Bremazocine: a potent, long-acting opiate kappa-agonist

The benzomorphan analogue bremazocine is a potent, centrally-acting analgesic with a long duration of action. In animal models it is free of physical and psychological dependence liability, produces no respiratory depression, and has a variety of other properties which justify its classification as a putative opiate kappa-receptor agonist.Binding studies with tritiated (?)-bremazocine on rat brain membrane preparations show that this molecule differs in its binding properties from previously investigated exogenous or endogenous opioids. Studies on isolated guinea-pig ileum and mouse vas deferens indicate a preference for opiate kappa-receptors.In mice (hot plate, tail flick) and rhesus monkeys (shock titration), bremazocine is a potent analgesic with a long duration of action. Here also, the actions of the antagonists naloxone and Mr 2266 suggest a preference for opiate kappa-receptors.Bremazocine differs from morphine in the non-production of mydriasis and the Straub tail phenomenon in mice, in its lack of effects on respiration in rats, in that it is not self-administered by rhesus monkeys, and in that programmed administration in the same species does not lead to a morphine-like withdrawal syndrome upon cessation of drug treatment or upon naloxone challenge. Prolonged treatment of animals with bremazocine leads to tolerance to its analgesic effects; morphine treatment of such tolerant animals causes analgesia. Conversely, treatment of morphine-tolerant animals with bremazocine does not cause analgesia; these findings suggest that morphine and bremazocine interact with different subpopulations of opiate receptors.     

2-Cyano-4-fluoro-1-thiovalylpyrrolidine analogues as potent inhibitors of DPP-IV

We report the synthesis and biological activity of a series of 2-cyano-4-fluoro-1-thiovalylpyrrolidine inhibitors of DPP-IV. Within this series, compound 19 provided a potent, selective, and orally active DPP-IV inhibitor which demonstrated a very long duration of action in both rat and dog.     

Effects of radix polygoni multiflori components on tyrosinase activity and melanogenesis

Radix Polygoni multiflori is a herb used effectively to prevent graying and treat skin depigmentation diseases in traditional Chinese medicine but its active ingredients have not been discovered yet. In this investigation, we tested six compounds isolated from Radix Polygoni multiflori, to discover the active component on melanogenesis. Three experiments were performed in the present investigation: mushroom tyrosinase activity, melanin content B16 cell proliferation assay. Among all the six components tested, THSG showed the most potent effects on tyrosinase activation and melanogenesis; it was shown to be a potent tyrosinase activator and a melanogenesis stimulator in this study. On the other hand, we found that gallic acid significantly inhibited tyrosinase and, in addition, anthraquinones were cytotoxic to melanoma cells. They were both harmful to melanogenesis. Therefore, we propose that THSG acts as the active ingredient of Radix Polygoni multiflori on melanogenesis.     

A novel anti-asthmatic quinone derivative, AA-2414 with a potent antagonistic activity against a variety of spasmogenic prostanoids

The anti-asthmatic activity of AA-2414 [(+/-)-7-(3,5,6-trimethyl-1,4-benzoquinon-2-yl)-7-phenylheptano ic acid] has been studied in vivo and in vitro. Experimental allergic asthma was inhibited by orally administered AA-2414 in a dose-dependent manner. AA-2414, 0.08-1.25 mg/kg (p.o.), inhibited the bronchconstriction in guinea pigs induced by a prostaglandin endoperoxide analogue (U-46619), leukotriene D4 (LTD4), and platelet activating factor (PAF) with a long duration of action. The compound did not inhibit histamine-induced bronchoconstriction. AA-2414 reduced the induction of pulmonary inflation caused by LTD4 aerosol inhalation. AA-2414 competitively inhibited the contractile response to U-46619 in guinea pig tracheal and parenchymal strips and dog saphenous vein strips with pA2 values of 7.69, 8.29 and 6.79, respectively. Furthermore, the contractile responses of guinea pig tracheal strip to PGD2, 9 alpha, 11 beta-PGF2 and PGF2 alpha were inhibited with pA2 values of 7.20, 7.79 and 5.71, respectively. These results suggest that AA-2414, a quinone derivative, is a novel, potent and orally active antagonist of a variety of spasmogenic prostanoids.     

