New cytotoxic cyclobutanoid amides, a new furanoid lignan and anti-platelet aggregation constituents from Piper arborescens

Three new cyclobutanoid amides with trans-trans-trans configurations, piperarborenine C, piperarborenine D and piperarborenine E, and a new furanoid lignan, (+)-arborone, together with twelve known compounds, were isolated from the stems of Piper arborescens. The structures of these new compounds were determined by means of spectral analyses. Piperarborenine C, (+)-diayangambin, piplartine, piperolactam B, piperolactam C, aristolactam BIII, goniothalactam, and methyl trans-3,4,5-trimethoxycinnamate possessed anti-platelet aggregation activity in vitro. Among them, piplartine showed the most potent anti-platelet aggregation activity induced by collagen and showed an IC50 value of 21.5 microM. Piperarborenines A - E, piperarborenine, aristololactam BIII and goniothalactam showed significant cytotoxic activity (IC50 values < 4 microg/mL) against P-388, HT-29 and A549 cell lines in vitro.     

Disposition and metabolic profiles of [14C]viramidine and [14C]ribavirin in rat and monkey red blood cells and liver

The disposition and metabolic profiles of [14C]viramidine and [14C]ribavirin were compared in rat and monkey red blood cells and liver. Our data reveal that the total ribavirin-related components (ribavirin plus its mono-, di-, and triphosphate metabolites) may account for most of the drug in monkey liver following prolonged oral administration of viramidine.     

Soluble guanylyl cyclase activator YC-1 inhibits human neutrophil functions through a cGMP-independent but cAMP-dependent pathway

3-(5'-Hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1), a novel type of soluble guanylyl cyclase (sGC) activator, is useful in investigating the signaling of cGMP and may provide a new approach for treating cardiovascular diseases. Herein, YC-1 was demonstrated to inhibit the generation of superoxide anion (O2-) and the release of beta-glucuronidase release, to diminish the membrane-associated p47phox and to accelerate resequestration of cytosolic calcium in formyl-l-methionyl-l-leucyl-l-phenylalanine-activated human neutrophils. YC-1 not only directly promoted sGC activity and cGMP formation but also dramatically potentiated sodium nitroprusside-induced sGC activity and cGMP formation in human neutrophils. However, the synergistic increase in the amount of cGMP was inconsistent with its cellular response. Moreover, neither an sGC inhibitor nor protein kinase G inhibitors reversed the inhibitory effect of YC-1. Interestingly, YC-1 also increased the cAMP concentration and protein kinase (PK)A activity. The inhibitory effect of YC-1 was significantly enhanced by prostaglandin (PG)E1 and isoproterenol, and almost abolished by PKA inhibitors. These results show that cAMP, but not cGMP, mediates the YC-1-induced inhibition of human neutrophils. YC-1 increased the PGE1- and forskolin-induced but not 3-isobutyl-1-methylxanthine-produced cAMP formation, suggesting inhibition of phosphodiesterase. These findings thus reveal novel mechanism-mediated anti-inflammatory properties of YC-1 in human neutrophils, which can influence the progression of cardiovascular disease. cAMP, but not cGMP, plays an important role in the regulation of respiratory burst and degranulation in human neutrophils.     

Digoniodiol, deoxygoniopypyrone A, and goniofupyrone A: three new styryllactones from Goniothalamus amuyon

Three new styrylpyrone analogues, digoniodiol (2), deoxygoniopypyrone A (3), and goniofupyrone A (4), along with ten known styryllactones, were isolated from the aerial parts of Goniothalamus amuyon. Among these compounds, 2 is the first example of a bis-styrylpyrone. Compound 4 represents a new skeleton for styryllactones. All structures were established on the basis of spectroscopic data. The stereochemistry of 2 and 4 was determined by X-ray crystallographic analysis. The absolute configuration of 3 and 4 was further confirmed by Mosher ester derivatives. All styryllactones were subjected to cytotoxicity assays. Among them, goniothalamin, goniothalamin epoxide, and 8-chlorogoniodiol showed significant cytotoxicity against the HepG2 cancer cell line with IC50 in the range of 0.19 - 0.64 microg/mL, and moderate activity toward Hep3B, MDA-MB-231, and MCF-7 cancer cell lines.     

