(-)-Clausenamide potentiates synaptic transmission in the dentate gyrus of rats

The effect of clausenamide on synaptic transmission in the dentate gyrus of rats in vivo and its possible mechanism of action were investigated in this study. Four of 16 enantiomers showed potentiating effects on basal synaptic transmission in anesthetized animals. By comparing one pair of enantiomers, (-)-clausenamide and (+)-clausenamide, we can report three primary findings: (1) (-)-clausenamide potentiated synaptic transmission in both anesthetized and freely moving animals while (+)-clausenamide showed no or little effect; (2) (-)-clausenamide increased the magnitude of long-term potentiation (LTP) induced by high-frequency stimulation (HFS) in anesthetized animals whereas (+)-clausenamide had no effect; (3) voltage-dependent calcium channels (VDCCs) calcineurin and calpain are involved in (-)-clausenamide-induced potentiation of synaptic transmission. Because hippocampal LTP is thought to reflect a cellular mechanism involved in learning and memory, our findings may provide the pharmacological basis for understanding the nootropic mechanisms of (-)-clausenamide, which is the first chiral nootropic agent developed in China.     

Mechanism of (-)clausenamide induced calcium transient in primary culture of rat cortical neurons

(-)clausenamide is a compound isolated from Clausena lansium (lour) Skeel with nootropic effects. At the present study, we investigated the clausenamide induced Ca2+ signaling in primary cultures of rat cortical neurons by using laser confocal microscopy. The mean amplitude of (-)clausenamide (1 microM) induced Ca2+ transient was similar in extracellular solution with or without calcium; and (-)clausenamide failed to trigger calcium transient after treatment with endoplasmic reticulum Ca2+ pumps inhibitor BHQ to exhaust intracellular Ca2+ stores. This result suggested that the primary source of (-)clausenamide induced Ca2+ transient was from internal stores. Application of IP3 receptor inhibitor MgCl2 and PLC-gamma inhibitor U73122 suppressed (-)clausenamide induced Ca2+ transient, suggesting that the major source of (-)clausenamide induced Ca2+ transient was from IP3 receptor pathway. We also found that mitochondria were involved in (-)clausenamide triggered Ca2+ transient. The distinctive spatial and temporal characteristic of (-)clausenamide induced Ca2+ transient may play an important role in its action.     

Preservation of plastic properties of synaptic transmission in long-lasting hippocampal slices under the effects of a peptide analog of piracetam, L-pGlu-D-Ala-NH2

The tetanic stimulation of the Schaffer collaterals (SC) in rat hippocamp slices after 6 hrs in vitro conditions did not produce long-term potentiation (LTP) of the field response amplitude in the CA1 pyramidal cell layer. In contrast, LTP after the late tetanization was well preserved in the slices that were perfused for 20 minutes with 0.5 mkM L-pGlu-D-Ala-NH2 (PGAA) after 4-4.5 hrs in vitro. There were no significant reactivity changes during the perfusion of the slices with this drug concentration. Two other drugs with nootropic activity, piracetam (100 mkM) and gamma-hydroxybutyrate (100 mkM, Na-salt) did not prevent the disappearance of LTP in the late period in vitro, while enhanced the reactivity during perfusion period. The maintenance of the plastic properties of the SC-CA1 synaptic transmission under the influence of PGAA is thought to be the result of some specific interaction of the drug with LTP induction mechanisms. LTP damaged in the late period in vitro might be a new model of memory disturbances and this model can turn out to be useful for the comparative estimation of the effectiveness of the drugs with proposed nootropic activity and for the analysis of the possible mechanisms of their action.     

Endogenous neuropeptides and regulation of the brain functional plasticity

This review analysed the data about the neuropeptides secreted from the different brain structures. Involvement of the endogenous neuropeptides in synaptic plasticity was tested at the model of long-term potentiation (LTP) as a form of learning and the memory formation. The most of these neuropeptides or their fragments involves in the induction and maintenance of the LTP and provides the transformation of short-term excitability of the neurones into the long-term one. They may be considered as nootropic compounds. It is proposed that the system of peptidergic regulation of neuronal plasticity functionates in the brain and there are a possibility to correct the activity of this system during the different pathology.     

