Inhibition mechanism of fisetin on acetylcholinesterase and its synergistic effect with galantamine

The search for acetylcholinesterase (AChE) inhibitors produced by natural sources is of great significance for the prevention and therapy of Alzheimer's disease and has been widely concerned. In this study, fisetin, a flavonoid compound of plant origin, displayed a mixed inhibition mode on AChE (IC50 = 8.88 ± 0.14 μM). Fluorescence spectra analysis revealed that fisetin statically quenched AChE fluorescence, and the ground state complex was formed by hydrogen bonds and hydrophobic interactions. Circular dichroism assays showed that fisetin induced AChE structure loosened with a decrease in α-helix structure (from 20.6 % to 19.5 %). Computer simulation exhibited that fisetin bound to both the peripheral anionic site (PAS) and the catalytic active site (CAS) and increased the stability of the AChE. Interestingly, the combination of fisetin and galantamine enhanced the binding affinity between AChE and galantamine and induced AChE structure further loosened, while the inhibition mode was still the mixed type. The heatmap analysis indicated that galantamine (0.2 μM) combined with fisetin (2.25 μM) had a significant synergy on AChE inhibition, probably because fisetin binding at the PAS-AChE induced conformation changes of the gorge and CAS, which enhanced galantamine binding affinity with CAS, and a further loose structure of AChE was induced by the mixture, so finally the interaction between the substrate and AChE was strongly affected. This work may offer a theoretical reference for the functional research of fisetin as a potential AChE inhibitor and an enhanced supplement for galantamine.

A Comparative Study between Lycorine and Galantamine Abilities to Interact with AMYLOID β and Reduce In Vitro Neurotoxicity

Galantamine is a natural alkaloid extracted from the Amaryllidaceae plants and is used as the active ingredient of a drug approved for the treatment of the early stages of Alzheimer's disease. It mainly acts as an acetylcholinesterase (AChE) inhibitor, increasing concentrations of the acetylcholine neurotransmitter. Recent cellular studies have also shown the ability of galantamine to protect SH-SY5Y cell lines against amyloid-β (Aβ)-induced toxicity. Such investigations have supported and validated further in-depth studies for understanding the chemical and molecular features associated with galantamine-protective abilities. In addition to galantamine, other natural alkaloids are known to possess AChE inhibitory activity; among them lycorine has been extensively investigated for its antibacterial, anti-inflammatory and antitumoral activities as well. Despite its interesting biological properties, lycorine's neuroprotective functions against Aβ-induced damages have not been explored so far. In this research study, the ability of galantamine and lycorine to suppress Aβ-induced in vitro neuronal toxicity was evaluated by investigating the chemical interactions of the two alkaloids with Aβ peptide. A multi-technique spectroscopic analysis and cellular cytotoxicity assays were applied to obtain new insights on these molecular associations. The comparison between the behaviors exhibited by the two alkaloids indicates that both compounds possess analogue abilities to interact with the amyloidogenic peptide and protect cells.

A Galantamine-Curcumin Hybrid Decreases the Cytotoxicity of Amyloid-Beta Peptide on SH-SY5Y Cells

Misfolded amyloid beta (Aβ) peptides aggregate and form neurotoxic oligomers. Membrane and mitochondrial damages, calcium dysregulation, oxidative stress, and fibril deposits are among the possible mechanisms of Aβ cytotoxicity. Galantamine (GAL) prevents apoptosis induced by Aβ mainly through the ability to stimulate allosterically the α7 nAChRs and to regulate the calcium cytosolic concentration. Here, we examined the cytoprotective effects of two GAL derivatives, namely compounds 4b and 8, against Aβ cytotoxicity on the human neuroblastoma cell line SH-SY5Y. The protective effects were tested at simultaneous administration, pre-incubation and post-incubation, with Aβ. GAL and curcumin (CU) were used in the study as reference compounds. It was found that 4b protects cells in a similar mode as GAL, while compound 8 and CU potentiate the toxic effects of Aβ. Allosteric stimulation of α7 nAChRs is suggested as a possible mechanism of the cytoprotectivity of 4b. These and previous findings characterize 4b as a prospective non-toxic multi-target agent against neurodegenerative disorders with inhibitory activity on acetylcholinesterase, antioxidant, and cytoprotective properties.

Gas-phase basicity and proton affinity measurements of Alzheimer's disease drugs by the extended kinetic method and a theoretical investigation

This study has been carried out to obtain the thermochemical parameters of drugs used for Alzheimer's disease. The measurement of gas-phase basicity (GB) and proton affinity (PA) values of four important and commercially available drugs for Alzheimer's disease namely, rivastigmine, galantamine, memantine, and tacrine, is attempted for the first time. This study also includes the measurement of GB and PA values for the proposed drug curcumin, a natural product. We calculated the GB and PA values for all these drugs by applying electrospray ionization tandem mass spectrometry (ESI-MS/MS) with the extended kinetic method. Since, all these drugs possessing amino groups (basic nature), the PA values for all these drugs are high i.e., the PA values range from 923.6 to 979.7 kJ/mol and the GB values range from 886.2 to 943.3 kJ/mol. The GB and PA values obtained from the mass spectrometric experiments are well supported with the theoretical calculations. A high-level theoretical B3LYP/6-311 + G(d,p) method is used for the PA and GB calculation and the deviations are in the acceptable range.

Galantamine-Curcumin Hybrids as Dual-Site Binding Acetylcholinesterase Inhibitors

Galantamine (GAL) and curcumin (CU) are alkaloids used to improve symptomatically neurodegenerative conditions like Alzheimer's disease (AD). GAL acts mainly as an inhibitor of the enzyme acetylcholinesterase (AChE). CU binds to amyloid-beta (Aβ) oligomers and inhibits the formation of Aβ plaques. Here, we combine GAL core with CU fragments and design a combinatorial library of GAL-CU hybrids as dual-site binding AChE inhibitors. The designed hybrids are screened for optimal ADME properties and BBB permeability and docked on AChE. The 14 best performing compounds are synthesized and tested in vitro for neurotoxicity and anti-AChE activity. Five of them are less toxic than GAL and CU and show activities between 41 and 186 times higher than GAL.

