Berberine derivatives as inhibitors of acetylcholinesterase: A systematic review

Alzheimer's disease (AD) is a chronic age-related neurodegenerative brain disorder characterized by the impairment of memory accompanied by worsening of thinking ability of an individual. The exact pathophysiology of AD is not fully understood. However low level of the neurotransmitter named acetylcholine (ACh), aggregation of Aβ peptide into toxic Aβ plaque, hyperphosphorylation of tau, bio-metal imbalance, and oxidative stress are the main hallmarks of this disease. Due to the complex pathophysiology of AD, no specific treatment is available in the market, and treatment is only limited to the symptomatic relief. So, there is an urgent need for the development of new drug candidate, which can have disease-modifying effect and improve learning and memory in AD patient. Therefore, berberine-based multifunction compounds with potential cholinesterase inhibitory properties were reviewed in this article. Structure–activity relationship (SAR) and biological activity provide highlights on the new derivatives used for the management of AD.     

Outcomes of Alzheimer's disease therapy with acetylcholinesterase inhibitors and memantine

Introduction: Alzheimer's disease (AD) is a world-wide health problem with implications for an increasing number of people and countries. Populations suffering from AD financially strain the healthcare budgets of rich and poor countries alike. Moreover, no effective treatment is available and current drugs merely slow the progression of cognitive function deterioration and overall health status toward an inevitable end point. An increasing number of novel approaches have been tested in numerous clinical trials, but none of them has proved safe and effective for treating AD.

Areas covered: This review summarizes all currently available compounds (donepezil, rivastigmine, galantamine, memantine) for the management of AD, concentrating on clinical aspects such as the mechanisms of action, pharmacokinetics, pharmacodynamics and clinical trials. This review also considers the mechanisms and side effects to provide perspective on current treatment options.

Expert opinion: Novel approaches in the treatment of AD are being intensively tested, but so far without any major success. Patients diagnosed with AD still mostly benefit from four compounds to significantly improve cognition functions and overall health and help manage other symptoms or even prolong the symptom-free period.     

Progress in acetylcholinesterase inhibitors for Alzheimer's disease: an update

Background: To date, the pharmacotherapy of Alzheimer's disease (AD) has been based on acetylcholinesterase inhibitors (AChEIs), and more recently on an N-methyl-d-aspartate receptor antagonist. By increasing acetylcholine concentration in the brain, AChEIs slow behavioral and functional impairments, improving cognitive function. Objective: The review provides an update on novel analogs of approved AChEIs, their combination with other anti-AD agents, natural AChEIs, and modern multitarget-directed ligands (MTDLs) able to hit different biological targets. Methods: We reviewed patents filed during 2005 – 2007 dealing with new AChEIs and their potential application for AD treatment. We point out new chemical structures and scaffolds for designing new AD therapeutic agents as well as new combinations or MTDLs. Results and conclusions: Compared to the limited number of novel commercially available AChEI analogs, many new natural compounds were patented for AD treatment. These might represent a starting point for the rational design of new MTDLs.     

Design,synthesis, biological evaluation,and docking study of 4‐isochromanone hybrids bearing N‐benzyl pyridinium moiety as dual binding site acetylcholinesterase inhibitors (part II)

A series of novel 4‐isochromanone compounds bearing N‐benzyl pyridinium moiety were designed and synthesized as acetylcholinesterase (AChE) inhibitors. The biological evaluation showed that most of the target compounds exhibited potent inhibitory activities against AChE. Among them, compound 1q possessed the strongest anti‐AChE activity with an IC₅₀ value of 0.15 nm and high AChE/BuChE selectivity (SI > 5,000). Moreover, compound 1q had low toxicity in normal nerve cells and was relatively stable in rat plasma. Together, the current finding may provide a new approach for the discovery of novel anti‐Alzheimer's disease agents.     

