Screening of β-secretase and acetylcholinesterase inhibitors from plant resources

Evaluation of Mollugo oppositifolia Linn. as cholinesterase and β-secretase enzymes inhibitor

Mollugo oppositifolia Linn. is traditionally used in neurological complications. The study aimed to investigate in-vitro neuroprotective effect of the plant extracts through testing against acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase linked to Alzheimer's disease (AD). To understand the safety aspects, the extracts were tested for CYP450 isozymes and human hepatocellular carcinoma cell (HepG2) inhibitory potential. The heavy metal contents were estimated using atomic absorption spectroscopy (AAS). Further, the antioxidant capacities as well as total phenolic content and total flavonoid content (TFC) were measured spectrophotometrically. UPLC-QTOF-MS/MS analysis was employed to identify phytometabolites present in the extract. The interactions of the ligands with the target proteins (AChE, BChE, and BACE-1) were studied using AutoDockTools 1.5.6. The results showed that M. oppositifolia extract has more selectivity towards BChE (IC₅₀ = 278.23 ± 1.89 μg/ml) as compared to AChE (IC₅₀ = 322.87 ± 2.05 μg/ml). The IC₅₀ value against β-secretase was 173.93 μg/ml. The extract showed a CC₅₀ value of 965.45 ± 3.07 μg/ml against HepG2 cells and the AAS analysis showed traces of lead 0.02 ± 0.001 which was found to be within the WHO prescribed limits. Moreover, the IC₅₀ values against CYP3A4 (477.03 ± 2.01 μg/ml) and CYP2D6 (249.65 ± 2.46 μg/ml) isozymes justify the safety aspects of the extract. The in silico molecular docking analysis of the target enzymes showed that the compound menthoside was found to be the most stable and showed a good docking score among all the identified metabolites. Keeping in mind the multi-targeted drug approach, the present findings suggested that M. oppositifolia extract have anti-Alzheimer's potential.

From kitchen to clinic: Pharmacotherapeutic potential of common spices in Indian cooking in age-related neurological disorders

Aging is described as an advanced time-related collection of changes that may negatively affect with the risk of several diseases or death. Aging is a main factor of several age-related neurological disorders, including neurodegenerative diseases (Alzheimer’s disease, Parkinson’s disease, and dementia), stroke, neuroinflammation, neurotoxicity, brain tumors, oxidative stress, and reactive oxygen species (ROS). Currently available medications for age-related neurological disorders may lead to several side effects, such as headache, diarrhea, nausea, gastrointestinal (GI) diseases, dyskinesia, and hallucinosis. These days, studies on plant efficacy in traditional medicine are being conducted because herbal medicine is affordable, safe, and culturally acceptable and easily accessible. The Indian traditional medicine system called Ayurveda uses several herbs and medicinal plants to treat various disorders including neurological disorders. This review aims to summarize the data on the neuroprotective potential of the following common Indian spices widely used in Ayurveda: cumin (Cuminum cyminum (L.), Apiaceae), black cumin (Nigella sativa (L.), Ranunculaceae), black pepper (Piper nigrum (L.), Piperaceae), curry leaf tree (Murraya koenigii (L.), Spreng Rutaceae), fenugreek (Trigonella foenum-graecum (L.), Fabaceae), fennel (Foeniculum vulgare Mill, Apiaceae), cardamom (Elettaria cardamomum (L.) Maton, Zingiberaceae), cloves (Syzygium aromaticum (L.) Merr. & L.M.Perry, Myrtaceae), and coriander (Coriandrum sativum (L.), Apiaceae) in age-related neurological disorders.

Mechanism and Regulation of Microglia Polarization in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is the most lethal subtype of stroke, but effective treatments are lacking, and neuroinflammation plays a key role in the pathogenesis. In the innate immune response to cerebral hemorrhage, microglia first appear around the injured tissue and are involved in the inflammatory cascade response. Microglia respond to acute brain injury by being activated and polarized to either a typical M1-like (pro-inflammatory) or an alternative M2-like (anti-inflammatory) phenotype. These two polarization states produce pro-inflammatory or anti-inflammatory. With the discovery of the molecular mechanisms and key signaling molecules related to the polarization of microglia in the brain, some targets that regulate the polarization of microglia to reduce the inflammatory response are considered a treatment for secondary brain tissue after ICH damage effective strategies. Therefore, how to promote the polarization of microglia to the M2 phenotype after ICH has become the focus of attention in recent years. This article reviews the mechanism of action of microglia’s M1 and M2 phenotypes in secondary brain injury after ICH. Moreover, it discusses compounds and natural pharmaceutical ingredients that can polarize the M1 to the M2 phenotype.

Piperine and Its Metabolite’s Pharmacology in Neurodegenerative and Neurological Diseases

Piperine (PIP) is an active alkaloid of black and long peppers. An increasing amount of evidence is suggesting that PIP and its metabolite’s could be a potential therapeutic to intervene different disease conditions including chronic inflammation, cardiac and hepatic diseases, neurodegenerative diseases, and cancer. In addition, the omnipresence of PIP in food and beverages made this compound an important investigational material. It has now become essential to understand PIP pharmacology and toxicology to determine its merits and demerits, especially its effect on the central nervous system (CNS). Although several earlier reports documented that PIP has poor pharmacokinetic properties, such as absorption, bioavailability, and blood–brain barrier permeability. However, its interaction with metabolic enzyme cytochrome P450 superfamily and competitive hydrophobic interaction at Monoamine oxide B (MAO-B) active site have made PIP both a xenobiotics bioenhancer and a potential MAO-B inhibitor. Moreover, recent advancements in pharmaceutical technology have overcome several of PIP’s limitations, including bioavailability and blood–brain barrier permeability, even at low doses. Contrarily, the structure activity relationship (SAR) study of PIP suggesting that its several metabolites are reactive and plausibly responsible for acute toxicity or have pharmacological potentiality. Considering the importance of PIP and its metabolites as an emerging drug target, this study aims to combine the current knowledge of PIP pharmacology and biochemistry with neurodegenerative and neurological disease therapy.

