Current drug targets for Alzheimer's disease treatment

Effects of Zizyphus jujube extract on memory and learning impairment induced by bilateral electric lesions of the nucleus Basalis of Meynert in rat

Alzheimer's disease (AD) is a common neurodegenerative condition that affects the elderly population. Its primary symptom is memory loss. The memory dysfunction in AD has been associated with cortical cholinergic deficiency and loss of cholinergic neurons of the nucleus basalis of Meynert (NBM). Zizyphus jujube (ZJ) activates choline acetyltransferase and may have beneficial effects in AD patients. This study investigates the effect of ZJ extract in intact rats and in rat model of AD. 49 male Wistar rats were divided into seven equal groups (1-control, without surgery, received water), 2-AD (bilateral NBM lesion, received water), 3 and 4-AD + ZJ (NBM bilateral lesion, received ZJ extract 500 and 1,000 mg/kg b.w. per day for 15 days), 5-sham (surgery: electrode introduced into NBM without lesion, received water), 6 and 7-without surgery and lesion, received ZJ extract-the same as groups 3 and 4). The learning and memory performance were assessed using passive avoidance paradigm, and the memory cognition for spatial learning and memory was evaluated by Morris water maze. In shuttle box test ZJ extract (500 and 1,000 mg) significantly increased step-through latency in AD + ZJ groups compared with AD group. In Morris water maze test (in probe day), both AD + ZJ groups receiving extract (500 and 1,000 mg) demonstrated significant preference for the quadrant in which the platform was located on the preceding day as compared with AD group. Our results suggested that ZJ has repairing effects on memory and behavioral disorders produced by NBM lesion in rats and may have beneficial effects in treatment of AD patients.

A preliminary investigation of anticholinesterase activity of some Iranian medicinal plants commonly used in traditional medicine

BACKGROUND

The aim of this study was to evaluate acetylcholinesterase inhibitory activity of some commonly used herbal medicine in Iran to introduce a new source for management of Alzheimer's disease. A total of 18 aqueous-methanolic extract (1:1; v/v) from the following plants: Brassica alba, Brassica nigra, Camellia sinensis, Cinchona officinalis, Citrus aurantifolia, Citrus x aurantium, Ferula assafoetida, Humulus lupulus, Juglans regia, Juniperus sabina, Myristica fragrans, Pelargonium graveolens, Pistacia vera, Punica granatum, Rheum officinale, Rosa damascena, Salix alba, and Zizyphus vulgaris were prepared and screened for their acetylcholinesterase inhibitory activity using in vitro Ellman spectrophotometric method.

RESULTS

According to the obtained results, the order of inhibitory activity (IC50 values, μg /ml) of extracts from highest to the lowest was: C. sinensis (5.96), C. aurantifolia (19.57), Z. vulgaris (24.37), B. nigra (84.30) and R. damascena (93.1).

CONCLUSIONS

The results indicated and confirmed the traditional use of these herbs for management of central nervous system disorders. C. sinensis showed the highest activity in inhibition of acetylcholinesterase. However, further investigations on identification of active components in the extracts are needed.

Therapeutic potential of turmeric in Alzheimer's disease: curcumin or curcuminoids?

Alzheimer's disease (AD) is the most common form of dementia. There is limited choice in modern therapeutics, and drugs available have limited success with multiple side effects in addition to high cost. Hence, newer and alternate treatment options are being explored for effective and safer therapeutic targets to address AD. Turmeric possesses multiple medicinal uses including treatment for AD. Curcuminoids, a mixture of curcumin, demethoxycurcumin, and bisdemethoxycurcumin, are vital constituents of turmeric. It is generally believed that curcumin is the most important constituent of the curcuminoid mixture that contributes to the pharmacological profile of parent curcuminoid mixture or turmeric. A careful literature study reveals that the other two constituents of the curcuminoid mixture also contribute significantly to the effectiveness of curcuminoids in AD. Therefore, it is emphasized in this review that each component of the curcuminoid mixture plays a distinct role in making curcuminoid mixture useful in AD, and hence, the curcuminoid mixture represents turmeric in its medicinal value better than curcumin alone. The progress in understanding the disease etiology demands a multiple-site-targeted therapy, and the curcuminoid mixture of all components, each with different merits, makes this mixture more promising in combating the challenging disease.

Alkaloids as a source of potential anticholinesterase inhibitors for the treatment of Alzheimer's disease

Objectives

The inhibition of acetylcholinesterase (AChE), the key enzyme in the breakdown of acetylcholine, is currently the main pharmacological strategy available for Alzheimer's disease (AD). In this sense, many alkaloids isolated from natural sources, such as physostigmine, have been long recognized as acetyl- and butyrylcholinesterase (BChE) inhibitors. Since the approval of galantamine for the treatment of AD patients, the search for new anticholinesterase alkaloids has escalated, leading to promising candidates such as huperzine A. This review aims to summarize recent advances in current knowledge on alkaloids as AChE and BChE inhibitors, highlighting structure–activity relationship (SAR) and docking studies.

Key findings

Natural alkaloids belonging to the steroidal/triterpenoidal, quinolizidine, isoquinoline and indole classes, mainly distributed within Buxaceae, Amaryllidaceae and Lycopodiaceae, are considered important sources of alkaloids with anti-enzymatic properties. Investigations into the possible SARs for some active compounds are based on molecular modelling studies, predicting the mode of interaction of the molecules with amino acid residues in the active site of the enzymes. Following this view, an increasing interest in achieving more potent and effective analogues makes alkaloids good chemical templates for the development of new cholinesterase inhibitors.