Novel tetrahydroacridine derivatives with iodobenzoic acid moiety as multifunctional acetylcholinesterase inhibitors

New synthesized series of 9‐amino‐1,2,3,4‐tetrahydroacridine derivatives with iodobenzoic acid moiety were studied for their inhibitory activity toward cholinesterase and against β‐amyloid aggregation. All novel molecules 3a–3i interacted with both cholinesterases—acetylcholinesterase and butyrylcholinesterase—delivered nanomolar IC₅₀ values. The structure–activity relationship showed that N‐butyl moiety derivatives are stronger inhibitors toward AChE and BuChE than N‐ethyl and N‐propyl moieties compounds. The most potent compound toward acetylcholinesterase was inhibitor 3f (IC₅₀ = 31.2 nm ), and it was more active than reference drug, tacrine (IC₅₀ = 100.2 nm ). Compound 3f showed strong inhibition of butyrylcholinesterase (IC₅₀ = 8.0 nm ), also higher than tacrine (IC₅₀ = 16.3 nm ). In the kinetic studies, compound 3f revealed mixed type of acetylcholinesterase inhibition. The computer modeling was carried out. The most active compound 3f was confirmed as peripheral anionic site inhibitor of acetylcholinesterase. Moreover, molecule 3f inhibited β‐amyloid aggregation (at the concentration 10 μm —24.96% of inhibition, 25 μm —72%, 50 μm —78.44%, and 100 μm —84.92%). Therefore, among all examined, compound 3f is the most promising molecule for further, more detailed research of novel multifunctional agents in the therapy of Alzheimer's disease.     

One-year treatment of Alzheimer's disease with acetylcholinesterase inhibitors: improvement on ADAS-cog and TMT A, no change or worsening on other tests

The aim of this study was to assess cognitive functioning measured by selected psychometric and neuropsychological tools in patients with Alzheimer's disease (AD) after 1-year treatment with acetylcholinesterase inhibitors. Seventy-six patients (22 male and 54 female) with a mild to moderate stage of AD, aged 56-86 (mean 68) years, were treated. Forty-seven received donepezil (mean dose 9.3 mg/d) and 29 rivastigmine (mean dose 8.5 mg/d). Cognitive measurements included: the mini mental state examination (MMSE), the Alzheimer disease assessment scale-cognitive (ADAS- cog), the trail making test (TMT) and the Stroop color word interference test. The assessments were made before and after 3, 6 and 12 months of treatment. A significant improvement in ADAS-cog (p < 0.001, 83% of patients improved) and a worsening in MMSE (84% of patients worsened, p < 0.01 after 6 and 12 months) was noted after the 1 year treatment. A majority of patients (57%) improved in the TMT-A (p < 0.001), measuring psychomotor speed and worsened in the TMT-B (p < 0.01, after 12 months), and Stroop B test (p < 0.001), measuring working memory and executive functions, 53% and 61%, respectively. Most patients (83%) did not change their performance in the Stroop A (improvement after 3 months, p < 0.001, worsening after 6 and 12 months p < 0.01) test measuring verbal abilities, after 1 year treatment. The results obtained suggest that the treatment with cholinergic drugs may improve global cognitive functioning (ADAS-cog) and psychomotor speed (TMT A), however, such treatment is unable to prevent the deterioration of working memory and executive functions.     

Synthesis and biological evaluation of tacrine-thiadiazolidinone hybrids as dual acetylcholinesterase inhibitors

The synthesis of tacrine-thiadiazolidinone hybrids is described. These compounds are designed as dual acetylcholinesterase inhibitors binding simultaneously to the peripheral and catalytic sites of the enzyme. All tested compounds exhibit significant AChE inhibitory activity. Competition assays using propidium as reference of selective ligand for the peripheral anionic site on acetylcholinesterase indicates the influence of the designed compounds over the peripheral site. They can be considered as new leads in the optimization of Alzheimer's disease modifying agents.     