A metabolite panel that differentiates Alzheimer's disease from other dementia types

Introduction

Alzheimer's disease (AD) is associated with altered metabolites. This study aimed to determine the validity of using circulating metabolites to differentiate AD from other dementias.

Methods

Blood metabolites were measured in three data sets. Data set 1 (controls, 27; AD, 28) was used for analyzing differential metabolites. Data set 2 (controls, 93; AD, 92) was used to establish a diagnostic AD model with use of a metabolite panel. The model was applied to Data set 3 (controls, 76; AD, 76; other dementias, 205) to verify its capacity for differentiating AD from other dementias.

Results

Data set 1 revealed 7 upregulated and 77 downregulated metabolites. In Data set 2, a panel of 11 metabolites was included in a model that could distinguish AD from controls. In Data set 3, this panel was used to successfully differentiate AD from other dementias.

Discussion

This study revealed an AD‐specific panel of 11 metabolites that may be used for AD diagnosis.

Inhibitory Activities of Sulfur Compounds in Garlic Essential Oil against Alzheimer's Disease-Related Enzymes and Their Distribution in the Mouse Brain

Alzheimer's disease (AD) is the most common neurodegenerative disease. Garlic reportedly has various physiological effects, including a role in protecting against dementia. However, the action mechanisms of garlic on AD are not entirely clear. In this study, we investigated the inhibitory activity of garlic essential oil (GEO) against AD-related enzymes and evaluated the distribution of active substances in GEO to the brain. We found that several sulfur compounds in GEO significantly inhibited AD-related enzymes. Sulfur compounds were detected in the serum and brain 6 h post administration. The ratios of allyl mercaptan (24.0 ± 3.9%) and allyl methyl sulfide (49.8 ± 15.6%) in the brain were significantly higher than those in GEO, while those of dimethyl trisulfide (0.89 ± 34.8%), allyl methyl trisulfide (0.41 ± 19.0%), and diallyl trisulfide (0.43 ± 72.8%) in the brain were significantly lower than those in GEO. Similar results were observed in the serum, suggesting that the organosulfur compounds were converted to allyl mercaptan or allyl methyl sulfide in the body. Although allyl mercaptan and allyl methyl sulfide are not the main components of GEO, they might be key molecules to understand the bioactivities of GEO in the body.

Acetylcholinesterase Inhibitory Potential of Various Sesquiterpene Analogues for Alzheimer's Disease Therapy

Alzheimer's disease (AD) is a gradually growing irreversible illness of the brain that almost affects every fifth person (aged > 80 years) in the world. World Health Organization (WHO) also revealed that the prevalence of this disease will enhance (upto double) significantly upto 2030. The poor cholinergic transmission at the synapse is considered to be one of the main reasons behind the progression and occurrence of this disorder. Natural inhibitors of acetylcholine (ACh) such as galanthamine and rivastigmine are used commercially in the treatmentof AD. The biomolecules such assesquiterpenes, possess a great structural diversity and are responsible for a plethora of pharmacological properties. The potential of various sesquiterpenes as anticholinesterase has been reviewed in this article. For this purpose, the various databases, mainly PubMed, Scopus, and Web of Science were investigatedwith different keywords such as "sesquiterpenes+acetylcholinesterase" and "sesquiterpenes+cholinesterase+inhibitors" in the surveyed time frame (2010-2020). A vast literature was evident in the last decade, which affirms the potential of various sesquiterpenes in the improvement of cholinergic transmission by inhibiting the AChE. After data analysis, it was found that 12 compounds out of a total of 58 sesquiterpenes were reported to possess IC50 < 9μM and can be considered as potential candidates for the improvement of learning and memory. Sesquiterpene is an important category of terpenoids, found to possess a large spectrum of biological activities. The outcome of the review clearly states that sesquiterpenes (such as amberboin, lipidiol,etc) from herbs could offer fresh, functional compounds for possible prevention and treatment of AD.

Designing peptide nanoparticles for efficient brain delivery

The targeted delivery of therapeutic compounds to the brain is arguably the most significant open problem in drug delivery today. Nanoparticles (NPs) based on peptides and designed using the emerging principles of molecular engineering show enormous promise in overcoming many of the barriers to brain delivery faced by NPs made of more traditional materials. However, shortcomings in our understanding of peptide self-assembly and blood-brain barrier (BBB) transport mechanisms pose significant obstacles to progress in this area. In this review, we discuss recent work in engineering peptide nanocarriers for the delivery of therapeutic compounds to the brain: from synthesis, to self-assembly, to in vivo studies, as well as discussing in detail the biological hurdles that a nanoparticle must overcome to reach the brain.

Neuroprotection: Targeting Multiple Pathways by Naturally Occurring Phytochemicals

With the increase in the expectancy of the life span of humans, neurodegenerative diseases (NDs) have imposed a considerable burden on the family, society, and nation. In defiance of the breakthroughs in the knowledge of the pathogenesis and underlying mechanisms of various NDs, very little success has been achieved in developing effective therapies. This review draws a bead on the availability of the nutraceuticals to date for various NDs (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, vascular cognitive impairment, Prion disease, Spinocerebellar ataxia, Spinal muscular atrophy, Frontotemporal dementia, and Pick's disease) focusing on their various mechanisms of action in various in vivo and in vitro models of NDs. This review is distinctive in its compilation to critically review preclinical and clinical studies of the maximum phytochemicals in amelioration and prevention of almost all kinds of neurodegenerative diseases and address their possible mechanism of action. PubMed, Embase, and Cochrane Library searches were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical updates. The results from preclinical studies demonstrate the efficacious effects of the phytochemicals in various NDs while clinical reports showing mixed results with promise for phytochemical use as an adjunct to the conventional treatment in various NDs. These studies together suggest that phytochemicals can significantly act upon different mechanisms of disease such as oxidative stress, inflammation, apoptotic pathways, and gene regulation. However, further clinical studies are needed that should include the appropriate biomarkers of NDs and the effect of phytochemicals on them as well as targeting the appropriate population.