Summary

The anticholinesterase activity of alkaloids, together with their structural diversity and physicochemical properties, makes them good candidate agents for the treatment of AD.

Synthesis, evaluation and molecular dynamics study of some new 4-aminopyridine semicarbazones as an antiamnesic and cognition enhancing agents

Some new semicarbazones of 4-aminopyridine were synthesized and evaluated for antiamnesic, cognition enhancing and anticholinesterase activities. The results illustrated a significant cognition enhancing effect on elevated plus maze model with a significant reversal of scopolamine-induced amnesia. A significant inhibition in acetycholinesterase (AChE) activity by all the synthesized compounds in specific brain regions that is, prefrontal cortex, hippocampus and hypothalamus was observed. Compound 4APi exhibited significant antiamnesic and cognition enhancing activity which was comparable with standard drug donepezil. Its enzyme kinetic study revealed a non-competitive inhibition of AChE and a competitive inhibition of butyrylcholinesterase (BChE). Docking studies predicted the binding modes of these compounds in AChE active site, which were further processed for molecular dynamics simulation for calculating binding free energies using Molecular Mechanics-Generalized Born Surface Area (MM/GBSA). All the computational study confirmed their consensual interaction with AChE justifying the experimental outcome.

Acetylcholinesterase inhibition and in vitro and in vivo antioxidant activities of Ganoderma lucidum grown on germinated brown rice

In this study, the acetylcholinesterase inhibition and in vitro and in vivo antioxidant activities of Ganoderma lucidum grown on germinated brown rice (GLBR) were evaluated. In antioxidant assays in vitro, GLBR was found to have strong metal chelating activity, DPPH, ABTS, hydroxyl and superoxide radical scavenging activity. Cell-based antioxidant methods were used, including lipid peroxidation on brain homogenate and AAPH-induced erythrocyte haemolysis. In antioxidant assays in vivo, mice were administered with GLBR and this significantly enhanced the activities of antioxidant enzymes in the mice sera, livers and brains. The amount of total phenolic and flavonoid compounds were 43.14 mg GAE/g and 13.36 mg CE/g dry mass, respectively. GLBR also exhibited acetylcholinesterase inhibitory activity. In addition, HPLC analyses of GLBR extract revealed the presence of different phenolic compounds. These findings demonstrate the remarkable potential of GLBR extract as valuable source of antioxidants which exhibit interesting acetylcholinesterase inhibitory activity.

Design, synthesis and evaluation of some new 4-aminopyridine derivatives in learning and memory

Some new anilide and imide derivatives of 4-aminopyridine (4AP) were synthesized and evaluated against antiamnesic, cognition enhancing and anticholinesterase activity through their respective in vitro and in vivo models. These newly synthesized derivatives have illustrated an enhanced cognition effect on elevated plus maze model and also demonstrated a significant reversal in scopolamine-induced amnesia in same model. The IC50 value of synthesized compounds showed maximum activity of 4APMb compared to standard drug donepezil and other derivatives, whereas its enzyme kinetic study revealed a non-competitive inhibition of acetycholinesterase (AChE) and a competetive inhibition of butyrylcholinesterase (BChE). Significant inhibitions in AChE activity by all the synthesized compounds were found in specific brain regions that is prefrontal cortex, hippocampus and hypothalamus. The docking study confirmed their consensual interaction with AChE, showed an affinity and binding with the key peripheral anionic site residues Trp-286, Tyr-124 and Tyr-341 of AChE.

Molecular docking and receptor-specific 3D-QSAR studies of acetylcholinesterase inhibitors

The reversible inhibition of acetylcholinesterase (AChE) has become a promising target for the treatment of Alzheimer's disease (AD) which is mainly associated with low in vivo levels of acetylcholine (ACh). The availability of AChE crystal structures with and without a ligand triggered the effort to find a structure-based design of acetylcholinesterase inhibitors (AChEIs) for AD. The major problem observed with the structure-based design was the feeble robustness of the scoring functions toward the correlation of docking scores with inhibitory potencies of known ligands. This prompted us to develop new prediction models using the stepwise regression analysis based on consensus of different docking and their scoring methods (GOLD, LigandFit, and GLIDE). In the present investigation, a dataset of 91 molecules belonging to 9 different structural classes of heterocyclic compounds with an activity range of 0.008 to 281,000 nM was considered for docking studies and development of AChE-specific 3D-QSAR models. The model (M1) developed using consensus of docking scores of scoring functions viz. Glide score, Gold score, Chem score, ASP score, PMF score, and DOCK score was found to be the best (R(2) = 0.938, Q(2) = 0.925, R(pred)(2) = 0.919, R(2)m((overall)) = 0.936) compared to other consensus models. Docking studies revealed that the molecules with proper alignment in the active site gorge and the ability to interact with all the crucial amino acid residues, in particular by forming π-π stacking interactions with Trp84 at the catalytic anionic site (CAS) and Trp279 at peripheral anionic site (PAS), showed augmented potencies with consequent improvement in patient cognition and reduced the formation of senile plaques associated with AD. Further, the descriptors that signify the association of the ligands with the receptor as well as ADME properties of the ligands were also analyzed by means of the set of ligands that have been pre-positioned with respect to a receptor after docking analysis and considered as independent variables to generate a linear model (M3 and M4) using a stepwise multiple linear regression method to get additional insight into the physicochemical requirements for effective binding of ligands with AChE as well as for prediction of AChE inhibition. The developed AChE-specific prediction models (M1-M4) satisfactorily reflect the structure-activity relationship of the existing AChEIs and have all the potential to facilitate the process of design and development of new potent AChEIs.

