Design, synthesis and biological evaluation of novel naturally-inspired multifunctional molecules for the management of Alzheimer's disease.

In our overall goal to overcome the limitations associated with natural products for the management of Alzheimer's disease and to develop in-vivo active multifunctional cholinergic inhibitors, we embarked on the development of ferulic acid analogs. A systematic SAR study to improve upon the cholinesterase inhibition of ferulic acid with analogs that also had lower logP was carried out. Enzyme inhibition and kinetic studies identified compound 7a as a lead molecule with preferential acetylcholinesterase inhibition (AChE IC50 = 5.74 ± 0.13 µM; BChE IC50 = 14.05 ± 0.10 µM) compared to the parent molecule ferulic acid (% inhibition of AChE and BChE at 20 µM, 15.19 ± 0.59 and 19.73 ± 0.91, respectively). Molecular docking and dynamics studies revealed that 7a fits well into the active sites of AChE and BChE, forming stable and strong interactions with key residues Asp74, Trp286, and Tyr337 in AChE and with Tyr128, Trp231, Leu286, Ala328, Phe329, and Tyr341 in BChE. Compound 7a was found to be an efficacious antioxidant in a DPPH assay (IC50 = 57.35 ± 0.27 µM), and it also was able to chelate iron. Data from atomic force microscopy images demonstrated that 7a was able to modulate aggregation of amyloid ß1-42. Upon oral administration, 7a exhibited promising in-vivo activity in the scopolamine-induced AD animal model and was able to improve spatial memory in cognitive deficit mice in the Y-maze model. Analog 7a could effectively reverse the increased levels of AChE and BChE in scopolamine-treated animals and exhibited potent ex-vivo antioxidant properties. These findings suggest that 7a can act as a lead molecule for the development of naturally-inspired multifunctional molecules for the management of Alzheimer's and other neurodegenerative disorders.

Hwangryunhaedok-Tang Exerts Neuropreventive Effect on Memory Impairment by Reducing Cholinergic System Dysfunction and Inflammatory Response in a Vascular Dementia Rat Model.

Hwangryunhaedok-tang (HRT) is a traditional oriental herbal formula used in Asian countries for treating inflammatory diseases and controlling fever. Our present study aimed to determine whether HRT has therapeutic effects for patients with vascular dementia (VaD) using a bilateral common carotid artery occlusion (BCCAO) rat model and assessing spatial memory impairment and activation of neuroinflammation. BCCAO was performed in male Sprague Dawley rats to induce VaD, and oral HRT was administered daily for 30 d. Our data showed that HRT ameliorated BCCAO-induced memory and cognitive impairment in behavioral tests. In addition, HRT reversed cholinergic dysfunction and neuronal damage in the hippocampus of BCCAO rats. Furthermore, HRT attenuated microglial activation and reduced the phosphorylation of p38 mitogen-activated protein kinase and c-Jun N-terminal kinase (JNK) induced by BCCAO. Simultaneous high-performance liquid chromatography analysis of HRT using index compounds from the herbal composition revealed that both HRT ethanol extract and commercial HRT granules primarily comprise geniposide, baicalin, and berberine. Our study showed that HRT administration resulted in the prevention of neuronal injury induced by BCCAO through improvement of cholinergic dysfunction and inhibition of neuroinflammatory responses, suggesting that HRT may have potential as a treatment for VaD.

New Flavone-Cyanoacetamide Hybrids with a Combination of Cholinergic, Antioxidant, Modulation of ß-Amyloid Aggregation, and Neuroprotection Properties as Innovative Multifunctional Therapeutic Candidates for Alzheimer's Disease and Unraveling Their Mechanism of Action with Acetylcholinesterase.

