The symptomatic and disease-modifying effects of butyrylcholinesterase (BuChE) inhibitors provide an encouraging premise for researching effective treatments for Alzheimer's disease. Here, we examined a series of compounds with a new chemical scaffold based on 3-(cyclohexylmethyl)amino-2-hydroxypropyl, and we identified a highly selective hBuChE inhibitor (29). Based on extensive in vitro and in vivo evaluations of the compound and its enantiomers, (R)-29 was identified as a promising candidate for further development. Compound (R)-29 is a potent hBuChE inhibitor (IC50 = 40 nM) with selectivity over AChE and relevant off-targets, including H1, M1, alpha1A and beta1 receptors. The compound displays high metabolic stability on human liver microsomes (90% of the parent compound after 2 h of incubation), and its safety was confirmed through examining the cytotoxicity on the HepG2 cell line (LC50 = 2.85 microM) and hERG inhibition (less than 50% at 10 microM). While (rac)-29 lacked an effect in vivo and showed limited penetration to the CNS in pharmacokinetics studies, compound (R)-29 exhibited a procognitive effect at 15 mg/kg in the novel object recognition task in scopolamine-treated mice.
The multitarget-directed ligands demonstrating affinity to histamine H(3) receptor and additional cholinesterase inhibitory potency represent a promising strategy for research into the effective treatment of Alzheimer's disease. In this study, a novel series of benzophenone derivatives was designed and synthesized. Among these derivatives, we identified compound 6 with a high affinity for H(3)R (K(i) = 8 nM) and significant inhibitory activity toward BuChE (IC(50) = 172 nM and 1.16 microM for eqBuChE and hBuChE, respectively). Further in vitro studies revealed that compound 6 (4-fluorophenyl) (4-((5-(piperidin-1-yl)pentyl)oxy)phenyl)methanone) displays moderate metabolic stability in mouse liver microsomes, good permeability with a permeability coefficient value (P(e)) of 6.3 x 10(-6) cm/s, and its safety was confirmed in terms of hepatotoxicity in the HepG2 cell line. Therefore, we investigated the in vivo activity of compound 6 in the Passive Avoidance Test and the Formalin Test. While compound 6 did not show a statistically significant influence on memory and learning, it showed analgesic properties in both acute (ED(50) = 20.9 mg/kg) and inflammatory (ED(50) = 17.5 mg/kg) pain.
Alzheimer's disease (AD) is a complex and incurable illness that requires the urgent approval of new effective drugs. However, since 2003, no new molecules have shown successful results in clinical trials, thereby making the common "one compound - one target" paradigm questionable. Recently, the multitarget-directed ligand (MTDL) approach has gained popularity, as compounds targeting at least two biological targets may be potentially more effective in treating AD. On the basis of these findings, we designed, synthesized, and evaluated through biological assays a series of derivatives of alicyclic amines linked by an alkoxy bridge to an aromatic lipophilic moiety of [1,1'-biphenyl]-4-carbonitrile. The research results revealed promising biological activity of the obtained compounds toward the chosen targets involved in AD pathophysiology; the compounds showed high affinity (mostly low nanomolar range of K(i) values) for human histamine H(3) receptors (hH(3)R) and good nonselective inhibitory potency (micromolar range of IC(50) values) against acetylcholinesterase from electric eel (eeAChE) and equine serum butyrylcholinesterase (eqBuChE). Moreover, micromolar/submicromolar potency against human monoamine oxidase B (hMAO B) was detected for some compounds. The study identified compound 5 as a multiple hH(3)R/eeAChE/eqBuChE/hMAO B ligand (5: hH(3)R K(i) = 9.2 nM; eeAChE IC(50) = 2.63 microM; eqBuChE IC(50) = 1.30 microM; hMAO B IC(50) = 0.60 microM). Further in vitro studies revealed that compound 5 exhibits a mixed type of eeAChE and eqBuChE inhibition, good metabolic stability, and moderate hepatotoxicity effect on HepG2 cells. Finally, compound 5 showed a beneficial effect on scopolamine-induced memory impairments, as assessed by the passive avoidance test, thus revealing the potential of this compound as a promising agent for further optimization for AD treatment.
Poisoning with organophosphorus compounds used as pesticides or misused as chemical weapons remains a serious threat to human health and life. Their toxic effects result from irreversible blockade of the enzymes acetylcholinesterase and butyrylcholinesterase, which causes overstimulation of the cholinergic system and often leads to serious injury or death. Treatment of organophosphorus poisoning involves, among other strategies, the administration of oxime compounds. Oximes reactivate cholinesterases by breaking the covalent bond between the serine residue from the enzyme active site and the phosphorus atom of the organophosphorus compound. Although the general mechanism of reactivation has been known for years, the exact molecular aspects determining the efficiency and selectivity of individual oximes are still not clear. This hinders the development of new active compounds. In our research, using relatively simple and widely available molecular docking methods, we investigated the reactivation of acetyl- and butyrylcholinesterase blocked by sarin and tabun. For the selected oximes, their binding modes at each step of the reactivation process were identified. Amino acids essential for effective reactivation and those responsible for the selectivity of individual oximes against inhibited acetyl- and butyrylcholinesterase were identified. This research broadens the knowledge about cholinesterase reactivation and demonstrates the usefulness of molecular docking in the study of this process. The presented observations and methods can be used in the future to support the search for new effective reactivators.
Neurodegenerative diseases, e.g., Alzheimer's disease (AD), are a key health problem in the aging population. The lack of effective therapy and diagnostics does not help to improve this situation. It is thought that ligands influencing multiple but interconnected targets can contribute to a desired pharmacological effect in these complex illnesses. Histamine H(3) receptors (H(3)Rs) play an important role in the brain, influencing the release of important neurotransmitters, such as acetylcholine. Compounds blocking their activity can increase the level of these neurotransmitters. Cholinesterases (acetyl- and butyrylcholinesterase) are responsible for the hydrolysis of acetylcholine and inactivation of the neurotransmitter. Increased activity of these enzymes, especially butyrylcholinesterase (BuChE), is observed in neurodegenerative diseases. Currently, cholinesterase inhibitors: donepezil, rivastigmine and galantamine are used in the symptomatic treatment of AD. Thus, compounds simultaneously blocking H(3)R and inhibiting cholinesterases could be a promising treatment for AD. Herein, we describe the BuChE inhibitory activity of H(3)R ligands. Most of these compounds show high affinity for human H(3)R (K(i) < 150 nM) and submicromolar inhibition of BuChE (IC(50) < 1 microM). Among all the tested compounds, 19 (E153, 1-(5-([1,1'-biphenyl]-4-yloxy)pentyl)azepane) exhibited the most promising in vitro affinity for human H(3)R, with a K(i) value of 33.9 nM, and for equine serum BuChE, with an IC(50) of 590 nM. Moreover, 19 (E153) showed inhibitory activity towards human MAO B with an IC(50) of 243 nM. Furthermore, in vivo studies using the Passive Avoidance Task showed that compound 19 (E153) effectively alleviated memory deficits caused by scopolamine. Taken together, these findings suggest that compound 19 can be a lead structure for developing new anti-AD agents.
