-bis(3-methyl-2-butenyl) coumarin (1) and 7-hydroxy-6-methoxy-3-(3-methyl-2-butenyl) coumarin (2), on the basis of 1D and 2D NMR techniques. The known compounds 3, 6-9 were isolated from this plant for the first time.

Coumarins↗
PubMed2006

Impact of short-term hypothyroidism on systemic anticoagulation in patients with thyroid cancer and coumarin therapy.

Unlike hyperthyroidism, few data exist regarding the impact of hypothyroidism on systemic anticoagulation with coumarin derivates. Therefore, we evaluated a potential impact of short-term hypothyroid conditions on systemic anticoagulation with coumarin derivates in patients after complete thyroidectomy for treatment of thyroid cancer. Fifteen patients with differentiated thyroid cancers and continued international normalized ratio (INR)-adjusted therapy with coumarin derivates were included in this retrospective analysis. A total of 88 laboratory tests was analyzed. INR values were compared between thyroid-stimulating hormone (TSH) values greater than 10 and 10 mU/L or less. An INR value of less than 2.0 was defined as being out of the therapeutic range. Analysis of significant differences between categorized TSH and INR values were performed by using X(2) analysis, correlation of continuous TSH and INR values by using the Pearson's analysis. When TSH was greater than 10 mU/L (n = 50) the INR value was less than 2.0 in 76.0% (n = 38) cases. In contrast, the INR value was less than 2.0 in only 21.1% (n = 8; p < 0.0001) of patients with TSH of 10 mU/L or less (n = 38). Correlation between continuous TSH and INR values was r = -0.589 (p < 0.0001). Based on the results of the present study, it seems to be necessary to monitor the anticoagulation parameters more often in patients with hypothyroidism and either to correct the hypothyroid state, or in cases of desired hypothyroid conditions, to adjust the therapy with coumarin derivates in order to ensure a sufficient anticoagulation.

Aged↗
PubMed1999

Cytostatic activity of coumarin metabolites and derivatives in the B16-F10 murine melanoma cell line.

Coumarin has antitumour effects in vivo and cytostatic effects in vitro. Its half-life in humans is short (1-1.5 h) and the monohydroxylated biotransformation products have significantly longer half-lives. One or several of these products may thus be responsible for the antitumoral effects. We have assayed the in vitro cytostatic activity of five monohydroxylated coumarins (3-, 4-, 6-, 7- and 8-monohydroxycoumarin), their acetates and methyl-ethers. Murine melanoma cells (cell line B16-F10) and murine fibroblasts (B82) were exposed to the test compounds at concentrations between 10 and 160 microg/ml. The cytostatic effects were estimated by reduction of the tetrazolium dye MTT. In the melanoma cells, some of the compounds inhibited growth after exposure for 1 day. In contrast, coumarin inhibited growth to a smaller extent, and only after exposure for 3 days. The most active compounds (3-acetoxycoumarin, 4-methoxycoumarin and 6-hydroxycoumarin), as well as coumarin, were also assayed in murine fibroblasts. The cytostatic effects of 4-methoxycoumarin and 6-hydroxycoumarin were less pronounced in fibroblasts than in melanoma cells. Our observations suggest that these compounds may have a greater therapeutic margin.

Animals↗
PubMed1992

Interindividual variability of coumarin 7-hydroxylation in healthy volunteers.

A test designed to estimate the extent and rate of formation of 7-hydroxycoumarin by measuring the urinary excretion of the metabolite in humans after administering 5 mg coumarin was developed. Coumarin was rapidly metabolized after oral administration and more than 95% of the 7OHC formed was excreted in 4 h. The total amount of 7OHC formed was 64 +/- 15% (mean +/- SD, variation 20-100%) of the dose given. The percentage of 7OHC excreted in 2 h, as compared with the 7OHC excretion in 4 h, was found to be a constant and stable individual characteristic for the rate of the formation of 7OHC ('2 h coumarin test'). In 110 volunteers, there was a great interindividual variability in the extent and rate of 7OHC formation. Four individuals had relatively 'slow' coumarin test values (50-60%), but much larger populations would be needed for the demonstration of polymorphism.