Synthesis and biological evaluation of tubulysin D analogs related to stereoisomers of tubuvaline

The synthesis and biological evaluation of stereoisomers in tubulysin D are described. The stereoselective synthesis of all possible stereoisomers of C-11 and C-13 positions in tubulysin D was achieved by employing 1′-epi-Tuv-Me, 3′-epi-Tuv-Me, and ent-Tuv-Me and their biological properties were evaluated. It is clear that the stereochemistries of the C-11 and C-13 positions in tubulysin D have no practical impact on the inhibition of tubulin polymerization but play a role in the potent antiproliferative activities.     

Nootropic and analgesic effects of Semax following different routes of administration

Heptapeptide Semax (MEHFPGP) is the fragment of ACTH(4-10) analogue with prolonged neurotropic activity. The aim of the present work was to study the Semax effects on learning capability and pain sensitivity in white rats following intraperitoneal and intranasal administration in different doses. Semax nootropic effects were studied in the test of acquisition of passive avoidance task. Pain sensitivity was estimated in Randall-Selitto paw-withdrawal test. It was shown that Semax exerts nootropic and analgesic activities following intraperitoneal administration. Analysis of dependence of these effects on dose resulted in different dose-response curves. Following intranasal administration, Semax was more potent in learning improvement compared to intraperitoneal administration. The peptide failed to affect the animal pain sensitivity following intranasal administration as opposed to intraperitoneal administration. The data obtained suggest different mechanisms and brain structures involved in realization of the nootropic and analgesic effects of Semax.     

CaM kinase II and protein kinase C activations mediate enhancement of long-term potentiation by nefiracetam in the rat hippocampal CA1 region

Nefiracetam is a pyrrolidine-related nootropic drug exhibiting various pharmacological actions such as cognitive-enhancing effect. We previously showed that nefiracetam potentiates NMDA-induced currents in cultured rat cortical neurons. To address questions whether nefiracetam affects NMDA receptor-dependent synaptic plasticity in the hippocampus, we assessed effects of nefiracetam on NMDA receptor-dependent long-term potentiation (LTP) by electrophysiology and LTP-induced phosphorylation of synaptic proteins by immunoblotting analysis. Nefiracetam treatment at 1-1000 nM increased the slope of fEPSPs in a dose-dependent manner. The enhancement was associated with increased phosphorylation of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor through activation of calcium/calmodulin-dependent protein kinase II (CaMKII) without affecting synapsin I phosphorylation. In addition, nefiracetam treatment increased PKCalpha activity in a bell-shaped dose-response curve which peaked at 10 nM, thereby increasing phosphorylation of myristoylated alanine-rich protein kinase C substrate and NMDA receptor. Nefiracetam treatment did not affect protein kinase A activity. Consistent with the bell-shaped PKCalpha activation, nefiracetam treatment enhanced LTP in the rat hippocampal CA1 region with the same bell-shaped dose-response curve. Furthermore, nefiracetam-induced LTP enhancement was closely associated with CaMKII and PKCalpha activation with concomitant increases in phosphorylation of their endogenous substrates except for synapsin I. These results suggest that nefiracetam potentiates AMPA receptor-mediated fEPSPs through CaMKII activation and enhances NMDA receptor-dependent LTP through potentiation of the post-synaptic CaMKII and protein kinase C activities. Together with potentiation of nicotinic acetylcholine receptor function, nefiracetam-enhanced AMPA and NMDA receptor functions likely contribute to improvement of cognitive function.     

Synthesis and biological evaluation of all eight stereoisomers of DPP-IV inhibitor saxagliptin

All eight stereoisomers of saxagliptin have been synthesized and evaluated for their inhibitory activity against DPP-IV. It was unambiguously confirmed that the configuration of saxagliptin was critical to potent inhibition of DPP-IV. Docking study was performed to elucidate the configuration–activity relationship of saxagliptin stereoisomers. Tyr662 and Tyr470 have been suggested as the key residues of DPP-IV interacting with the inhibitors. This work provides valuable information for further inhibitor design against DPP-IV.     