The pyridinium-2-carbaldoximes with quinolinium carboxamide moiety were designed and synthesised as cholinesterase reactivators. The prepared compounds showed intermediate-to-high inhibition of both cholinesterases when compared to standard oximes. Their reactivation ability was evaluated in vitro on human recombinant acetylcholinesterase (hrAChE) and human recombinant butyrylcholinesterase (hrBChE) inhibited by nerve agent surrogates (NIMP, NEMP, and NEDPA) or paraoxon. In the reactivation screening, one compound was able to reactivate hrAChE inhibited by all used organophosphates and two novel compounds were able to reactivate NIMP/NEMP-hrBChE. The reactivation kinetics revealed compound 11 that proved to be excellent reactivator of paraoxon-hrAChE better to obidoxime and showed increased reactivation of NIMP/NEMP-hrBChE, although worse to obidoxime. The molecular interactions of studied reactivators were further identified by in silico calculations. Molecular modelling results revealed the importance of creation of the pre-reactivation complex that could lead to better reactivation of both cholinesterases together with reducing particular interactions for lower intrinsic inhibition by the oxime.
Looking for an effective anti-Alzheimer's agent is very challenging; however, a multifunctional ligand strategy may be a promising solution for the treatment of this complex disease. We herein present the design, synthesis and biological evaluation of novel hydroxyethylamine derivatives displaying unique, multiple properties that have not been previously reported. The original mechanism of action combines inhibitory activity against disease-modifying targets: beta-secretase enzyme (BACE1) and amyloid beta (Abeta) aggregation, along with an effect on targets associated with symptom relief - inhibition of butyrylcholinesterase (BuChE) and gamma-aminobutyric acid transporters (GATs). Among the obtained molecules, compound 36 exhibited the most balanced and broad activity profile (eeAChE IC50 = 2.86 microM; eqBuChE IC50 = 60 nM; hBuChE IC50 = 20 nM; hBACE1 IC50 = 5.9 microM; inhibition of Abeta aggregation = 57.9% at 10 microM; mGAT1 IC50 = 10.96 microM; and mGAT2 IC50 = 19.05 microM). Moreover, we also identified 31 as the most potent mGAT4 and hGAT3 inhibitor (IC50 = 5.01 microM and IC50 = 2.95 microM, respectively), with high selectivity over other subtypes. Compounds 36 and 31 represent new anti-Alzheimer agents that can ameliorate cognitive decline and modify the progress of disease.
Multifunctional ligands as an essential variant of polypharmacology are promising candidates for the treatment of multi-factorial diseases like Alzheimer's disease. Based on clinical evidence and following the paradigm of multifunctional ligands we have rationally designed and synthesized a series of compounds targeting processes involved in the development of the disease. The biological evaluation led to the discovery of two compounds with favorable pharmacological characteristics and ADMET profile. Compounds 17 and 35 are 5-HT(6)R antagonists (K(i) = 13 nM and K(i) = 15 nM respectively) and cholinesterase inhibitors with distinct mechanisms of enzyme inhibition. Compound 17, a tacrine derivative is a reversible inhibitor of acetyl- and butyrylcholinesterase (IC(50) = 8 nM and IC(50) = 24 nM respectively), while compound 35 with rivastigmine-derived phenyl N-ethyl-N-methylcarbamate fragment is a selective, pseudo-irreversible inhibitor of butyrylcholinesterase (IC(50) = 455 nM). Both compounds inhibit aggregation of amyloid beta in vitro (75% for compound 17 and 68% for 35 at 10 microM) moreover, compound 35 is a potent tau aggregation inhibitor in cellulo (79%). In ADMET in vitro studies both compounds showed acceptable metabolic stability on mouse liver microsomes (28% and 60% for compound 17 and 35 respectively), no or little effect on CYP3A4 and 2D6 up to a concentration of 10 microM and lack of toxicity on HepG2 cell line (IC(50) values of 80 and 21 microM, for 17 and 35 respectively). Based on the pharmacological characteristics and favorable pharmacokinetic properties, we propose compounds 17 and 35 as an excellent starting point for further optimization and in-depth biological studies.
The lack of an effective treatment makes Alzheimer's disease a serious healthcare problem and a challenge for medicinal chemists. Herein we report interdisciplinary research on novel multifunctional ligands targeting proteins and processes involved in the development of the disease: BuChE, 5-HT6 receptors and beta-amyloid aggregation. Structure-activity relationship analyses supported by crystallography and docking studies led to the identification of a fused-type multifunctional ligand 50, with remarkable and balanced potencies against BuChE (IC50 = 90 nM) and 5-HT6R (Ki = 4.8 nM), and inhibitory activity against Abeta aggregation (53% at 10 microM). In in vitro ADME-Tox and in vivo pharmacokinetic studies compound 50 showed good stability in the mouse liver microsomes, favourable safety profile and brain permeability with the brain to plasma ratio of 6.79 after p.o. administration in mice, thus being a promising candidate for in vivo pharmacology studies and a solid foundation for further research on effective anti-AD therapies.
The inverse correlation observed between Alzheimer's disease (AD) and cancer has prompted us to look for cholinesterase-inhibiting activity in phenothiazine derivatives that possess anticancer properties. With the use of in silico and in vitro screening methods, our study found a new biological activity in anticancer polycyclic, tricyclic, and tetracyclic compounds. The virtual screening of a library of 120 ligands, which are the derivatives of azaphenothiazine, led to the identification of 25 compounds that can act as potential inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Biological assays revealed the presence of selective inhibitors of eeAChE (electric eel AChE) or eqBuChE (equine serum BuChE) and nonselective inhibitors of both enzymes among the tested compounds. Their potencies against eeAChE were in a submicromolar-to-micromolar range with IC50 values from 0.78 to 19.32 muM, while their IC50 values against eqBuChE ranged from 0.46 to 10.38 muM. The most potent among the compounds tested was the tetracyclic derivative, 6-(4-diethylaminobut-2-ynyl)-9-methylthioquinobenzothiazine 24, which was capable of inhibiting both enzymes. 9-Fluoro-6-(1-piperidylethyl)quinobenzothiazine 23 was found to act as a selective inhibitor of eqBuChE with an IC50 value of 0.46 muM. Compounds with such a dual antitumor and cholinesterase-inhibitory activity can be considered as a valuable combination for the treatment of both cancer and AD prevention. The results presented in this study might open new directions of research on the group of tricyclic phenothiazine derivatives.