Metabolomics markers in Neurology: current knowledge and future perspectives for therapeutic targeting

INTRODUCTION

Metabolomics is an emerging approach providing new insights into the metabolic changes and underlying mechanisms involved in the pathogenesis of neurological disorders.

AREAS COVERED

Here, the authors present an overview of the current knowledge of metabolic profiling (metabolomics) to provide critical insight on the role of biochemical markers and metabolic alterations in neurological diseases.

EXPERT OPINION

Elucidation of characteristic metabolic alterations in neurological disorders is crucial for a better understanding of their pathogenesis, and for identifying potential biomarkers and drug targets. Nevertheless, discrepancies in diagnostic criteria, sample handling protocols, and analytical methods still affect the generalizability of current study results.

β-Caryophyllene Inhibits Cell Proliferation through a Direct Modulation of CB2 Receptors in Glioblastoma Cells

Glioblastomas are aggressive cancers characterized by uncontrolled proliferation and inflammation. b-caryophyllene (BCP) is a cannabinoid receptor 2 (CB2) agonist that showed an important anti-inflammatory effect through the interaction of CB2 and peroxisome proliferator-activated receptor gamma (PPARg) receptors. BCP effects were investigated in an in vitro model of glioblastoma. U-373 and U87, derived from a human glioblastoma, and human glioma stem-like cells (GSCs) were treated with BCP at different doses and time-points. AM360, a specific CB2 antagonist, was added 2 h before BCP treatment. BCP showed a significant anti-proliferative effect, reducing cell viability, inhibiting cell cycle, and increasing apoptosis, as demonstrated by Tunel assay, caspase-3 and caspase -9 activation. In addition, the pro-apoptotic BAX expression was increased, whereas the anti-apoptotic Bcl-2 expression was reduced. Treatment with BCP decreased Beclin-1, LC3 and p62/SQSTM1 expression, indicating a possible switch of autophagy to apoptosis. BCP’s anti-inflammatory effect was demonstrated by NF-κB reduction, PPARg activation and TNF-a decrease; BCP significantly reduced Jun N-Terminal Kinase (JNK) expression as a consequence of TNF-α inhibition. AM360 abrogated BCP effects, thus demonstrating the BCP mechanism of action through the CB2 receptor. These findings let us hypothesize that BCP may act as a tumor suppressor in glioblastoma, acting on CB2 receptor and modulating JNK.

The Additive Effects of Low Dose Intake of Ferulic Acid, Phosphatidylserine and Curcumin, Not Alone, Improve Cognitive Function in APPswe/PS1dE9 Transgenic Mice

Alzheimer's disease (AD) is the most common form of dementia and its prevention and treatment is a worldwide issue. Many natural components considered to be effective against AD have been identified. However, almost all clinical trials of these components for AD reported inconclusive results. We thought that multiple factors such as amyloid β (Aβ) and tau progressed the pathology of AD and that a therapeutic effect would be obtained by using multiple active ingredients with different effects. Thus, in this study, we treated ferulic acid (FA), phosphatidylserine (PS) and curcumin (Cur) in combination or alone to APPswe/PS1dE9 transgenic mice and evaluated cognitive function by Y-maze test. Consequently, only the three-ingredient group exhibited a significant improvement in cognitive function compared to the control group. In addition, we determined the amounts of Aβ, brain-derived neurotrophic factor (BDNF), interleukin (IL)-1β, acetylcholine and phosphorylated tau in the mouse brains after the treatment. In the two-ingredient (FA and PS) group, a significant decrease in IL-1β and an increasing trend in acetylcholine were observed. In the Cur group, significant decreases in Aβ and phosphorylated tau and an increasing trend in BDNF were observed. In the three-ingredient group, all of them were observed. These results indicate that the intake of multiple active ingredients with different mechanisms of action for the prevention and treatment of AD.

Potential Therapeutic Approaches to Alzheimer's Disease By Bioinformatics, Cheminformatics And Predicted Adme-Tox Tools

BACKGROUND

Alzheimer's disease (AD) is considered a severe, irreversible and progressive neurodegenerative disorder. Currently, the pharmacological management of AD is based on a few clinically approved acethylcholinesterase (AChE) and N-methyl-D-aspartate (NMDA) receptor ligands, with unclear molecular mechanisms and severe side effects.

METHODS

Here, we reviewed the most recent bioinformatics, cheminformatics (SAR, drug design, molecular docking, friendly databases, ADME-Tox) and experimental data on relevant structurebiological activity relationships and molecular mechanisms of some natural and synthetic compounds with possible anti-AD effects (inhibitors of AChE, NMDA receptors, beta-secretase, amyloid beta (Aβ), redox metals) or acting on multiple AD targets at once. We considered: (i) in silico supported by experimental studies regarding the pharmacological potential of natural compounds as resveratrol, natural alkaloids, flavonoids isolated from various plants and donepezil, galantamine, rivastagmine and memantine derivatives, (ii) the most important pharmacokinetic descriptors of natural compounds in comparison with donepezil, memantine and galantamine.