Synthesis of isotopically labelled [14C]ZT‐1 (Debio‐9902), [d3]ZT‐1 and (−)‐[d3]huperzine A,a new generation of acetylcholinesterase inhibitors

A method has been developed for the synthesis of two isotopically labelled forms of a pro‐drug of the acetylcholinesterase inhibitor (?)‐huperzine A. These labelled compounds,[¹⁴C]ZT‐1 (Debio‐9902) and [d₃]ZT‐1, were used in clinical studies to evaluate a potential treatment for Alzheimer's disease. The pro‐drug [¹⁴C]ZT‐1 was isolated with a radiochemical purity of >98% and a gravimetric specific activity of 129 μCi/mg in a seven‐step synthesis starting from [U‐¹⁴C]phenol in 7% yield. Subsequently, the deuterium labelled target (?)‐[d₃]huperzine A was achieved in six steps with an overall yield of 15% and gave an isotopic distribution of d₂ (1.65% huperzine A) and d₃ (97.93% huperzine A) with a chemical purity of 98.5%. Condensation of the substrate (?)‐[d₃]huperzine A with 5‐chloro‐o‐vanillin gave the Schiff base [d₃]ZT‐1 in a chemical yield of 80%. Reduction of the Schiff base gave reduced‐[d₃]ZT‐1, which was converted into the hydrochloride salt with an isotopic distribution of d₂ (1.60%) and d₃ (98.02%). Copyright © 2011 John Wiley & Sons, Ltd.     

Comparison of chlorpyrifos-oxon and paraoxon acetylcholinesterase inhibition dynamics: potential role of a peripheral binding site.

The primary mechanism of action for organophosphorus (OP) insecticides, like chlorpyrifos and parathion, is to inhibit acetylcholinesterase (AChE) by their oxygenated metabolites (oxons), due to the phosphorylation of the serine hydroxyl group located in the active site of the molecule. The rate of phosphorylation is described by the bimolecular inhibitory rate constant (k(i)), which has been used for quantification of OP inhibitory capacity. It has been proposed that a peripheral binding site exists on the AChE molecule, which, when occupied, reduces the capacity of additional oxon molecules to phosphorylate the active site. The aim of this study was to evaluate the interaction of chlorpyrifos oxon (CPO) and paraoxon (PO) with rat brain AChE to assess the dynamics of AChE inhibition and the potential role of a peripheral binding site. The k(i) values for AChE inhibition determined at oxon concentrations of 1-100 nM were 0.206 +/- 0.018 and 0.0216 nM(-1)h(-1) for CPO and PO, respectively. The spontaneous reactivation rates of the inhibited AChE for CPO and PO were 0.084-0.087 (two determinations) and 0.091 +/- 0.023 h(-1), respectively. In contrast, the k(i) values estimated at a low oxon concentration (1 pM) were approximately 1,000- and 10,000-fold higher than those determined at high CPO and PO concentrations, respectively. At low concentrations, the k(i) estimates were approximately similar for both CPO and PO (150-180 [two determinations] and 300 +/- 180 nM(-1)h(-1), respectively). This implies that, at low concentrations, both oxons exhibited similar inhibitory potency in contrast to the marked difference exhibited at higher concentrations. These results support the potential importance of a secondary peripheral binding site associated with AChE kinetics, particularly at low, environmentally relevant concentrations.     