Design and development of multitarget-directed ligands (MTDLs) has become a very important approach in the search of new therapies for Alzheimer's disease (AD). In our present research, a number of xanthone derivatives were first designed using a pharmacophore model for histamine H(3) receptor (H(3)R) antagonists/inverse agonists, and virtual docking was then performed for the enzyme acetylcholinesterase. Next, 23 compounds were synthesised and evaluated in vitro for human H(3)R (hH(3)R) affinity and inhibitory activity on cholinesterases. Most of the target compounds showed hH(3)R affinities in nanomolar range and exhibited cholinesterase inhibitory activity with IC(50) values in submicromolar range. Furthermore, the inhibitory effects of monoamine oxidases (MAO) A and B were investigated. The results showed low micromolar and selective human MAO B (hMAO B) inhibition. Two azepane derivatives, namely 23 (2-(5-(azepan-1-yl)pentyloxy)-9H-xanthen-9-one) and 25 (2-(5-(azepan-1-yl)pentyloxy)-7-chloro-9H-xanthen-9-one), were especially very promising and showed high affinity for hH(3)R (K(i) = 170 nM and 100 nM respectively) and high inhibitory activity for acetylcholinesterase (IC(50) = 180 nM and 136 nM respectively). Moreover, these compounds showed moderate inhibitory activity for butyrylcholinesterase (IC(50) = 880 nM and 394 nM respectively) and hMAO B (IC(50) = 775 nM and 897 nM respectively). Furthermore, molecular docking studies were performed for hH(3)R, human cholinesterases and hMAO B to describe the mode of interactions with these biological targets. Next, the two most promising compounds 23 and 25 were selected for in vivo studies. The results showed significant memory-enhancing effect of compound 23 in dizocilpine-induced amnesia in rats in two tests: step-through inhibitory avoidance paradigm (SIAP) and transfer latency paradigm time (TLPT). In addition, favourable analgesic effects of compound 23 were observed in neuropathic pain models. Therefore, compound 23 is a particularly promising structure for further design of new MTDLs for AD.
Effective therapy of Alzheimer's disease (AD) requires treatment with a combination of drugs that modulate various pathomechanisms contributing to the disease. In our research, we have focused on the development of multi-target-directed ligands - 5-HT(6) receptor antagonists and cholinesterase inhibitors - with disease-modifying properties. We have performed extended in vitro (FRET assay) and in cellulo (Escherichia coli model of protein aggregation) studies on their beta-secretase, tau, and amyloid beta aggregation inhibitory activity. Within these multifunctional ligands, we have identified compound 17 with inhibitory potency against tau and amyloid beta aggregation in in cellulo assay of 59% and 56% at 10 microM, respectively, hBACE IC(50)=4 microM, h5TH6 K (i)=94 nM, hAChE IC(50)=26 nM, and eqBuChE IC(50)=5 nM. This study led to the development of multifunctional ligands with a broad range of biological activities crucial not only for the symptomatic but also for the disease-modifying treatment of AD.
Multi-target-directed ligands seem to be an interesting approach to the treatment of complex disorders such as Alzheimer's disease. The aim of the present study was to find novel multifunctional compounds in a non-imidazole histamine H3 receptor ligand library. Docking-based virtual screening was applied for selection of twenty-six hits which were subsequently evaluated in Ellman's assay for the inhibitory potency toward acetyl- (AChE) and butyrylcholinesterase (BuChE). The virtual screening with high success ratio enabled to choose multi-target-directed ligands. Based on docking results, all selected ligands were able to bind both catalytic and peripheral sites of AChE and BuChE. The most promising derivatives combined the flavone moiety via a six carbon atom linker with a heterocyclic moiety, such as azepane, piperidine or 3-methylpiperidine. They showed the highest inhibitory activities toward cholinesterases as well as well-balanced potencies against H3R and both enzymes. Two derivatives were chosen - 5 (IC50=0.46muM (AChE); 0.44muM (BuChE); Ki=159.8nM(H3R)) and 17 (IC50=0.50muM (AChE); 0.76muM (BuChE); Ki=228.2nM(H3R)), and their inhibition mechanism was evaluated in kinetic studies. Both compounds displayed non-competitive mode of AChE and BuChE inhibition. Compounds 5 and 17 might serve as good lead structures for further optimization and development of novel multi-target anti-Alzheimer's agents.
In the search for new treatments for complex disorders such as Alzheimer's disease the Multi-Target-Directed Ligands represent a very promising approach. The aim of the present study was to identify multifunctional compounds among several series of non-imidazole histamine H3 receptor ligands, derivatives of 1-[2-thiazol-5-yl-(2-aminoethyl)]-4-n-propylpiperazine, 1-[2-thiazol-4-yl-(2-aminoethyl)]-4-n-propylpiperazine and 1-phenoxyalkyl-4-(amino)alkylopiperazine using in vitro and in vivo pharmacological evaluation and computational studies. Performed in vitro assays showed moderate potency of tested compounds against acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). Molecular modeling studies have revealed possible interactions between the active compounds and both AChE and BuChE as well as the human H3 histamine receptor. Computational studies showed the high drug-likeness of selected compounds with very good physicochemical profiles. The parallel artificial membrane permeation assay proved outstanding blood-brain barrier penetration in test conditions. The most promising compound, A12, chemically methyl(4-phenylbutyl){2-[2-(4-propylpiperazin-1-yl)-1,3-thiazol-5-yl]ethyl}amine, possesses good balanced multifunctional profile with potency toward studied targets - H3 antagonist activity (pA2=8.27), inhibitory activity against both AChE (IC50=13.96muM), and BuChE (IC50=14.62muM). The in vivo pharmacological studies revealed the anti-amnestic properties of compound A12 in the passive avoidance test on mice.
New tritarget small molecules combining Ca(2+) channels blockade, cholinesterase, and H3 receptor inhibition were obtained by multicomponent synthesis. Compound 3p has been identified as a very promising lead, showing good Ca(2+) channels blockade activity (IC50 = 21 +/- 1 muM), potent affinity against hH3R (Ki = 565 +/- 62 nM), a moderate but selective hBuChE inhibition (IC50 = 7.83 +/- 0.10 muM), strong antioxidant power (3.6 TE), and ability to restore cognitive impairment induced by lipopolysaccharide.
Complex pathomechanism of Alzheimer's disease (AD) prompts researchers to develop multifunctional molecules in order to find effective therapy against AD. We designed and synthesized novel multifunctional ligands for which we assessed their activities towards butyrylcholinesterase, beta secretase, amyloid beta (Abeta) and tau protein aggregation as well as antioxidant and metal-chelating properties. All compounds showed dual anti-aggregating properties towards Abeta and tau protein in the in cellulo assay in Escherichia coli. Of particular interest are compounds 24b and 25b, which efficiently inhibit aggregation of Abeta and tau protein at 10 muM (24b: 45% for Abeta, 53% for tau; 25b: 49% for Abeta, 54% for tau). They display free radical scavenging capacity and antioxidant activity in ABTS and FRAP assays, respectively, and selectively chelate copper ions. Compounds 24b and 25b are also the most potent inhibitors of BuChE with IC50 of 2.39 muM and 1.94 muM, respectively. Promising in vitro activities of the presented multifunctional ligands as well as their original scaffold are a very interesting starting point for further research towards effective anti-AD treatment.
Selective butyrylcholinesterase inhibitors could be the promising drug candidates, used in treatment of Alzheimer's disease. The study describes the synthesis and biological activity of novel carbamate derivatives with N-phenylpiperazine, N-benzylpiperazine and 4-benzylpiperidine moieties. Biological studies revealed that most of these compounds displayed significant activity against BuChE. Compound 16 (3-(4-phenyl-piperazin-1-ylmethyl)-phenyl phenylcarbamate) turned out to be the most active (IC50=2.00muM for BuChE). For all synthesized compounds lipophilicity and other physicochemical properties were calculated using computer programs. Relationship between these properties and activity was also checked. Binding mode with enzyme and the ensuing differences in activity were explained by the molecular modeling studies.