RESULTS

In silico and experimental methods applied to synthetic compounds led to the identification of new AChE inhibitors, NMDA antagonists, multipotent hybrids targeting different AD processes and metal-organic compounds acting as Aβ inhibitors. Natural compounds appear as multipotent agents, acting on several AD pathways: cholinesterases, NMDA receptors, secretases or Aβ, but their efficiency in vivo and their correct dosage should be determined.

CONCLUSION

Bioinformatics, cheminformatics and ADME-Tox methods can be very helpful in the quest for an effective anti-AD treatment, allowing the identification of novel drugs, enhancing the druggability of molecular targets and providing a deeper understanding of AD pathological mechanisms.

Chemical Diversity of β-Secretase Inhibitors From Natural Resources

Reports on β-secretase inhibitors of natural origin are listed in order to reveal their chemical diversity. Various types of compounds were found to inhibit β-secretase, and natural resources included a wide spectrum of biological species. Among them, some triterpenes and moracin derivatives, which are nonpeptidic compounds, were determined to be competitive inhibitors. In addition, no peptide compounds were reported from natural resources. These points will be clarified in future studies.

High-resolution metabolomic profiling of Alzheimer's disease in plasma

Background

Alzheimer’s disease (AD) is a complex neurological disorder with contributions from genetic and environmental factors. High‐resolution metabolomics (HRM) has the potential to identify novel endogenous and environmental factors involved in AD. Previous metabolomics studies have identified circulating metabolites linked to AD, but lack of replication and inconsistent diagnostic algorithms have hindered the generalizability of these findings. Here we applied HRM to identify plasma metabolic and environmental factors associated with AD in two study samples, with cerebrospinal fluid (CSF) biomarkers of AD incorporated to achieve high diagnostic accuracy.

Methods

Liquid chromatography‐mass spectrometry (LC–MS)‐based HRM was used to identify plasma and CSF metabolites associated with AD diagnosis and CSF AD biomarkers in two studies of prevalent AD (Study 1: 43 AD cases, 45 mild cognitive impairment [MCI] cases, 41 controls; Study 2: 50 AD cases, 18 controls). AD‐associated metabolites were identified using a metabolome‐wide association study (MWAS) framework.

Results

An MWAS meta‐analysis identified three non‐medication AD‐associated metabolites in plasma, including elevated levels of glutamine and an unknown halogenated compound and lower levels of piperine, a dietary alkaloid. The non‐medication metabolites were correlated with CSF AD biomarkers, and glutamine and the unknown halogenated compound were also detected in CSF. Furthermore, in Study 1, the unknown compound and piperine were altered in MCI patients in the same direction as AD dementia.

Conclusions

In plasma, AD was reproducibly associated with elevated levels of glutamine and a halogen‐containing compound and reduced levels of piperine. These findings provide further evidence that exposures and behavior may modify AD risks.

β-Caryophyllene protects against ischemic stroke by promoting polarization of microglia toward M2 phenotype via the TLR4 pathway

AIMS

The objective of the study was to determine whether β-caryophyllene (BCP) exerts a neuroprotective effect in cerebral ischemia-reperfusion (I/R) injury by inhibiting microglial activation and modulating their polarization via the TLR4 pathway.

MAIN METHODS

Wild-type (WT) and TLR4 knockout (KO) C57BL/6J mice were subjected to cerebral I/R injury and neurologic dysfunction, cerebral infarct volume, brain edema, microglia activation and polarization, and TLR4 expression were determined. In vitro, primary microglia were stimulated with LPS and IFN-γ or IL-4 to induce polarization of microglia toward M1 or M2 phenotypes.

KEY FINDINGS

BCP reduced cerebral infarct volume, brain edema, and neurologic deficits in WT mice after I/R. The optimal dose of BCP, 72 mg/kg body weight, inhibited microglial activation and reduced the secretion of proinflammatory cytokines interleukin (IL)-1β, tumor necrosis factor (TNF)-α, and IL-6 by microglia of WT mice. BCP inhibited the level of TLR4 in WT mice, and partially reduced neurologic deficits, infarct volume, and brain edema in TLR4 KO mice. Importantly, BCP reduced the number of activated M1-type microglia and increased the number of M2-type microglia in the ipsilateral cortex of both WT and TLR4 KO mice. In vitro, BCP decreased the secretion of proinflammatory cytokines induced by LPS plus IFN-γ, downregulated the level of TLR4 protein, and polarized microglia towards the M2 phenotype.

SIGNIFICANCES

The decrease in TLR4 activity mediated, at least in part, the anti-inflammatory effects of BCP and its ability to shift microglia polarization from the M1 to M2 phenotype.

Inhibitory Effects of Essential Oil Extracts From Panax Plants Against β-Secretase, Cholinesterase, and Amyloid Aggregation

Numerous pharmacological studies on Panax plants have been performed. However, these studies were limited to ginsenosides, which are typical constituents in Panax plants. In our research program to discover novel agents to prevent dementia and improve dementia symptoms, especially Alzheimer’s disease (AD), we investigated the inhibitory activities of essential oil (EO) extracts from 4 Panax plants against β-secretase, amyloid β (Aβ) aggregation, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE). An EO extract of Panax japonicus showed the most potent activity with 51.3% inhibition at 500 μg/mL against β-secretase. Panax ginseng showed the most potent inhibitory activity against AChE and BChE with 70.4% and 84.4% inhibition at 50 μg/mL, respectively. Panax notoginseng extract showed the most potent activity with 57.3% inhibition at 500 μg/mL against Aβ aggregation. From these results, an EO extract of P. ginseng could be an effective agent to improve AD symptoms, while EO extracts of P. japonicus and P. notoginseng could be suitable for AD prevention.

