Mutasynthesis of Physostigmines in Myxococcus xanthus.

The alkaloid physostigmine is an approved anticholinergic drug and an important lead structure for the development of novel therapeutics. Using a complementary approach that merged chemical synthesis with pathway refactoring, we produced a series of physostigmine analogues with altered specificity and toxicity profiles in the heterologous host Myxococcus xanthus. The compounds that were generated by applying a simple feeding strategy include the promising drug candidate phenserine, which was previously accessible only by total synthesis.

Discovery of new acetylcholinesterase inhibitors for Alzheimer's disease: virtual screening and in vitro characterisation.

For more than two decades, the development of potent acetylcholinesterase (AChE) inhibitors has been an ongoing task to treat dementia associated with Alzheimer's disease and improve the pharmacokinetic properties of existing drugs. In the present study, we used three docking-based virtual screening approaches to screen both ZINC15 and MolPort databases for synthetic analogs of physostigmine and donepezil, two highly potent AChE inhibitors. We characterised the in vitro inhibitory concentration of 11 compounds, ranging from 14 to 985 µM. The most potent of these compounds, S-I 26, showed a fivefold improved inhibitory concentration in comparison to rivastigmine. Moderate inhibitors carrying novel scaffolds were identified and could be improved for the development of new classes of AChE inhibitors.

Combined Pre- and Posttreatment of Paraoxon Exposure.

AIMS: Organophosphates (OPCs), useful agents as pesticides, also represent a serious health hazard. Standard therapy with atropine and established oxime-type enzyme reactivators is unsatisfactory. Experimental data indicate that superior therapeutic results can be obtained when reversible cholinesterase inhibitors are administered before OPC exposure. Comparing the protective efficacy of five such cholinesterase inhibitors (physostigmine, pyridostigmine, ranitidine, tacrine, or K-27), we observed best protection for the experimental oxime K-27. The present study was undertaken in order to determine if additional administration of K-27 immediately after OPC (paraoxon) exposure can improve the outcome. METHODS: Therapeutic efficacy was assessed in rats by determining the relative risk of death (RR) by Cox survival analysis over a period of 48 h. Animals that received only pretreatment and paraoxon were compared with those that had received pretreatment and paraoxon followed by K-27 immediately after paraoxon exposure. RESULTS: Best protection from paraoxon-induced mortality was observed after pretreatment with physostigmine (RR = 0.30) and K-27 (RR = 0.34). Both substances were significantly more efficacious than tacrine (RR = 0.67), ranitidine (RR = 0.72), and pyridostigmine (RR = 0.76), which were less efficacious but still significantly reduced the RR compared to the no-treatment group (paraoxon only). Additional administration of K-27 immediately after paraoxon exposure (posttreatment) did not further reduce mortality. Statistical analysis between pretreatment before paraoxon exposure alone and pretreatment plus K-27 posttreatment did not show any significant difference for any of the pretreatment regimens. CONCLUSIONS: Best outcome is achieved if physostigmine or K-27 are administered prophylactically before exposure to sublethal paraoxon dosages. Therapeutic outcome is not further improved by additional oxime therapy immediately thereafter.

(-)-Phenserine tartrate (PhenT) as a treatment for traumatic brain injury.

AIM: Traumatic brain injury (TBI) is one of the most common causes of morbidity and mortality of both young adults and the elderly, and is a key contributing factor in about 30% of all injury-associated deaths occurring within the United States of America. Albeit substantial impact has been made to improve our comprehension of the mechanisms that underpin the primary and secondary injury stages initiated by a TBI incident, this knowledge has yet to successfully translate into the development of an effective TBI pharmacological treatment. Developing consent suggests that a TBI can concomitantly trigger multiple TBI-linked cascades that then progress in parallel and, if correct, the multifactorial nature of TBI would make the discovery of a single effective mechanism-targeted drug unlikely. DISCUSSION: We review recent data indicating that the small molecular weight drug (-)-phenserine tartrate (PhenT), originally developed for Alzheimer's disease (AD), effectively inhibits a broad range of mechanisms pertinent to mild (m) and moderate (mod)TBI, which in combination underpin the ensuing cognitive and motor impairments. In cellular and animal models at clinically translatable doses, PhenT mitigated mTBI- and modTBI-induced programmed neuronal cell death (PNCD), oxidative stress, glutamate excitotoxicity, neuroinflammation, and effectively reversed injury-induced gene pathways leading to chronic neurodegeneration. In addition to proving efficacious in well-characterized animal TBI models, significantly mitigating cognitive and motor impairments, the drug also has demonstrated neuroprotective actions against ischemic stroke and the organophosphorus nerve agent and chemical weapon, soman. CONCLUSION: In the light of its tolerability in AD clinical trials, PhenT is an agent that can be fast-tracked for evaluation in not only civilian TBI, but also as a potentially protective agent in battlefield conditions where TBI and chemical weapon exposure are increasingly jointly occurring.