Alkaloids from Some Amaryllidaceae Species and Their Cholinesterase Activity

Alkaloid extracts of four Amaryllidaceae species were studied with respect to their acetylcholinesterase and butyrylcholinesterase inhibitory activity and alkaloid patterns. Twenty-one alkaloids were determined by GC/MS, and seventeen of them identified from their mass spectra and retention times. The GC/MS analysis of the alkaloid extract of Nerine filamentosa is the first phytochemical investigation of this species. Promising erythrocytic acetylcholinesterase inhibitory activity was demonstrated by the alkaloid extracts of Narcissus poeticus var recurvus, Nerine filifolia and N. filamentosa (IC50,HuAChE = 6.0 ± 0.1 μg/mL; IC50,HuAChE = 18.5 ± 0.8 μg/mL, IC50,HuAChE = 21.6 ± 1.1 μg/mL). The most potent inhibitory activity against serum butyrylcholinesterase was shown by extracts of Sternbergia lutea and Nerine filamentosa (IC50,HuBuChE = 3.7 ± 0.1 μg/mL; IC50,HuBuChE = 13.0 ± 0.7 μg/mL).

Effects of lavender oil inhalation on improving scopolamine-induced spatial memory impairment in laboratory rats

Lavender is reported to be an effective medical plant in treating inflammation, depression, stress and mild anxiety in Europe and the USA. The present study investigated the effects of two different lavender essential oils from Lavandula angustifolia ssp. angustifolia Mill. (Lamiaceae) and Lavandula hybrida Rev. (Lamiaceae) on neurological capacity of male Wistar rats subjected to scopolamine (0.7mg/kg)-induced dementia rat model. Chronic exposures to lavender essential oils (daily, for 7 continuous days) significantly reduced anxiety-like behavior and inhibited depression in elevated plus-maze and forced swimming tests, suggesting anxiolytic and antidepressant activity. Also, spatial memory performance in Y-maze and radial arm-maze tasks was improved, suggesting positive effects on memory formation. Taken together, multiple exposures to lavender essential oils could effectively reverse spatial memory deficits induced by dysfunction of the cholinergic system in the rat brain and might provide an opportunity for management neurological abnormalities in dementia conditions.

Investigation of the in vitro and ex vivo acetylcholinesterase and antioxidant activities of traditionally used Lycopodium species from South America on alkaloid extracts

ETHNOPHARMACOLOGICAL RELEVANCE

The study was aimed at evaluating medicinal and therapeutic potentials of two Lycopodiaceae species, Lycopodium clavatum (L.) and Lycopodium thyoides (Humb. & Bonpl. ex Willd), both used in South American folk medicine for central nervous system conditions. Alkaloid extracts were evaluated for chemical characterization, acetylcholinesterase and antioxidant activities.

MATERIALS AND METHODS

The alkaloid extracts obtained by alkaline extraction were determined for each species by GC/MS examination. The evaluation of the anticholinesterase and the antioxidant activities of the extracts were tested by determining in vitro and ex vivo models. Effects on acetylcholinesterase (AChE) were tested in vitro using rat brain homogenates and ex vivo after a single administration (25, 10 and 1mg/kg i.p.) of the alkaloid extracts in mice. The in vitro antioxidant effects were tested for the 2-deoxyribose degradation, nitric oxide (NO) interaction, 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activity and total reactive antioxidant potential (TRAP). After an acute administration (25 and 10mg/kg i.p.) of the extracts in middle-aged (12 months) mice, the antioxidant effects were estimated through the thiobarbituric acid reactive substances test (TBARS), and the antioxidant enzymes activities for catalase (CAT) and superoxide dismutase (SOD) were measured.

RESULTS

AChE activity was inhibited in vitro by the alkaloid-enriched extracts of both Lycopodium species in a dose and time-dependent manner in rat cortex, striatum and hippocampus. A significant inhibition was also observed in areas of the brain after acute administration of extracts, as well as decreased lipid peroxidation and increased CAT activity in the cortex, hippocampus and cerebellum. A moderate antioxidant activity was observed in vitro for the extracts. Chemically, the main alkaloids found for the two species were lycopodine and acetyldihidrolycopodine.

CONCLUSION

This study showed that the biological properties of the folk medicinal plants Lycopodium clavatum and Lycopodium thyoides include AChE inhibitory activity and antioxidant effects, two possible mechanisms of action in Alzheimer's related processes.

Synthesis, Acetylcholinesterase and Alkaline Phosphatase Inhibition of Some New 1,2,4-Triazole and 1,3,4-Thiadiazole Derivatives

A new series of 4,5-disubstituted-2,4-dihydro-3H-1,2,4-triazole-3-thiones (6a–s) and 2,5-disubstituted-1,3,4-thiadiazoles (7a–h) was synthesized by intramolecular dehydrocyclization of various 1,4-disubstituted thiosemicarbazide derivatives (5a–s) by refluxing in 4 N aqueous sodium hydroxide and by overnight stirring with polyphosphoric acid, respectively. The structures of these compounds were characterized by IR, 1H and 13C NMR, elemental analysis and mass spectroscopic studies. All the synthesized compounds were screened for their acetylcholinesterase and alkaline phosphatase inhibition studies. Most of the tested compounds showed promising activities, amongst them (6k) and (6q) showed excellent acetylcholinesterase inhibitory activity with IC50 0.241 ± 0.012 and 0.260 ± 0.013 µM, respectively, as compared with those of standard drug whereas the compound (6p), with IC50 0.044 ± 0.001 µM, was found to be the most potent inhibitor of alkaline phosphatase.