Adult↗
PubMed1998

A new deleted allele in the human cytochrome P450 2A6 (CYP2A6) gene found in individuals showing poor metabolic capacity to coumarin and (+)-cis-3,5-dimethyl-2-(3-pyridyl)thiazolidin-4-one hydrochloride (SM-12502).

The S-oxidation of (4)-cis-3,5-dimethyl-2-(3-pyridyl)thiazolidin-4-one hydrochloride (SM-12502) and the 7-hydroxylation of coumarin are primarily catalyzed by cytochrome P450 2A6 (CYP2A6). The activities of SM-12502 S-oxidase and coumarin 7-hydroxylase were investigated with liver microsomes from 20 human individuals. Liver microsomes from individual H16 showed the lowest activities of both enzymes. The expression of CYP2A6 protein was not detectable in liver microsomes from individuals H4, H5, H7, H8, H12 and H16. CYP2A6 mRNA was hardly detectable in the liver of the individual H16. A new SacI-restriction fragment length polymorphism showing the lack of a 2.6 kb fragment was found in two of forty genomic DNA preparations from individuals H16 and No. 594, using CYP2A6 cDNA as a probe. This deletional 2.6 kb fragment was isolated from a genomic library prepared from one individuals showing normal coumarin 7-hydroxylase activity and was sequenced. This fragment contained a CYP2A6 gene region from 319 bp upstream of a putative exon 6 to a SacI site in exon 9, indicating that this region was deleted in the two individuals in this study. We also demonstrated by polymerase chain reaction analysis that the exon 8 of CYP2A6 gene was deleted in individuals H16 and No. 594. These results indicate that the reduced activity of SM-12502 S-oxidase and no activity of coumarin 7-hydroxylase are caused by the lack of CYP2A6 mRNA and CYP2A6 protein caused by the CYP2A6 gene deletion.

Aryl Hydrocarbon Hydroxylases↗
PubMed1992

gyrB mutations which confer coumarin resistance also affect DNA supercoiling and ATP hydrolysis by Escherichia coli DNA gyrase.

Coumarins are inhibitors of the ATP hydrolysis and DNA supercoiling reactions catalysed by DNA gyrase. Their target is the B subunit of gyrase (GyrB), encoded by the gyrB gene. The exact mode and site of action of the drugs is unknown. We have identified four mutations conferring coumarin resistance to Escherichia coli: Arg-136 to Cys, His or Ser and Gly-164 to Val. In vitro, the ATPase and supercoiling activities of the mutant GyrB proteins are reduced relative to the wild-type enzyme and show resistance to the coumarin antibiotics. Significant differences in the susceptibility of mutant GyrB proteins to inhibition by either chlorobiocin and novobiocin or coumermycin have been found, suggesting wider contacts between coumermycin and GyrB. We discuss the significance of Arg-136 and Gly-164 in relation to the notion that coumarin drugs act as competitive inhibitors of the ATPase reaction.

Adenosine Triphosphate↗
PubMed1994

The 24 kDa N-terminal sub-domain of the DNA gyrase B protein binds coumarin drugs.

A number of lines of evidence suggest that the N-terminal sub-domain of the DNA gyrase B protein contains the binding site for the coumarin antibiotics. We have engineered a clone which encodes a 24 kDa protein which represents this domain. Bacteria which overproduce this protein show an elevated level of resistance to coumarins, suggestive of binding of the 24 kDa protein to the drugs in vivo. In vitro we find that the 24 kDa protein does not interact with the gyrase A or B proteins or with DNA, and fails to hydrolyse ATP or show significant binding to ATP, ADP or ADPNP. However, we show that the 24 kDa protein binds coumarin drugs as tightly as the intact B protein. A number of experiments suggest that the interaction of the coumarins with the protein is predominantly hydrophobic in nature.