Bioactive Compounds, Antioxidant Activity and Inhibition of Key Enzymes Relevant to Alzheimer's Disease from Sweet Pepper (Capsicum annuum) Extracts

Sweet pepper is a non-pungent chili of the Capsicum annuum species and is an important ingredient in daily diets due to its characteristics such as pungency, aromas, and flavors. Sweet pepper is a rich source of bioactive compounds such as phenols, carotenoids, and flavonoids, which can promote potential health benefits against various non-communicable diseases. However, research focused on anti-Alzheimer’s disease (AD) properties of sweet peppers is limited. Thus, this study aimed investigate bioactive compounds (flavonoids, phenolic acids, and carotenoids), antioxidant activity and anti-AD properties of four colored sweet peppers (green, red, orange, and yellow) via their abilities to inhibit key enzymes relevant to AD [acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and β-secretase (BACE1)]. Extraction solvents [hexane, ethyl acetate, and 70% (v/v) aqueous ethanol] were also investigated. Results suggested that yellow sweet pepper have the highest content of flavonoids, while green sweet pepper have the highest contents of phenolic acids and red sweet peppers have the highest content of carotenoids. In terms of anti-AD properties, green sweet peppers exhibited the highest antioxidant, anti-BChE, and anti-BACE1 activities; however, yellow sweet pepper extract exhibited the highest amounts of AChE inhibition. Bioactive compounds in sweet red peppers may therefore have anti-AD properties, and may be useful for AD prevention.

Synergistic Effects of Curcumin and Piperine as Potent Acetylcholine and Amyloidogenic Inhibitors With Significant Neuroprotective Activity in SH-SY5Y Cells via Computational Molecular Modeling and in vitro Assay

Hallmarks of Alzheimer's disease (AD) pathology include acetylcholine (ACh) deficiency and plaque deposition. Emerging studies suggest that acetylcholinesterase (AChE) may interact with amyloid β (Aβ) to promote aggregation of insoluble Aβ plaques in brains of patients. Current therapeutic options available for AD patients, such as AChE inhibitors, provide only symptomatic relief. In this study, we screened four natural compounds believed to harbor cognitive benefits-curcumin, piperine, bacoside A, and chebulinic acid. In the first section, preliminary screening through computational molecular docking simulations gauged the suitability of the compounds as novel AChE inhibitors. From here, only compounds that met the in silico selection criteria were selected for the second section through in vitro investigations, including AChE enzyme inhibition assay, 3-(4,5-dimenthylthiazol-2-yl)-2,5-dimethyltetrazolium bromide (MTT) assay, Thioflavin T (ThT) assay, and biochemical analysis via a neuronal cell line model. Of the four compounds screened, only curcumin (-9.6 kcal/mol) and piperine (-10.5 kcal/mol) showed favorable binding affinities and interactions towards AChE and were hence selected. In vitro AChE inhibition demonstrated that combination of curcumin and piperine showed greater AChE inhibition with an IC50 of 62.81 ± 0.01 μg/ml as compared to individual compounds, i.e., IC50 of curcumin at 134.5 ± 0.06 μg/ml and IC50 of piperine at 76.6 ± 0.08 μg/ml. In the SH-SY5Y cell model, this combination preserved cell viability up to 85%, indicating that the compounds protect against Aβ-induced neuronal damage (p < 0.01). Interestingly, our results also showed that curcumin and piperine achieved a synergistic effect at 35 μM with an synergism quotient (SQ) value of 1.824. Synergistic behavior indicates that the combination of these two compounds at lower concentrations may provide a better outcome than singularly used for Aβ proteins. Combined curcumin and piperine managed to inhibit aggregation (reduced ThT intensity at 0.432 a.u.; p < 0.01) as well as disaggregation (reduced ThT intensity at 0.532 a.u.; p < 0.01) of fibrillar Aβ42. Furthermore, combined curcumin and piperine reversed the Aβ-induced up-regulation of neuronal oxidative stress (p < 0.01). In conclusion, curcumin and piperine demonstrated promising neuroprotective effects, whereas bacoside A and chebulinic acid may not be suitable lead compounds. These results are hoped to advance the field of natural products research as potentially therapeutic and curative AD agents.

Inhibitory Effects of Essential Oil Extracts From Panax ginseng Against β-Secretase and Cholinesterases

Panax ginseng C.A. Meyer is recognized as one of the most important crude drugs in ancient Chinese medicine. Numerous pharmacological studies investigated P. ginseng; however, these studies were limited to ginsenosides, which are typical constituents in P. ginseng. We focused on the essential oil (EO) from P. ginseng as it has a typical aroma. Herein, we report the inhibitory activities of EO against β-secretase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE), which were investigated in order to demonstrate the potential of EO as a preventative and therapeutic agent against Alzheimer’s disease (AD). Essential oil (250 µg/mL) showed 41.4% inhibition against β-secretase, 77.4% inhibition against AChE, and 94.1% inhibition against BChE. In addition, spathulenol (8.82%, content % in EO), bicyclogermacrene (6.23%), β-elemene (3.94%), and α-humulene (3.69%) were identified as high content by Gas chromatography mass spectrometry (GC/MS) analysis. Furthermore, β-elemene and α-humulene showed high activity among 3 compounds with 50% inhibitory concentration (IC50) values of 77.2 and 137.3 µM for AChE, and 298.2 and >2000 µM for BChE, respectively. In this report, we showed the inhibitory activity of EO from P. ginseng against β-secretase, AChE, and BChE, and demonstrated that EO could be a candidate to treat AD. This is the first research to report the anti-AD effect of EO and determination of its volatile components. Especially, β-elemene and α-humulene are expected to be highly bio-available compounds due to their small molecular size and lipophilicity. From these results, EO from P. ginseng may be a promising candidate for AD treatment.