In line with the modern multi-target-directed ligand paradigm of Alzheimer's disease (AD), a series of 19 compounds composed of flavone and cyanoacetamide groups have been synthesized and evaluated as multifunctional agents against AD. Biological evaluation demonstrated that compounds 7j, 7n, 7o, 7r, and 7s exhibited excellent inhibitory potency (AChE, IC50 of 0.271 ± 0.012 to 1.006 ± 0.075 µM) and good selectivity toward acetylcholinesterase, significant antioxidant activity, good modulation effects on self-induced Aß aggregation, low cytotoxicity, and neuroprotection in human neuroblastoma SK-N-SH cells. Further, an inclusive study on the interaction of 7j, 7n, 7o, 7r, and 7s with AChE at physiological pH 7.2 using fluorescence, circular dichroism, and molecular docking methods suggested that these derivatives bind strongly to the peripheral anionic site of AChE mostly through hydrophobic interactions. Overall, the multifunctional profiles and strong AChE binding affinity highlight these compounds as promising prototypes for further pursuit of innovative multifunctional drugs for AD.

Novel cinnamamide-dibenzylamine hybrids: Potent neurogenic agents with antioxidant, cholinergic, and neuroprotective properties as innovative drugs for Alzheimer's disease.

By using fragments endowed with interesting and complementary properties for the treatment of Alzheimer's disease (AD), a novel series of cinnamamide-dibenzylamine hybrids have been designed, synthesized, and evaluated biologically. In vitro assay indicated that most of the target compounds exhibited a significant ability to inhibit ChEs, strong potency inhibitory of self-induced ß-amyloid (Aß) aggregation and to act as potential antioxidants and biometal chelators. A Lineweaver-Burk plot and molecular modeling study showed that compound 7f targeted both the CAS and PAS of AChE. In addition, compound 7f could chelate metal ions, reduce PC12 cells death induced by oxidative stress and penetrate the blood-brain barrier (BBB). Overall, all of these outstanding in vitro results in combination with promising in vivo outcomes highlighted derivative 7f as the lead structure worthy of further investigation.

Anxiolytic-like, stimulant and neuroprotective effects of Ilex paraguariensis extracts in mice.

Yerba-mate (Ilex paraguariensis St. Hil.) is the most used beverage in Latin America with approximately 426 thousand of tons consumed per year. Considering the broad use of this plant, we aimed to investigate the anxiety-like and stimulant activity of both the hydroethanolic (HE) and aqueous (AE) extracts from leaves of I. paraguariensis. Swiss mice were treated with I. paraguariensis HE or AE chronically or acutely, respectively, followed by evaluation in the elevated plus-maze (EPM; anxiety-like paradigm), open field (OF; locomotor activity) or the step-down avoidance task (memory assessment). Following behavioral protocols the brains were collected for evaluation of acetylcholinesterase (AChE) activity ex vivo. Chronic treatment with HE induced an anxiolytic-like effect and increased motor activity besides augmented AChE activity. Additionally, acute treatment with AE prevented the scopolamine-induced memory deficit in the step-down avoidance task. Overall, our results indicate the importance of the I. paraguariensis-induced CNS effects, since it is a widely used nutraceutical. We have reported anxiolytic, stimulant and neuroprotective effects for this plant species. These effects are potentially modulated by the cholinergic system as well as by caffeine.

Aqueous extracts of Cordyceps militaris (Ascomycetes) lower the levels of plasma glucose by activating the cholinergic nerve in streptozotocin-induced diabetic rats.

In our previous research, Cordyceps militaris (CM) had a hypoglycemic effect in normal rats. In this study we wanted to elucidate whether CM also had an effect on diabetic rats. Twelve rats with streptozotocin-induced diabetes were separated randomly into 2 groups. First, aqueous extracts of CM 10 mg/kg (CM group) or saline (control group) was fed to the rats; then the plasma glucose levels were assayed. Second, the signaling proteins IRS-1 and GLUT-4 collected from the muscle were detected. Finally, another 2 groups of rats were injected with atropine 0.1 mg/kg intraperitoneally just before the CM/saline feeding, and the assays mentioned above were repeated. Blood glucose decreased 7.2% in the CM group but only 1.5% in the control group (P < 0.05). The IRS-1 signal was 2.9-fold higher than actin in the CM group but only 0.8-fold higher in the control group (P < 0.005). In GLUT-4 signal, the difference was 1.7- vs. 0.6-fold, respectively, compared with actin (P < 0.05). However, atropine injection made CM-induced hypoglycemia or elevation of IRS-1 and GLUT-4 not significant. In conclusion, CM had a hypoglycemic effect in diabetic rats and atropine blocked it. Therefore, the cholinergic activation also was considered to be involved in the hypoglycemic effect of CM in rats with streptozotocin-induced diabetes.