Actinorhodin is a redox‐active antibiotic with a complex mode of action against Gram‐positive cells

Actinorhodin is a blue‐pigmented, redox‐active secondary metabolite that is produced by the bacterium Streptomyces coelicolor. Although actinorhodin has been used as a model compound for studying secondary metabolism, its biological activity is not well understood. Indeed, redox‐active antibiotics in general have not been widely investigated at the mechanistic level. In this work, we have conducted a comprehensive chemical genetic investigation of actinorhodin's antibacterial effect on target organisms. We find that actinorhodin is a potent, bacteriostatic, pH‐responsive antibiotic. Cells activate at least three stress responses in the presence of actinorhodin, including those responsible for managing oxidative damage, protein damage and selected forms of DNA damage. We find that mutations in the Staphylococcus aureus walRKHI operon can confer low‐level resistance to actinorhodin, indicating possible targeting of the cell envelope. Our study indicates a complex mechanism of action, involving multiple molecular targets, that is distinct from other antibiotics.     

Inhibition of ammonia monooxygenase in Nitrosomonas europaea by carbon disulfide.

Carbon disulfide has long been recognized as a potent inhibitor of nitrification, and it is the likely active component in several nitrification inhibitors suitable for field use. The effects of this compound on Nitrosomonas europaea have been investigated, and the site of action has been determined. Low concentrations of CS2 (less than 400 microM) produced a time-dependent inhibition of ammonia-dependent O2 uptake but did not inhibit hydrazine-oxidizing activity. CS2 also produced distinct changes in difference spectra of whole cells. These results suggest that ammonia monooxygenase (AMO) is the site of action of CS2. Unlike the case for thiourea and acetylene, saturating concentrations of CS2 did not fully inhibit AMO, and the inhibition resulted in a low but significant rate of ammonia-dependent O2 uptake. The effects of CS2 were not competitive with respect to ammonia concentration, and the inhibition by CS2 did not require the turnover of AMO to take effect. The ability of CS2-treated cells to incorporate [14C]acetylene into the 28-kilodalton polypeptide of AMO was used to demonstrate that the effects of CS2 are compatible with a mode of action which involves a reduction of the rate of turnover of AMO without effects on the catalytic mechanism. It is proposed that CS2 may act on AMO by reversibly reacting with a suitable nucleophilic amino acid in close proximity to the active site copper.     

Pharmacological profile of the abeorphine 201-678, a potent orally active and long lasting dopamine agonist

The central dopaminergic effects of an abeorphine derivative 201-678 were compared to those of apomorphine and bromocriptine in different model systems. After oral administration, this compound induced contralateral turning in rats with 6-hydroxydopamine induced nigral lesions and exhibited strong anti-akinetic properties in rats with 6-hydroxydopamine induced hypothalamic lesions. It decreased dopamine metabolism in striatum and cortex, but did not modify noradrenaline and serotonin metabolism in the rat brain. 201-678 counteracted the in vivo increase of tyrosine hydroxylase activity induced by gamma-butyrolactone. In vitro it stimulated DA-sensitive adenylate cyclase and inhibited acetylcholine release from rat striatal slices. This compound had high affinity for 3H-dopamine and 3H-clonidine binding sites. These results indicate that 201-678 is a potent, orally active dopamine agonist with a long duration of action. Furthermore it appears more selective than other dopaminergic drugs.     

Neurokinin A (NK2) receptor revisited with SR 48968, a potent non-peptide antagonist.

SR 48968, a new non-peptide antagonist of NK2 receptors, has been tested in a variety of isolated smooth muscle preparations from rats, guinea pigs, rabbits, hamsters and men, in order to assess its selectivity for NK2 receptors as well as its competitivity and specificity. The compound has been found to be inactive as a stimulant or relaxant in all preparations but to exert a potent, competitive antagonism, particularly in tissues obtained from rabbits (pA2 9.8-10.3), guinea pigs (10.5), rats (9.4-9.6), men (9.36-9.6) and hamsters (7.45-8.6). SR 48968 is therefore more active on the NK2A than on the NK2B receptor subtype and the human receptor is close to the NK2A subtype. SR 48968 exerts an antagonism of the competitive type and is therefore suitable for receptor classification despite its slow reversibility in vitro. The sensitivity of NK2A receptors to SR 48968 is at least 1000 times higher than those of NK1 and NK3 receptors. The compound does not affect the effects of bradykinin, angiotensin or bombesin. Because of its activity in human tissues, its potency and long duration of action, SR 48968 is a new promising pharmacologic and possibly therapeutic agent.     