姜黄素衍生物Cur20通过抑制乙酰胆碱酯酶改善阿尔茨海默病小鼠的记忆和认知能力实验研究

目的 研究姜黄素类似物Cur20对乙酰胆碱酯酶（AChE）的作用,评价其对阿尔茨海默病（AD）的治疗潜力。方法 昆明小鼠随机分4组：对照组、模型组、姜黄素（20 μmol·kg^-1）组和Cur20 （20 μmol·kg^-1）组,每天ig给药1次,给药体积10 mL·kg^-1,除对照组外,其他各组小鼠每次给药30 min后ip东莨菪碱1 mg·kg^-1制备AD模型,共给药16 d。第11天开始进行5 d的Morris水迷宫实验,第16天进行Y迷宫实验,检测小鼠的行为认知情况;第17天处死小鼠,取脑分离出海马组织,试剂盒法检测乙酰胆碱（ACh）含量;体外实验检测姜黄素和Cur20对AChE、丁酰胆碱酯酶（BuChE）活性的影响;分子对接实验预测Cur20与AChE的作用模式。结果 小鼠实验结果表明,与模型组比较,Cur20在总游泳距离、游泳速度无显著差异的情况下,能够显著降低水迷宫的逃避潜伏期、增加目标象限的停留时间和路程比例（P<0.05、0.01）,明显增加平台穿越次数;在入臂次数无显著性差异的情况下,Cur20组小鼠的自发交替率明显升高;Cur20组海马组织ACh水平显著升高（P<0.01）。体外实验结果表明,Cur20对AChE的半数抑制浓度（IC₅₀）为（32.44±4.46）μmol·L^-1,50 μmol·L^-1 Cur20对BuChE抑制率为（-1.8±2.3）%,Cur20对AChE的抑制作用具有良好的选择性。分子对接实验表明Cur20能与AChE的活性部位结合。结论 Cur20能抑制AChE活性、提高ACh含量,显著改善东莨菪碱所致的学习记忆损伤,可能是一种潜在的治疗AD的药物。     

Effect of long-term exposure to simazine on brain and muscle acetylcholinesterase activity of common carp (Cyprinus carpio)

Several water-contamination incidents with simazine have occurred in the province of Badajoz (Spain), due to its excessive use for controlling weeds in olive trees and vineyards. Simazine residues were also detected in drinking water, increasing public health concern. However, little is known on the effects that low levels of simazine pose to environment organisms. We investigated if residues of simazine in the natural waters would affect brain and muscle acetylcholinesterase activity in common carps captured in areas in which simazine residues were detected at average levels of 4.5 microg/L. Results confirmed depression on brain and muscle acetylcholinesterase activity of 20% and 29%, respectively, in carps inhabiting one of the simazine-contaminated ponds, termed "Molinos de Matachel." To assess the biological significance of this finding, we developed a controlled laboratory study in which carps were exposed to simazine at 45 microg/L (10-fold that of the natural water levels) for 90 days. The results obtained in the field study were not confirmed in our laboratory experiment, since carps did not show evidence or brain or muscle acetylcholinesterase activity depression for the duration of the experiment, and therefore, we can conclude that acetylcholinesterase depression found in carps collected in "Molinos de Matachel" should be ascribed to other compounds or mixtures of xenobiotics.     

Pyrazolopyridines as inhibitors of the kinase LRRK2: a patent evaluation (WO2011141756)

Scientific evaluation of a patent aiming for the development of pyrazolopyridine derivatives as LRRK2 kinase inhibitors, a potential therapeutic target for combating Parkinson's disease.     

Insulin-like effect of (-)epicatechin on erythrocyte membrane acetylcholinesterase activity in type 2 diabetes mellitus

1. Changes in the activity of acetylcholinesterase (AChE) have been reported in diabetes mellitus that have been linked to certain brain defects. The erythrocyte membrane AChE is reported to be similar to AChE present in the brain. 2. Epicatechin, a member of a group of polyphenolic compounds collectively known as "catechins" that are present in tea and belong to the flavonoid family, has been reported to possess insulin-like activity. 3. In the present study, the in vitro effect of (-)epicatechin and/or insulin was tested on erythrocyte membrane AChE in normal and type 2 diabetic patients. The aim of the study was to test the efficacy of (-)epicatechin to mimic insulin in its effect on erythrocyte membrane AChE. 4. Acetylcholinesterase activity was significantly lower in type 2 diabetic patients than in normal controls and in vitro insulin treatment restored this activity to normal levels. Epicatechin (1 mmol/L) also caused an elevation in AChE activity in diabetic erythrocytes, an effect that was similar to the effect of insulin. 5. Epicatechin has a pronounced insulin-like effect on erythrocyte membrane-bound AChE in type 2 diabetic patients; however, the mechanism of action of epicatechin remains speculative.     