Adenine Nucleotides↗
PubMed1988

Purification and characterization of a liver microsomal cytochrome P-450 isoenzyme with a high affinity and metabolic capacity for coumarin from pyrazole-treated D2 mice.

Microsomal coumarin 7-hydroxylase activity is regulated differently from several other monooxygenase enzymes, at least in mice [Wood, A. W. and Conney, A. H. (1974) Science (Wash. DC) 612-614]. Recently we found that in D2 mice this activity is strongly and selectivity induced by pyrazole [Juvonen, R. O., Kaipainen, P. K. and Lang, M. A. (1985) Eur. J. Biochem. 152-3-8]. This paper describes the purification of the pyrazole-inducible cytochrome P-450 isoenzyme. Because of the lability of the protein, a special procedure for the purification was developed. The procedure is based on a combination of hydrophobic and ion-exchange chromatography and the presence of 100 microM coumarin in the preparations throughout the whole purification. Coumarin effectively protected the P-450 from degradation and also converted the pyrazole-inducible P-450 to its high-spin state. This enabled us to choose only those fractions for further purification where the P-450(s) was in its high-spin state (rather than measuring the content of the total P-450). As a result the purified protein had an apparent molecular mass of 49.7 kDa, a specific content of 19.9 nmol/mg protein and a very high affinity and metabolic capacity for coumarin.

Animals↗
PubMed2006

Widespread skin necrosis associated with unfractionated heparin therapy in a patient under chronic coumarin anticoagulation.

Coumarins and heparins are commonly used for temporary or long-term anticoagulation. These molecules have potentially devastating side-effects, including widespread skin necrosis. We report the case of an elderly patient under oral anticoagulation with coumarins, who developed widespread necrotic cutaneous lesions upon introduction of intravenous and subcutaneous unfractionated heparin administration for a surgical procedure. Laboratory investigations revealed the presence of circulating antibodies directed against heparin-platelet factor 4. The lesions slowly resolved after withdrawal of heparin, whereas oral coumarin was re-introduced without complications. This case illustrates the rare occurrence of skin necrosis as a result of unfractionated heparin in a patient under chronic coumarin medication. Recognition of this rare complication and appropriate laboratory testing is mandatory for prompt institution of alternative anticoagulant therapies.

Aged↗
PubMed1994

Spectroscopic studies of coumarin in micelles.

Steady-state and time-resolved emission spectroscopic techniques have been employed to characterize the coumarin species and identify which species is solubilized in the hydrocarbon core micelles of triton X-100 (neutral), hexadecyltrimethyl ammonium bromide (cationic) and dodecyl lithium sulfate (anionic) solutions under physiological conditions at 77 K. The emission and absorption spectra for the following species of coumarin-monomer, hydrogenbonded complex, molecular aggregation and strong hydrophobic aggregates-were recorded in methylcyclohexane (MCH), ethanol, buffers and aqueous solutions. The fluorescence and phosphorescence emissions of monomer in MCH at 77 K are assigned as resulting from 1(pi, pi*)1 and 3(pi, pi*)1 states, respectively, originated from the ethylenic bond and carbonyl of the pyrone ring. Molecular orbital calculations using the Hydrogenic Atoms in Molecule, version 3, method were carried out to help interpretation of the spectroscopic results. The photophysical properties from each species are used to probe which species penetrates in the hydrophobic region of micelles. It was found that a fifth species of coumarin assigned as the "action species" is solubilized into the interior of micelles. These observations could lend some insight into the mechanism of transporting coumarins across the membrane.

Coumarins↗
PubMed1993

Structural requirements for the direct and cytochrome P450-dependent reaction of cyclic alpha,beta-unsaturated carbonyl compounds with glutathione: a study with coumarin and related compounds.