The complex nature of Alzheimer's disease calls for multidirectional treatment. Consequently, the search for multi-target-directed ligands may lead to potential drug candidates. The aim of the present study is to seek multifunctional compounds with expected activity against disease-modifying and symptomatic targets. A series of 15 drug-like various substituted derivatives of 2-(benzylamino-2-hydroxyalkyl)isoindoline-1,3-diones was designed by modification of cholinesterase inhibitors toward beta-secretase inhibition. All target compounds have been synthesized and tested against eel acetylcholinesterase (eeAChE), equine serum butyrylcholinesterase (eqBuChE), human beta-secretase (hBACE-1), and beta-amyloid (Abeta-aggregation). The most promising compound, 12 (2-(5-(benzylamino)-4-hydroxypentyl)isoindoline-1,3-dione), displayed inhibitory potency against eeAChE (IC50 = 3.33 muM), hBACE-1 (43.7% at 50 muM), and Abeta-aggregation (24.9% at 10 muM). Molecular modeling studies have revealed possible interaction of compound 12 with the active sites of both enzymes-acetylcholinesterase and beta-secretase. IN CONCLUSION: modifications of acetylcholinesterase inhibitors led to the discovery of a multipotent anti-Alzheimer's agent, with moderate and balanced potency, capable of inhibiting acetylcholinesterase, a symptomatic target, and disease-modifying targets: beta-secretase and Abeta-aggregation.
The multitarget approach is a promising paradigm in drug discovery, potentially leading to new treatment options for complex disorders, such as Alzheimer's disease. Herein, we present the discovery of a unique series of 1-benzylamino-2-hydroxyalkyl derivatives combining inhibitory activity against butyrylcholinesterase, beta-secretase, beta-amyloid, and tau protein aggregation, all related to mechanisms which underpin Alzheimer's disease. Notably, diphenylpropylamine derivative 10 showed balanced activity against both disease-modifying targets, inhibition of beta-secretase (IC50 hBACE-1 = 41.60 muM), inhibition of amyloid beta aggregation (IC50 Abeta = 3.09 muM), inhibition of tau aggregation (55% at 10 muM); as well as against symptomatic targets, butyrylcholinesterase inhibition (IC50 hBuChE = 7.22 muM). It might represent an encouraging starting point for development of multifunctional disease-modifying anti-Alzheimer's agents.
Alzheimer's disease (AD) is a major public health problem, which is due to its increasing prevalence and lack of effective therapy or diagnostics. The complexity of the AD pathomechanism requires complex treatment, e.g. multifunctional ligands targeting both the causes and symptoms of the disease. Here, we present new multitarget-directed ligands combining pharmacophore fragments that provide a blockade of serotonin 5-HT6 receptors, acetyl/butyrylcholinesterase inhibition, and amyloid beta antiaggregation activity. Compound 12 has displayed balanced activity as an antagonist of 5-HT6 receptors ( Ki = 18 nM) and noncompetitive inhibitor of cholinesterases (IC50 hAChE = 14 nM, IC50 eqBuChE = 22 nM). In further in vitro studies, compound 12 has shown amyloid beta antiaggregation activity (IC50 = 1.27 muM) and ability to permeate through the blood-brain barrier. The presented findings may provide an excellent starting point for further studies and facilitate efforts to develop new effective anti-AD therapy.
A novel series of 9-amino-1,2,3,4-tetrahydroacridine derivatives with 2-fluorobenzoic acid or 3-fluorobenzoic acid moiety were designed, synthesized and evaluated as inhibitors of cholinesterases and aggregation of beta-amyloid. In the study target compounds were very potent inhibitors of AChE and BChE. The most promising agents had higher inhibitory potency than the reference drugs which was tacrine. Ultimately, the kinetic assay shows the most active target compound 3c against AChE. Almost all of them were more potent against BChE than AChE. Compound 3c in various concentrations was tested by aggregation experiment. Inhibition of beta-amyloid aggregation was 77.32% and 80.43% at 50microM and 100microM, respectively. Therefore, compound 3c is a promising agent for the treatment of AD.
Title: Lipophilic properties of anti-Alzheimer's agents determined by micellar electrokinetic chromatography and reversed-phase thin-layer chromatography Godyn J, Hebda M, Wieckowska A, Wieckowski K, Malawska B, Bajda M Ref: Electrophoresis, 38:1268, 2017 : PubMed
Lipophilicity as one of the most important physicochemical properties of the biologically active compounds is closely related to their pharmacokinetic parameters and therefore, it is taken into account at the design stage of new drugs. Among the novel, fast, and reliable methods for determination of the lipophilicity of compounds micellar electrokinetic chromatography (MEKC) is considered to be an appropriate one for bioactive molecules, as it closely mimics the physiological conditions. In this paper MEKC was used for the estimation of log P values for 49 derivatives of phthalimide, tetrahydroisochinoline and indole, designed and synthesized as potential anti-Alzheimer's agents with cholinesterase inhibitory activity. RP-TLC method was applied for determination of another lipophilicity descriptor - RM0 . The results of both experimental methods were compared with each other giving satisfactory correlation (R = 0.784), and with computational methods (Marvin, ChemOffice Software) resulting in weaker correlation (R = 0.466-0.687). The lipophilicity-activity relationship was finally established, showing significant influence of lipophilicity on cholinesterase inhibition in some subgroups of phthalimide derivatives.
The emergence of a multitarget design approach in the development of new potential anti-Alzheimer's disease agents has resulted in the discovery of many multifunctional compounds focusing on various targets. Among them the largest group comprises inhibitors of both cholinesterases, with additional anti-beta-amyloid aggregation activity. This review describes recent advances in this research area and presents the most interesting compounds reported over a 2-year span (2015-2016). The majority of hybrids possess heterodimeric structures obtained by linking structurally active fragments interacting with different targets. Multipotent cholinesterase inhibitors with beta-amyloid antiaggregating activity may additionally possess antioxidative, neuroprotective or metal-chelating properties or less common features such as anti-beta-secretase or tau-antiaggregation activity.
We report herein the straightforward two-step synthesis and biological assessment of novel racemic benzochromenopyrimidinones as non-hepatotoxic, acetylcholinesterase inhibitors with antioxidative properties. Among them, compound 3Bb displayed a mixed-type inhibition of human acetylcholinesterase (IC50 = 1.28 +/- 0.03 muM), good antioxidant activity, and also proved to be non-hepatotoxic on human HepG2 cell line.
Given the complex nature of Alzheimer's disease (AD), compounds that are able to simultaneously address two or more AD-associated targets show greater promise for development into drugs for AD therapy. Herein we report an efficient two-step synthesis and biological evaluation of new racemic benzochromene derivatives as antioxidants, inhibitors of cholinesterase and beta-amyloid (Abeta1-42 ) aggregation. Based on the results of the primary screening, we identified 15-(3-methoxyphenyl)-9,11,12,15-tetrahydro-10H,14H-benzo[5,6]chromeno[2,3-d]pyrid o[1,2-a]pyrimidin-14-imine (3 e) and 16-(3-methoxyphenyl)-9,10,11,12,13,16-hexahydro-15H-benzo[5',6']chromeno[2',3':4, 5]pyrimido[1,2-a]azepin-15-imine (3 f) as new potential multitarget-directed ligands for AD therapy. Further in-depth biological analysis showed that compound 3 f is a good human acetylcholinesterase inhibitor [IC50 =(0.36+/-0.02) mum], has strong antioxidant activity (3.61 mumol Trolox equivalents), and moderate Abeta1-42 antiaggregating power (40.3 %).
