Cytotoxic sesquiterpene lactones from Inula britannica

Cytotoxicity-guided fractionation of the flowers of Inula britannica led to the isolation of four sesquiterpene lactones, 4 alpha, 6 alpha-dihydroxyeudesman-8 beta, 12-olide (1), ergolide (2), 8-epi-helenalin (3), and bigelovin (4). Compound 1 was isolated as a new natural product. These compounds showed cytotoxicity against human tumor cell lines.     

Celahinine A, a new sesquiterpene pyridine alkaloid from Celastrus hindsii

A new sesquiterpene pyridine alkaloid, celahinine A [1], and the related known polyester celahin A, as well as the known cytotoxic sesquiterpene pyridine alkaloid emarginatine A [2], were isolated from Celastrus hindsii. The structure of 1 was determined by 2D nmr techniques and was also confirmed by spectral comparison with the related 2.     

Case of multiple posterior mediastinal and retroperitoneal neurinomas

Total methanol extract of Saussurea lappa radix (Compositae) showed potent inhibitory effect on the production of tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, in murine macrophage-like cell (RAW264.7 cells) in our previous screening studies on 120 Korean medicinal plants. The activity-guided purification of the plant resulted in the isolation of three components. The chemical structures of the components isolated were established by spectroscopic analyses as sesquiterpene lactones [cynaropicrin (1), reynosin (2), and santamarine (3)]. These three compounds inhibited TNF-alpha production in a dose-dependent manner. The molar concentrations of cynaropicrin, reynosin, and santamarine producing 50% inhibition (IC50) of TNF-alpha production were 2.86 micrograms/ml (8.24 microM), 21.7 micrograms/ml (87.4 microM), and 26.2 micrograms/ml (105 microM), respectively. However, treatment with sulphydryl (SH) compounds such as L-cysteine, dithiothreitol, and 2-mercaptoethanol abrogated the inhibitory effect of cynaropicrin on TNF-alpha production. Therefore, we conclude that the principal inhibitory component of Saussurea lappa is cynaropicrin and its inhibitory effect is mediated through conjugation with SH-groups of target proteins.     

Evaluation of perioperative myocardial tissue damage in ischemically preconditioned human heart during aorto coronary bypass surgery

In the course of our screening for small molecule modulators of erythropoietin gene expression, two novel sesquiterpene tropolones and pycnidone were isolated from a culture of OS-F69284 (ATCC 74390). Their structures were elucidated by extensive 1H and 13C NMR spectroscopic studies and chemical reactions. These compounds induced erythropoietin gene expression 5-fold at a concentration of 1-1.6 microM.     

New ideas on the pathophysiology and treatment of lung disease

In the present study, the effects of compounds extracted from Tanacetum microphyllum, four flavonoids and one sesquiterpene lactone, on arachidonic acid metabolism in cellular systems were examined. In the PGE2- and LTC4-release assay, most compounds did not exhibit any significant effect. Only hydroxyachillin, and the flavonoids centaureidin and 5,3'-dihydroxy-4'-methoxy-7-methoxycarbonylflavonol showed a significant effect, although with less potency than the reference drugs, indomethacin and NDGA. However, all compounds inhibited the release of TXB2 from ionophore-stimulated human platelets. The action is more marked with the flavonoids santin and ermanin.     

Search for chlorinated sesquiterpene lactones in the neurotoxic thistle Centaurea solstitialis by liquid chromatography-mass spectrometry, and model studies on their possible artifactual formation

An HPLC method has been developed for the analysis of sesquiterpene lactones of the neurotoxic plant Centaurea solstitialis (Asteraceae). The presence of sesquiterpene lactone chlorohydrins in extracts was investigated by means of liquid chromatography-thermospray mass spectrometry. In contrast to earlier reports of a series of mono- and dichlorohydrins from this plant, traces only of two monochlorohydrins could be detected in lipophilic extracts. Model studies carried out with extracts and with the genuine sesquiterpene diepoxide repin and its epimer subluteolide showed that (i) monochlorohydrins can be formed in CHCl3 under usual laboratory conditions; (ii) the epoxide moiety at C-4 of the sesquiterpenes is extremely labile, reacting immediately and quantitatively with traces of HCl to the corresponding monohydrins; (iii) epoxide ring opening at the acyl side chain occurs only at higher HCl concentrations. Confirmation of the peak identity was obtained by the isotope ratio of chlorinated compounds and comparison with authentic samples. The structures of the mono- and dichlorohydrins were established by NMR spectroscopy.     