Essential oil and methanolic extract of Zataria multiflora Boiss with anticholinesterase effect

One of the most common strategies in the treatment of cognitive disorders is enhancing the acetylcholine level in the brain through the inhibition of acetylcholinesterase. Despite the effectiveness of current modern drugs, more attention has been paid for finding new anticholinesterase agents from medicinal plants. Zatraia multiflora Boiss. is an endemic plant to Iran which has different uses in traditional medicine as anti-inflammatory, antimicrobial, anti spasmodic. We intended to evaluate the in vitro anticholinesterase and free radical scavenging activity of the essential oil and methanolic extract of Z. multiflora. The essential oil and methanolic extract of the plant were evaluated for anticholinesterase activity using modified Ellman method. The free radical scavenging effect of the samples were studied by using of the diphenylpicrylhydrazyl (DPPH). IC50 and the percent of inhibition of acetylcholinesterase was calculated from regression equation. The results showed that both the essential oil and methanolic extract of the plant exhibited high anticholinesterase activity (95.3 +/- 3.4 and 87.9 +/- 2.2% inhibition, respectively) which was similar to eserine (96.2 +/- 1.7% inhibition). The IC50 value of essential oil was determined as 0.97 +/- 0.12 microg mL(-1) in comparison to eserine (0.13 +/- 0.02 microg mL(-1)). The results of antioxidant assay showed that both the essential oil and methanolic extract potentially inhibit DPPH free radical (94.8 +/- 2.4 and 93.2 +/- 1.7% inhibition, respectively). The essential oil and methanolic extract of Z. multiflora have beneficial effect in health promotion and this plant would be good candidate for further studies.

Isolation and Cholinesterase Activity of Amaryllidaceae Alkaloids from Nerine bowdenii

Amaryllidaceae species are known as ornamental plants. Some contain galanthamine, an acetylcholinesterase inhibitor. The chemical composition of the alkaloid extract of bulbs of Nerine bowdenii Watson has been analyzed by means of GC/MS. Twenty-two compounds were detected and nineteen of them identified, one of which was belladine. The alkaloid extract showed promising cholinesterase inhibitory activities against human blood acetylcholinesterase (HuAChE; IC50= 87.9±3.5 μg/mL) and human plasma butyrylcholinesterase (HuBuChE; IC50 = 14.8±1.1 μg/mL). Belladine inhibited HuAChE and HuBuChE in a dose-dependent manner with IC50 values of 781±12.5 μM and 284.8±4.2 μM, respectively.

GC/MS Analysis of Three Amaryllidaceae Species and Their Cholinesterase Activity

Alzheimer's disease (AD), characterized by the death of nerve cells in the cerebral cortex, is the most common subtype of dementia. Despite the exponential growth in the number of AD patients, acetylcholinesterase (AChE) inhibitors are currently used to treat AD. Plants of the Amaryllidaceae family are known to synthesize a particular type of bioactive compounds, named Amaryllidaceae alkaloids, which have shown AChE inhibitory activity. Alkaloid extracts of three species of Amaryllidaceae were studied with respect to their acetylcholinesterase and butyrylcholinesterase inhibitory activity and alkaloid patterns. Eleven alkaloids were identified by GC/MS. Significant cholinesterase inhibitory activity was demonstrated by the alkaloid extract of N. undulata (IC50,HuAChE = 14.3 ± 1.2 μg/mL; IC50,HuBuChE = 33.9 ± 1.9 μg/mL).

Aqueous extract of lavender (Lavandula angustifolia) improves the spatial performance of a rat model of Alzheimer's disease

OBJECTIVE

Alzheimer's disease (AD) is one of the most important neurodegenerative disorders. It is characterized by dementia including deficits in learning and memory. The present study aimed to evaluate the effects of aqueous extract of lavender (Lavandula angustifolia) on spatial performance of AD rats.

METHODS

Male Wistar rats were first divided into control and AD groups. Rat model of AD was established by intracerebroventricular injection of 10 μg Aβ1-42 20 d prior to administration of the lavender extract. Rats in both groups were then introduced to 2 stages of task learning (with an interval of 20 d) in Morris water maze, each followed by one probe test. After the first stage of spatial learning, control and AD animals received different doses (50, 100 and 200 mg/kg) of the lavender extract.

RESULTS

In the first stage of experiment, the latency to locate the hidden platform in AD group was significantly higher than that in control group. However, in the second stage of experiment, control and AD rats that received distilled water (vehicle) showed similar performance, indicating that the maze navigation itself could improve the spatial learning of AD animals. Besides, in the second stage of experiment, control and AD rats that received lavender extract administration at different doses (50, 100, and 200 mg/ kg) spent less time locating the platform (except for the AD rats with 50 mg/kg extract treatment), as compared with their counterparts with vehicle treatment, respectively. In addition, lavender extract significantly improved the performance of control and AD rats in the probe test, only at the dose of 200 mg/kg, as compared with their counterparts with vehicle treatment.

CONCLUSION

The lavender extract can effectively reverse spatial learning deficits in AD rats.

The Alzheimer's amyloid β-peptide (Aβ) binds a specific DNA Aβ-interacting domain (AβID) in the APP, BACE1, and APOE promoters in a sequence-specific manner: characterizing a new regulatory motif

Deposition of extracellular plaques, primarily consisting of amyloid β peptide (Aβ), in the brain is the confirmatory diagnostic of Alzheimer's disease (AD); however, the physiological and pathological role of Aβ is not fully understood. Herein, we demonstrate novel Aβ activity as a putative transcription factor upon AD-associated genes. We used oligomers from 5'-flanking regions of the apolipoprotein E (APOE), Aβ-precursor protein (APP) and β-amyloid site cleaving enzyme-1 (BACE1) genes for electrophoretic mobility shift assay (EMSA) with different fragments of the Aβ peptide. Our results suggest that Aβ bound to an Aβ-interacting domain (AβID) with a consensus of "KGGRKTGGGG". This peptide-DNA interaction was sequence specific, and mutation of the first "G" of the decamer's terminal "GGGG" eliminated peptide-DNA interaction. Furthermore, the cytotoxic Aβ25-35 fragment had greatest DNA affinity. Such specificity of binding suggests that the AβID is worth of further investigation as a site wherein the Aβ peptide may act as a transcription factor.