Selective Inhibition of Platelet-Derived Growth Factor (PDGF) Receptor Autophosphorylation and PDGF-Mediated Cellular Events by a Quinoline Derivative

This report describes the biological effects of our original compound, Ki6783 ((3,4-dimethoxy)-4-phenoxy-6,7-dimethoxyquinoline), a potent and selective inhibitor of platelet-derived growth factor (PDGF) receptor autophosphorylation. This compound strongly inhibited autophosphorylation of the PDGF β-receptor in cultured rat glomerular mesangial cells (MC) bearing this receptor (IC₅₀0.1 μM), although it did not inhibit autophosphorylation of other growth factor receptors even at 100 μM.In a cell-free kinase experiment, it showed selective inhibition of PDGF β-receptor tyrosine kinase. A kinetic study of the compound to this tyrosine kinase revealed a competitive mode of action to ATP. [³H]Thymidine incorporation and cell proliferation of MC were inhibited by Ki6783 in a dose-dependent manner after Ki6783 and PDGF-BB were added to the culture medium. Furthermore, this compound normalized the fibrotic cell shape of v-sis-transformed NIH3T3 cells, which grow in an autocrine manner via the PDGF receptor. These effects could be explained by the inhibition of intracellular signal transduction triggered by PDGF receptor autophosphorylation, in which activation of mitogen-activated protein kinase occurs. These results suggest that Ki6783 is one of the more potent and selective inhibitors of PDGF receptor autophosphorylation and that it may be useful in ameliorating cell abnormalities due to excess action of PDGF and its receptor systems in several diseases.     

The discovery of a potent, intracellular, orally bioavailable, long duration inhibitor of human neutrophil elastase--GW311616A a development candidate

The discovery of a potent intracellular inhibitor of human neutrophil elastase which is orally active and has a long duration of action is described. The pharmacodynamic and pharmacokinetic properties of a trans-lactam development candidate, GW311616A, are described.     

Artemisinin inhibits chloroplast electron transport activity: mode of action

Artemisinin, a secondary metabolite produced in Artemisia plant species, besides having antimalarial properties is also phytotoxic. Although, the phytotoxic activity of the compound has been long recognized, no information is available on the mechanism of action of the compound on photosynthetic activity of the plant. In this report, we have evaluated the effect of artemisinin on photoelectron transport activity of chloroplast thylakoid membrane. The inhibitory effect of the compound, under in vitro condition, was pronounced in loosely and fully coupled thylakoids; being strong in the former. The extent of inhibition was drastically reduced in the presence of uncouplers like ammonium chloride or gramicidin; a characteristic feature described for energy transfer inhibitors. The compound, on the other hand, when applied to plants (in vivo), behaved as a potent inhibitor of photosynthetic electron transport. The major site of its action was identified to be the Q(B); the secondary quinone moiety of photosystemII complex. Analysis of photoreduction kinetics of para-benzoquinone and duroquinone suggest that the inhibition leads to formation of low pool of plastoquinol, which becomes limiting for electron flow through photosystemI. Further it was ascertained that the in vivo inhibitory effect appeared as a consequence of the formation of an unidentified artemisinin-metabolite rather than by the interaction of the compound per se. The putative metabolite of artemisinin is highly reactive in instituting the inhibition of photosynthetic electron flow eventually reducing the plant growth.     

Identification of swainsonine as a probable contributory mycotoxin in moldy forage mycotoxicoses.

When infested with the fungus Rhizoctonia leguminicola, certain forages, e.g., red clover hay, can cause a "slobber syndrome" of varying severity when consumed by ruminants. The causative agent has been presumed to be slaframine [(1S,6S,8aS)-1-acetoxy-6-aminooctahydroindolizine], which is produced by R. leguminicola. In one serious outbreak of the slobber syndrome in horses, the red clover forage involved was carefully examined and found to contain R. leguminicola and slaframine. An identical hay sample is shown here by ion-exchange chromatographic and gas chromatographic-mass spectrometric analysis of appropriate hay extracts to also contain swainsonine [(1S,2R,8R,8aR)-1,2,8-trihydroxyoctahydroindolizine], a potent alpha-mannosidase inhibitor. Swainsonine has previously been isolated from pure cultures of R. leguminicola and from higher plants, namely the Darling pea (Swainsona canescens) and spotted locoweed (Astragalus lentiginosus). Consumption of Darling pea and spotted locoweed by livestock results in a severe neurological condition resembling that observed in hereditary mannosidosis in cattle and humans. Our findings indicate that swainsonine may be viewed as a mycotoxin when present in moldy forages consumed by livestock. The extent to which slaframine and swainsonine mycotoxicosis pose threats to animal husbandry and, indeed, to humans, if these alkaloids were to enter the human food chain, deserves serious consideration.     