N6,C8-distributed adenosine derivatives as partial agonists for adenosine A1 receptors

The synthesis and biological evaluation of N6, C8-disubstituted derivatives of adenosine as potential partial agonists for adenosine receptors is described. Via three routes, two series of compounds were prepared, viz., N6-cyclopentyladenosine derivatives 3a-e and C8-(cyclopentylamino)adenosine analogs 3e and 9a-d, respectively. The X-ray structure determination of one of these compounds, N6-ethyl-8(cyclopentylamino)adenosine (9b), was carried out (orthorhombic, space group P2(1)2(1)2(1) (No. 19) with a = 11.039(3), b = 8.708(2), and c = 24.815(12) angstrom, Z=4,R1=0.0974,R2(W) = 0.2455). Due to intramolecular hydrogen bonding, the ribose moiety of this compound is in an anti conformation. The compounds were tested in vitro in radioligand binding studies, yielding their affinities for A1 and A2a adenosine receptors. All compounds appeared A1 selective, with affinities in the high nanomolar, low micromolar range. On A1 receptors the so-called GTP shift was also determined, i.e., the ratio between the affinities measured in the presence and absence of 1 mM GTP. All GTP shifts (values between 1.1 and 3.8) were lower than the GTP shift for CPA (6.0). This GTP shift appeared indicative for partial agonism in vivo, since the N6-cyclopentyladenosine derivatives showed lower intrinsic activities than the prototypic full agonist N6-cyclopentyladenosine on the decrease in heart rate in conscious, normotensive rats.     

Five new bioactive sesquiterpenes from the fungus Radulomyces confluens (Fr.) Christ

The three protoilludanes radulone A (1), radulone B (2) and radudiol (3), the illudalane radulactone (4) and the illudane radulol (5) were isolated from the extracts of the culture fluids of the basidiomycete Radulomyces confluens. The structures of the five new compounds were determined by spectroscopic techniques. Radulone A (1) is a potent inhibitor of human and bovine platelet aggregation stimulated by different agonists, inhibiting preferentially the aggregation of human platelets induced by ADP with an IC50 value of 2 microM. In addition 1 exhibits cytotoxic and antimicrobial activities. The other four compounds exhibited weak antimicrobial and cytotoxic activity.     

Four new cytotoxic germacranolides from Carpesium divaricatum

In a bioassay-guided search for cytotoxic compounds from higher plants of South Korea, four new sesquiterpenes of the germacranolide type, named cardivins A (1), B (2), C (3), and D (4), have been isolated from the aerial parts of Carpesium divaricatum. Structures of these compounds were elucidated on the basis of spectroscopic techniques. Compounds 1, 2, 3, and 4 showed cytotoxicity to the human tumor cells, A-549 (nonsmall cell lung), SK-OV-3 (ovary), SK-MEL-2 (skin), XF-498 (central nervous system), and HCT-15 (colon).     

Inhibition of human cytochrome P450-catalyzed oxidations of xenobiotics and procarcinogens by synthetic organoselenium compounds

The effects of synthetic chemopreventive organoselenium compounds 1,2-, 1,3-, and 1,4-phenylenebis(methylene)selenocyanate (o-, m-, and p-XSC, respectively), benzyl selenocyanate (BSC), and dibenzyl diselenide (DDS) and inorganic sodium selenite on the oxidation of xenobiotics and procarcinogens by human cytochrome P450 (P450 or CYP) enzymes were determined in vitro. Spectral studies showed that BSC and three XSC compounds (but not sodium selenite or DDS) induced type II difference spectrum when added to the suspension of liver microsomes isolated from beta-naphthoflavone-treated rats, with m-XSC being the most potent in inducing spectral interactions with P450 enzymes; m-XSC also produced a type II spectral change with human liver microsomes. o-, m-, and p-XSC inhibited 7-ethoxyresorufin O-deethylation catalyzed by human liver microsomes when added at concentrations below 1 microM levels, but BSC and DDS were less effective. All of these compounds inhibited the oxidation of model substrates for human P450s to varying extents. We studied the effects of these compounds on the activation of procarcinogens by recombinant human CYP1A1, 1A2, and 1B1 enzymes using Salmonella typhimurium NM2009 tester strain for the detection of DNA damage. The three XSCs were found to be very potent inhibitors of metabolic activation of 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole, 2-amino-3,5-dimethylimidazo[4,5-f]quinoline, and 2-aminoanthracene, catalyzed by CYP1A1, 1A2, and 1B1, respectively. The potency of inhibition of m-XSC on CYP1B1-dependent activation of 2-aminoanthracene was compatible to those of alpha-naphthoflavone. These inhibitory actions may, in part, account for the mechanisms responsible for cancer prevention by organoselenium compounds in laboratory animals.     