Chemical and Biological Aspects of Montanine-Type Alkaloids Isolated from Plants of the Amaryllidaceae Family

Plants of the Amaryllidaceae family are promising therapeutic tools for human diseases and have been used as alternative medicines. The specific secondary metabolites of this plant family, called Amaryllidaceae alkaloids (AA), have attracted considerable attention due to their interesting pharmacological activities. One of them, galantamine, is already used in the therapy of Alzheimer’s disease as a long acting, selective, reversible inhibitor of acetylcholinesterase. One group of AA is the montanine-type, such as montanine, pancracine and others, which share a 5,11-methanomorphanthridine core. So far, only 14 montanine-type alkaloids have been isolated. Compared with other structural-types of AA, montanine-type alkaloids are predominantly present in plants in low concentrations, but some of them display promising biological properties, especially in vitro cytotoxic activity against different cancerous cell lines. The present review aims to summarize comprehensively the research that has been published on the Amaryllidaceae alkaloids of montanine-type.

Discovery of Novel Acetylcholinesterase Inhibitors as Potential Candidates for the Treatment of Alzheimer's Disease

Acetylcholinesterase (AChE) catalyzes the hydrolysis of neurotransmitter acetylcholine to acetate and choline in a synaptic cleft. Deficits in cholinergic neurotransmitters are linked closely with the progression of Alzheimer’s disease (AD), which is a neurodegenerative disorder characterized by memory impairment, and a disordered cognitive function. Since the previously approved AChE inhibitors, donepezil (Aricept), galantamine (Reminyl), and rivastigmine (Exelon), have side effects and several studies are being carried out out to develop novel AD drugs, we have applied a three-dimensional quantitative structure−activity relationship (3D QSAR) and structure-based pharmacophore modeling methodologies to identify potential candidate inhibitors against AChE. Herein, 3D QSAR and structure-based pharmacophore models were built from known inhibitors and crystal structures of human AChE in complex with donepezil, galantamine, huperzine A, and huprine W, respectively. The generated models were used as 3D queries to screen new scaffolds from various chemical databases. The hit compounds obtained from the virtual screening were subjected to an assessment of drug-like properties, followed by molecular docking. The final hit compounds were selected based on binding modes and molecular interactions in the active site of the enzyme. Furthermore, molecular dynamics simulations for AChE in complex with the final hits were performed to evaluate that they maintained stable interactions with the active site residues. The binding free energies of the final hits were also calculated using molecular mechanics/Poisson-Boltzmann surface area method. Taken together, we proposed that these hits can be promising candidates for anti-AD drugs.

Hypothesis: apo-lactoferrin-Galantamine Proteo-alkaloid Conjugate for Alzheimer's disease Intervention

Alzheimer's disease (AD) is known to be caused by the accumulation of deformed beta amyloid and hyperphosphorylated tau proteins resulting into formation and aggregation of senile plaques and neurofibrillary tangles in the brain. Additionally, AD is associated with the accumulation of iron or metal ions in the brain which causes oxidative stress. Galantamine (Gal) is one of the therapeutic agents that has been approved for the treatment of AD, but still saddled with numerous side effects and could not address the issue of iron accumulation in the brain. The use of metal chelators to address the iron accumulation has not been successful due to toxicity and inability to address the aggregation of the plaques. We therefore hypothesize a combinatorial antioxidant-metal-chelator approach by formulating a single dosage form that has the ability to prevent the formation of free radicals, plaques and accumulation of iron in the brain. This can be achieved by conjugating Gal with apo-lactoferrin (ApoLf), a natural compound that has high binding affinity for iron, to form an apo-lactoferrin-galantamine proteo-alkaloid conjugate (ApoLf-Gal) as a single dosage form for AD management. The conjugation is achieved through self-assembly of ApoLf which results in encapsulation of Gal. ApoLf changes its conformational structure in the presence of iron; therefore, ApoLf-Gal is proposed to deliver Gal and pick up excess iron when in contact with iron. This strategy has the potential to proffer a dual neuroprotection and neurotherapeutic interventions for the management of AD.

Galanthamine, Plicamine, and Secoplicamine Alkaloids from Zephyranthes candida and Their Anti-acetylcholinesterase and Anti-inflammatory Activities

Sixteen new alkaloids belonging to the galanthamine (1-6), plicamine (7-14), and secoplicamine (15 and 16) classes, together with eight known analogues (17-24), were isolated from Zephyranthes candida. The structures of 1-16 were determined by extensive spectroscopic analyses, and the absolute configurations of 1, 2, 7, 8, and 17 were confirmed by single-crystal X-ray diffraction analysis. The orientation of 3-OCH3 in N-methyl-5,6-dihydroplicane (22) was revised. Alkaloids 3, 12-14, and 18-21 exhibited anti-acetylcholinesterase activities with IC50 values ranging from 0.48 to 168.7 μM. Compounds 10-12, 14, and 16 showed in vitro anti-inflammatory activities with IC50 values ranging from 7.50 to 23.55 μM.

Galantamine-loaded PLGA nanoparticles, from nano-emulsion templating, as novel advanced drug delivery systems to treat neurodegenerative diseases

Polymeric nanoparticles could be promising drug delivery systems to treat neurodegenerative diseases. Among the various methods of nanoparticle preparation, nano-emulsion templating was used in the present study to prepare galantamine-loaded nano-emulsions by a low-energy emulsification method followed by solvent evaporation to obtain galantamine-loaded polymeric nanoparticles. This approach was found to be suitable because biocompatible, biodegradable and safe nanoparticles with appropriate features (hydrodynamic radii around 20 nm, negative surface charge and stability higher than 3 months) for their intravenous administration were obtained. Encapsulation efficiencies higher than 90 wt% were obtained with a sustained drug release profile as compared to that from aqueous and micellar solutions. The enzymatic activity of the drug was maintained at 80% after its encapsulation into nanoparticles that were non-cytotoxic at the required therapeutic concentration. Therefore, novel galantamine-loaded polymeric nanoparticles have been designed for the first time using the nano-emulsification approach and showed the appropriate features to become advanced drug delivery systems to treat neurodegenerative diseases.

Monoterpene indole alkaloids from the twigs of Kopsia arborea

The phytochemistry of Kopsia arborea Blume has received considerable attention, which has resulted in the isolation of a number of new unusual indole alkaloids with intriguing structures. In this study, a new eburnane-type alkaloid, phutdonginin (1), together with eight known alkaloids: 19-OH-(-)- eburnamonine (2), melodinine E (3), kopsinine (4), kopsilongine (5), kopsamine (6), (-)-methylenedioxy-1 1,12-kopsinaline (7), decarbomethoxykopsiline (8), and vincadifformine (9), were isolated from the twigs of K. arborea. Their structures were characterized extensively by 1D and 2D NMR spectroscopy and HR-ESI-MS. All compounds were submitted to TLC screening for acetylcholinesterase inhibitory activities. Only kopsamine and decarbomethoxykopsiline showed AChE inhibition with MIR values of 12.5 and 6.25 μg, respectively, compared with galanthamine (positive control, 0.004 μg). In addition, compounds 1 and 2 inhibited moderate antibacterial activity against E. coli TISTR 780 with the MIC value of 32 .g/mL.