The interaction of glutathione (GSH) with coumarin, or one of a series of compounds related to coumarin, was assessed in the absence and presence of liver microsomes (direct reaction and indirect reaction, respectively) to determine the structural requirements for direct and mono-oxygenase-mediated reaction of cyclic alpha,beta-unsaturated carbonyls with GSH. Acrolein was used as a positive control for the direct reaction, and produced complete or nearly complete depletion of GSH under all assay conditions. 5,6-Dihydro-2H-pyran-2-one and 2-cyclohexen-1-one also produced substantial depletion of GSH in the direct reaction, which was not increased by the addition of liver microsomes. Coumarin, 2H-pyran-2-one and precocene I (a substituted pyran lacking the 2-one structure) were not substrates for the direct reaction but did cause depletion of GSH when incubated in the presence of rat or human liver microsomes. These depletions were dependent on a functioning mono-oxygenase system as judged by the effects of omission of cofactors, addition of competitive or inactivating inhibitors of cytochrome P450, and induction. Dihydrocoumarin, delta-valerolactone, cyclohexanone and 4H-pyran-4-one were not substrates for either the direct or indirect reaction. These findings are rationalized on the basis of a direct nucleophilic attack of GSH on the alpha,beta-centre of the alpha,beta-unsaturated carbonyl compounds, which is hindered by benzenoid resonance in coumarin and 2H-pyran-2-one, for which enzyme-mediated reaction with GSH, probably via a 3,4-epoxide, is the favoured mechanism.

Aged↗
PubMed1969

Vitamin K and coumarin anticoagulants: dependence of anticoagulant effect on inhibition of vitamin K transport.

Coumarin anticoagulants inhibit the release of plasma clotting factor VII by vitamin K in liver slices from vitamin K-deficient animals without inhibition of protein synthesis. When the ratio of vitamin K to coumarin anticoagulant is kept constant, but the concentrations are increased, the inhibition disappears. This suggests that the pharmacological action of coumarin anticoagulants depends on irreversible inhibition of normal vitamin K transport to its site of action. At higher concentrations of vitamin K the inhibition can be surmounted, because vitamin K can enter the cell by an alternate route that is not inhibited by coumarin anticoagulants.

Animals↗
PubMed1988

Coumarin and quinolone action in archaebacteria: evidence for the presence of a DNA gyrase-like enzyme.

The action of novobiocin and coumermycin (two coumarins which interact with the gyrB subunit of eubacterial DNA gyrase) and ciprofloxacin (a fluoroquinolone which interacts with the gyrA subunit of DNA gyrase) was tested on several archaebacteria, including five methanogens, two halobacteria, and a thermoacidophile. Most strains were sensitive to doses of coumarins (0.02 to 10 micrograms/ml) which specifically inhibit DNA gyrase in eubacteria. Ciprofloxacin inhibited growth of the haloalkaliphilic strain Natronobacterium gregoryi and of the methanogen Methanosarcina barkeri. In addition, ciprofloxacin partly relieved the sensitivity to coumarins (and vice versa). Novobiocin inhibited DNA replication in Halobacterium halobium rapidly and specifically. Topological analysis has shown that the 1.7-kilobase plasmid from Halobacterium sp. strain GRB is negatively supercoiled; this plasmid was relaxed after novobiocin treatment. These results support the existence in archaebacteria of a coumarin and quinolone target related to eubacterial DNA gyrase.

Aminocoumarins↗
PubMed2005

Site-directed mutagenesis of coumarin-type anticoagulant-sensitive VKORC1: evidence that highly conserved amino acids define structural requirements for enzymatic activity and inhibition by warfarin.