A sensitive and specific method for the determination of total ribavirin in monkey liver by high-performance liquid chromatography with tandem mass spectrometry

A sensitive and specific method using high-performance liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the analysis of total ribavirin in monkey liver is developed and validated. In this method, ribavirin and its phosphorylated metabolites are extracted with perchloric acid. The metabolites are converted to ribavirin using acid phosphatase and further purified using a NH2 solid-phase extraction (SPE) cartridge prior to LC-MS/MS analysis. [13C]Ribavirin is added with the extraction solution as an internal standard to obtain better accuracy and precision of the analysis. The MS/MS was selected to monitor 245-->113 and 250-->113 transitions using positive electrospray ionization for ribavirin and [(13)C]ribavirin. The calibration curve is linear over a concentration of 1.0-100 microg/g with a limit of quantitation (LOQ) of 1.0 microg/g. Mean inter-assay accuracy for QC at 1.0, 10 and 100 microg/g are 108, 99.7 and 99.7%, respectively. Mean inter-assay precision (CV) for QC at 1.0, 10 and 100 microg/g are 5.34, 5.24 and 4.59%, respectively. Extractability of total ribavirin from liver has been confirmed with liver obtained from monkey dosed with [14C]ribavirin. The method has been proven to be useful in the determination of total ribavirin concentration in liver from monkeys in mass balance study (10 mg/kg) and in 28 days toxicology study (300 mg/kg/day). It is also used to determine the total ribavirin concentration in human livers from hepatitis C patients received dose of 600 mg ribavirin twice daily.     

Multiple-Dose Pharmacokinetics of Ceftibuten in Healthy Adults and Geriatric Volunteers

The steady-state pharmacokinetics of ceftibuten, an orally active cephalosporin were investigated in 12 healthy male volunteers (19--38 years) and in 12 geriatric volunteers (65--76 years). Each received one 200-mg ceftibuten capsule every 12 h on days 1--3 and one capsule in the morning on day 4. Plasma and urine samples were collected at various times on days 1--4 and assayed by high-pressure liquid chromatographic method for ceftibuten and ceftibuten-trans, a conversion product. The T(max) for ceftibuten and ceftibuten-trans occurred at about 2 and 3 h, respectively, in both populations. The C(max) and AUC((0--12 h)) ranged from 10.8 to 12.4 &mgr;g ml(minus sign1) and from 47.5 to 55.1 &mgr;g h ml(minus sign1), respectively, for normal volunteers compared to 12.9--17.5 &mgr;g ml(minus sign1) and 62.3--87.1 &mgr;g h ml(minus sign1), respectively, for geriatric volunteers. The respective values for ceftibuten-trans in normal and geriatric volunteers were 1.3 and 1.3 &mgr;g ml(minus sign1), respectively, and 6.9--8.2 and 5.9--9.8 &mgr;g h ml(minus sign1). At steady state, the C(max) and AUC((0--12 h)) of ceftibuten-trans were about 10--11% and 13--16% those of ceftibuten in normal volunteers and about 8--9% and 9--11% those of ceftibuten, respectively, in geriatric volunteers. The accumulation factor of ceftibuten in normal volunteers was 1.1 as compared to 1.3 in geriatric volunteers. The terminal phase half-life was 2.5 h in healthy volunteers and 3.2 h in geriatric volunteers. Urinary excretion appeared to be the major route of elimination in both populations accounting for more than 90% of the dose recovered in the urine during the dosing interval. The results of this study demonstrate that ceftibuten, 200 mg given twice a day, is safe and well tolerated, is well absorbed, and that steady-state is achieved on days 3 and 4. There is some accumulation in the elderly, but dosage regimen based on age is not warranted.     