Herein we report an efficient two step synthesis and biological assessment of 12 racemic tetrahydropyranodiquinolin-8-amines derivatives as antioxidant, cholinesterase inhibitors and non-hepatotoxic agents. Based on the results of the primary screening, we identified 7-(3-methoxyphenyl)-9,10,11,12-tetrahydro-7H-pyrano[2,3-b:5,6-h']diquinolin-8-ami ne (2h) as a particularly interesting non-hepatotoxic compound that shows moderate antioxidant activity (1.83 equiv Trolox in the ORAC assay), a non competitive inhibition of hAChE (IC50 = 0.75 +/- 0.01 muM), and brain permeable as determined by the PAMPA-Blood Brain Barrier assay.
Alzheimer's disease (AD) is considered to be the most common cause of dementia and is an incurable, progressive neurodegenerative disorder. Current treatment of the disease, essentially symptomatic, is based on three cholinesterase inhibitors and memantine, affecting the glutamatergic system. Since 2003, no new drugs have been approved for treatment of AD. This article presents current directions in the search for novel, potentially effective agents for the treatment of AD, as well as selected promising treatment strategies. These include agents acting upon the beta-amyloid, such as vaccines, antibodies and inhibitors or modulators of gamma- and beta-secretase; agents directed against the tau protein as well as compounds acting as antagonists of neurotransmitter systems (serotoninergic 5-HT6 and histaminergic H3). Ongoing clinical trials with Abeta antibodies (solanezumab, gantenerumab, crenezumab) seem to be promising, while vaccines against the tau protein (AADvac1 and ACI-35) are now in early-stage trials. Interesting results have also been achieved in trials involving small molecules such as inhibitors of beta-secretase (MK-8931, E2609), a combination of 5-HT6 antagonist (idalopirdine) with donepezil, inhibition of advanced glycation end product receptors by azeliragon or modulation of the acetylcholine response of alpha-7 nicotinic acetylcholine receptors by encenicline. Development of new effective drugs acting upon the central nervous system is usually a difficult and time-consuming process, and in the case of AD to-date clinical trials have had a very high failure rate. Most phase II clinical trials ending with a positive outcome do not succeed in phase III, often due to serious adverse effects or lack of therapeutic efficacy.
Cholinesterases and amyloid beta are one of the major biological targets in the search for a new and efficacious treatment of Alzheimer's disease. The study describes synthesis and pharmacological evaluation of new compounds designed as dual binding site acetylcholinesterase inhibitors. Among the synthesized compounds, two deserve special attention-compounds 42 and 13. The former is a saccharin derivative and the most potent and selective acetylcholinesterase inhibitor (EeAChE IC50 = 70 nM). Isoindoline-1,3-dione derivative 13 displays balanced inhibitory potency against acetyl- and butyrylcholinesterase (BuChE) (EeAChE IC50 = 0.76 muM, EqBuChE IC50 = 0.618 muM), and it inhibits amyloid beta aggregation (35.8% at 10 muM). Kinetic studies show that the developed compounds act as mixed or non-competitive acetylcholinesterase inhibitors. According to molecular modelling studies, they are able to interact with both catalytic and peripheral active sites of the acetylcholinesterase. Their ability to cross the blood-brain barrier (BBB) was confirmed in vitro in the parallel artificial membrane permeability BBB assay. These compounds can be used as a solid starting point for further development of novel multifunctional ligands as potential anti-Alzheimer's agents.
Alzheimer's disease (AD) is characterized by severe basal forebrain cholinergic deficit, which results in progressive and chronic deterioration of memory and cognitive functions. Similar to acetylcholinesterase, butyrylcholinesterase (BChE) contributes to the termination of cholinergic neurotransmission. Its enzymatic activity increases with the disease progression, thus classifying BChE as a viable therapeutic target in advanced AD. Potent, selective and reversible human BChE inhibitors were developed. The solved crystal structure of human BChE in complex with the most potent inhibitor reveals its binding mode and provides the molecular basis of its low nanomolar potency. Additionally, this compound is noncytotoxic and has neuroprotective properties. Furthermore, this inhibitor moderately crosses the blood-brain barrier and improves memory, cognitive functions and learning abilities of mice in a model of the cholinergic deficit that characterizes AD, without producing acute cholinergic adverse effects. Our study provides an advanced lead compound for developing drugs for alleviating symptoms caused by cholinergic hypofunction in advanced AD.
In recent years, multitarget-directed ligands have become an interesting strategy in a search for a new treatment of Alzheimer's disease. Combination of both: a histamine H3 receptor antagonist/inverse agonist and a cholinesterases inhibitor in one molecule could provide a new therapeutic opportunity. Here, we present biological evaluation of histamine H3 receptor ligands-chlorophenoxyalkylamine derivatives against cholinesterases: acetyl- and butyrylcholinesterase. The target compounds showed cholinesterase inhibitory activity in a low micromolar range. The most potent in this group was 1-(7-(4-chlorophenoxy)heptyl)homopiperidine (18) inhibiting the both enzymes (EeAChE IC50=1.93muM and EqBuChE IC50=1.64muM). Molecular modeling studies were performed to explain the binding mode of 18 with histamine H3 receptor as well as with cholinesterases.
The complexity of Alzheimer's disease (AD) calls for search of multifunctional compounds as potential candidates for effective therapy. A series of phthalimide and saccharin derivatives linked by different alicyclic fragments (piperazine, hexahydropyrimidine, 3-aminopyrrolidine or 3-aminopiperidine) with phenylalkyl moieties attached have been designed, synthesized, and evaluated as multifunctional anti-AD agents with cholinesterase, beta-secretase and beta-amyloid inhibitory activities. In vitro studies showed that the majority of saccharin derivatives with piperazine moiety and one phthalimide derivative with 3-aminopiperidine fragment exhibited inhibitory potency toward acetylcholinesterase (AChE) with EeAChE IC50 values ranging from 0.83 muM to 19.18 muM. The target compounds displayed inhibition of human beta-secretase-1 (hBACE1) ranging from 26.71% to 61.42% at 50 muM concentration. Among these compounds, two multifunctional agents (26, [2-(2-(4-benzylpiperazin-1-yl)ethyl)benzo[d]isothiazol-3(2H)-one 1,1-dioxide] and 52, 2-(2-(3-(3,5-difluorobenzylamino)piperidin-1-yl)ethyl)isoindoline-1,3-dione) have been identified. Compound 26 exhibited the highest inhibitory potency against EeAChE (IC50 = 0.83 muM) and inhibitory activity against hBACE1 (33.61% at 50 muM). Compound 52 is a selective AChE inhibitor (IC50 AChE = 6.47 muM) with BACE1 inhibitory activity (26.3% at 50 muM) and it displays the most significant Abeta anti-aggregating properties among all the obtained compounds (39% at 10 muM). Kinetic and molecular modeling studies indicate that 26 may act as non-competitive AChE inhibitor able to interact with both catalytic and peripheral active site of the enzyme.