Highly selective and ultra-sensitive electrochemical sensor behavior of 3D SWCNT-BODIPY hybrid material for eserine detection.

In this work, 4,4-difluoro-8-(4-hydroxyphenyl)- 2,6-diethynly-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (BODIPY) having double terminal ethynyl groups was synthesized. Three dimensional single walled carbon nanotube (SWCNT)-BODIPY hybrid material (3D SWCNT-BODIPY) was synthesized by the reaction of BODIPY bearing double terminal ethynyl groups with azido containing SWCNTs via "Click" reaction. The structural properties and electrochemical detection of eserine (a pesticide) on BODIPY functionalized SWCNTs as a three dimensional (3D) material were investigated. A glassy carbon electrode (GCE) was modified by 3D SWCNT-BODIPY hybrid material for the determination of eserine in the range of 0.25-2.25 µM. In the study by the square wave voltammetry (SWV), the bare GCE showed no response, while the new peak at - 0.6 V appeared in the case of the modified electrode. The detection limit and quantification were determined as 160 nM and 528 nM for eserine on the 3D SWCNT-BODIPY modified electrode, respectively. Eserine was also determined with a standard addition method in different brands of orange juices, and the recovery of eserine was obtained to be in the range of 102.09% and 103.22%. This study clearly indicates that the 3D SWCNT-BODIPY modified electrode tested as an electrochemical sensor was found to be highly selective and sensitive to eserine.

The development of a butyrylcholinesterase porous pellet for innovative detection of cholinesterase inhibitors.

The aim of the presented research was the preparation of an innovative carrier with significantly improved properties for the fast and sensitive detection of cholinesterase inhibitors such as nerve agents. This innovative carrier was in the form of spherical pellets containing different amounts of Neusilin. Neusilin is a synthetic and amorphous form of magnesium aluminometasilicate with a high specific surface area, and the immobilized enzyme butyrylcholinesterase with an activity of 50nkat·g-1. Pellets were prepared by the extrusion-spheronization method and dried in a hot air oven under two conditions - at 30°C for 72h and at 60°C for 24h. Dried pellets were consequently impregnated with a solution containing butyrylcholinesterase. Impregnated pellets were evaluated for their quality parameters, enzymatic activity and inhibition. Activity and inhibition were tested according to the standard Ellman's method. It was observed that the addition of Neusilin significantly increased the hardness, intraparticular porosity, sphericity and activity of the carriers as well as intensity of the color transition. Therefore it is shown that these carriers have unquestionable advantages over common carriers of their kind. Drying temperatures have been shown to have no effect on properties of pellets except for a change in their size. Results were confirmed by statistical evaluation using ANOVA and PCA.

Intramolecular 1,5-H transfer reaction of aryl iodides through visible-light photoredox catalysis: a concise method for the synthesis of natural product scaffolds.

The intramolecular 1,5-H transfer reaction of the aryl radicals generated from unactivated aryl iodides by photocatalysis is described. The features of this transformation are operational simplicity, excellent yields, mild reaction conditions, and good functional group tolerance. With this approach, a more concise formal synthesis of (±)-coerulescine and (±)-physovenine is accomplished.

Unified Approach to the Spiro(pyrrolidinyl-oxindole) and Hexahydropyrrolo[2,3-b]indole Alkaloids: Total Syntheses of Pseudophrynamines 270 and 272A.

The first enantioselective total syntheses of architecturally interesting prenylated pyrroloindole alkaloids, (-)-pseudophrynamines 272A (3d) and 270 (3b), have been achieved starting from enantioenriched 2-oxindoles having all-carbon quaternary stereocenters. A common strategy involving a thio-urea catalyzed aldol reaction is employed for the total synthesis of both spiro(pyrrolidinyl-oxindole) and hexahydropyrrolo[2,3-b]indole alkaloids.

An expeditious route to both enantiomers of all carbon quaternary stereocenters at C-3 carbon of lactams via [3,3]-sigmatropic rearrangement: total synthesis of (-)-physostigmine.