Role of class II P fimbriae and cytokine response in the pathogenesis of Escherichia coli kidney infection in diabetic mice

Background

The role of class II P fimbriae (P fimbriae II) in diabetic kidney infections is uncertain, although some genetic and epidemiological studies suggest a lower prevalence of P fimbriae II genes in Escherichia coli strains isolated from diabetic patients with complicated kidney infections.

Pharmacokinetics of Loratadine in Pediatric Subjects

The pharmacokinetics of loratadine, a new nonsedating antihistamine, was studied in 14 pediatric volunteers between the ages of 8 to 12 years. In an open-label design, one volunteer (with body weight less than 30 kg) received 5 mg of loratadine syrup and 13 volunteers (with body weights greater than 30 kg) received 10 mg of loratadine syrup. Blood samples were collected up to 72 h after dosing. Plasma concentrations of loratadine and its metabolite, descarboethoxyloratadine, were determined by a specific and sensitive gas-liquid chromatographic method. Following a 10-mg dose as a syrup, plasma concentrations of loratadine and descarboethoxyloratadine could be determined up to 8 and 48 h, respectively. The maximum concentration (C(max)) of loratadine and descarboethoxyloratadine were approximately 4 ng ml(minus sign1) each. However, the AUC of the metabolite was about six times that of loratadine. The elimination phase half-life of descarboethoxyloratadine averaged about 13.8 hr. The pharmacokinetics of loratadine in pediatric subjects was similar to that in healthy adult volunteers.     

Synthesis and pharmacological evaluation of novel beta-nitrostyrene derivatives as tyrosine kinase inhibitors with potent antiplatelet activity

Protein tyrosine kinases have been known to be involved in regulation of platelet aggregation, suggesting a potential target for antiplatelet therapy. Our previous study showed that 3,4-methylenedioxy-beta-nitrostyrene (MNS) prevented platelet aggregation caused by various stimulators, and this action was accompanied by inhibition of tyrosine kinases. In the present study, in order to examine the structural determinants required for the actions of MNS and to develop more potent tyrosine kinase inhibitors and antiplatelet agents, a new series of beta-nitrostyrene derivatives were synthesized and pharmacologically characterized. The beta-nitrostyrene derivatives inhibited thrombin- or collagen-induced human platelet aggregation, ATP secretion, GPIIb/IIIa activation and protein tyrosine phosphorylation. In recombinant enzyme assay, some beta-nitrostyrene derivatives also demonstrated potent inhibition of Src and/or Syk kinase activity. Furthermore, there was a good correlation between the inhibitory potency of these compounds on tyrosine kinases and on platelet activation/aggregation. Among them, a benzoyl ester derivative (compound 10) possess up to 8-fold greater potency than MNS and over two orders of magnitude greater potency than genistein or tyrphostin A47 in inhibiting platelet responses to thrombin. Our data suggest that beta-nitrostyrenes may represent a new class of tyrosine kinase inhibitors with potent antiplatelet activity.     

Comparison of the effects of PAR1 antagonists, PAR4 antagonists, and their combinations on thrombin-induced human platelet activation

Thrombin activates human platelets through proteolytic activation of two protease-activated receptors (PARs), PAR1 and PAR4. In the present study, we show that, RWJ-56110, a potent synthetic PAR1 antagonist, inhibited platelet aggregation caused by a low concentration (0.05 U/ml) of thrombin, but lost its effectiveness when higher concentrations of thrombin were used as stimulators. YD-3, a non-peptide PAR4 antagonist, alone had little or no effect on thrombin-induced platelet aggregation, significantly enhanced the anti-aggregatory activity of PAR1 antagonist. In addition, we demonstrate for the first time that P-selectin expression in thrombin-stimulated platelets can be synergistically prevented by combined treatment of PAR1 antagonist and PAR4 antagonist. These results indicate that thrombin-induced platelet activation cannot be effectively inhibited by just blocking either single thrombin receptor pathway, and suggest a rationale for potential combination therapy in arterial thrombosis.