As currently postulated, a complex treatment may be key to an effective therapy for Alzheimer's disease (AD). Recent clinical trials in patients with moderate AD have shown a superior effect of the combination therapy of donepezil (a selective acetylcholinesterase inhibitor) with idalopirdine (a 5-HT6 receptor antagonist) over monotherapy with donepezil. Here, we present the first report on the design, synthesis and biological evaluation of a novel class of multifunctional ligands that combines a 5-HT6 receptor antagonist with a cholinesterase inhibitor. Novel multi-target-directed ligands (MTDLs) were designed by combining pharmacophores directed against the 5-HT6 receptor (1-(phenylsulfonyl)-4-(piperazin-1-yl)-1H-indole) and cholinesterases (tacrine or N-benzylpiperidine analogues). In vitro evaluation led to the identification of tacrine derivative 12 with well-balanced potencies against the 5-HT6 receptor (Kb = 27 nM), acetylcholinesterase and butyrylcholinesterase (IC50hAChE = 12 nM, IC50hBuChE = 29 nM). The compound also showed good in vitro blood-brain-barrier permeability (PAMPA-BBB assay), which was confirmed in vivo (open field study). Central cholinomimetic activity was confirmed in vivo in rats using a scopolamine-induced hyperlocomotion model. A novel class of multifunctional ligands with compound 12 as the best derivative in a series represents an excellent starting point for the further development of an effective treatment for AD.
A novel series of 9-amino-1,2,3,4-tetrahydroacridine derivatives with 4-dimethylaminobenzoic acid moiety was synthesized and tested towards inhibition of cholinesterases and amyloid beta aggregation. Target compounds were designed as dual binding site cholinesterase inhibitors able to bind to both the catalytic and the peripheral site of the enzyme and therefore potentially endowed with other properties. The obtained derivatives were very potent inhibitors of both cholinesterases (EeAChE, EqBChE) with IC50 values ranging from sub-nanomolar to nanomolar range, and the inhibitory potency of the most promising agents was higher than that of the reference drugs (rivastigmine and tacrine). The kinetic studies of the most active compound 3a revealed competitive type of AChE inhibition. Moreover, all target compounds were more potent inhibitors of human AChE than tacrine with the most active compound 3b (IC50=19nM). Compound 3a was also tested and displayed inhibitory potency against AChE-induced Abeta 1-42 aggregation (80.6% and 91.3% at 50muM and 100muM screening concentration, respectively). Moreover, cytotoxicity assay performed on A549 cells did not indicate toxicity of this agent. Compound 3a is a promising candidate for further development of novel multi-functional agents in the therapy of AD.
A virtual screening of the ZINC database was applied for the identification of novel cholinesterase inhibitors. The first step allowed to select compounds with favorable physicochemical properties. Then, the compounds were screened with the pharmacophore models built using crystal structures of donepezil, tacrine, decamethonium and bis-7-tacrine with acetylcholinesterase and well characterized interactions of bis-nor-meptazinol with butyrylcholinesterase. The selected compounds from the group of donepezil were docked to acetyl-cholinesterase giving 7 structures for further studies. These compounds were tested against cholinesterases and two of them, 1-[4-(1H-indol-3-ylmethyl)piperazin-1-yl]-2-phenoxyethanone 2 and 2-[(1-benzylpiperidine-4- yl)amino]-1-phenylethanol 4 displayed, respectively, 50.1% and 79.5% of inhibition against butyryl- cholinesterase at the concentration of 100 microM.
The presented study describes the synthesis, pharmacological evaluation (AChE and BCHE inhibition, beta amyloid anti-aggregation effect and neuroprotective effect), molecular modeling and crystallographic studies of a novel series of isoindoline-1,3-dione derivatives. The target compounds were designed as dual binding site acetylcholinesterase inhibitors with an arylalkylamine moiety binding at the catalytic site of the enzyme and connected via an alkyl chain to a heterocyclic fragment, capable of binding at the peripheral anionic site of AChE. Among these molecules, compound 15b was found to be the most potent and selective AChE inhibitor (IC50EeAChE = 0.034 muM). Moreover, compound 13b in addition to AChE inhibition (IC50 EeAChE = 0.219 muM) possesses additional properties, such as the ability to inhibit Abeta aggregation (65.96% at 10 muM) and a neuroprotective effect against Abeta toxicity at 1 and 3 muM. Compound 13b emerges as a promising multi-target ligand for the further development of the therapy for age-related neurodegenerative disorders.
Title: Recent development of multifunctional agents as potential drug candidates for the treatment of Alzheimer's disease Guzior N, Wieckowska A, Panek D, Malawska B Ref: Curr Med Chem, 22:373, 2015 : PubMed
Alzheimer's disease (AD) is a complex and progressive neurodegenerative disorder. The available therapy is limited to the symptomatic treatment and its efficacy remains unsatisfactory. In view of the prevalence and expected increase in the incidence of AD, the development of an effective therapy is crucial for public health. Due to the multifactorial aetiology of this disease, the multi-target-directed ligand (MTDL) approach is a promising method in search for new drugs for AD. This review updates information on the development of multifunctional potential anti-AD agents published within the last three years. The majority of the recently reported structures are acetylcholinesterase inhibitors, often endowed with some additional properties. These properties enrich the pharmacological profile of the compounds giving hope for not only symptomatic but also causal treatment of the disease. Among these advantageous properties, the most often reported are an amyloid-beta antiaggregation activity, inhibition of beta-secretase and monoamine oxidase, an antioxidant and metal chelating activity, NOreleasing ability and interaction with cannabinoid, NMDA or histamine H3 receptors. The majority of novel molecules possess heterodimeric structures, able to interact with multiple targets by combining different pharmacophores, original or derived from natural products or existing therapeutics (tacrine, donepezil, galantamine, memantine). Among the described compounds, several seem to be promising drug candidates, while others may serve as a valuable inspiration in the search for new effective therapies for AD.
Title: Isoindoline-1,3-dione derivatives targeting cholinesterases: Design, synthesis and biological evaluation of potential anti-Alzheimer's agents Guzior N, Bajda M, Rakoczy J, Brus B, Gobec S, Malawska B Ref: Bioorganic & Medicinal Chemistry, 23:1629, 2015 : PubMed
Alzheimer's disease is a fatal neurodegenerative disorder with a complex etiology. Because the available therapy brings limited benefits, the effective treatment for Alzheimer's disease remains the unmet challenge. Our aim was to develop a new series of donepezil-based compounds endowed with inhibitory properties against cholinesterases and beta-amyloid aggregation. We designed the target compounds as dual binding site acetylcholinesterase inhibitors with N-benzylamine moiety interacting with the catalytic site of the enzyme and an isoindoline-1,3-dione fragment interacting with the peripheral anionic site of the enzyme. The results of pharmacological evaluation lead us to identify a compound 3b as the most potent and selective human acetylcholinesterase inhibitor (hAChE IC50=0.361muM). Kinetic studies revealed that 3b inhibited acetylcholinesterase in non-competitive mode. The result of the parallel artificial membrane permeability assay for the blood-brain barrier indicated that the compound 3b would be able to cross the blood-brain barrier and reach its biological targets in the central nervous system. The selected compound 3b represents a potential lead structure for further development of anti-Alzheimer's agents.