A diastereoselective route to all carbon quaternary stereocenters at the C-3 position of cyclic lactams has been developed via Johnson-Claisen rearrangement of γ-hydroxy-α, ß-unsaturated lactams. It has been observed that olefin geometry plays an important role in the development of the absolute stereochemistry of the product. The dependence of the product configuration on the olefin geometry is explained by postulating probable transition states. The success of this method has been shown for the multigram scale synthesis of these substituted lactams from commercially available cheap starting materials. The synthetic usefulness of this method is also demonstrated by carrying out the total synthesis of (-)-physostigmine.

Phosphine-catalyzed enantioselective γ-addition of 3-substituted oxindoles to 2,3-butadienoates and 2-butynoates: use of prochiral nucleophiles.

The first phosphine-catalyzed enantioselective γ-addition with prochiral nucleophiles and 2,3-butadienoates as the reaction partners has been developed. Both 3-alkyl- and 3-aryl-substituted oxindoles could be employed in this process, which is catalyzed by a chiral phosphine that is derived from an amino acid, thus affording oxindoles that bear an all-carbon quaternary center at the 3-position in high yields and excellent enantioselectivity. The synthetic value of these γ-addition products was demonstrated by the formal total synthesis of two natural products and by the preparation of biologically relevant molecules and structural scaffolds.

Copper(I)-catalyzed aryl or vinyl addition to electron-deficient alkenes cascaded by cationic cyclization.

An exoselective copper-catalyzed arylation- and vinylation-carbocyclization of electron-deficient alkenes was developed to provide rapid and efficient access to a variety of functionalized 3,3-disubstituted oxindoles. With this method, a highly efficient and concise formal synthesis of (±)-physostigmine and (±)-physovenine has been completed.

Functional study on the mutations in the silkworm (Bombyx mori) acetylcholinesterase type 1 gene (ace1) and its recombinant proteins.

The acetylcholinesterase of Lepidoptera insects is encoded by two genes, ace1 and ace2. The expression of the ace1 gene is significantly higher than that of the ace2 gene, and mutations in ace1 are one of the major reasons for pesticide resistance in insects. In order to investigate the effects of the mutations in ace1's characteristic sites on pesticide resistance, we generated mutations for three amino acids using site-directed mutagenesis, which were Ala(GCG)303Ser(TCG), Gly(GGA)329Ala(GCA) and Leu (TCT)554Ser(TTC). The Baculovirus expression system was used for the eukaryotic expression of the wild type ace1 (wace1) and the mutant ace1 (mace1). SDS-PAGE and Western blotting were used to detect the targeting proteins with expected sizeof about 76 kDa. The expression products were purified for the determination of AChE activity and the inhibitory effects of physostigmine and phoxim. We observed no significant differences in the overall activity of the wild type and mutant AChEs. However, with 10 min of physostigmine (10 µM) inhibition, the remaining activity of the wild type AChE was significantly lower than that of the mutant AChE. Ten min inhibition with 33.4 µM phoxim also resulted in significantly lower remaining activity of the wild type AChE than that of the mutant AChE. These results indicated that mutations for the three amino acids reduced the sensitivity of AChE to physostigmine and phoxim, which laid the foundation for future in vivo studies on AChE's roles in pesticide resistance.

Pharmacodynamics of cholinesterase inhibitors suggests add-on therapy with a low-dose carbamylating inhibitor in patients on long-term treatment with rapidly reversible inhibitors.

Despite three decades of intensive research in the field of Alzheimer's disease (AD) and numerous clinical trials of new therapeutic agents, cholinesterase inhibitors (ChEIs) are still the mainstay of therapeutics for AD and dementia with Lewy bodies. Pharmacodynamic analyses of ChEIs provide paradoxical observations. Treatment with the rapidly reversible, noncarbamylating ChEIs (donepezil, galantamine, and tacrine) increases acetylcholinesterase (AChE) protein expression, whereas the carbamylating agent, rivastigmine, produces sustained inhibition with no significant change in AChE protein expression. Still, the symptomatic clinical efficacies of all these agents are similar. We report here for the first time that treatment with phenserine, another carbamylating ChEI, produces a sustained but mild inhibition of AChE in cerebrospinal fluid (CSF) of AD patients. We also show that phenserine treatment reverses donepezil-induced elevation of AChE expression. Further analyses on CSF of another larger patient cohort treated with donepezil revealed that, in addition to its main mode of action, donepezil produced two other pharmacodynamics with potentially contradictory outcomes. Donepezil-induced AChE expression favored an AChE-driven amyloid-ß peptide (Aß) aggregation, whereas donepezil itself concentration-dependently counteracted the AChE-induced Aß aggregation, most likely by competing with the Aß peptides for peripheral anionic site on the AChE protein. The reduction of AChE protein expression in the donepezil-treated patients by concomitant administration of the carbamylating agent, phenserine, could allow the donepezil molecule to only prevent interaction between Aß and AChE. The current study suggests that an add-on therapy with a low-dose formulation of a carbamylating agent in patients on long-term donepezil treatment should be explored as a strategy for enhancing the clinical efficacy of these agents in dementia disorders.