Biopharmaceutical Monotargeting versus 'Universal Targeting' of Late-Onset Alzheimer's Disease Using Mixtures of Pleiotropic Natural Compounds

A five-year close reading of the scientific literature on late-onset Alzheimer’s disease (AD) has prompted the invention of a novel therapeutic method that biomechanistically targets the targetable disease-process targets of AD with one or another mixture of non-toxic pleiotropic natural compounds. The featured mixture herein is comprised of curcumin, resveratrol, and EGCG. The mixture’s targets include central pathological elements of AD (including amyloid, tau, synaptic dysfunction, oxidative stress, mitochondrial dysfunction, and aberrant neuroinflammation), modifiable risk factors, comorbidities, and epigenetic elements. The featured mixture and other such mixtures are suitable for long-term use, and may be applied to any stage of AD, including primary and secondary prevention. Such mixtures also would be amenable for use as pre-treatment, co-treatment, and post-treatment applications with certain biopharmaceutical agents. The targeting focus here is the major credible hypotheses of AD. The focus of future such articles will include other AD-related targets, modifiable risk factors and comorbidities, APOE4, epigenetic factors, bioavailability, dose response, and implications for clinical testing. The “universal targeting” method described herein—that is, “targeting the targetable targets” of AD using certain mixtures of natural compounds—is reprogrammable and thus is applicable to other chronic neurological conditions, including Parkinson’s disease, vascular dementia, ischemic-stroke prevention and recovery, and sports-related head injuries and sequelae leading to chronic traumatic encephalopathy.

Piperine attenuates cognitive impairment in an experimental mouse model of sporadic Alzheimer's disease

Piperine, the major alkaloid constituent of black pepper, has been reported to possess a wide range of pharmacological effects on the central nervous system, including antidepressant, anticonvulsant and anti-ischemic activities. In the present study, we aimed to investigate the therapeutic potential and neuroprotective mechanisms of piperine in an experimental mouse model of sporadic Alzheimer's disease (sAD) induced by intracerebroventricular (ICV) infusion of streptozotocin (STZ). STZ was infused bilaterally at a dose of 1.5 mg/kg/day on day 1 and day 3. From day 8, piperine (2.5-10 mg/kg body weight) was administered intraperitoneally once daily for 15 consecutive days. The locomotor activity and cognitive performance of mice were evaluated using open field test and Morris water maze test, respectively. On day 23, all animals were sacrificed, and the hippocampus was used for biochemical, neurochemical and neuroinflammatory determinations. Our data revealed that the ICV-STZ-infused sAD mouse showed an increased oxidative-nitrosative stress, an altered neurotransmission and an elevated neuroinflammation in hippocampus, as well as significant cognitive deficits. All these alterations can be ameliorated by piperine in a dose-dependent manner. In summary, our findings predict a therapeutic potential of piperine against cognitive deficits in sAD mouse. This effect might be due to its abilities to ameliorate oxidative-nitrosative stress, restore neurotransmission and reduce neuroinflammation.

Computational insight to putative anti-acetylcholinesterase activity of Commiphora myrrha (Nees), Engler, Burseraceae: a lessen of archaeopharmacology from Mesopotamian Medicine I

Commiphora spp., Burseraceae family and their resinous matter, myrrh, are used in Mesopotamian medicine as fragrance or antiinsectant. Based on in vitro, leaves, bark, and resin methyl alcohol extract of C. myrrha showed similar inhibitory effects of 17.00, 26.00, and 29.33% for acetylcholinesterase (AChE) as compared to eserine, respectively. The ADMET properties and putative anticholinesterase activity of phytochemicals of myrrh were computationally predicted using in silico tools. Phytochemicals of C. myrrha had acceptable binding affinity (BA) towards principal sites of AChE ranging from - 5.8 (m-cresol) to - 10.5 (abietic acid) kcal/mol. In this regard, all terpenoid compounds (25 out of 28) of myrrh were dual inhibitors since they hydrophobically interacted with both catalytic triad and peripheral anionic site (PAS) of AChE while alpha-terpineol, elemol, and eugenol employed hydrogen bonds with AChE. Cuscohygrine as a pyrrolidine alkaloid has been docked with AChE through hydrogen bonds with PAS and through hydrophobic interactions with catalytic triad thereby we initially proposed it as dual inhibitor of AChE. M-cresol as a methylphenol has been loosely docked with AChE via hydrogen bond and would be a hit molecule for further drug synthesis. This study not only confirmed archaeopharmacological applications of myrrh as antiinsectant or nootropics but also offered an array of terpenoid compounds, cuscohygrine, and m-cresol as a good starting point for hit-to-lead-to-drug optimization phase in synthesis of phyto-nootropics and ecofriendly insecticides.

Multidisciplinary approaches for targeting the secretase protein family as a therapeutic route for Alzheimer's disease

The continual increase of the aging population worldwide renders Alzheimer's disease (AD) a global prime concern. Several attempts have been focused on understanding the intricate complexity of the disease's development along with the on- andgoing search for novel therapeutic strategies. Incapability of existing AD drugs to effectively modulate the pathogenesis or to delay the progression of the disease leads to a shift in the paradigm of AD drug discovery. Efforts aimed at identifying AD drugs have mostly focused on the development of disease-modifying agents in which effects are believed to be long lasting. Of particular note, the secretase enzymes, a group of proteases responsible for the metabolism of the β-amyloid precursor protein (βAPP) and β-amyloid (Aβ) peptides production, have been underlined for their promising therapeutic potential. This review article attempts to comprehensively cover aspects related to the identification and use of drugs targeting the secretase enzymes. Particularly, the roles of secretases in the pathogenesis of AD and their therapeutic modulation are provided herein. Moreover, an overview of the drug development process and the contribution of computational (in silico) approaches for facilitating successful drug discovery are also highlighted along with examples of relevant computational works. Promising chemical scaffolds, inhibitors, and modulators against each class of secretases are also summarized herein. Additionally, multitarget secretase modulators are also taken into consideration in light of the current growing interest in the polypharmacology of complex diseases. Finally, challenging issues and future outlook relevant to the discovery of drugs targeting secretases are also discussed.