The study presents the discovery of novel butyrylcholinesterase (BCHE) inhibitors among derivatives of azaphenothiazines by application of in silico and in vitro screening methods. From an in-house library of compounds, 143 heterocyclic molecules derived from the azaphenothiazine scaffold were chosen for virtual screening. Based on results of the docking procedure, 15 compounds were identified as exhibiting the best fit for the two screening complexes (ligand - AChE and ligand - BCHE). Five compounds displayed moderate AChE and good BCHE inhibitory activity at screening concentrations of 10 microM. The IC50 values for active BCHE inhibitors were in the 11.8-122.2 nM range. Three of the most active inhibitors are tetra- or pentacyclic derivatives of azaphenothiazines with the same N-methyl-2-piperidinethyl substituent.
Title: Multiple Ligands Targeting Cholinesterases and beta-Amyloid: Synthesis, Biological Evaluation of Heterodimeric Compounds with Benzylamine Pharmacophore Szalaj N, Bajda M, Dudek K, Brus B, Gobec S, Malawska B Ref: Arch Pharm (Weinheim), 348:556, 2015 : PubMed
Alzheimer's disease (AD) is a fatal and complex neurodegenerative disorder for which effective treatment remains the unmet challenge. Using donepezil as a starting point, we aimed to develop novel potential anti-AD agents with a multidirectional biological profile. We designed the target compounds as dual binding site acetylcholinesterase inhibitors, where the N-benzylamine pharmacophore is responsible for interactions with the catalytic anionic site of the enzyme. The heteroaromatic fragment responsible for interactions with the peripheral anionic site was modified and three different heterocycles were introduced: isoindoline, isoindolin-1-one, and saccharine. Based on the results of the pharmacological evaluation, we identified compound 8b with a saccharine moiety as the most potent and selective human acetylcholinesterase inhibitor (IC50 = 33 nM) and beta amyloid aggregation inhibitor. It acts as a non-competitive acetylcholinesterase inhibitor and is able to cross the blood-brain barrier in vitro. We believe that compound 8b represents an important lead compound for further development as potential anti-AD agent.
Due to the complex nature of Alzheimer's disease, multi-target-directed ligand approaches are one of the most promising strategies in the search for effective treatments. Acetylcholinesterase, butyrylcholinesterase and beta-amyloid are the predominant biological targets in the search for new anti-Alzheimer's agents. Our aim was to combine both anticholinesterase and beta-amyloid anti-aggregation activities in one molecule, and to determine the therapeutic potential in vivo. We designed and synthesized 28 new compounds as derivatives of donepezil that contain the N-benzylpiperidine moiety combined with the phthalimide or indole moieties. Most of these test compounds showed micromolar activities against cholinesterases and aggregation of beta-amyloid, combined with positive results in blood-brain barrier permeability assays. The most promising compound 23 (2-(8-(1-(3-chlorobenzyl)piperidin-4-ylamino)octyl)isoindoline-1,3-dione) is an inhibitor of butyrylcholinesterase (IC50=0.72muM) that has beta-amyloid anti-aggregation activity (72.5% inhibition at 10muM) and can cross the blood-brain barrier. Moreover, in an animal model of memory impairment induced by scopolamine, the activity of 23 was comparable to that of donepezil. The selected compound 23 is an excellent lead structure in the further search for new anti-Alzheimer's agents.
Cholinesterases are important biological targets responsible for regulation of cholinergic transmission, and their inhibitors are used for the treatment of Alzheimer's disease. To design new cholinesterase inhibitors, of different structure-based design strategies was followed, including the modification of compounds from a previously developed library and a fragment-based design approach. This led to the selection of heterodimeric structures as potential inhibitors. Synthesis and biological evaluation of selected candidates confirmed that the designed compounds were acetylcholinesterase inhibitors with IC values in the mid-nanomolar to low micromolar range, and some of them were also butyrylcholinesterase inhibitors.
Computer simulations constitute the basis of the design and discovery of new drugs. This approach is not only significant with regards to finding new structures, but also for selecting the molecules with the highest probability of being useful in the diagnostic process and treatment of numerous diseases. In our work, we used computational software to analyze 32 new acetylcholinesterase (AChE) inhibitors and formulate ADMET predictions. To understand the influence of the structure of our derivatives on binding mode, we docked all structures to the active site of AChE and assigned some pharmacophoric features. Finally, we undertook a chemometric analysis of all the compounds on the basis of FT-IR, which gave us the possibility of performing a fast categorization of the analyzed compounds and design compounds with similar structures.
Title: Design, synthesis and evaluation of novel 2-(aminoalkyl)-isoindoline-1,3-dione derivatives as dual-binding site acetylcholinesterase inhibitors Ignasik M, Bajda M, Guzior N, Prinz M, Holzgrabe U, Malawska B Ref: Arch Pharm (Weinheim), 345:509, 2012 : PubMed
A new series of 2-(diethylaminoalkyl)-isoindoline-1,3-dione derivatives intended as dual binding site cholinesterase inhibitors were designed using molecular modeling and evaluated as inhibitors of acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and the formation of the beta-amyloid (Abeta) plaques. For AChE inhibitory activity, the spectrophotometric method of Ellman and the electrophoretically mediated microanalysis assay were used, giving good results. Most of the synthesized compounds had AChE inhibitory activity with IC(50) values ranging from IC(50) = 0.9 to 19.5 microM and weak Abeta anti-aggregation inhibitory activity. These results support the outcome of docking studies which tested compounds targeting both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. The most promising selective AChE inhibitors are compounds 10 (IC(50) = 1.2 microM) and 11 (IC(50) = 1.1 microM), with 6-7 methylene chains, which also inhibit Abeta fibril formation.
Title: Synthesis, biological activity and molecular modeling of 4-fluoro-N-[omega-(1,2,3,4-tetrahydroacridin-9-ylamino)-alkyl]-benzamide derivatives as cholinesterase inhibitors Szymanski P, Markowicz M, Bajda M, Malawska B, Mikiciuk-Olasik E Ref: Arzneimittelforschung, 62:655, 2012 : PubMed
The aim of this study was to synthesize and determine the biological activity of new derivatives of 4-fluorobenzoic acid and tetrahydroacridine towards inhibition of cholinesterases. Compounds were synthesized in condensation reaction between 9-aminoalkyl-tetrahydroacridines and the activated 4-fluorobenzoic acid. Properties towards inhibition of acetyl- and butyrylcholinesterase were estimated according to Ellman's spectrophotometric method. Among synthesized compounds the most active were compounds 4a and 4d. These compounds, in comparison with tacrine, were characterized by the similar values of IC50. Among all obtained compounds, 4d presented the highest selectivity towards inhibition of acetylcholinesterase. Molecular modeling studies revealed that all derivatives presented similar extended conformation in the gorge of acetylcholinesterase, however, there were 2 main conformations in the active center of butyrylcholinesterase: bent and extended conformation.