Cytotoxic activity of butane type of 1,7-seco-2,7′-cyclolignanes and apoptosis induction by Caspase 9 and 3

All stereoisomers of methoxybutane and fluorobutane type of 1,7-seco-2,7′-cyclolignane were synthesized and cytotoxic activities of these compounds were compared with those of all stereoisomers of butane and butanol type compounds. Both enantiomers of butane type secocyclolignane showed higher cytotoxic activity (IC₅₀ = 16–20 μM) than methoxy type compounds, whereas none was observed for all the stereoisomers of butanol type secocyclolignane, however, (−)-Kadangustin J showed stereospecific cytotoxic activity (IC₅₀ = 47–67 μM). Since (R)-9′-fluoro derivative 23 was most potent (IC₅₀ = 19 μM) among the corresponding fluoro stereoisomers, (R)-9′-alkyl derivatives were synthesized, hydrophobic 9′-heptyl derivative 27 showing highest activity (IC₅₀ = 3.7 μM against HL-60, IC₅₀ = 3.1 μM against HeLa) in this experiment. Apoptosis induction caused by Caspase 3 and 9 for (R)-9′-heptyl derivative 27 was observed in the research on the mechanism. A degradation of DNA into small fragments was also shown by DNA ladder assay.     

Inhibition of Calpains by Calmidazolium and Calpastatin

Abstract

Several prolinal derivatives were synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain and their possible properties as nootropic agents. Almost all the compounds tested inhibited the activity of both enzymes at low IC₅₀ values of the order of nM, but a specificity difference was observed with alkylacyl-prolinal derivatives which strongly inhibited only the bacterial enzyme. Prolyl-prolinal derivatives were the most effective inhibitors for both enzymes. In the passive avoidance test using amnesic rats experimentally induced with scopolamine, the prolinal derivatives that have potent inhibitory activity toward post-proline cleaving enzymes showed also strong anti-amnesic activities at doses of 10 ~ 1000μg/kg, i.p. Some of the compounds showed a bell-shape dose dependency. These results suggest that the post-proline cleaving enzymes play an important role in the regulation of learning and memory consolidation in the brain and inhibitors of these enzymes are suggested as possible candidates for nootropic agents, particularly for an anti-amnesic drug.     

Absolute configuration determination of isoflavan-4-ol stereoisomers

Elucidation of the correct stereochemistry of the metabolite is essential for the mechanistic study of bioactive compounds. Isoflavan-4-ol has the same chiropical chromophore as THD, the biosynthetic precursor of the potent phytoestrogen S-equol. Interested in the correct absolute configuration of isoflavan-4-ol stereoisomers and to compare the available practical approaches for the absolute configuration determination, complete absolute configuration analysis of isoflavan-4-ol stereoisomers has been carried out with by means of ECD and VCD spectroscopy as well as modified Mosher method. Theoretical TD-DFT computations resulted in a poor simulation of the observed experimental ECD spectra, and thus inconclusive absolute configuration assignments of isoflavan-4-ol stereoisomers were obtained. However, DFT-assisted VCD spectroscopic analyses successfully determined correct absolute configurations, and further confirmed by modified Mosher method.     

Synthesis,characterization, and biological assessment of the four stereoisomers of the H3 receptor antagonist 5-fluoro-2-methyl-N-[2-methyl-4-(2-methyl[1,3′]bipyrrolidinyl-1′-yl)phenyl]benzamide

This Letter describes the asymmetric synthesis of the four stereoisomers (8a–8d) of a potent and highly selective histamine H₃ receptor (H₃R) antagonist, 5-fluoro-2-methyl-N-[2-methyl-4-(2-methyl[1,3′]bipyrrolidinyl-1′-yl) phenyl]benzamide (1). The physico-chemical properties, in vitro H₃R affinities and ADME of 8a–8d were determined. Stereoisomer 8c (2S,3′S) displayed superior in vitro H₃R affinity over other three stereoisomers and was selected for further profiling in in vivo PK and drug safety. Compound 8c exhibited excellent PK properties with high exposure, desired brain to plasma ratio and reasonable brain half life. However, all stereoisomers showed similar unwanted hERG affinities.     