Anti-cholinesterase Activity of Crude Drugs Selected from the Ingredients of Incense Sticks and Heartwood of Chamaecyparis obtusa

An effective agent for the treatment and/or prevention of Alzheimer's disease (AD) is needed due to the number of patients in the acute curve. In our research program to investigate effective agents for AD, we focused on crude drugs which consisted of incense sticks widely used in Asian countries including Japan. We selected 9 drugs as “aromatic” crude drugs and 2 as basal crude drugs. Among the samples tested, the essential oil obtained from the leaf of Cryptomeria japonica showed the most potent anti-acetylcholinesterase activity with 64.8% of inhibition at 100 μg/mL. In addition, no sample showed significant inhibition against β-secretase. From these results, the crude drugs selected in this study may be effective for AD therapy rather than prevention. The active principles of anti-acetylcholinesterase were investigated by activity-guided fractionation, and kaur-16-ene, nezukol and ferruginol were successfully identified, the IC50 values were 640, 300 and 95 μM, respectively. Kaur-16-ene and nezukol inhibited acetylcholinesterase in the mixed type mode, while ferruginol inhibited it in the competitive mode. In addition, nezukol and ferruginol showed anti-butyrylcholinesterase activity, the IC50 values were 155 and 22 μM, respectively. We also focused on the heartwood of Chamaecyparis obtusa, since this tree has been used as a building material for the heartwood of C. japonica. Ethyl acetate extract of C. obtusa showed anti-acetylcholinesterase activity of 37.7% inhibition at 100 μg/mL. The active principle was determined to be (-)-hinokinin by activity-guided fractionation and the IC50 value was 176 μM. These results suggest that the leaf of C. japonica and heartwood of C. obtusa may be suitable agents for AD therapy when administered through the nasal system as an aroma supplement.

DMC is not better than TMZ on intracranial anti-glioma effects

Previous studies showed Demethoxycurcumin (DMC) has stronger anti-glioma and anti-GSCs effects both in vitro and in vivo. In addition, DMC seems to be lower toxicity than TMZ on nude mice. However, this conclusion was confirmed to be wrong in this study. We have evaluated the antitumor efficacy of DMC or TMZ treatment by an orthotopic glioblastoma xenograft model. Nude mice were injected with U87MG-luc cells in the caudate nucleus of the brain and treated with DMC (30 mg/kg q.d.) or TMZ (10 mg/kg q.d.) by intraperitoneal injection. Bioluminescence imaging (BLI) was used to monitoring tumor growth and response to therapy. Western blot was used to detect the expression of p-Akt, cleaved-caspase-3 and Bax. The average value of BLI showed TMZ determined a significant tumor regression while DMC had a mild regression effect on tumor growth compared with control group. Immunohistochemistry for Ki67, proliferating cell nuclear antigen (PCNA), and TUNEL demonstrated that TMZ more effectively inhibited the expression of Ki67 and PCNA, and increased the ratio of TUNEL-positive cells in in situ tumor tissue. Western blot analysis also indicated that TMZ but not DMC more significantly decreased p-Akt and increased cleaved-caspase-3 and Bax expression.These findings suggested a fact that TMZ appear to be more effective in controlling the growth of glioblastoma than DMC in an orthotopic glioblastoma xenograft model.

Role of Plant Derived Alkaloids and Their Mechanism in Neurodegenerative Disorders

Neurodegenerative diseases are conventionally demarcated as disorders with selective loss of neurons. Conventional as well as newer molecules have been tested but they offer just symptomatic advantages along with abundant side effects. The discovery of more compelling molecules that can halt the pathology of these diseases will be considered as a miracle of present time. Several synthetic compounds are available but they may cause several other health issues. Therefore, natural molecules from the plants and other sources are being discovered to replace available medicines. In conventional medicational therapies, several plants have been reported to bestow remedial effects. Phytochemicals from medicinal plants can provide a better and safer alternative to synthetic molecules. Many phytochemicals have been identified that cure the human body from a number of diseases. The present article reviews the potential efficacy of plant-derived alkaloids, which possess potential therapeutic effects against several NDDs including Alzheimer's disease (AD), Huntington disease (HD), Parkinson's disease (PD), Epilepsy, Schizophrenia, and stroke. Alkaloids include isoquinoline, indole, pyrroloindole, oxindole, piperidine, pyridine, aporphine, vinca, β-carboline, methylxanthene, lycopodium, and erythrine byproducts. Alkaloids constitute positive roles in ameliorating pathophysiology of these illnesses by functioning as muscarinic and adenosine receptors agonists, anti-oxidant, anti-amyloid and MAO inhibitors, acetylcholinestrase and butyrylcholinesterase inhibitor, inhibitor of α-synuclein aggregation, dopaminergic and nicotine agonist, and NMDA antagonist.

Screening of Spice Extracts Possessing Anti-Acetylcholinesterase Activity and Active Principle of Bitter Ginger, Rhizome of Zingiber zerumbet

In our research program for investigating anti-dementia agents from natural plant resources, we screened extracts from 15 spice samples. Among the plant extracts tested, ethyl acetate extract prepared from rhizome of Zingiber zerumbet showed potent activity. Activity-guided purification led to determination of afzelin and its acetylated compound as the active principles. Afzelin showed moderate inhibitory activity against acetylcholinesterase and may also be expected to possess anti-butyrylcholinesterase activity. This is the first report to reveal the anti-cholinesterase activities of ethyl acetate extract of Z. zerumbet and afzelin. Furthermore, Z. zerumbet may be a potential therapeutic agent for the improvement of dementia, especially Alzheimer's disease.