Study on novel galantaminehydrobromide sustained-release capsules and itsin vitro releasing property

In present study, we prepared a novel galantamine hydro bromide sustained-release capsules with the new manufacturing technology, extrusion-spheronization method, and the optimized preparative formulation. A simple, rapid and accurate high performance liquid chromatography method (HPLC) was developed and validated for the quantification and release evaluation of galantamine hydro bromide. Experimental results showed that the method was specific, sensitive and reliable, could be effectively applied to the in vitro release study of galantamine hydro bromide sustained-release capsules. Our resulting samples had superior properties, worked better as sustained-release carriers and lasted longer hours to release drugs compared with the marketed control, Razadyne ER. The in vitro releasing characteristics of different batches of preparations are quite similar with each other, the total release proportions of galantamine hydro bromide from sustained-release capsules reached higher than 90 % within 12 h. The testing sustained-release preparation may be a promising new product for curing the related diseases.

Assessment of anti-amyloidogenic activity of marine red alga G. acerosa against Alzheimer's beta-amyloid peptide 25-35

OBJECTIVE

The amyloid hypothesis stimulates the discovery of compounds, which promotes beta-amyloid peptide (Aβ) clearance, thereby altering the underlying pathophysiology of Alzheimer's disease (AD). Hence, the present study aims at the evaluation of anti-amyloidogenic potential of Gelidiella acerosa.

METHODS

Prevention of Aβ 25-35 aggregate formation and disaggregation of pre-formed fibrils by G. acerosa was evaluated in three phases by thioflavin T spectrophotometric assay. The results were further validated by confocal microscopic analysis. The conformational changes in the aggregated and non-aggregated Aβ in the presence of G. acerosa were analyzed by Fourier transform infrared (FTIR) spectroscopic analysis.

RESULTS

Phase-I study shows that G. acerosa reverts (4.56 ± 0.35 AU at 96 hours) the increase in fluorescence intensity of aggregated Aβ (18.76 ± 0.99 AU) significantly (P < 0.05) as that of non-aggregated peptides, which suggests that G. acerosa prevents the formation of oligomers from monomers. The seaweed also prevents the fibril formation even after the aggregation process was initiated at 20 hours, which was verified by the significant (P < 0.05) decrease in the fluorescence intensity (2.94 ± 0.0721 AU) at 36 hours (Phase II). In addition, G. acerosa promotes fibrillar destabilization (Phase III), which was further substantiated by confocal microscopic analysis. Fourier transform infrared spectroscopy reveals that alteration in amide I and amide II band spectrum, which occurs due to Aβ 25-35 aggregation was restored upon co-treatment with G. acerosa benzene extract.

CONCLUSION

Overall, the results suggest that G. acerosa might have direct interaction with the aggregated peptide, thereby preventing oligomerization and fibrillation of Aβ 25-35.

[Effect of precursor on growth and accumulation of alkaloids of Lycoris radiata suspension cells]

In order to investigate the effects of phenylalanine, tyrosine and tyramine on the growth of Lycoris radiata suspension cells and the accumulation of alkaloids, the growth quantity of the cells as well as the content of alkaloids in cells were determined, which were treated with above three kinds of precursors alone and phenylalanine combined with tyrosine respectively. The results indicate that the addition of phenylalanine alone and addition of phenylalanine on the basis of tyrosine at high concentration (200 micromol/L) had no significant effect on the growth of Lycoris radiata suspension cells and the content of alkaloids in cells; whereas tyrosine and tyramine promoted the growth of the cells and alkaloids accumulation. Treated with tyrosine at high concentration (200 micromol/L), the content of alkaloids of the cells was 2.56-fold higher than that of the control group, the amounts of lycoramine (3.77 mg/g) and galanthamine (4.46 mg/g) were 6.61-fold and 6.97-fold higher than that of the control group, respectively. When treated with tyramine (200 micromol/L), the amount of alkaloids in Lycoris radiata suspension cells was 2.63-fold higher than that of the control group, and the amounts of lycoramine (4.45 mg/g) and galanthamine (5.14 mg/g) were 9.08-fold and 9.18-fold higher than that of the control group, respectively. The above results demonstrate that adding tyrosine and tyramine in the media significantly promoted the growth of the Lycoris radiata suspension cells and alkaloids accumulation in the cells.

From nature to market: examples of natural products that became drugs

Nature is an irrefutable source of inspiration for the modern man in many aspects. The observation and understanding of nature have allowed the development of new materials, new sources of energies, new drugs etc. Specifically, natural products provide a great contribution to the development of new agents for the treatment of infections and antitumor agents. However, obtaining natural products directly from animals, fungi, bacteria, plants etc has been considered not enough to attend the high demand by pharmaceutical industries. In this regard, various strategies based on biotechnological processes or synthetic approaches have been developed. In this scenario the total synthesis can be undoubtedly a useful and powerful tool for obtaining higher amounts of natural products and/or structural modifications thereof. Herein, we emphasize successful examples of total synthesis of galanthamine, morphine, paclitaxel and podophyllotoxin - natural products approved as pharmaceuticals.

Seasonal accumulation of major alkaloids in organs of pharmaceutical crop Narcissus Carlton

Narcissus pseudonarcissus (L.) cv. Carlton is being cultivated as a main source of galanthamine from the bulbs. After galanthamine, haemanthamine and narciclasine are the next most abundant alkaloids in this cultivar. Both these compounds are promising chemical scaffolds for potential anticancer drugs. For further research and drug development, a reliable supply of these compounds will be needed. In this study a field experiment was conducted to investigate the levels of galanthamine, haemanthamine and narciclasine in plants of N. pseudonarcissus cv. Carlton. In a field experiment alkaloids in the bulbs, leaves and roots were analyzed by quantitative (1)H NMR to monitor the variations during the growing season. Major primary and secondary metabolites were identified in the various plant parts. Multivariate data analysis was performed on the (1)H NMR spectra to investigate how metabolites changed in the plant organs over time. The results show that the leaves have relatively high concentrations of the alkaloids before flowering. The bulbs had lower concentrations of the compounds of interest but would have a higher total yield of alkaloids due to bigger biomass. Narcissus pseudonarcissus cv. Carlton represents a good source of galanthamine, and can potentially be a source of the other major alkaloids depending on choice of organ and harvest time.