Discovery of a selective M4 positive allosteric modulator based on the 3-amino-thieno[2,3-b]pyridine-2-carboxamide scaffold: development of ML253, a potent and brain penetrant compound that is active in a preclinical model of schizophrenia.

Herein we report a next generation muscarinic receptor 4 (M(4)) positive allosteric modulator (PAM), ML253 which exhibits nanomolar activity at both the human (EC(50)=56 nM) and rat (EC(50)=176 nM) receptors and excellent efficacy by the left-ward shift of the ACh concentration response curve (fold shift, human=106; rat=50). In addition, ML253 is selective against the four other muscarinic subtypes, displays excellent CNS exposure and is active in an amphetamine-induced hyperlocomotion assay.

Gastrointestinal stimulant effect of Urginea indica Kunth. and involvement of muscarinic receptors.

Urginea indica Kunth. (Family; Liliaceae) was studied for its gastrointestinal stimulant effect to rationalize the traditional medicinal uses as a digestive aid, stomachic and laxative. The crude aqueous-methanol extract of Urginea indica bulb (Ui.Cr) was tested on mice and isolated gut preparations. Ui.Cr, which was tested positive for alkaloids, tannins and coumarins, increased faecal output and accelerated charcoal meal transit in mice (6-12 mg/kg, p.o.), similar to that caused by carbachol (10 mg/kg). Ui.Cr (0.01-1 mg/mL) caused a spasmogenic effect in guinea-pig ileum that was reproduced in rabbit jejunum (0.01-0.3 mg/mL) followed by relaxation at a higher concentration. Like carbachol, the stimulant effect of Ui.Cr was blocked by atropine, suggesting the activation of muscarinic receptors mediating the prokinetic effect. Ui.Cr (0.01-5.0 mg/mL) also inhibited K(+) (80 mm)-induced contraction in rabbit jejunum and shifted the Ca(2+) concentration-response curves to the right, similar to verapamil, a standard calcium channel blocker. These data, indicating the presence of a gastrointestinal stimulant effect in Urginea indica possibly mediated through a cholinergic mechanism, provide a rationale for the use of Urginea indica in indigestion and constipation. The presence of a calcium antagonist effect in the plant may help to alleviate untoward effects of the plant that may result from an excessive increase in gut motility.

Muscarinic-dependent inhibition of gastric emptying and intestinal motility by fractions of Maytenus ilicifolia Mart ex. Reissek.

ETHNOPHARMACOLOGICAL RELEVANCE: Maytenus ilicifolia Mart. ex. Reissek (Celastraceae) is widely used in Brazilian folk medicine to treat gastric disturbances. AIM OF THE STUDY: This work intended to characterize the effects of Maytenus ilicifolia on gastrointestinal motility. MATERIALS AND METHODS: Gastric emptying and intestinal transit were measured in the same animal. Mice received a semisolid marked with phenol red, half an hour after treatment with extracts. The amount of marker in the stomach and the distance reached in the intestine after 15 min were measured as index of gastrointestinal emptying and intestinal transit, respectively. RESULTS: Intraperitoneal administration of a flavonoid-rich extract potently reduced the gastric emptying (ED(50)=89 mg/kg) and the intestinal transit (ED(50)=31 mg/kg) of mice. Bio-guided purification of the flavonoid-rich extract by chemical partition with solvents of decreasing polarity yielded fraction insF with about 12-14 times higher activity than the initial flavonoid extract in both the gastric emptying and the intestinal transit. The inhibitory effects of the insF (9.7 mg/kg, i.p.) on gastric emptying and intestinal transit were reversed by co-administration of bethanechol (10 mg/kg, s.c.) but not by co-administration of metoclopramide (30 mg/kg, p.o.) indicating muscarinic but not dopaminergic interaction of the compounds of Maytenus. Chemical investigation of the insF fraction by HPLC-MS allowed the identification of 4 free flavonoids (catechin, epicatechin, quercetin and kaempferol), 29 flavonol glycosides and 8 tannins. The flavonol glycosides ranged from 1 to 4 monosaccharide units, having mainly quercetin and kaempferol as aglycone moieties, and the tannins were composed by catechin/epicatechin and/or afzelechin/epiafzelechin. CONCLUSIONS: Overall, the results indicate that the components of Maytenus ilicifolia have a potential use in the treatment of gastrointestinal motility disturbances such as diarrhea.