In the present study we describe the synthesis and biological assessment of new tacrine analogs in the course of inhibition of acetylcholinesterase. The obtained molecules were synthesized in a condensation reaction between activated 6-BOC-hydrazinopyridine-3-carboxylic acid and 8-aminoalkyl derivatives of 2,3-dihydro-1H-cyclopenta[b]quinoline. Activities of the newly synthesized compounds were estimated by means of Ellman's method. Compound 6h (IC(50) = 3.65 nM) was found to be most active. All obtained novel compounds present comparable activity to that of tacrine towards acetylcholinesterase (AChE) and, simultaneously, lower activity towards butyrylcholinesterase (BChE). Apart from 6a, all synthesized compounds are characterized by a higher affinity for AChE and a lower affinity for BChE in comparison with tacrine. Among all obtained molecules, compound 6h presented the highest selectivity towards inhibition of acetylcholinesterase. Molecular modeling showed that all compounds demonstrated a similar binding mode with AChE and interacted with catalytic and peripheral sites of AChE. Also, a biodistribution study of compound 6a radiolabeled with (99m)Tc was performed.
Among the various drug discovery methods, a very promising modern approach consists in designing multi-target-directed ligands (MTDLs). This methodology has been specifically developed for treatment of disorders with complex pathological mechanisms. One such disorder is Alzheimer's disease (AD), currently the most common multifactorial neurodegenerative disease. AD is related to increased levels of the amyloid beta peptide (Abeta) and the hyperphosphorylated tau protein, along with loss of neurons and synapses. Moreover, there is some evidence pointing to the role of oxidative stress, metal ion deregulation, inflammation and cell cycle regulatory failure in its pathogenesis. There are many attractive targets for the development of anti-AD drugs, and the multi-factor nature of this disease calls for multi-target-directed compounds which can be beneficial for AD treatment. This review presents the discovery of dualand multi-acting anti-AD drug candidates, focusing on the novel design strategy and the compounds it yields - particularly hybrids obtained by linking structurally active moieties interacting with different targets. The first group of compounds includes cholinesterase inhibitors acting as dual binding site inhibitors and/or inhibitors with additional properties. These compounds are characterized by increased potency against acetylcholinesterase (AChE) and Abeta plaque formation with additional properties such as antioxidant activity, neuroprotective, and metal-complexing property, voltage-dependent calcium channel antagonistic activity, inhibitory activity against glutamate-induced excitotoxicity, histamine H(3) receptor antagonism, cannabinoid CB(1) receptor antagonism and beta-secretase (BACE1) inhibition. A novel class of compounds represents the combination of dual BACE1 inhibitors with metal chelators, and dual modulators of gamma-secretase with peroxisome proliferator-ativated receptor gamma (PPARgamma). We have reviewed the latest reports (2008-2011) presenting new multi-target-directed compounds in Alzheimer's disease treatment.
Title: Novel alkyl- and arylcarbamate derivatives with N-benzylpiperidine and N-benzylpiperazine moieties as cholinesterases inhibitors Wieckowska A, Bajda M, Guzior N, Malawska B Ref: Eur Journal of Medicinal Chemistry, 45:5602, 2010 : PubMed
The study presents synthesis and biological activity of novel alkyl- and arylcarbamate derivatives with N-benzylpiperidine and N-benzylpiperazine moieties designed as cholinesterases inhibitors. These fragments turned out to determine compounds' selectivity between AChE and BuChE. Derivatives of N-benzylpiperazine (16-25) were selective BuChE inhibitors with 3-(2-(4-benzylpiperazin-1-yl)-2-oxoethyl)-phenyl butylcarbamate (22) being the most potent compound (pIC50=5.00) while a series of carbamate derivatives of N-benzylpiperidine (5-14) displayed non-selective BuChE/AChE inhibitory activity. Molecular modelling studies point out significant differences between orientations of these two groups of compounds in the active site of AChE, which can be an explanation of their different biological activity.
Title: Electrophoretically mediated microanalysis technique as a tool for the rapid screening of novel acetylcholinesterase inhibitors Bajda M, Wieckowska A, Malawska B Ref: Acta Pol Pharm, 66:357, 2009 : PubMed
An electrophoretically mediated microanalysis technique was developed for the rapid screening of acetylcholinesterase inhibitors. Activity of four original compounds, N-benzylpiperidine, carbamoyloxyphenyl derivatives and reference inhibitor--tacrine was determined and compared with the data obtained from Ellman's assay. Percentage of enzyme inhibition detected at inhibitor concentration of 3.33.10(-4) M was between 0 and 78% and was the highest for tacrine. The comparison of data obtained from the EMMA assay and Ellman's test proved inhibitory activity of novel compounds.
Title: Recent developments in cholinesterases inhibitors for Alzheimer's disease treatment Musial A, Bajda M, Malawska B Ref: Curr Med Chem, 14:2654, 2007 : PubMed
Alzheimer's disease (AD) is a progressive neurodegenerative disorder of the central nervous system (CNS) which is the most common cause of dementia in the elderly. It is characterized by the deficits in the cholinergic system and presence of characteristic hallmarks: neurofibrillary tangles and amyloid plaques. Since the cholinergic system plays an important role in the regulation of learning and memory processes it became a target for the design of anti-alzheimer drugs. Cholinesterase inhibitors enhance cholinergic transmission indirectly, by inhibiting the enzyme which hydrolyses acetylcholine. It has been also demonstrated that acetylcholinesterase (AChE) is involved in the development of amyloid plaques. Therefore, substances which are AChE inhibitors (AChEI) are the only drugs approved for the symptomatic treatment of AD. This review presents the main classes of cholinesterase inhibitors developed recently for the treatment of AD. We have started with the analogues of the existing drugs: tacrine, donepezil, rivastigmine and galantamine which are still of interest for many research groups. Among them there is a very interesting group--dual binding site inhibitors characterized by increased inhibitory potency against AChE and amyloid plaques formation. There is also a group of compounds with additional properties such as: antioxidant activity, affinity to 5-HT(3) receptors, inhibition of N-methyltransferase that metabolize histamine, which can be beneficial for the treatment of AD. Furthermore there are some interesting compounds which belong to different chemical groups also of natural origin. In this review we sum up current research concerned with development of AChEIs which can be more effective in the future treatment of AD.
Title: Synthesis of novel N-alkyl carbamates of a-substituted amides of g-hydroxybutyric acid as potential acetylcholinesterase inhibitors Musial A, Malawska B Ref: Acta Pol Pharm, 61 Suppl:94, 2004 : PubMed
In a search for new acetylcholinesterase (AChE) inhibitors, derivatives of N-alkyl carbamates of a-substituted N-benzylamides of g-hydroxybutyric acid (GHB) 2(a-d); 3(a-d); 4(a-d) were obtained. Starting from 3-bromo-tetrahydrofuran-2-one, and N-phenylpiperazine 3-(4-phenylpiperazin-1-yl) tetrahydrofuran-2-one (1) was obtained. The aminolysis of lactone 1 with 4-substituted derivatives of benzylamine yielded N-substituted benzylamides of a-(4-phenylpiperazin-1-yl)-g-hydroxy-butyric acid (2-4). The target compounds were prepared by refluxing N-substituted benzyl-amides of a-(4-phenylpiperazinyl-1-)-GHB with ethyl-, i-propyl-, n-propyl- or n-butyl-isocyanate in dry acetonitrile. The inhibitory potency of AChE was evaluated by means of Ellman's in vitro test.