The crystal structure of oxylipin-conjugated barley LTP1 highlights the unique plasticity of the hydrophobic cavity of these plant lipid-binding proteins

The barley lipid transfer protein (LTP1) adducted by an α-ketol, (9-hydroxy-10-oxo-12(Z)-octadecenoic acid) exhibits an unexpected high lipid transfer activity. The crystal structure of this oxylipin-adducted LTP1, (LTP1b) was determined at 1.8 Å resolution. The covalently bound oxylipin was partly exposed at the surface of the protein and partly buried within the hydrophobic cavity. The structure of the oxylipidated LTP1 emphasizes the unique plasticity of the hydrophobic cavity of these plant lipid-binding proteins when compared to the other members of the family. The plasticity of the hydrophobic cavity and increase of its surface hydrophobicity induced by the oxylipin account for the improvement of the lipid transfer activity of LTP1b. These observations open new perspectives to explore the different biological functions of LTPs, including their allergenic properties.     

Syntheses of 6-(2-hydroxy-6-phenylhexyl)-5,6-dihydro-2H-pyran-2-one derivatives and their cytotoxicities

The cytotoxicities against cancer cells (HL-60, HeLa) and insect cells (Sf9) of four stereoisomers of 6-(2-hydroxy-6-phenylhexyl)− 5,6-dihydro-2H-pyran-2-one (1) were evaluated, and then their structure-activity relationships examined. The 2′-dehydroxy derivative 5 of (6 R,2′R)- and (6 R,2′S)-1 showed the highest activity against HeLa cells (IC₅₀ = 1.4 μM). To evaluate the effect of the 2′-hydroxy group of 1, 6R-and 6S-oxetane derivatives were also synthesized and their activities examined. Against HeLa and HL-60 cells, the activities of the less potent stereoisomers were enhanced 3–4-fold by the introduction of the oxetane moieties at the 2′-position. Against the insect cell line (Sf9), phenyl derivative 7 showed the highest activity with an IC₅₀ value of 8.0 μM.     

Effect of Modification of the N-Terminal Region of Semax on the Expression of Nootropic Effect of Semax Analogs

A comparative study of nootropic activity of semax (MEHFPGP), an analog of ACTH_4–10, and some of its derivatives, in which the N-terminal methionine was modified or substituted with other amino acid residues, was performed. The effect of these peptides on learning of albino rats in tests with positive (food) and negative (pain) reinforcement was studied. In the case of modification of methionine by attachment of the gluconic-acid residue or substitution of methionine with lysine, the nootropic effect of the peptide was retained. The substitution of methionine with tryptophan or serine resulted in a decrease in the nootropic activity. The substitution of methionine with glycine, threonine, or alanine caused a complete loss of the nootropic activity of the peptide. Therefore, the amino acid residue located at position 1 of the heptapeptide analog semax, plays a key role in retaining the nootropic effects of the peptide and determines the degree of their expression.__________Translated from Izvestiya Akademii Nauk, Seriya Biologicheskaya, No. 4, 2005, pp. 460–466.Original Russian Text Copyright © 2005 by Glazova, Sebentsova, Levitskaya, Andreeva, Alfeeva, Kamenskii, Myasoedov.     

Synthesis and inhibitory activity of acyl-peptidyl-prolinalderivatives toward post-proline cleaving enzyme as nootropic agents

Several prolinal derivatives were synthesized and examined for their inhibitory activity on post-proline cleaving enzymes from Flavobacterium meningosepticum and bovine brain and their possible properties as nootropic agents. Almost all the compounds tested inhibited the activity of both enzymes at low IC50 values of the order of nM, but a specificity difference was observed with alkylacyl-prolinal derivatives which strongly inhibited only the bacterial enzyme. Prolyl-prolinal derivatives were the most effective inhibitors for both enzymes. In the passive avoidance test using amnesic rats experimentally induced with scopolamine, the prolinal derivatives that have potent inhibitory activity toward post-proline cleaving enzymes showed also strong anti-amnesic activities at dose of 10-1000 micrograms/kg, i.p. Some of the compounds showed a bell-shape dose dependency. These results suggest that the post-proline cleaving enzymes play an important role in the regulation of learning and memory consolidation in the brain and inhibitors of these enzymes are suggested as possible candidates for nootropic agents, particularly for an anti-amnesic drug.     