新型乙酰胆碱酯酶抑制剂5H-噻唑并[3,2-a]嘧啶类化合物的设计、合成与生物活性研究

目的 寻找作为乙酰胆碱酯酶抑制剂的具有新化学结构类型的化合物。方法 采用分子对接的虚拟筛选方法寻找新型乙酰胆碱酯酶抑制剂，设计了10个5H-噻唑并[3,2-a]嘧啶类化合物。以芳醛、硫脲等为起始原料，通过Biginelli反应生成二氢嘧啶类化合物，再与氯代苯乙酮作用经Hantzsch环合反应制得目标化合物，其结构经红外光谱、质谱、核磁共振氢谱和碳谱确证。采用Ellman方法进行体外抑制乙酰胆碱酯酶活性测试。 结果 合成了10个5H-噻唑并[3,2-a]嘧啶类化合物，体外抑制乙酰胆碱酯酶活性测试结果显示，所有目标化合物均具有乙酰胆碱酯酶抑制活性，其中3个目标化合物在10 μmol.L^-1时抑制活性均超过50%。结论5H-噻唑并[3,2-a]嘧啶类化合物是潜在的乙酰胆碱酯酶抑制剂。将计算机辅助药物分子设计、有机合成和生物活性测试相结合是发现和设计新型乙酰胆碱酯酶抑制剂的有效途径。     

Reversible inhibition of acetylcholinesterase by eseroline,an opioid agonist structurally related to physostigmine (eserine) and morphine

The action of eseroline—(3aS, 8aR)-1,2,3,3a,8,8a-hexahydro-1,3a,8-trimethylpyrrolo[2,3-b] indol-5-ol—salicylate was tested on preparations of ChE from different sources and on the longitudinal muscle of guinea-pig ileum. While eseroline is extremely weak-acting on horse serum BuChE (K_i = 208 ± 42 μM), it is a rather strong competitive inhibitor of AChE's, its K_i being 0.15 ± 0.08 μM, 0.22 ± 0.10 μM and 0.61 ± 0.12 μM in electric eel, human RBC and rat brain, respectively. Eseroline inhibitory action on AChE is independent of the duration of pre-incubation and appears fully developed in less than 15 sec. This action is also rapidly reversible; after pre-incubation followed by dilution, maximum enzymic activity is regained within 15 sec. The electrically-evoked contractions of the longitudinal strip were inhibited by concentrations of eseroline in the range 0.2–15 μM, while they were increased by concentrations over 20 μM. In the same preparation, without electrical stimulation, but in the presence of naloxone, eseroline induced contractions at concentrations higher than 5 μM. This effect was antagonized by atropine. The inhibitory activity of eseroline parallels, as regards selectivity, potency and kinetics, that of the phenolic anticurare agent edrophonium, while it differs markedly from that of physostigmine.     

1,3-Oxazines as BACE1 and/or BACE2 inhibitors: a patent evaluation (WO2012156284)

This patent review covers the contents of Hoffman-La Roche and Siena Biotech's patent application WO2012156284 titled ‘1,3-Oxazines as BACE1 and/or BACE2 Inhibitors.' Beta-site amyloid precursor protein-converting enzyme (BACE1) and BACE2 activities are reported to support the claimed compounds' use as therapeutics for Alzheimer's disease and type II diabetes, respectively. A common core motif of the claimed compounds is the six-membered 1,3-oxazine system. To gain access to the S3 and S3 subpocket of the BACE1 active site, various linkers are described including nitrogen- and oxygen-based, aryl, and amide-based linkers. Of the 65 compounds claimed, 6 had IC50s less than 100 nM in the BACE1 cell assay. Cellular BACE2 inhibition data are reported for 20 compounds with 2 under 100 nM.     