Ligand-functionalized nanoliposomes for targeted delivery of galantamine

The purpose of this study was to design ligand-functionalized nanoliposomes that are proficient in providing effective intracellular delivery of an alkaloid drug (galantamine) into PC12 neuronal cells in response to managing Alzheimer's disease (AD). Ligand-functionalized nanoliposomes were produced and validated for their physicochemical properties, in silico molecular mechanics energy relationships, ex vivo cytotoxicity, peptide coupling efficiency (PCE), drug entrapment efficiency (DEE), drug release, fluorometry and confocal microscopy. Particle sizes of the nanoliposomes ranged from 127 nm to 165 nm (PdI=0.39-0.03), zeta potential values of -18 mV to -36 mV, PCE from 40% to 78% while DEE ranged from 42% to 79%. The surface morphology of the nanoliposomes was stable, spherically and uniform in shape. Thermal behavior and Fourier transform infrared (FTIR) analyses confirmed that galantamine and the peptide-ligand were incorporated into the inner core and surface of the nanoliposomes, respectively. The optimized formulation showed sustained drug release (30% of drug released within 48 h). Fluorometry and confocal microscopy revealed that the ligand-functionalized nanoliposomes facilitated galantamine uptake into PC12 neuronal cells via the Serpin Enzyme Complex Receptor in a mediated manner. CytoTox-Glo™ cytotoxicity assay established the low cytotoxicity on PC12 neuronal cells when exposed to native nanoliposomes and the ligand-functionalized nanoliposomes. Response surface analysis demonstrated there was a high degree of correlation between the experimental and fitted values. Furthermore, ex vivo studies showed that the high galantamine accumulation into PC12 neuronal cells was influenced by the post-engineering of peptides on the surface of the galantamine-loaded nanoliposomes. MMER analysis aptly corroborated the experimental findings.

GC-MS of amaryllidaceous galanthamine-type alkaloids

Galanthamine-type alkaloids produced by plants of the Amaryllidaceae family are potent acetylcholinesterase inhibitors. One of them, galanthamine, has been marketed as a hydrobromide salt for the treatment of Alzheimer's disease. In the present work, gas chromatography with electron impact mass spectrometry (GC-EIMS) fragmentation of 12 reference compounds isolated from various amaryllidaceous plants and identified by spectroscopic methods (1D and 2D nuclear magnetic resonance, circular dichroism, high-resolution MS (HRMS) and EIMS) was studied by tandem mass spectrometry (GC-MS/MS) and accurate mass measurements (GC-HRMS). The studied compounds showed good peak shape and efficient GC separation with a GC-MS fragmentation pattern similar to that obtained by direct insertion probe. With the exception of galanthamine-N-oxide and N-formylnorgalanthamine, the galanthamine-type compounds showed abundant [M](+.) and [M-H](+) ions. A typical fragmentation pattern was also observed, depending on the substituents of the skeleton. Based on the fragmentation pathways of reference compounds, three other galanthamine-type alkaloids, including 3-O-(2'-butenoyl)sanguinine, which possesses a previously unelucidated structure, were identified in Leucojum aestivum ssp. pulchelum, a species endemic to the Balearic islands. GC-MS can be successfully applied to Amaryllidaceae plant samples in the routine screening for potentially new or known bioactive molecules, chemotaxonomy, biodiversity and identification of impurities in pharmaceutical substances.

Kinetic study of the rearrangement of deuterium-labeled 4'-O-methylnorbelladine in Leucojum aestivum shoot cultures by mass spectrometry. Influence of precursor feeding on amaryllidaceae alkaloid accumulation

Alkaloids from plants of the family Amaryllidaceae have important pharmacological properties and can be regarded as derivatives of the common precursor 4'-O-methylnorbelladine (6) via intramolecular oxidative phenol coupling. Their biosynthetic pathway, particularly in Leucojum aestivum, has not yet been totally elucidated. Therefore, shoot cultures of this plant were subcultured in medium containing the labeled precursor 4'-O-methyl-d(3)-norbelladine (3) at various concentrations (0.05, 0.10, and 0.20 g/L) and were incubated for various periods of time (15, 30, and 40 days). The aim of this work was to study the influence of this precursor on both labeled and native alkaloid accumulation. Biotransformation into galanthamine (1) and lycorine (2) in shoot cultures was demonstrated using HPLC coupled to mass spectrometry. A maximal amount of 0.16% of 1 referred to the dry weight was obtained at day 15 in shoots fed with 0.10 g/L of precursor. In addition, a 20.5% dry weight of 2 was reached after 40 days of feeding with 0.20 g/L of precursor.

Inhibition of human P-glycoprotein transport and substrate binding using a galantamine dimer

The human multidrug resistance transporter P-glycoprotein (P-gp) prevents the entry of compounds into the brain by an active efflux mechanism at the blood-brain barrier (BBB). Treatment of neurodegenerative diseases, therefore, has become a challenge and the development of new reversible inhibitors of P-gp is pertinent to overcome this problem. We report the design and synthesis of a crosslinked agent based on the Alzheimer's disease treatment galantamine (Gal-2) that inhibits P-gp-mediated efflux from cultured cells. Gal-2 was found to inhibit the efflux of the fluorescent P-gp substrate rhodamine 123 in cancer cells that over-express P-gp with an IC(50) value of approximately 0.6 microM. In addition, Gal-2 was found to inhibit the efflux of therapeutic substrates of P-gp, such as doxorubicin, daunomycin and verapamil with IC(50) values ranging from 0.3 to 1.6 microM. Through competition experiments, it was determined that Gal-2 modulates P-gp mediated efflux by competing for the substrate binding sites. These findings support a potential role of agents, such as Gal-2, as inhibitors of P-gp at the BBB to augment treatment of neurodegenerative diseases.

The Enantioselective Synthesis of (−)-Lycoramine with the Birch−Cope Sequence

The first enantioselective synthesis of (-)-lycoramine has been achieved in 14 steps and 5% overall yield from the biaryl derivative 1. The synthesis applies the previously developed Birch-Cope sequence to create the key arylic quaternary stereocenter of (-)-lycoramine with excellent enantioselective control. The product of the Birch-Cope sequence, a versatile 4,4-disubstituted-2-carboxamide-2-cyclohexen-1-one, was elaborated through an intramolecular conjugate addition of a phenol to create the dihydrofuran ring. Chemoselective elaboration of the allyl group into an amide followed by a modified Pictet-Spengler reaction generated the azepine ring.