Evaluation of the cholinergic and adrenergic effects of two tropane alkaloids from Erythroxylum pervillei.

Pervilleine A is an aromatic ester tropane alkaloid from Erythroxylum pervillei that has shown promising activity as a multidrug resistance inhibitor. Due to its structural similarity with the well known (-)-hyoscyamine and (-)-cocaine, the cholinergic and adrenergic activities of pervilleine A were evaluated. At 30 microm (+/-)-pervilleine A hydrochloride exhibited non-competitive inhibition of the cholinergic response in the guinea-pig ileum and did not affect the carbachol-induced contraction of the rat anococcygeus smooth muscle. (+/-)-Pervilleine A hydrochloride blocked nonspecifically the vascular response of (-)-norepinephrine in the rat aorta ring, while the contractile response of rat vas deferens to (-)-norepinephrine was not affected significantly at a 100 microm concentration. An analogue of pervilleine A, (+/-)-pervilleine H, without a 6-O-trans-3,4,5-trimethoxycinnamoyl ester substituent required for anti-multidrug resistance activity, did not exhibit any effects in these experiments. The data suggest that (+/-)-pervilleine A hydrochloride has weak nonspecific anticholinergic and vascular antiadrenergic activities. The lack of significant cholinergic and adrenergic receptor-mediated activities may be considered advantageous for the further development of pervilleine A as a new adjuvant in cancer chemotherapy.

Phosphate concentrations in antiglaucoma medication.

BACKGROUND: Eye drops may contain phosphates as part of their buffer system. In the presence of epithelial keratopathy a high concentration of phosphate favours corneal calcification. To date European legislation does not require a quantitative declaration of the phosphates since buffers are regarded as additives. The knowledge of the phosphate concentration in medications helps to prevent corneal calcifications. Our study gives an overview on the amount of phosphate contained in antiglaucoma drops. METHODS: 21 samples of commercially available antiglaucoma drops were tested. The quantification of phosphate was performed using the molybdate method on a Modular P autoanalyzer. RESULTS: 10 of 21 (47 %) glaucoma drops had a phosphate concentration above physiological levels (> 1.45 mmol/L). A concentration higher than 100 mmol/L was found in four preparations that contained timolol. CONCLUSIONS: Many antiglaucoma drops contain unphysiological levels of phosphate, very high concentrations are found in some beta-blockers. These preparations have the potential to favour the formation of insoluble crystalline calcium phosphate deposits when used on a damaged corneal surface, and should therefore be avoided.

Presence of cholinergic and calcium antagonist constituents in Saussurea lappa explains its use in constipation and spasm.

This study was carried out to provide a scientific basis for the traditional use of Saussurea lappa, in constipation and spasms. Isolated tissue preparations were used to see if the aqueous-methanol crude extract of the S. lappa root (Sl.Cr) contains gut stimulatory and inhibitory constituents. In isolated guinea-pig ileum, a quiescent preparation, Sl.Cr caused a concentration-dependent (0.3-5.0 mg/mL) spasmogenic effect, with the maximum effect reaching 91% of the acetylcholine maximum. A further increase in concentration caused a declining effect, indicating the presence of spasmolytic constituent(s). The spasmolytic effect was more marked in the spontaneously contracting rabbit jejunum and in the atropinized preparations. The spasmolytic effect was mediated through calcium channel blocking (CCB) activity, as evident by its inhibitory effect against high K(+) (80 mm)-induced contraction and displacement of the Ca(++) concentration-response curves to the right. These data indicate that the crude extract of Sl.Cr contains gut stimulatory constituent(s) of cholinergic-type providing a scientific basis for its use in constipation. The presence of spasmolytic constituents of CCB-type more evident in the spontaneous contracting gut preparation may explain its use in spasms.