Inhibitory Activities of Essential Oil Obtained from Turmeric and Its Constituents against β-Secretase

The need for a preventive agent against dementia led us to screen natural plant resources. Among the herbs and spices tested, turmeric, from rhizomes of Curcuma longa, showed high potency against β-secretase. The active principles were determined as α-turmerone, β-turmerone and ar-turmerone, with IC50 values of 39, 62 and 92 μM respectively. In this study, the efficiency of collecting the essential oil using steam distillation of the volatile substance was disclosed. The active principles were explored, and four sesquiterpenoids and five monoterpenoids were revealed as active principles against β-secretase. On the other hand, α-turmerone, β-turmerone and ar-turmerone were also investigated in a pharmacokinetic absorption experiment. After oral administration, these compounds were detected in an intact form in the brain and serum. These results suggest that consumption of turmeric constituents may prevent dementia.

Inhibitory Activities of Sesame Seed Extract and its Constituents against β-Secretase

The need for a preventive agent against dementia led us to screen natural plant resources. Among the herbs and spices tested, sesame seed prepared from Sesamum indicum seeds showed potent β-secretase inhibitory activity. The active principles were determined to be sesamin and sesamolin, typical lignans in S. indicum. The IC50 values of sesamin and sesamolin were 257 and 140 μM, respectively. These compounds were investigated in a preliminary absorption experiment. After oral administration, these compounds were detected in an intact form in the brain and serum. These results suggest that consumption of sesame seeds may prevent dementia by sesamin and sesamolin, the constituents in sesame seeds.

β-Caryophyllene protects in vitro neurovascular unit against oxygen-glucose deprivation and re-oxygenation-induced injury

β-Caryophyllene (BCP) mediates neuroprotection in cerebral ischemic animals. The neurovascular unit (NVU) acts as an intricate network to maintain the neuronal homeostatic microenvironment. However, the effects exerted by BCP on NVU remain unclear. Therefore, we established an in vitro NVU model to investigate the effects of BCP on oxygen-glucose deprivation and re-oxygenation (OGD/R)-induced injury. This model involved the co-culture of brain microvascular endothelial cells, neurons, and astrocytes. BCP (10 μmol/L) was applied for 24 h prior to OGD/R and maintained throughout OGD/R. Blood-brain barrier (BBB) integrity and neuronal apoptosis were analyzed. BCP pre-treatment prior to the initiation of OGD/R significantly (i) decreased BBB permeability and neuronal apoptosis, (ii) mitigated oxidative stress damage and the release of inflammatory cytokines, (iii) down-regulated Bax expression, metalloproteinase-9 activity and expression, and (iv) up-regulated claudin-5, occludin, ZO-1, growth-associated protein-43 and Bcl-2 expression. Thus, BCP pre-treatment exerted multiple protective effects on NVU in the context of OGD/R-induced injury. These protective effects potentially occur via reductions in oxidative stress damage and inflammatory cytokines that induce BBB breakdown, subsequently resulting in reduced neuronal apoptosis. The NVU serves as putative therapeutic targets for cerebral ischemia, and the results of this study provide new insights for the application of BCP as a neuroprotective agent.

Search for β-Secretase Inhibitors from Natural Spices

The growing number of Alzheimer's disease (AD) patients prompted us to seek effective natural resources for the prevention of AD. We focused on the inhibition of β-secretase, which is known to catalyze the production of senile plaque. Sixteen spices used in Asian countries were selected for the screening. Among the extracts tested, hexane extracts obtained from turmeric, cardamom, long pepper, cinnamon, Sichuan pepper, betel, white turmeric and aromatic ginger showed potent inhibitory activities. Their active principles were identified as sesquiterpenoids, monoterpenoids, fatty acid derivatives and phenylpropanoids using GC-MS analyses. The chemical structures and IC50 values of the compounds are disclosed. The results suggest that long-term consumption of aromatic compounds from spices could be effective in the prevention of AD.

In-vitro anti-cholinesterase activity of essential oil from four tropical medicinal plants

The chemical inhibition of acetyl-cholinesterase (AChE) is a potent strategy for addressing signal related neuropathology and natural products are potential sources of compounds with such properties. Essential oil extracts from leaf, seed, stem and rhizome of four medicinal plants [Aframomum melegueta K. Schum, Crassocephalum crepidioides (Benth S. More), Monodora myristica (Gaertn.), and Ocimum gratissimum (Linn)] were tested for acetyl-cholinesterase inhibitory activity (AChEI) using Ellman's colorimentric method and compared to a reference acetyl-cholinesterase inhibitor (galantamine). The seed (IC₅₀ = 6.71 mg/l) and leaf (IC₅₀ = 6.54 mg/l) extracts from O. gratissimum showed values that matched the capacity of the reference inhibitor (IC₅₀ = 6.62 mg/l). The least potent extract was rhizome extracts of A. melegueta (IC₅₀ = 28.97 mg/l) about four times that of the reference inhibitor. Principal component analysis (PCA) showed that the intrinsic properties (bioactive ingredient factor) of each extract (PC1 = 29.50%) was the most important factor defining the difference or similarity in potency to the reference acetyl-cholinesterase inhibitor while 'dose response' (PC2 = 11.38%) was the second most important factor. The outstanding AChEI property of O. gratissimum extracts could largely be attributed to the high monoterpene content while the weak potency of rhizome extracts of A. melegueta may be attributed to its predominant concentrations of sesquiterpenes. Since potency could be related to interaction between bioactive components, understanding the interaction between ratios of monoterpene and sesquiterpene in extracts could be important in determining their potency for AChEI.