High-performance liquid chromatographic method with UV photodiode-array, fluorescence and mass spectrometric detection for simultaneous determination of galantamine and its phase I metabolites in biological samples

Galantamine, an alkaloid isolated from the bulbs and flowers of Caucasian snowdrop (Galanthus woronowii, Amaryllidaceae) and related species, is employed in human medicine for the treatment of various neuromuscular and neurodegenerative diseases. After the administration, the products of oxidative biotransformation (O-desmethyl-galantamine, N-desmethyl-galantamine, galantamine-N-oxide) and chiral conversion (epigalantamine) are formed in various concentrations from parent compound. For the identification and determination of galantamine and its phase I metabolites in blood plasma and tissues, a new bioanalytical method based on a reversed-phase high-performance liquid chromatography with UV photodiode-array, fluorescence and mass spectrometric detection was developed, validated and applied to pharmacokinetic and biotransformation studies. Sample preparation included a homogenization of the rat tissues (liver, brain, hypophysis) in a phosphate buffer 0.05 mol/L pH 7.4. Plasma samples and tissue homogenates were purified using a mixed-mode solid-phase extraction (Waters Oasis MCX cartridges). Galantamine, its above-mentioned metabolites and the internal standard codeine were separated on a Discovery HS F5 column (Supelco, 150 mmx4.6 mm I.D., 5 microm) at flow rate of 1 mL/min using a linear gradient elution. UV photodiode-array and mass spectrometric detection were employed for the identification of individual galantamine metabolites in various biomatrices, the fluorescence detection (lambdaexcit=280 nm/lambdaemiss=310 nm) was chosen for the quantification of galantamine and its metabolites. The developed method was applicable in liver tissue in the range from 0.50 to 63.47 nmol/g of galantamine, from 0.32 to 41.42 nmol/g of O-desmethyl-galantamine, from 0.54 to 69.40 nmol/g of N-desmethyl-galantamine and from 0.70 to 89.03 nmol/g of epigalantamine. Limit of detection was found to be 0.04 nmol/g for galantamine, 0.19 nmol/g for O-desmethyl-galantamine, and 0.07 nmol/g for N-desmethyl-galantamine and epigalantamine.

Stereocontrolled Synthesis of (−)-Galanthamine

An enantioselective synthesis of (-)-galanthamine has been realized in 11 linear steps starting from isovanillin. A Mitsunobu aryl ether forming reaction was used to assemble the galanthamine backbone, which was stitched together using enyne ring-closing metathesis, Heck, and N-alkylation reactions affording the tetracyclic ring system. Control of relative and absolute stereochemistry was derived from an easily accessible enantiomerically enriched propargylic alcohol 13.

Galanthamine and non-competitive inhibitor binding to ACh-binding protein: evidence for a binding site on non-alpha-subunit interfaces of heteromeric neuronal nicotinic receptors

Rapid neurotransmission is mediated through a superfamily of Cys-loop receptors that includes the nicotinic acetylcholine (nAChR), gamma-aminobutyric acid (GABA(A)), serotonin (5-HT(3)) and glycine receptors. A class of ligands, including galanthamine, local anesthetics and certain toxins, interact with nAChRs non-competitively. Suggested modes of action include blockade of the ion channel, modulation from undefined extracellular sites, stabilization of desensitized states, and association with annular or boundary lipid. Alignment of mammalian Cys-loop receptors shows aromatic residues, found in the acetylcholine or ligand-binding pocket of nAChRs, are conserved in all subunit interfaces of neuronal nAChRs, including those that are not formed by alpha subunits on the principal side of the transmitter binding site. The amino-terminal domain containing the ligand recognition site is homologous to the soluble acetylcholine-binding protein (AChBP) from mollusks, an established structural and functional surrogate. We assess ligand specificity and employ X-ray crystallography with AChBP to demonstrate ligand interactions at subunit interfaces lacking vicinal cysteines (i.e. the non-alpha subunit interfaces in nAChRs). Non-competitive nicotinic ligands bind AChBP with high affinity (K(d) 0.015-6 microM). We mutated the vicinal cysteine residues in loop C of AChBP to mimic the non-alpha subunit interfaces of neuronal nAChRs and other Cys loop receptors. Classical nicotinic agonists show a 10-40-fold reduction in binding affinity, whereas binding of ligands known to be non-competitive are not affected. X-ray structures of cocaine and galanthamine bound to AChBP (1.8 A and 2.9 A resolution, respectively) reveal interactions deep within the subunit interface and the absence of a contact surface with the tip of loop C. Hence, in addition to channel blocking, non-competitive interactions with heteromeric neuronal nAChR appear to occur at the non-alpha subunit interface, a site presumed to be similar to that of modulating benzodiazepines on GABA(A) receptors.

In vitro formulation optimization of intranasal galantamine leading to enhanced bioavailability and reduced emetic response in vivo

The purpose of the current investigation was to optimize an intranasal (IN) galantamine (an acetylcholinesterase inhibitor used for treatment of Alzheimer's disease) formulation using an in vitro tissue model, to correlate those results to in vivo bioavailability, and to compare emetic response to oral dosing. A design-of-experiments (DOE) based formulation screening employing an in vitro tissue model of human nasal epithelium was used to assess drug permeability, tight junction modulation, and cellular toxicity. In vivo studies in rats compared pharmacokinetic (PK) profiles of different formulations dosed intranasally. Finally, studies in ferrets evaluated PK and gastrointestinal (GI) related side effects of oral compared to nasal dosage forms. Galantamine permeation was enhanced without increasing cytotoxicity. Pharmacokinetic testing in rats confirmed the improved drug bioavailability and demonstrated an in vitro-in vivo correlation. Compared to oral dosing, IN galantamine resulted in a dramatically lowered incidence of GI-related side effects, e.g., retching and emesis. These findings illustrate that IN delivery represents an attractive alternative to oral dosing for this important Alzheimer's disease therapeutic. To our knowledge, the data herein represent the first direct confirmation of reducing GI-related side effects for IN galantamine compared to oral dosing.

Augmentation of near infrared diffuse reflectance and transmittance spectral data for the development of robust PLSBC models for classifying double blind clinical trial tablets

The water content of clinical trial tablets can be different between and within different tablet batches, depending on the relative humidity conditions during their production, packaging, storage and analysis. These water variations lead to important spectral variations in the near infrared spectral region which can lead to a wrong identification if the classification model was based on unrepresentative data towards the water content. As model development for clinical trial studies needs to be extremely fast - within one working day - with generally only one batch available, the principle of data augmentation has to be applied to render more robust classification models. Therefore, tablets available for constructing the model are being processed in order to increase or decrease their water content and to make them more representative for tablets to be tested in the future. The inclusion of a deliberate water variation is the most efficient way to develop a model, for which no additional model redevelopment will be required to pass the system suitability tests and to obtain a correct identification.