Novel (E)-5-(2-iodovinyl)-2'-deoxyuridine derivatives as potential cytostatic agents against herpes simplex virus thymidine kinase gene transfected tumors

(E)-5-(2-Iodovinyl)-2'-deoxyuridine (IVDU), its 2'-fluoro-substituted derivatives IVFRU (with fluorine in the ribo configuration), IVFAU (with fluorine in the ara configuration), and the corresponding 3'-chemical delivery system (CDS), or 3'-O-(1-methyl-1,4-dihydropyridyl-3-carbonyl)- substituted derivatives IVDU-CDS, IVFRU-CDS and IVFAU-CDS were evaluated for their cytostatic activity against wild-type (FM3A/O), thymidine kinase (TK)-deficient (FM3A/TK-), and herpes simplex virus type 1 (HSV-1) or HSV-2 thymidine kinase (tk) gene-transfected murine mammary carcinoma FM3A cells (FM3A TK-/HSV-1 TK+ and FM3A TK-/HSV-2 TK+). The test compounds proved highly inhibitory to the proliferation of HSVtk gene-transfected FM3A cells. Their cytostatic activity was within the 0.002 to 0.80 microM range, a compound concentration that is 1000- to 10,000-fold lower than that required to inhibit proliferation of wild-type FM3A/O cells. The target for the cytostatic activity of the test compounds is the cellular thymidylate synthase. In contrast to the parent IVDU compound, IVFRU and IVFAU and their CDS-substituted derivatives proved resistant to phosphorolytic cleavage by human and bacterial thymidine phosphorylase and should be considered as promising candidate compounds for further evaluation for combined gene/chemotherapy of HSVtk gene-transfected tumor cells in animal models.     

New indole derivatives as potent and selective serotonin uptake inhibitors

A series of new indole derivatives (2-28) has been prepared in the search for novel 5-HT uptake inhibitors. These compounds were obtained by the condensation of N-(chloroalkyl) naphthalenesultam derivatives with the appropriate amine in presence of a base, at reflux of DMF or THF. The yields were moderate (12-56%), except for the piperazine derivative 20 (85%). The affinity of the compounds for uptake site and 5-HT2, alpha 1, and D2 receptors was measured. Some compounds were studied in vivo by their potentiating effect of 5-HTP-induced symptomatology. The most potent and selective (uptake, 5-HT2 versus alpha 1, D2 sites) compounds contain a 3-[(4-piperidinyl)methyl]indole moiety. 5-Fluoro-3-[(4-piperidinyl)methyl]indole itself (compound 1) displayed a high affinity for the uptake site but was devoided of in vivo activity. N-Methylation of this compound abolished the affinity. In contrast N-substitution by a two-carbon chain linked to a naphthalenesultam or related heterocycle led to compounds exhibiting high affinity for the uptake site. One of them, 1-[2-[4-((5-fluoro-1H-indol-3-yl)methyl-1- piperidinyl]ethyl]-5,6-dihydro-1H,4H-1,2,5-thiadiazolo[4,3,2- ij]quinoline 2,2-dioxide (compound 24), was found as active as fluoxetine in vivo.     

trans-2-Aryl-N,N-dipropylcyclopropylamines: synthesis and interactions with 5-HT(1A) receptors