Domino Rh-catalyzed hydroformylation-double cyclization of o-amino cinnamyl derivatives: applications to the formal total syntheses of physostigmine and physovenine.

A parallel, versatile and efficient route to synthesis of pyrrolidinoindoline and tetrahydrofuranoindoline alkaloids from cinnamyl derivatives has been developed, featuring a domino Rh-catalyzed hydroformylation-double cyclization sequence. This method can be applied to the syntheses of anti-Alzheimer drugs such as physostigmine and physovenine.

Neurotrophic and neuroprotective actions of (-)- and (+)-phenserine, candidate drugs for Alzheimer's disease.

Neuronal dysfunction and demise together with a reduction in neurogenesis are cardinal features of Alzheimer's disease (AD) induced by a combination of oxidative stress, toxic amyloid-ß peptide (Aß) and a loss of trophic factor support. Amelioration of these was assessed with the Aß lowering AD experimental drugs (+)-phenserine and (-)-phenserine in neuronal cultures, and actions in mice were evaluated with (+)-phenserine. Both experimental drugs together with the metabolite N1-norphenserine induced neurotrophic actions in human SH-SY5Y cells that were mediated by the protein kinase C (PKC) and extracellular signal-regulated kinases (ERK) pathways, were evident in cells expressing amyloid precursor protein Swedish mutation (APP(SWE)), and retained in the presence of Aß and oxidative stress challenge. (+)-Phenserine, together with its (-) enantiomer as well as its N1- and N8-norphenserine and N1,N8-bisnorphenserine metabolites, likewise provided neuroprotective activity against oxidative stress and glutamate toxicity via the PKC and ERK pathways. These neurotrophic and neuroprotective actions were evident in primary cultures of subventricular zone (SVZ) neural progenitor cells, whose neurosphere size and survival were augmented by (+)-phenserine. Translation of these effects in vivo was assessed in wild type and AD APPswe transgenic (Tg2576) mice by doublecortin (DCX) immunohistochemical analysis of neurogenesis in the SVZ, which was significantly elevated by 16 day systemic (+)-phenserine treatment, in the presence of a (+)-phenserine-induced elevation in brain- derived neurotrophic factor (BDNF).

Multitarget drugs of plants origin acting on Alzheimer's disease.

The etiopathology of Alzheimer's disease (AD) is extremely complex and heterogeneous, often associated with comorbidities. As a result it may be unlikely that AD may be mitigated by drug acting on a single specific target. The current tendency in drug design and discovery in AD is the rational design or "serendipitous" discovery of new drug entities challenging multiple targets. Since two of the presently approved drugs for AD are based on natural products (galantamine and the physostigmine-derivative rivastigmine), many plants are now under investigation as a potential source of new drugs. Multifunctional drugs often have their origin in natural sources. This review is limited to plant chemicals having different targets with actual (galantamine) or promising (drugs from Crocus sativus, Ginkgo biloba, Salvia species, and Huperzia serrata) clinical evidence in people with dementia or AD.

Synthesis of the Alzheimer drug Posiphen into its primary metabolic products (+)-N1-norPosiphen, (+)-N8-norPosiphen and (+)-N1, N8-bisnorPosiphen, their inhibition of amyloid precursor protein, α-Synuclein synthesis, interleukin-1ß release, and cholinergic action.