Pharmacological effects of Eugenia punicifolia (Myrtaceae) in cholinergic nicotinic neurotransmission.

The effects of the aqueous crude extract (5%) of Eugenia punicifolia on cholinergic nicotinic neurotransmission were investigated. Actions of aqueous crude extract over the inhibitory effect of the cholinergic nicotinic antagonists gallamine or pancuronium, on contractions induced by electrical stimulation of phrenic nerve of rat diaphragm, were studied. Tissues were mounted as for isotonic contractions and stimulation was delivered at submaximal voltage. Addition of Eugenia punicifolia did not alter the amplitude of twitch contraction. Gallamine (IC(50): 28.8+/-0.51 microM) or pancuronium (IC(50): 3.16+/-0.11 microM) completely inhibited twitch contractions. After the maximum effect of the antagonists was achieved, addition of the aqueous crude extract (0.5-1.0 mL) totally recovered the responses to electrical stimulation. Neostigmine, a reversible acethylcholinesterase inhibitor, partially recovered responses (49.70+/-6.90% at 1 microM). In another series of experiments, previous incubation of the extract (0.5 mL) shifted to the right inhibitory concentration-response curves for the antagonists gallamine (IC(50) before E. punicifolia: 35.8+/-1.61 microM; IC(50), after E. punicifolia: 2.24+/-0.04 mM) and pancuronium (IC(50), before E. punicifolia: 3.55+/-0.13 microM; IC(50), after E. punicifolia: 0.39+/-0.01 mM). Our results show that the aqueous extract of E. punicifolia recovered the action of competitive nicotinic antagonists at the neuromuscular junction. A receptor-mediated mechanism or the possibilities of interactions of the extract with the enzyme acethylcholinesterase, however, remain to be investigated.

Medicinal plants and Alzheimer's disease: from ethnobotany to phytotherapy.

The use of complementary medicines, such as plant extracts, in dementia therapy varies according to the different cultural traditions. In orthodox Western medicine, contrasting with that in China and the Far East for example, pharmacological properties of traditional cognitive- or memory-enhancing plants have not been widely investigated in the context of current models of Alzheimer's disease. An exception is Gingko biloba in which the gingkolides have antioxidant, neuroprotective and cholinergic activities relevant to Alzheimer's disease mechanisms. The therapeutic efficacy of Ginkgo extracts in Alzheimer's disease in placebo controlled clinical trials is reportedly similar to currently prescribed drugs such as tacrine or donepezil and, importantly, undesirable side effects of Gingko are minimal. Old European reference books, such as those on medicinal herbs, document a variety of other plants such as Salvia officinalis (sage) and Melissa officinalis (balm) with memory-improving properties, and cholinergic activities have recently been identified in extracts of these plants. Precedents for modern discovery of clinically relevant pharmacological activity in plants with long-established medicinal use include, for example, the interaction of alkaloid opioids in Papaver somniferum (opium poppy) with endogenous opiate receptors in the brain. With recent major advances in understanding the neurobiology of Alzheimer's disease, and as yet limited efficacy of so-called rationally designed therapies, it may be timely to re-explore historical archives for new directions in drug development. This article considers not only the value of an integrative traditional and modern scientific approach to developing new treatments for dementia, but also in the understanding of disease mechanisms. Long before the current biologically-based hypothesis of cholinergic derangement in Alzheimer' s disease emerged, plants now known to contain cholinergic antagonists were recorded for their amnesia- and dementia-inducing properties.