Total Synthesis of (±)-Galanthamine

[reaction: see text] A practical and efficient total synthesis of (+/-)-galanthamine was achieved from commercially available materials through a novel approach, in which the construction of its core structure and the special allylic alcohol group were based on a successive semipinacol rearrangement/desilyation/cyclization and Saegusa-Ito oxidation, respectively.

Divergent enantioselective synthesis of (-)-galanthamine and (-)-morphine

An efficient divergent synthetic strategy for the synthesis of the opiate and amaryllidaceae alkaloids emerges by employing a Pd-catalyzed asymmetric allylic alkylation (AAA) to set the stereochemistry. Three generations of syntheses of galanthamine are discussed in detail with particular focus on the scope of the palladium-catalyzed AAA reactions and intramolecular Heck reactions. The pivotal tricyclic intermediate is available in six steps from 2-bromovanillin and the monoester of methyl 6-hydroxycyclohexene-1-carboxylate. This intermediate requires only two steps to convert to (-)-galanthamine. Using a Heck vinylation, we found that the fourth ring of codeine/morphine could be formed. The final ring formation involves a novel visible light-promoted hydroamination. Thus, six steps are required to convert the pivotal tricyclic intermediate into codeine, which has been demethylated in high yield to morphine.

Determination of therapeutics with growth-hormone secretagogue activity in human urine for doping control purposes

The administration of growth-promoting agents such as human growth hormone as well as compounds with respective secretagogue activity is prohibited in sports according to the regulations of the World Anti-Doping Agency. Acetylcholine esterase inhibitors have been demonstrated to stimulate growth-hormone secretion in elderly humans, and new orally active drugs have been developed to provide alternatives to therapeutic injections of growth-hormone preparations. Preventive anti-doping strategies include method development for emerging drugs and potentially misused compounds. Hence, the mass spectrometric dissociation behavior of three acetylcholine esterase inhibitors (donepezil, galantamine and rivastigmine) and a structural analogue to the growth-hormone secretagogue SM-130686 were studied using high-resolution/high-accuracy orbitrap mass spectrometry. These data provided substantial information for screening procedures, complementing common methods of sports drug testing. Using liquid-liquid extraction and subsequent liquid chromatography/tandem mass spectrometry (LC/MS/MS) analysis, the four target analytes were determined at urinary concentrations of 15-20 ng/mL, recoveries ranged from 55-97%, and assay precisions were calculated at 5.2-15.8% (intraday) and 10.2-21.6% (interday) for all compounds. The applicability of the developed assay to authentic urine specimens was tested using two administration study urine samples after application of Reminyl (galantamine) and Aricept (donepezil). In both cases, the administered drug and the respective desmethylated metabolites were detected.

Development of a novel high-concentration galantamine formulation suitable for intranasal delivery

The goal of the current study was to develop an intranasal (IN) formulation of the acetylcholinesterase inhibitor galantamine, an important therapeutic for treating Alzheimer's disease. To allow for delivering a therapeutically relevant dose, it was necessary to greatly enhance drug solubility. Various approaches were examined to this end, including adding co-solvents, cyclodextrins, and counterion exchange. Of these, the latter, for example, replacement of bromide ion with lactate or gluconate, resulted in a dramatic drug solubility increase, more than 12-fold. NMR confirmed the molecular structure of new drug salt forms. An in vitro epithelial tissue model was used to assess drug permeability and cellular toxicity. In vitro, galantamine lactate formulations performed as well as or better than their hydrobromide (HBr) counterparts with respect to drug permeation across the epithelial membrane with minimal toxicity. In vivo studies in rats compared pharmacokinetic (PK) profiles of different formulations. The in vivo studies confirmed that IN galantamine achieves systemic blood levels comparable to those of conventional oral administration. Both the in vitro and in vivo data support the feasibility of IN administration of this important drug.

The Complex of a Bivalent Derivative of Galanthamine withTorpedoAcetylcholinesterase Displays Drastic Deformation of the Active-Site Gorge: Implications for Structure-Based Drug Design

Bifunctional derivatives of the alkaloid galanthamine, designed to interact with both the active site of the enzyme acetylcholinesterase (AChE) and its peripheral cation binding site, have been assayed with Torpedo californica AChE (TcAChE), and the three-dimensional structures of their complexes with the enzyme have been solved by X-ray crystallography. Differences were noted between the IC(50) values obtained for TcAChE and those for Electrophorus electricus AChE. These differences are ascribed to sequence differences in one or two residues lining the active-site gorge of the enzyme. The binding of one of the inhibitors disrupts the native conformation of one wall of the gorge, formed by the loop Trp279-Phe290. It is proposed that flexibility of this loop may permit the binding of inhibitors such as galanthamine, which are too bulky to penetrate the narrow neck of the gorge formed by Tyr121 and Phe330 as seen in the crystal structure.

Galanthamine pattern in Narcissus confusus plants

Galanthamine is an Amaryllidaceae-type alkaloid with acetylcholinesterase inhibitory activity which is used in the treatment of Alzheimer's disease. The distribution of galanthamine and four other alkaloids in different organs of Narcissus confusus plants, as well as the variations occurring during the ontogenic cycle of this plant species, was studied. The five alkaloids were found to be present in all the organs at every stage, with the exception of haemanthamine in senescent flowers. The highest amount of alkaloids occurred in the bulb at the emerging stage, galanthamine being the most abundant, reaching a concentration of up to 2.5 % referred to dry weight.

Molecular recognition between 4aS/R-galanthamine diastereoisomers and ?-cyclodextrin

Molecular recognition between 4a S/R-galanthamine diastereoisomers (1: 4a S-galanthamine;2: 4a R-galanthamine) and alpha-cyclodextrin (alpha-CD) were studied by use of docking and molecular dynamics (MD) simulation approaches. The binding energy of constructed 2...alpha-CD complexes is approximately 17 kcal mol(-1) lower than that of 1...alpha-CD, implying a stronger binding ability of 2 with alpha-CD than that of1. The theoretical modeling result is consistent with our previous CZE result, which demonstrated that alpha-CD is an efficient chiral additive for separating 1 and 2. The modeling result also indicates that both hydrophobic interaction and H-bond force may work as major factors for molecular recognition between the galanthamine diastereoisomers and alpha-CD.