Prevention of scopolamine-induced memory deficits by schisandrin B, an antioxidant lignan from Schisandra chinensis in mice

The preventive effect of schisandrin B (Sch B), an antioxidant ingredient of Schisandra chinensis, was studied on scopolamine-induced dementia in mouse. Scopolamine developed oxidative stress in the brain with the decreased levels of antioxidant enzymes and increased nitrite level. At the same time, a significant impairment of learning and memory occurred when evaluated by passive avoidance task (PAT) and Morris water maze (MWM) with concomitant increase of acetylcholinesterase (AChE) activity and decreased acetylcholine levels. Pre-treatment by Sch B (10, 25, 50 mg/kg) effectively prevented scopolamine-induced oxidative stress and improved behavioural tasks. Further, the scopolamine-induced increase in AChE activity was significantly suppressed and the level of acetylcholine was maintained as normal by Sch B treatment. These results suggest that Sch B have protective function against cerebral functional defects such as dementia not only by antioxidant prevention but also exerting its potent cognitive-enhancing activity through modulation of acetylcholine level.

Analysis of Amaryllidaceae Alkaloids from Chlidanthus Fragrans by GC-MS and their Cholinesterase Activity

The underivatized alkaloid mixture extracted from the bulbs of Chlidanthus fragrans Herb. was investigated by capillary GC/MS for the first time. Fifteen known Amaryllidaceae alkaloids of five structure types were identified. The main alkaloids were tazzetine (9, tazettine-type), chlidanthine (2, galanthamine-type), belladine (8, belladine-type) and lycorine (12, lycorine-type). The alkaloid extract from the bulbs showed promising human blood acetylcholinesterase (IC50 = 20.1 ± 2.9 μg/mL) and human plasma butyrylcholinesterase (IC50 = 136.8 ± 6.9 μg/mL) inhibitory activity.

Aqueous Extract of Black Maca (Lepidium meyenii) on Memory Impairment Induced by Ovariectomy in Mice

The present study aims to test two different doses of aqueous extract of black maca on learning and memory in ovariectomized (OVX) mice and their relation with malonalehyde (MDA), acetylcholinesterase (Ache) and monoamine oxidase (MAO) brain levels. Female mice were divided into five groups: (i) naive (control), (ii) sham, (iii) OVX mice and OVX mice treated with (iv) 0.50 g kg⁻¹ and (v) 2.00 g kg⁻¹ black maca. Mice were orally treated with distilled water or black maca during 35 days starting 7 days after surgery. Memory and learning were assessed using the water Morris maze (from day 23–27) and the step-down avoidance test (days 34 and 35). At the end of each treatment, mice were sacrificed by decapitation and brains were dissected out for MDA, Ache and MAO determinations. Black maca (0.5 and 2.0 g/kg) increased step-down latency when compared to OVX control mice. Black maca decreased MDA and Ache levels in OVX mice; whereas, no differences were observed in MAO levels. Finally, black maca improved experimental memory impairment induced by ovariectomy, due in part, by its antioxidant and Ache inhibitory activities.

Therapeutic applications of compounds in the Magnolia family

The bark and/or seed cones of the Magnolia tree have been used in traditional herbal medicines in Korea, China and Japan. Bioactive ingredients such as magnolol, honokiol, 4-O-methylhonokiol and obovatol have received great attention, judging by the large number of investigators who have studied their pharmacological effects for the treatment of various diseases. Recently, many investigators reported the anti-cancer, anti-stress, anti-anxiety, anti-depressant, anti-oxidant, anti-inflammatory and hepatoprotective effects as well as toxicities and pharmacokinetics data, however, the mechanisms underlying these pharmacological activities are not clear. The aim of this study was to review a variety of experimental and clinical reports and, describe the effectiveness, toxicities and pharmacokinetics, and possible mechanisms of Magnolia and/or its constituents.

Acetylcholinesterase and Butyrylcholinesterase Inhibitory Compounds from Chelidonium Majus (Papaveraceae)

The roots and aerial parts of Chelidonium majus L. were extracted with EtOH and fractionated using CHCl3 and EtOH. Repeated column chromatography, preparative TLC and crystallization led to the isolation of five isoquinoline alkaloids, stylopine (3), chelidonine (4), homochelidonine (5), protopine (6), and allocryptopine (7), along with two isolation artifacts 6-ethoxydihydrosanguinarine (1) and 6-ethoxydihydrochelerythrine (2). All isolated compounds were tested for human blood acetylcholinesterase (HuAChE) and human plasma butyrylcholinesterase (HuBuChE) inhibitory activity. The isolation artifacts exhibited the highest activity against HuAChE and HuBuChE with IC50 values of 0.83 ± 0.04 μM and 4.20 ± 0.19 μM for 6-ethoxydihydrochelerythrine and 3.25 ± 0.24 μM and 4.51 ± 0.31 μM for 6-ethoxydihydrosanguinarine. The most active of the naturally-occurring alkaloids was chelidonine, which inhibited both HuAChE and HuBuChE in a dose-dependent manner with IC50 values of 26.8 ± 1.2 μM and 31.9 ± 1.4 μM, respectively.