Homocysteine is a potent modulator of plasma membrane electron transport systems

The deregulation of homocysteine metabolism leads to hyperhomocysteinemia, a condition described as an independent cardiovascular disease risk factor. Ubiquitous plasma membrane redox systems can play a dual pro-oxidant and anti-oxidant role in defense. In this study, we test the hypothesis that homocysteine, as a redox active compound, could modulate the endothelial plasma membrane redox system. We show that homocysteine behaves as a very potent stimulator of this activity. Furthermore, we show that this inducing effect is also produced on tumor cells and that it can be observed at both the activity and protein levels. On the other hand, homocysteine treatment decreases the activity of the specific ectocellular tumor NADH oxidase. Taken together, these results underscore a potential antitumoral action of homocysteine.     

Synthesis,pharmacology and molecular docking on multifunctional tacrine-ferulic acid hybrids as cholinesterase inhibitors against Alzheimer’s disease

The cholinergic hypothesis has long been a “polar star” in drug discovery for Alzheimer’s disease (AD), resulting in many small molecules and biological drug candidates. Most of the drugs marketed for AD are cholinergic. Herein, we report our efforts in the discovery of cholinesterases inhibitors (ChEIs) as multi-target-directed ligands. A series of tacrine-ferulic acid hybrids have been designed and synthesised. All these compounds showed potent acetyl-(AChE) and butyryl cholinesterase(BuChE) inhibition. Among them, the optimal compound 10g, was the most potent inhibitor against AChE (electrophorus electricus (eeAChE) half maximal inhibitory concentration (IC₅₀)?=?37.02?nM), it was also a strong inhibitor against BuChE (equine serum (eqBuChE) IC₅₀?=?101.40?nM). Besides, it inhibited amyloid β-protein self-aggregation by 65.49% at 25?μM. In subsequent in vivo scopolamine-induced AD models, compound 10g obviously ameliorated the cognition impairment and showed preliminary safety in hepatotoxicity evaluation. These data suggest compound 10g as a promising multifunctional agent in the drug discovery process against AD.     

Synthesis of α-oxycarbanilinophosphonates and their anticholinesterase activities: the most potent derivative is bound to the peripheral site of acetylcholinesterase

A novel method has been developed for the synthesis of α-oxycarbanilino phosphonates through a reaction of α-hydroxyphosphonates with isocyanate under microwave irradiation. The synthesized compounds were evaluated for their acetylcholinesterase (AChE) inhibition potency through IC₅₀determination. Molecular modelling studies suggest that the most potent inhibitor (compound 4h, IC₅₀ = 6.36 µM) is bound to the peripheral site of AChE, which suggests that it decreases the catalytic activity not through binding to the active site but through blocking the entrance of the active site gorge. This puts forward the potential of compound 4h and its derivatives to be used in the design of dual inhibitors: inhibition of the catalytic activity of AChE and of amyloid β aggregation.     

Identification of swainsonine as a probable contributory mycotoxin in moldy forage mycotoxicoses

When infested with the fungus Rhizoctonia leguminicola, certain forages, e.g., red clover hay, can cause a "slobber syndrome" of varying severity when consumed by ruminants. The causative agent has been presumed to be slaframine [(1S,6S,8aS)-1-acetoxy-6-aminooctahydroindolizine], which is produced by R. leguminicola. In one serious outbreak of the slobber syndrome in horses, the red clover forage involved was carefully examined and found to contain R. leguminicola and slaframine. An identical hay sample is shown here by ion-exchange chromatographic and gas chromatographic-mass spectrometric analysis of appropriate hay extracts to also contain swainsonine [(1S,2R,8R,8aR)-1,2,8-trihydroxyoctahydroindolizine], a potent alpha-mannosidase inhibitor. Swainsonine has previously been isolated from pure cultures of R. leguminicola and from higher plants, namely the Darling pea (Swainsona canescens) and spotted locoweed (Astragalus lentiginosus). Consumption of Darling pea and spotted locoweed by livestock results in a severe neurological condition resembling that observed in hereditary mannosidosis in cattle and humans. Our findings indicate that swainsonine may be viewed as a mycotoxin when present in moldy forages consumed by livestock. The extent to which slaframine and swainsonine mycotoxicosis pose threats to animal husbandry and, indeed, to humans, if these alkaloids were to enter the human food chain, deserves serious consideration.     