Twelve N,N-dipropyl-substituted derivatives of trans-2-arylcyclopropylamine have been prepared and assayed for their ability to displace [(3)H]-8-OH-DPAT from rat brain 5-HT(1A) receptors. The new derivatives include phenyl (7a), bromo- (7b) and fluorophenyl (7c-e), 2-methoxy-5-fluorophenyl (7h), and 2-hydroxy-5-fluorophenyl (7l) as well as trifluoromethylphenyl (7f) and 2,3-dichlorophenyl (7g) analogues. In the present series of compounds, electron-withdrawing substituents in the phenyl ring appear to decrease the affinity for 5-HT(1A) receptors. In contrast, electron-rich aryl groups, such as 2- or 3-thienyl (7j and 7k, respectively), provide compounds with high affinity. The additional bulk produced by the aromatic moiety in the 2-benzothienyl derivative 7i appears to be detrimental to 5-HT(1A) receptor affinity. The racemic mixtures of the interesting 7j and 7l were resolved into the enantiomers; 7j and 7l exhibited a high enantiomeric 5-HT(1A) receptor affinity ratio (75-fold and 100-fold, respectively). The enantiomers of 7j and 7l were evaluated in vivo by use of biochemical and behavioral tests in rats. Compound (1R,2R)-7j behaved as a partial agonist whereas (1R,2S)-7l appeared as an efficacious 5-HT(1A) receptor agonist, stimulating both autoreceptors and postsynaptic receptors.     

2-Alkynyl derivatives of adenosine-5'-N-ethyluronamide: selective A2 adenosine receptor agonists with potent inhibitory activity on platelet aggregation

A series of new 2-alkynyl and 2-cycloalkynyl derivatives of adenosine-5'-N-ethyluronamide (NECA) and of N-ethyl-1'-deoxy-1'-(6-amino-2-hexynyl-9H-purin-9-yl)-beta-D- ribofuranuronamide (1, HE-NECA), bearing hydroxy, amino, chloro, and cyano groups in the side chain, were synthesized. The compounds were studied in binding and functional assays to assess their potency for the A2 compared to A1 adenosine receptor. The presence of an alpha-hydroxyl group in the alkynyl chain of NECA derivatives accounts for the A2 agonist potency, leading to compounds endowed with sub-nanomolar affinity in binding studies. However, these analogues also possess good A1 receptor affinity resulting in low A2 selectivity. From functional experiments the 4-hydroxy-1-butynyl (6) and the 4-(2-tetrahydro-2H-pyranyloxy)-1-butynyl (16) derivatives appear to be very potent in inducing vasorelaxation without appreciable effect on heart rate. The new compounds were also tested as inhibitors of platelet aggregation induced by ADP. Introduction of an alpha-hydroxyl group in the alkynyl side chain caused a greater increase in antiaggregatory activity than either NECA or HE-NECA, resulting in the most potent inhibitors of platelet aggregation so far known in the nucleoside series. The presence of an alpha-quaternary carbon such as the 3-hydroxy-3,5-dimethyl-1-hexynyl (12) and the 3-hydroxy-3-phenyl-1-butynyl (15) derivatives markedly reduced the antiaggregatory potency without affecting the A2 affinity. The hydrophobicity index (k') of the new nucleosides barely correlated with the binding data, whereas high k' values were associated with increased A2 vs A1 selectivity but with reduced activity in all functional assays. Some of the compounds synthesized possess interesting pharmacological properties. Compounds having an appropriate balance between vasorelaxation and antiplatelet activity, if confirmed in vivo, deserve further development for the treatments of cardiovascular disorders.     

Synthesis and structure-activity relationships of 3,7-dimethyl-1-propargylxanthine derivatives, A2A-selective adenosine receptor antagonists

A series of 8-substituted derivatives of 3,7-dimethyl-1-propargylxanthine (DMPX) was synthesized and investigated as A2A adenosine receptor antagonists. Different synthetic strategies for the preparation of DMPX derivatives and analogues were explored. A recently developed synthetic procedure starting from 3-propargyl-5,6-diaminouracil proved to be the method of choice for the preparation of this type of xanthine derivatives. The novel compounds were investigated in radioligand binding studies at the high-affinity adenosine receptor subtypes A1 and A2A and compared with standard A2A adenosine receptor antagonists. Structure-activity relationships were analyzed in detail. 8-Styryl-substituted DMPX derivatives were identified that exhibit high affinity and selectivity for A2A adenosine receptors, including 8-(m-chlorostyryl)-DMPX (CS-DMPX, Ki A2A = 13 nM, 100-fold selective), 8-(m-bromostyryl)-DMPX (BS-DMPX, Ki A2A = 8 nM, 146-fold selective), and 8-(3,4-dimethoxystyryl)-DMPX (Ki A2A = 15 nM, 167-fold selective). These and other novel compounds are superior to the standard A2A adenosine receptor antagonists KF17837 (4) and CSC (5) with respect to A2A affinity and/or selectivity.     