Design, synthesis and anticholinesterase activity of a novel series of 1-benzyl-4-((6-alkoxy-3-oxobenzofuran-2(3H)-ylidene) methyl) pyridinium derivatives

A novel series of benzofuranone-ylidene-methyl benzylpyridinium derivatives (6a-u) were synthesized as acetylcholinesterase inhibitors. The anticholinesterase activity of synthesized compounds was measured using colorimetric Ellman's method. It was revealed that some synthesized compounds exhibited high anticholinesterase activity, among them compound 6b was the most active compound (IC(50)=10 + or - 6.87 nM).

Acetylcholinesterase and Butyrylcholinesterase Inhibitory Compounds from Eschscholzia californica (Papaveraceae)

The roots and aerial parts of Eschscholzia californica Cham. (Papaveraceae) were extracted with ethanol. Repeated column chromatography, preparative TLC, and crystallization led to the isolation of fourteen isoquinoline alkaloids, the structures of which were determined on the basis of spectroscopic techniques and by comparison with literature values. One of the compounds isolated, 1-(3-hydroxy-4-methoxybenzyl)-2-methyl-6,7-methylenedioxy-1,2,3,4-tetrahydroisoquinoline (14), has not previously been isolated from a natural source. All isolated compounds were tested for human blood acetylcholinesterase (HuAChE) and human plasma butyrylcholinesterase (HuBuChE) inhibition activity. None of the compounds isolated significantly inhibited both HuAChE and HuBuChE, but the two benzylisoquinoline alkaloids, reticuline 9 and 14, showed promising inhibitory activity against HuBuChE.

Synthesis and In Vitro Evaluation of Imidazo[1,2-b]pyridazines as Ligands for β-Amyloid Plaques

A series of imidazo[1,2-b]pyridazine derivatives were synthesized and evaluated for binding to amyloid plaques in vitro using synthetic aggregates of Aβ1-40. Binding affinities of these compounds were found to range from 11.0 to >1000 nM, depending on the various substitution patterns in the 6-position and 2-position. 2-(4'-Dimethylaminophenyl)-6-(methylthio)imidazo[1,2-b]pyridazine (4) showed high binding affinity (K i = 11.0 nM) and might be useful for the development of novel positron emission tomography radiotracers for imaging Aβ plaques.

Procyanidins extracted from the lotus seedpod ameliorate scopolamine-induced memory impairment in mice

The major purpose of this study was to determine the effect of procyanidins extracted from the lotus seedpod (LSPC) on the learning and memory impairments induced by scopolamine (1 mg/kg, i.p.) in mice. The capacities of memory and learning were evaluated by the Morris water maze and the step-down avoidance test. LSPC (50, 100, 150 mg/kg BW, p.o.) significantly reversed scopolamine-induced learning and memory impairments in the Morris water maze test, as evaluated by shortened escape latency and swimming distance. In the step-down avoidance test, LSPC (50, 100, 150 mg/kg BW, p.o.) treatment significantly reduced the number of errors and shortened latency compared with that of scopolamine. In addition, LSPC was also found to inhibit acetyl cholinesterase (AChE) activity. These results of this study suggest that LSPC may play a useful role in the treatment of cognitive impairment caused by AD and aging.

Cognitive-enhancing activity of loganin isolated from Cornus officinalis in scopolamine-induced amnesic mice

We examined anti-amnesic activity of the methanolic extract of Cornus officinalis fruits (COT) and a major constituent, loganin using scopolamine-induced (1 mg/kg body weight, s.c.) amnesic mice with both passive avoidance and the Morris water maze tests. Oral treatment of mice with COT (100 mg/kg body weight) and loganin (1 and 2 mg/kg body weight) significantly mitigated scopolamine-induced memory deficits in passive avoidance test. In the Morris water maze test, oral treatment of loganin significantly ameliorated scopolamine-induced memory deficits showing the formation of long-term and/or short-term spatial memory. Moreover, loganin (2 mg/kg body weight) significantly inhibited acetylcholinesterase activity by as much as 45% of control in the mouse hippocampus. These results indicate that loganin may exert antiamnesic activity in in vivo through acetylcholinesterase inhibition.

QSAR studies on N-aryl derivative activity towards Alzheimer's disease

A Quantitative Structure Activity Relationship (QSAR) study has been an attempted on a series of 88 N-aryl derivatives which display varied inhibitory activity towards both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), targets in Alzheimer’s drug discovery. QSAR models were derived for 53 and 61 compounds for each target, respectively, with the aid of genetic function approximation (GFA) technique using topological, molecular shape, electronic and structural descriptors. The predictive ability of the QSAR model was evaluated using a test set of 26 compounds for AChE (r² _pred = 0.857), (q² = 0.803) and 20 compounds for BChE (r² _pred = 0.882), (q² = 0.857). The QSAR models point out that AlogP98, Wiener, Kappa-1-AM, Dipole-Mag, and CHI-1 are the important descriptors effectively describing the bioactivity of the compounds.