Coumarin and homologous compounds are the most widely used anticoagulant drugs worldwide. They function as antagonists of vitamin K, an essential cofactor for the posttranslational gamma-glutamyl carboxylation of the so-called vitamin K-dependent proteins. As vitamin K hydroquinone is converted to vitamin K epoxide (VKO) in every carboxylation step, the epoxide has to be recycled to the reduced form by the vitamin K epoxide reductase complex (VKOR). Recently, a single coumarin-sensitive protein of the putative VKOR enzyme complex was identified in humans (vitamin K epoxide reductase complex subunit 1, VKORC1). Mutations in VKORC1 result in two different phenotypes: warfarin resistance (WR) and multiple coagulation factor deficiency type 2 (VKCFD2). Here,we report on the expression of site-directed VKORC1 mutants, addressing possible structural and functional roles of all seven cysteine residues (Cys16, Cys43, Cys51, Cys85, Cys96, Cys132, Cys135), the highly conserved residue Ser/Thr57, and Arg98, known to cause VKCFD2 in humans. Our results support the hypothesis that the C132-X-X-C135 motif in VKORC1 comprises part of the redox active site that catalyzes VKO reduction and also suggest a crucial role for the hydrophobic Thr-Tyr-Ala motif in coumarin binding. Furthermore, our results support the concept that different structural components of VKORC1 define the binding sites for vitamin K epoxide and coumarin.

Amino Acid Sequence↗
PubMed2006

Apoptosis inducing activity of 4-substituted coumarins from Calophyllum brasiliense in human leukaemia HL-60 cells.

With the objective of identifying anti-tumour-promoting agents, we carried out a primary screening of ten 4-substituted coumarins isolated from Calophyllum brasiliense Camb. (Guttiferae), to determine the ability of these compounds to inhibit proliferation of the human leukaemia cell line HL-60. Among the 4-substituted coumarins isolated, calophyllolide (2) and mammea B/BB (3) showed significant cytotoxicity against HL-60 cells. Fluorescence microscopy with Hoechst 33342 staining revealed that the percentage of apoptotic cells with fragmented nuclei and condensed chromatin increased in a time-dependent manner after treatment with calophyllolide (2) or mammea B/BB (3). In addition, the activity of caspase-9 and caspase-3 was also enhanced in a time-dependent manner upon treatment with the 4-substituted coumarins 2 and 3. Caspase-9 and caspase-3 inhibitors suppressed apoptosis induced by 4-substituted coumarins 2 and 3. These results suggest that calophyllolide (2) and mammea B/ BB (3) induced apoptosis in HL-60 cells through activation of the caspase-9/caspase-3 pathway, which is triggered by mitochondrial dysfunction.

Antineoplastic Agents↗
PubMed1985

Calcium antagonist-like actions of coumarins isolated from "Qian-Hu" on anaphylactic mediator release from mast cell induced by concanavalin A.

The effects of coumarins on anaphylactic mediator release from rat mast cells were investigated. Since Pd-Ia (3'-angeloyloxy-4'-acetoxy-3',4'-dihydroseselin) causes relaxation of smooth muscle by inhibiting calcium influx, and since mediator release is a calcium-dependent process, studies were made on whether coumarins block calcium influx into rat mast cells stimulated by concanavalin A. Pd-Ia isolated from Peucedanum praeruptorum Dunn and related compounds, named Pd-C-II, Pd-C-III and Pd-C-IV, from Peucedanum decursivum Maxim., (Angelica decursiva Fr. et Sav.) inhibited anaphylactic mediator release from purified mast cells induced by concanavalin A with phosphatidylserine; their IC50 values were 79, 100, 102 and 73 microM, respectively. Pd-III, decursidin and water-soluble analogues of Pd-Ia (Pd-Ia-OH, Pd-Ia-OCH2CH3) did not inhibit the release. Thus the inhibitory actions of coumarins on calcium influx seemed to depend on the chemical structures of these compounds; an acetoxyl residue at position 3' or 4' on the seselin or xanthyletin skeleton might be essential for an inhibitory effect. Furthermore, Pd-Ia and Pd-C-III caused more than 40% reduction in 45Ca uptake induced by concanavalin A, whereas decursidin had little effect on it. Therefore, the inhibitions of mediator release of mast cells by some of coumarins from "Qian-Hu" seem to depend on their effects in blocking calcium influx.

Anaphylaxis↗