A major pathological hallmark of Alzheimer disease (AD) is the appearance in the brain of senile plaques that are primarily composed of aggregated forms of ß-amyloid peptide (Aß) that derive from amyloid precursor protein (APP). Posiphen (1) tartrate is an experimental AD drug in current clinical trials that reduces Aß levels by lowering the rate of APP synthesis without toxicity. To support the clinical development of Posiphen (1) and elucidate its efficacy, its three major metabolic products, (+)-N1-norPosiphen (15), (+)-N8-norPosiphen (17) and (+)-N1, N8-bisnorPosiphen (11), were required in high chemical and optical purity. The efficient transformation of Posiphen (1) into these metabolic products, 15, 17 and 11, is described. The biological activity of these metabolites together with Posiphen (1) and its enantiomer, the AD drug candidate (-)-phenserine (2), was assessed against APP,α-synuclein and classical cholinergic targets. All the compounds potently inhibited the generation of APP and α-synuclein in neuronal cultures. In contrast, metabolites 11 and 15, and (-)-phenserine (2) but not Posiphen (1) or 17, possessed acetyl cholinesterase inhibitory action and no compounds bound either nicotinic or muscarinic receptors. As Posiphen (1) lowered CSF markers of inflammation in a recent clinical trial, the actions of 1 and 2 on proinflammatory cytokine interleukin (IL)-1ß release human peripheral blood mononuclear cells was evaluated, and found to be potently inhibited by both agents.

Molecular interaction study of N1-p-fluorobenzyl-cymserine with TNF-α , p38 kinase and JNK kinase.

Alzheimer's disease (AD) is an age-related neurodegenerative disease distinguished by progressive memory loss and cognitive decline. It is accompanied by classical neuropathological changes, including cerebral deposits of amyloid- beta peptide (Aß) containing senile plaques, neurofibrillary tangles (NFTs) of phosphorylated tau (p-tau), and clusters of activated glial cells. Postmortem studies strongly support a critical role for neuroinflammation in the pathogenesis of AD, with activated microglia and reactive astrocytes surrounding senile plaques and NFTs. These are accompanied by an elevated expression of inflammatory mediators that further drives Aß and p-tau generation. Although epidemiological and experimental studies suggested that long-term use of non-steroidal anti-inflammatory drugs (NSAIDs) may lessen AD risk by mitigating inflammatory responses, primary NSAID treatment trials of AD have not proved successful. Elevated systemic butyrylcholinesterase (BuChE) levels have been considered a marker of low-grade systemic inflammation, and BuChE levels are reported elevated in AD brain. Recent research indicates that selective brain inhibition of BuChE elevates acetylcholine (ACh) and augments cognition in rodents free of the characteristic undesirable actions of acetylcholinesterase- inhibitors (AChE-Is). Hence, centrally active BuChE-selective-inhibitors, cymserine analogs, have been developed to test the hypothesis that BuChE-Is would be efficacious and better tolerated than AChE-Is in AD. The focus of the current study was to undertake an in-silico evaluation of an agent to assess its potential to halt the self-propagating interaction between inflammation,Aß and p-tau generation. Molecular docking studies were performed between the novel BuChE-I, N1-p-fluorobenzyl-cymserine (FBC) and inflammatory targets to evaluate the potential of FBC as an inhibitor of p38, JNK kinases and TNF-α with respect to putative binding free energy and IC50 values. Our in-silico studies support the ability of FBC to bind these targets in a manner supportive of anti-inflammatory action that is subject to molecular dynamics and physiochemical studies for auxiliary confirmation.

Diastereoselective intramolecular carbamoylketene/alkene [2 + 2] cycloaddition: enantioselective access to pyrrolidinoindoline alkaloids.

A novel and highly diastereoselective intramolecular carbamoylketene/alkene [2 + 2] cycloaddition has been developed, and the methodology was successfully applied to the enantioselective syntheses of (-)-esermethole and Takayama's intermediate for (+)-psychotrimine.

Synthesis of phenserine analogues and evaluation of their cholinesterase inhibitory activities.

Phenserine is a potentially attractive drug for Alzheimer's disease. In order to further expand SAR study for inhibitions of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), the methyl group at the 3a-position of phenserine was replaced with an alkyl or alkenyl group, and its phenylcarbamoyl moiety was substituted at the o- or p-position. The synthetic methodology for these phenserine analogues includes the efficient cascade reactions for introduction of the 3a-substituent and assembly of the quaternary carbon center followed by reductive cyclization to the key pyrroloindoline structure. The bulkiness of the substituent at 3a-position of phenserine derivatives tends to reduce the inhibitory effect on AChE activity in the following order: methyl > ethyl > vinyl > propyl ≈ allyl > reverse-prenyl groups. Among the series synthesized, the 3a-ethyl derivative demonstrated the highest AChE selectivity. In construct, the 3a-reverse-prenyl derivative indicated modest BuChE selectivity.