IDENTIFICATION OF CYLINDROSPERMOPSIN IN APHANIZOMENON OVALISPORUM (CYANOPHYCEAE) ISOLATED FROM LAKE KINNERET,ISRAEL1

Aphanizomenon ovalisporum (Forti) was identified and isolated from Lake Kinneret upon its first appearance as a dominant bloom in late 1994. This cyanobacterial species, not previously known to be toxic, was evaluated by a commonly used mouse bioassay and was demonstrated to induce toxic symptoms that were distinguishable from the typical symptoms of the neurotoxins previously reported in Aphanizomenon flos-aquae (L.) Ralfs. Mice died 5–24 h after crude extracts were injected intraperitoneally, and the LD₅₀ value was estimated as 465 mg dry wt biomass · kg^?1 mouse. A toxicity-guided fractionation of the active extract indicated that the potent substance is polar an nature. The structure of the active compound was determined by its mass spectrometry and NMR data. The compound was found to be the sulfate-guanidinium zwitterion, cylindrospermopsin, previously isolated from the cyanobacterium Cylindrospermopsis raciborskii (Woloszynska) and recently also reported in Umezakia natans (Watanabe). This is the first time that Aphanizomenon ovalisporum has been reported to contain a toxic compound.     

Localization of electrical current flow across the chorionated unfertilized egg of the locust,Locusta migratoria.

Summary

Extracellular currents near the surface of the electrically excitable egg of Locusta migratoria have been studied through the combined use of the 2-dimensional vibrating probe and an intracellular microelectrode. Intracellular current injection increased extracellular current densities to levels readily detectable by the vibrating probe, and it has been possible to show that injected current traverses the egg in the posterior end containing the micropylar zone. Extracellular currents could not be detected during the rising, plateau or falling phases of the long duration (>100s) action potential in the egg. Increases in current density during the hyperpolarizing after potential which lasts for 6–10 min after termination of the action potential were also restricted to the posterior end of the egg. The results suggest that the primary region at which current traverses the chorionated egg is near or at the micropylar zone.     

In silico studies of urease inhibitors to explore ligand-enzyme interactions

In continuation of our previous study on the urease inhibition by a number of chalcones, 2,3-dihydro-1,5-benzothiazepines and 2,3,4,5-tetrahydro-1,5-benzothiazepines, FlexX docking has been exploited to get a deeper insight into the mechanism of their inhibitory action. A comparison of the IC₅₀ values of the active compounds reveals that, of the three classes of compounds studied, 2,3-dihydro-1,5-benzothiazepines were the most potent urease inhibitors. An in silico examination of these compounds showed that the activity is related to the interaction of ligand with the nickel metallocentre, its interaction with two amino acid residues, Asp224 and Cys322, in addition to the orientation of rings A and B in the catalytic core of the enzyme. The most active compound 2,3-dihydro-1,5-benzothiazepine (4) anchor tightly through a network of interactions with Ni701 and Ni702. This includes a number of hydrogen bonds and hydrophobic contacts with the amino acid residues in its vicinity. For their reduced analogs, the difference in the activity of different diastereomers has been observed to be configuration-dependent. This may be ascribed mainly to the difference in the orientation of ring B of the two stereoisomers and the extent of their interaction with Asp224 and Cys322 present in the catalytic core of the enzyme.     

Effects of radix polygoni multiflori components on tyrosinase activity and melanogenesis

Radix Polygoni multiflori is a herb used effectively to prevent graying and treat skin depigmentation diseases in traditional Chinese medicine but its active ingredients have not been discovered yet. In this investigation, we tested six compounds isolated from Radix Polygoni multiflori, to discover the active component on melanogenesis. Three experiments were performed in the present investigation: mushroom tyrosinase activity, melanin content B16 cell proliferation assay. Among all the six components tested, THSG showed the most potent effects on tyrosinase activation and melanogenesis; it was shown to be a potent tyrosinase activator and a melanogenesis stimulator in this study. On the other hand, we found that gallic acid significantly inhibited tyrosinase and, in addition, anthraquinones were cytotoxic to melanoma cells. They were both harmful to melanogenesis. Therefore, we propose that THSG acts as the active ingredient of Radix Polygoni multiflori on melanogenesis.