Protective effect of the ethanol extract of Magnolia officinalis and 4-O-methylhonokiol on scopolamine-induced memory impairment and the inhibition of acetylcholinesterase activity

Magnolol, honokiol, and obovatol are well-known bioactive constituents of the bark of Magnolia officinalis and have been used as traditional Chinese medicines for the treatment of neurosis, anxiety, and stroke. We recently isolated novel active compound (named 4-O-methylhonokiol) from the ethanol extract of Magnolia officinalis. The present study aimed to test two different doses of ethanol extracts of Magnolia officinalis (5 and 10 mg/kg/mouse, p.o., 1 week) and 4-O-methylhonokiol (0.75 and 1.5 mg/kg/mouse, p.o., 1 week) administered for 7 days on memory impairment induced by scopolamine (1 mg/kg body weight i.p.) in mice. Memory and learning were evaluated using the Morris water maze and the step-down avoidance test. Both the ethanol extract of Magnolia officinalis and 4-O-methylhonokiol prevented memory impairment induced by scopolamine in a dose-dependent manner. The ethanol extract of Magnolia officinalis and 4-O-methylhonokiol also dose-dependently attenuated the scopolamine-induced increase of acetylcholinesterase (AChE) activity in the cortex and hippocampus of mice, and inhibited AChE activity in vitro with IC₅₀ (12 nM). This study, therefore, suggests that the ethanol extract of Magnolia officinalis and its major ingredient, 4-O-methylhonokiol, may be useful for the prevention of the development or progression of AD.

Cholinergic treatments with emphasis on m1 muscarinic agonists as potential disease-modifying agents for Alzheimer's disease

The only prescribed drugs for treatment of Alzheimer's disease (AD) are acetylcholinesterase inhibitors (e.g., donepezil, rivastigmine, galantamine, and tacrine) and memantine, an NMDA antagonist. These drugs ameliorate mainly the symptoms of AD, such as cognitive impairments, rather than halting or preventing the causal neuropathology. There is currently no cure for AD and there is no way to stop its progression, yet there are numerous therapeutic approaches directed against various pathological hallmarks of AD that are extensively being pursued. In this context, the three major hallmark characteristics of AD (i.e., the CNS cholinergic hypofunction, formation of beta-amyloid plaques, and tangles containing hyperphosphorylated tau proteins) are apparently linked. Such linkages may have therapeutic implications, and this review is an attempt to analyze these versus the advantages and drawbacks of some cholinergic compounds, such as acetylcholinesterase inhibitors, M1 muscarinic agonists, M2 antagonists, and nicotinic agonists. Among the reviewed treatments, M1 selective agonists emerge, in particular, as potential disease modifiers.

Production of the Acetylcholinesterase Inhibitor from Yarrowia lipolytica S-3

The acetylcholinesterase (AChE) inhibitor of Yarrowia lipolytica S-3 was maximally produced when it was incubated at 30℃ for 36 h in an optimal medium containing 1% yeast extract, 2% peptone and 2% glucose, with an initial pH 6.0. The final AChE inhibitory activity under these conditions was an IC50 value of 64 mg/ml. After partial purification of the AChE inhibitor by means of systematic solvent extraction, the final IC50 value of the partially purified AChE inhibitor was 0.75 mg/ml. We prepared a test product by using the partially purified AChE inhibitor and then determined its stability for the development of a new antidementia commercial product. The test product was stable at room temperature for 15 weeks.

Differential effects of two hexahydropyrroloindole carbamate-based anticholinesterase drugs on the amyloid beta protein pathway involved in Alzheimer's disease

One of the main hallmarks of Alzheimer's disease (AD) is the brain deposition of senile plaques made up of toxic amyloid beta-peptide (Abeta), which is derived from a larger protein called the beta-amyloid precursor protein (APP). Both APP processing and cholinesterase activity are affected in the AD brain, but, yet, cholinesterase inhibitors (ChEI) remain the primary Food and Drug Administration approved drugs for AD within the United States. Herein, we evaluated the effects of two clinically relevant drugs on the APP pathway, which is presumably involved in AD pathogenesis. Specifically, we compared the actions of the classical ChEI physostigmine (PHY) and its analog phenserine (PHE) on neuronal cell viability, on IC50 and on levels of different amyloid proteins. Interestingly, these drugs share the same chemical backbone, inhibit acetylcholinesterase with similar potency, but differentially affect APP processing. PHE treatment decreased levels of APP in the human neuroblastoma cells (p=0.009) whereas PHY showed a similar but less-pronounced trend, which did not attain statistical significance. PHE treatment significantly decreased levels of Abeta in human neuroblastoma cells (p=0.02) whereas PHY showed no significant change under the same conditions. The divergent actions of these two structurally related drugs on the amyloid pathway indicate that the mechanisms underpinning the cholinergic and the amyloid-lowering properties for this class of drugs are independent of each other.

Molecular docking and 3D-QSAR studies of 2-substituted 1-indanone derivatives as acetylcholinesterase inhibitors

AIM

To explore the binding mode of 2-substituted 1-indanone derivatives with acetylcholinesterase (AChE) and provide hints for the future design of new derivatives with higher potency and specificity.

METHODS

The GOLD-docking conformations of the compounds in the active site of the enzyme were used in subsequent studies. The highly reliable and predictive three-dimensional quantitative structure-activity relationship (3D-QSAR) models were achieved by comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) methods. The predictive capabilities of the models were validated by an external test set. Moreover, the stabilities of the 3D-QSAR models were verified by the leave-4-out cross-validation method.

RESULTS

The CoMFA and CoMSIA models were constructed successfully with a good cross-validated coefficient (q(2)) and a non-cross-validated coefficient (r(2)). The q(2)and r(2)obtained from the leave-1-out cross validation method were 0.784 and 0.974 in the CoMFA model and 0.736 and 0.947 in the CoMSIA model, respectively. The coefficient isocontour maps obtained from these models were compatible with the geometrical and physicochemical properties of AChE.