Antioxidant properties of galantamine hydrobromide

The antioxidant properties of galantamine hydrobromide ((4alpha,6beta)-4a,5,9,10,11,12-hexahydro-3-methoxy-11-methyl-6H-benzofuro[3a,3,2-ef][2]benzazepin-6-ol hydrobromide) were studied in vitro, using luminol-dependent chemiluminescence and spectrophotometry. It was found that this compound was a scavenger of reactive oxygen species (ROS). By comparing the antioxidant effects of galantamine ((4alpha,6beta)-4a,5,9,10,11,12-hexahydro-3-methoxy-11-methyl-6H-benzofuro[3a,3,2-ef][2]benzazepin-6-ol), galantamine hydrobromide, narwedine (4a,5,9,10,11,12-hexahydro-3-methoxy-11-methyl-6H-benzofuro[3a,3,2-ef][2]benzazepin-6-one), and narwedine hydrobromide it was found that the antioxidant activity depended on the enolic OH group in the molecule. The presence of a quaternary nitrogen in the compound increased the strength of the scavenging effect. It is proposed that the antioxidant properties observed in vitro may contribute to the therapeutical effect of galantamine hydrobromide on patients with brain degeneration.

Extended lifetime of reagentless detector for multiple inhibitors of acetylcholinesterase

Competitive inhibitors of acetylcholinesterase (AChE) are detected using an evanescent wave technique to monitor changes in the absorbance spectrum of an AChE-monosulfonate tetraphenyl porphyrin (TPPS(1)) complex immobilized on the surface of a glass slide. In this technique, porphyrin is displaced from the AChE active site by the inhibitor. The loss in absorbance intensity of the characteristic absorbance peak for the AChE-TPPS(1) complex at 446 nm is linearly dependent on the log of the inhibitor concentration. This technique yields detection limits at 3:1 S/N of 37 ppt for eserine, 50 ppt for galanthamine, 100 ppt for scopolamine, 250 ppt for tetracaine, 45 ppt for diazinon, and 83 ppb for Triton X-100. When stored under vacuum, the enzymatic lifetime of the immobilized AChE surface is greater than 73 days while the responsive lifetime of the immobilized AChE-TPPS(1) surface is currently 49 days.

Capillary electrophoresis as an orthogonal technique in HPLC method validation

High-performance liquid chromatography is usually used to assay the main compound and organic impurity content of drug substance and drug product during pharmaceutical development. A crucial validation parameter of these methods is specificity--the ability to unequivocally assess the analyte in the presence of component expected to be present. Typically, these include impurities, degradation products, and matrices. Besides adequate chromatographic separation with sufficient selectivity, additional 2- or 3-D spectroscopic or chromatographic tools are frequently necessary for this purpose. In our current practice, HPLC is used with ultraviolet photodiode array detection and on-line mass spectrometry (LC-UVDAD-MS) during the assessment of specificity. Although this approach is very powerful and can solve the majority of problems, separation of isomers of the main compound is still difficult. Since HPLC usually cannot offer the required selectivity and because of the similar molecular weights, structural isomers are not specifically detected using LC-MS. Capillary electrophoresis, on the other hand, offers high separation efficiency and can be applied as an adjunct to HPLC. Therefore, a set of highly selective CE methods is used orthogonally in the specificity assessment of HPLC methods.

Solid-phase extraction and reversed-phase high-performance liquid chromatography of the five major alkaloids in Narcissus confusus

A novel, fast and precise method, combining solid-phase extraction and reversed-phase high-performance liquid chromatography is described for the quantitative determination of five alkaloids (galanthamine, N-formylnorgalanthamine, haemanthamine, homolycorine and tazettine/pretazettine) from bulbs of wild Narcissus confusus, a high galanthamine-containing plant species growing in the Iberian Peninsula.

Galanthamine as bis-functional ligand for the acetylcholinesterase

Acetylcholinesterase plays a key role in the development of Alzheimer's disease as this enzyme is responsible for cleavage of the neurotransmitter acetylcholine, and, according to recent investigations, also promotes aggregation of beta-amyloid peptides, which causes plaque formation in synaptic areas. We have performed a molecular modeling study to investigate bis-galanthamine derivatives connected by a methylene spacer of varying length as dual acting acetylcholinesterase ligands. Our results suggest that such ligands indeed can interact simultaneously with both biological functions of the enzyme and should therefore serve as the basis for a further development of bis-functional Alzheimer drugs.

Accurate prediction of the bound conformation of galanthamine in the active site of Torpedo californica acetylcholinesterase using molecular docking

The alkaloid (-)-galanthamine is known to produce significant improvement of cognitive performances in patients with the Alzheimer's disease. Its mechanism of action involves competitive and reversible inhibition of acetylcholinesterase (AChE). Herein, we correctly predict the orientation and conformation of the galanthamine molecule in the active site of AChE from Torpedo californica (TcAChE) using a combination of rigid docking and flexible geometry optimization with a molecular mechanics force field. The quality of the predicted model is remarkable, as indicated by the value of the RMS deviation of approximately 0.5A when compared with the crystal structure of the TcAChE-galanthamine complex. A molecular model of the complex between TcAChE and a galanthamine derivative, SPH1107, with a long chain substituent on the nitrogen has been generated as well. The side chain of this ligand is predicted to extend along the enzyme active site gorge from the anionic subsite, at the bottom, to the peripheral anionic site, at the top. The docking procedure described in this paper can be applied to produce models of ligand-receptor complexes for AChE and other macromolecular targets of drug design.

Current status and new developments with galantamine in the treatment of Alzheimer's disease

Galantamine is a newly available cholinergic drug that offsets reductions in central cholinergic neurotransmission in Alzheimer's disease (AD) by specifically and reversibly inhibiting acetylcholinesterase (AChE) and by allosterically modulating nicotinic cholinergic receptors. The clinical impact of this latter mechanism of action has not been fully elucidated. Galantamine has favourable pharmacokinetic features including linear elimination kinetics, a relatively short half-life and high oral bioavailability. The efficacy of galantamine has been studied in an extensive clinical development program. During randomised, double-blind, placebo-controlled trials of up to 6 months' duration, galantamine 16 and 24 mg/day consistently produced a broad spectrum of beneficial effects on cognitive and non-cognitive AD symptoms. Patients' cognition, global function and abilities to perform both instrumental and basic activities of daily living were maintained, the emergence of behavioural symptoms was postponed and apparent reductions in caregiver burden were seen. In long-term studies (> or = 12 months), galantamine maintained cognitive and functional abilities at or near baseline levels for at least 12 months. Again, these benefits were associated with decreases in caregiver burden. The incidence of adverse events, which are typically mild or moderate in severity, is generally low with galantamine. Cholinergically mediated adverse events affecting mainly the gastrointestinal system can be minimised using the recommended slow dose-escalation regimen. Galantamine may therefore help reduce the overall burden and cost involved in caring for AD patients. Being approved for the treatment of mild-to-moderately severe AD in both the US and in Europe, with trials of its efficacy in other dementia types already yielding positive results, galantamine ranks as a first-line therapy for dementia.