A new indole derivative from the red alga Chondria atropurpurea. Isolation, structure determination, and anthelmintic activity

Chondriamide C (3), a new bis(indole) amide, was isolated from the red alga Chondria atropurpurea, and its structure was established from spectroscopic data and chemical transformations. A new natural product, 3-indoleacrylamide (4), and the previously described chondriamides A and B (1, 2) and 3-indoleacrylic acid (5) were also isolated. The anthelmintic activities of compounds 1, 3, 4, and 6 (the O,N1,N1'-trimethyl derivative of compound 2) against Nippostrongylus brasiliensis in vitro were evaluated.     

2-aminotetralin-derived substituted benzamides with mixed dopamine D2, D3, and serotonin 5-HT1A receptor binding properties: a novel class of potential atypical antipsychotic agents

A new chemical class of potential atypical antipsychotic agents, based on the pharmacological concept of mixed dopamine D2 receptor antagonism and serotonin 5-HT1A receptor agonism, was designed by combining the structural features of the 2-(N,N-di-n-propylamino)tetralins (DPATs) and the 2-pyrrolidinylmethyl-derived substituted benzamides in a structural hybrid. Thus, a series of 35 differently substituted 2-aminotetralin-derived substituted benzamides was synthesized and the compounds were evaluated for their ability to compete for [3H]-raclopride binding to cloned human dopamine D2A and D3 receptors, and for [3H]-8-OH-DPAT binding to rat serotonin 5-HT1A receptors in vitro. The lead compound of the series, 5-methoxy-2-[N-(2-benzamidoethyl)-N-n-propylamino]tetralin (12a), displayed high affinities for the dopamine D2A receptor (Ki = 3.2 nM), the dopamine D3 receptor (Ki = 0.58 nM) as well as the serotonin 5-HT1A receptor (Ki = 0.82 nM). The structure-affinity relationships of the series suggest that the 2-aminotetralin moieties of the compounds occupy the same binding sites as the DPATs in all three receptor subtypes. The benzamidoethyl side chain enhances the affinities of the compounds for all three receptor subtypes, presumably by occupying an accessory binding site. For the dopamine D2 and D3 receptors, this accessory binding site may be identical to the binding site of the 2-pyrrolidinylmethyl-derived substituted benzamides.     

Gastric cytoprotective activity of 2-cyclopenten-1-one and related compounds

The cytoprotective activity of the isolated functional groups of several sesquiterpene lactones is reported. Among them the highest activity is shown by alpha-methylen-gamma-butyrolactone and 2-cyclopenten-1-one. The activity shown by those Michael acceptors with a beta carbon hindered by an alkyl substituent was always lower or almost null. A three-way mechanism of action is proposed: a) reduced glutathione synthesis, b) prostaglandin synthesis and c) mucosal glycoprotein synthesis.     

Synthesis of adenine derivatives and their activities against herpes virus in vitro

A series of 9-(N4-substituted acetaldehyde thiosemicarbazone) adenines were synthesized and evaluated for antiherpes virus activity. Compounds 4a-l were prepared by condensation of 9-(acetaldehyde) adenine(6) and the corresponding N4-substituted thiosemicarbazides (10). The antiviral effects of all compounds 4a-l were tested in vitro in primary rabbit kidney cell cultures infected with herpes simplex virus type 1 (HSV-1) and varicella-herpes zoster virus (VZV), and in primary human embryo cell cultures infected with herpes simplex virus type 2 (HSV-2). The results showed that the minimum inhibitory concentrations (MIC) of 4e and 4f for HSV-1 and VZV were 20, 40, 20 and 20 micrograms.ml-1, respectively, and other compounds were 200 micrograms.ml-1. For HSV-2, the MIC of all tested compounds were 300 micrograms.ml-1. We also evaluated the antiherpetic effect of 4e (and 4f) by combination with acyclovir (ACV) in the ratio of 1:1 in vitro. The MIC of the combined compounds were 2 micrograms.ml-1 for 4e and 6 micrograms.ml-1 for 4f, while their minimum cytotoxicities (MCC) in the cell were markedly reduced compared with the individual compounds.