Inhibitory effect of(-),( )clausenamide on acetylcholinesterase in vitro

用Ｅｌｍａｎ比色法测定乙酰胆碱酯酶（ＡＣｈＥ）的活性，观察（－），（＋）黄皮酰胺对小鼠脑组织海马，前脑皮层和红细胞膜ＡＣｈＥ活性的影响，以探索药物作用机制并比较左右旋体黄皮酰胺作用的异同．结果表明：（－），（＋）黄皮酰胺对海马和皮层ＡＣｈＥ均有抑制作用，（－）黄皮酰胺对小鼠脑皮层和海马ＡＣｈＥ抑制的ＩＣ５０（９５％可信限）值分别为０．３１（０．２７－０．３６）和０．３３（０．２８－０．３９）ｍｍｏｌ·Ｌ－１；（＋）黄皮酰胺对小鼠脑皮层和海马ＡＣｈＥ抑制的ＩＣ５０（９５％可信限）值分别为０．７１（０．５３－０．９４）和０．７７（０．５５－１．０７）ｍｍｏｌ·Ｌ－１．（－），（＋）黄皮酰胺对红细胞膜ＡＣｈＥ的抑制作用是可逆性的，抑制特点属于竞争与非竞争混合型抑制，（－）黄皮酰胺的Ｋｉ值为０．２６ｍｍｏｌ·Ｌ－１，Ｋｉ′值为１．２０５ｍｍｏｌ·Ｌ－１；（＋）黄皮酰胺Ｋｉ值为０．７２ｍｍｏｌ·Ｌ－１，Ｋｉ′值为１．８５６ｍｍｏｌ·Ｌ－１．提示：（－）黄皮酰胺作用强于（＋）黄皮酰胺．黄皮酰胺的抑制ＡＣｈＥ作用存在手性选择性．     

Pharmacokinetics and urinary excretion of DMXBA (GTS-21), a compound enhancing cognition

DMXBA (3-(2, 4-dimethoxybenzylidene)-anabaseine, also known as GTS-21) is currently being tested as a possible pharmacological treatment of cognitive dysfunction in Alzheimer's disease. In this study, plasma and brain pharmacokinetics as well as urinary excretion of this compound have been evaluated in adult rats. DMXBA concentrations were determined by HPLC. Following a 5 mg kg⁻¹ iv dose, DMXBA plasma concentration declined bi-exponentially with mean (±SE) absorption and elimination half-lives of 0.71±0.28 and 3.71±1.12 h, respectively. The apparent steady state volume of distribution was 2150±433 mL kg⁻¹, total body clearance was 1480±273 mL h⁻¹ kg⁻¹, and AUC_0–∞ was 3790±630 ng h mL⁻¹. Orally administered DMXBA was rapidly absorbed. After oral administration of 10 mg kg⁻¹, a peak plasma concentration of 1010±212 ng mL⁻¹ was observed at 10 min after dosing. Elimination half-life was 1.740±0.34 h, and AUC_0–∞ was 1440±358 ng h mL⁻¹. DMXBA peak brain concentration after oral administration was 664±103 ng g⁻¹ tissue, with an essentially constant brain–plasma concentration ratio of 2.61±0.34, which indicates that the drug readily passes across the blood–brain barrier. Serum protein binding was 80.3±1.1%. Apparent oral bioavailability was 19%. Renal clearance (21.8 mL h⁻¹ kg⁻¹) was less than 2% of the total clearance (1480±273 mL h⁻¹ kg⁻¹); urinary excretion of unchanged DMXBA over a 96 h period accounted for only 0.28±0.03% of the total orally administered dose. Our data indicates that DMXBA oral bioavailability is primarily limited by hepatic metabolism. © 1998 John Wiley & Sons, Ltd.