Three-dimensional structure of a complex of galanthamine (Nivalin) with acetylcholinesterase from Torpedo californica: implications for the design of new anti-Alzheimer drugs

The 3D structure of a complex of the anti-Alzheimer drug galanthamine with Torpedo californica acetylcholinesterase is reported. Galanthamine, a tertiary alkaloid extracted from several species of Amarylidacae, is so far the only drug that shows a dual activity, being both an acetylcholinesterase inhibitor and an allosteric potentiator of the nicotinic response induced by acetylcholine and competitive agonists. The X-ray structure, at 2.5A resolution, shows an unexpected orientation of the ligand within the active site, as well as unusual protein-ligand interactions. The inhibitor binds at the base of the active site gorge, interacting with both the acyl-binding pocket and the principal quaternary ammonium-binding site. However, the tertiary amine group of galanthamine does not directly interact with Trp84. A docking study using the program AUTODOCK correctly predicts the orientation of galanthamine in the active site. The docked lowest-energy structure has a root mean square deviation of 0.5A with respect to the corresponding crystal structure of the complex. The observed binding mode explains the affinities of a series of structural analogs of galanthamine and provides a rational basis for structure-based drug design of synthetic derivatives with improved pharmacological properties. Proteins 2001;42:182-191.

Review of the acetylcholinesterase inhibitor galanthamine

Galanthamine (or galantamine, Reminyl) is a tertiary alkaloid acetylcholinesterase inhibitor (AChEI) which has been approved in several countries for the symptomatic treatment of senile dementia of the Alzheimer's type. Derived from bulbs of the common snowdrop and several Amaryllidaceae plants, (-)-galanthamine (GAL) has long been used in anaesthetics to reverse neuromuscular paralysis induced by turbocurarine-like muscle relaxants and more recently, has been shown to attenuate drug- and lesion-induced cognitive deficits in animal models of learning and memory. GAL directly inhibits acetylcholinesterase activity, while demonstrating much weaker activity on butyrylcholinesterase (BuChE). GAL also stimulates pre- and postsynaptic nicotinic receptors, although the clinical significance of this finding is yet unclear. Numerous variants and analogues of GAL have also been developed, with varying potency in inhibiting AChE activity. GAL is readily absorbed after oral administration, with a t(max) of 52 min and a plasma elimination t(1/2) of 5.7 h. The efficacy of GAL administered to Alzheimer's disease (AD) patients has been well demonstrated by large-scale clinical trials. Typical of AChEIs, the most common adverse events associated with GAL are nausea and vomiting. In conclusion, evidence to date suggests galanthamine to be similar to other AChEIs in improving cognitive function in AD patients.

The application of HPLC with on-line coupled UV/MS-biochemical detection for isolation of an acetylcholinesterase inhibitor from narcissus 'Sir Winston Churchill'

An HPLC with on-line coupled UV/MS-biochemical detection method for acetylcholinesterase (AChE) inhibitors in natural sources has been developed. The potential of this method is shown by the isolation of a new AChE inhibitor from the alcoholic extract of Narcissus 'Sir Winston Churchill'. Combining a prefractionation technique using centrifugal partition chromatography with the on-line HPLC-UV/MS-biochemical detection resulted in the isolation of the active compound that was identified as ungiminorine. This alkaloid shows a mild inhibitory effect on AChE.

Structure of acetylcholinesterase complexed with (-)-galanthamine at 2.3 A resolution

(-)-Galanthamine (GAL), an alkaloid from the flower, the common snowdrop (Galanthus nivalis), shows anticholinesterase activity. This property has made GAL the target of research as to its effectiveness in the treatment of Alzheimer's disease. We have solved the X-ray crystal structure of GAL bound in the active site of Torpedo californica acetylcholinesterase (TcAChE) to 2.3 A resolution. The inhibitor binds at the base of the active site gorge of TcAChE, interacting with both the choline-binding site (Trp-84) and the acyl-binding pocket (Phe-288, Phe-290). The tertiary amine group of GAL does not interact closely with Trp-84; rather, the double bond of its cyclohexene ring stacks against the indole ring. The tertiary amine appears to make a non-conventional hydrogen bond, via its N-methyl group, to Asp-72, near the top of the gorge. The hydroxyl group of the inhibitor makes a strong hydrogen bond (2.7 A) with Glu-199. The relatively tight binding of GAL to TcAChE appears to arise from a number of moderate to weak interactions with the protein, coupled to a low entropy cost for binding due to the rigid nature of the inhibitor.

Enantiomeric resolution of galanthamine and related drugs used in anti-Alzheimer therapy by means of capillary zone electrophoresis employing derivatized cyclodextrin selectors

An analytical assay is presented for the determination of the enantiomeric composition of galanthamine and related synthetic and natural compounds. (-)-Galanthamine is isolated from Galanthus nivalis and is used in this optical pure form in the therapy of Alzheimer's disease. Recent efforts for a total synthesis of unichiral (-)-galanthamine is connected with the need for a fast and reliable assay for the determination of the optical purity of the end product, as well as for optimizing and controlling the final steps in total synthesis particularly the asymmetric transformation of narwedine. In this paper the enantiomeric resolution of these compounds is reported employing a capillary electrophoretic system with beta-cyclodextrin derived chiral selectors. With the proposed system a number of galanthamine and narwedine derived analogous compounds could be separated, including 1-bromo- and N-alkyl-substituted compounds.

Potent acetylcholinesterase inhibitors: design, synthesis, and structure-activity relationships of bis-interacting ligands in the galanthamine series

New galanthamine derivatives, especially bis-interacting ligands 3-5 and 7-9 were prepared in order to interact with the catalytic and the peripheral sites of acetylcholinesterase (AChE). The synthesis, the anticholinesterase activities, and the structure-activity relationships of bis-interacting ligands are reported. Compounds 4d-e were found to be more potent than galanthamine and tacrine in inhibiting AChE.