CONCLUSION

The contour map demonstrated that the binding affinity could be enhanced when the small protonated nitrogen moiety was replaced by a more hydrophobic and bulky group with a highly partial positive charge. The present study provides a better understanding of the interaction between the inhibitors and AChE, which is helpful for the discovery of new compounds with more potency and selective activity.

Discovery of amide and heteroaryl isosteres as carbamate replacements in a series of orally active gamma-secretase inhibitors

The design of amide and heteroaryl amide isosteres as replacements for the carbamate substructure in previously disclosed 2,6-disubstituted piperidine N-arylsulfonamides is described. In several cases, amides lessened CYP liabilities in this class of gamma-secretase inhibitors. Selected compounds showed significant reduction of Abeta levels upon oral dosing in a transgenic murine model of Alzheimer's disease.

Aqueous and hydroalcoholic extracts of Black Maca (Lepidium meyenii) improve scopolamine-induced memory impairment in mice

Lepidium meyenii Walp. (Brassicaceae), known as Maca, is a Peruvian hypocotyl growing exclusively between 4,000 and 4,500 m altitude in the central Peruvian Andes, particularly in Junin plateau. Previously, Black variety of Maca showed to be more beneficial than other varieties of Maca on learning and memory in ovariectomized mice on the water finding test. The present study aimed to test two different doses of aqueous (0.50 and 2.00 g/kg) and hydroalcoholic (0.25 and 1.00 g/kg) extracts of Black Maca administered for 35 days on memory impairment induced by scopolamine (1mg/kg body weight i.p.) in male mice. Memory and learning were evaluated using the water Morris maze and the step-down avoidance test. Brain acetylcholinesterase (AChE) and monoamine oxidase (MAO) activities in brain were also determined. Both extracts of Black Maca significantly ameliorated the scopolamine-induced memory impairment as measured in both the water Morris maze and the step-down avoidance tests. Black Maca extracts inhibited AChE activity, whereas MAO activity was not affected. These results indicate that Black Maca improves scopolamine-induced memory deficits.

Acetylcholinesterase and butyrylcholinesterase inhibitory compounds from Corydalis cava Schweigg. & Kort

In the course of screening plants used in Danish folk medicine as memory enhancers, a crude methanolic extract of tubers from Corydalis cava showed significant acetylcholinesterase inhibitory activity in a dose-dependent manner. Activity guided fractionation of the methanolic extract resulted in the isolation of three alkaloids, bulbocapnine (1), corydaline (2) and corydine (3) as active constituents. Bulbocapnine inhibited acetylcholinesterase as well as butyrylcholinesterase in a dose-dependent manner with IC(50) values of 40+/-2 microM and 83+/-3 microM, respectively. Corydaline inhibited acetylcholinesterase in a dose-dependent manner with an IC(50) value of 15+/-3 microM and corydine inhibited butyrylcholinesterase in a dose-dependent manner with an IC(50) value of 52+/-4 microM. Corydaline was considered inactive against butyrylcholinesterase and corydine against acetylcholinesterase, due to IC(50)>100 microM.

A practical synthesis of a gamma-secretase inhibitor

A practical and scaleable synthesis of the gamma-secretase inhibitor 1 is reported. The inhibitor consists of a central trisubstituted cyclohexane core with appended propionic acid, 2,5-difluorophenyl, and 4-chlorophenylsulfonyl moieties. Two alternative synthetic strategies, proceeding by way of a common disubstituted cyclohexanone derivative 5, were studied. In the preferred route, conjugate reduction of acrylonitrile derivative 4 with L-Selectride configures the desired relative stereochemistry of the cyclohexane core with >99.9:0.1 dr. A second strategy, based on catalyst-controlled hydrogenation of racemic cyclohexene derivative 2, is more convergent but less diastereoselective (up to 75:25 dr). The common cyclohexanone intermediate 5 was constructed by a regioselective Diels-Alder condensation of a 1,1-disubstituted vinyl sulfone 6 with 2-trimethylsiloxybutadiene.

Mass spectrometry-based screening for inhibitors of beta-amyloid protein aggregation

Alzheimer's disease is the most common cause of the loss of cognitive function among the elderly, and the aggregation and deposition of misfolded beta-amyloid protein (Abeta) contribute to this progressive central nervous system decline. Therefore, compounds that inhibit or even reverse Abeta aggregation might be useful for the treatment or prevention of Alzheimer's disease. To identify potential therapeutic agents for the treatment of Alzheimer's disease, a mass spectrometry-based screening assay was developed to identify and rank order compounds that inhibit the aggregation of Abeta. To carry out this assay, Abeta was incubated with a test compound at 37 degrees C for 20 h followed by ultrafiltration to separate the monomeric Abeta from its aggregates. Aliquots of the ultrafiltrate were analyzed for monomeric Abeta using positive ion electrospray mass spectrometry based on the abundance the quadruply protonated molecule of Abeta at m/z 1083. The calibration curve for Abeta was linear with a correlation coefficient (r2) of >0.99 over the range of at least 11-110 microM. The limit of detection was 0.224 ng (5.18 nM, 10-microL injection), and the limit of quantitation was 0.747 ng (17.2 nM, 10-microL injection). Based on previous reports of compounds that either bind to Abeta or are useful in treating Alzheimer's disease, melatonin, methysticin, 3-indolepropionic acid, and daunomycin were assayed and ranked in order of inhibition of Abeta aggregation. The most effective inhibitor of aggregation of Abeta protein was daunomycin followed in descending order by 3-indolepropionic acid, melatonin, and then methysticin. These data suggest that this ultrafiltration LC-MS screening assay may be used to identify potential therapeutic agents for the treatment of Alzheimer's disease based on the prevention of Abeta aggregation.