Discovery of a small-molecule inhibitor and cellular probe of Keap1–Nrf2 protein–protein interaction

A high-throughput screen (HTS) of the MLPCN library using a homogenous fluorescence polarization assay identified a small molecule as a first-in-class direct inhibitor of Keap1–Nrf2 protein–protein interaction. The HTS hit has three chiral centers; a combination of flash and chiral chromatographic separation demonstrated that Keap1-binding activity resides predominantly in one stereoisomer (SRS)-5 designated as ML334 (LH601A), which is at least 100× more potent than the other stereoisomers. The stereochemistry of the four cis isomers was assigned using X-ray crystallography and confirmed using stereospecific synthesis. (SRS)-5 is functionally active in both an ARE gene reporter assay and an Nrf2 nuclear translocation assay. The stereospecific nature of binding between (SRS)-5 and Keap1 as well as the preliminary but tractable structure–activity relationships support its use as a lead for our ongoing optimization     

Novel Sunifiram-carbamate hybrids as potential dual acetylcholinesterase inhibitor and NMDAR co-agonist: simulation-guided analogue design and pharmacological screening

An efficient method for synthesising NMDAR co-agonist Sunifiram (DM235), in addition to Sunifram-carbamate and anthranilamide hybrids, has been developed in high yields via protecting group-free stepwise unsymmetric diacylation of piperazine using N-acylbenzotiazole. Compounds 3f, 3d, and 3i exhibited promising nootropic activity by enhancing acetylecholine (ACh) release in A549 cell line. Moreover, the carbamate hybrid 3f was found to exhibit higher in vitro potency than donepezil with IC₅₀ = 18 ± 0.2 nM, 29.9 ± 0.15 nM for 3f and donepezil, respectively. 3f was also found to effectively inhibit AChE activity in rat brain (AChE = 1.266 ng/mL) compared to tacrine (AChE = 1.137 ng/ml). An assessment of the ADMET properties revealed that compounds 3f, 3d, and 3i are drug-like and can penetrate blood–brain barrier. Findings presented here showcase highly potential cholinergic agents, with expected partial agonist activity towards glycine binding pocket of NMDAR which could lead to development and optimisation of novel nootropic drugs.     

A simple synthesis of four stereoisomers of roseoside and their inhibitory activity on leukotriene release from mice bone marrow-derived cultured mast cells

Four stereoisomers of roseoside (vomifoliol glucosides) were synthesized using glucose as a chiral resolving reagent. The four synthetic stereoisomers exhibited inhibitory activity on leukotriene release from mouse bone marrow-derived cultured mast cells (BMCMC). The (6S)-isomers of roseoside were about twice as active as (6R)-isomers.     

Pachastrissamine (jaspine B) and its stereoisomers inhibit sphingosine kinases and atypical protein kinase C

Sphingosine kinases (SphKs) are oncogenic enzymes that regulate the critical balance between ceramide and sphingosine-1-phosphate. Much effort has been dedicated to develop inhibitors against these enzymes. Naturally occurring pachastrissamine (jaspine B) and all its stereoisomers were prepared and evaluated for their inhibitory effects against SphKs. All eight stereoisomers exhibited moderate to potent inhibitory activity against SphK1 and SphK2. Inhibitory effects were profiled against protein kinase C (PKC) isoforms by in vitro experiments. Atypical PKCs (PKCζ and PKCι) were inhibited by several pachastrissamine stereoisomers. The improved activity over N,N-dimethylsphingosine suggests that the cyclic scaffold in pachastrissamines facilitates potential favorable interactions with SphKs and PKCs.