Protective effect of quercetin in primary neurons against Abeta(1-42): relevance to Alzheimer's disease

Plants' Impact on the Human Brain-Exploring the Neuroprotective and Neurotoxic Potential of Plants

BACKGROUND

Plants have long been recognized for their potential to influence neurological health, with both neuroprotective and neurotoxic properties. This review explores the dual nature of plant-derived compounds and their impact on the human brain.

DISCUSSION

Numerous studies have highlighted the neuroprotective effects of various phytoconstituents, such as those found in Ginkgo biloba, Centella asiatica, Panax ginseng, Withania somnifera, and Curcuma longa. The neuroprotective compounds have demonstrated antioxidant, anti-inflammatory, and cognitive-enhancing properties, making them promising candidates for combating neurodegenerative diseases and improving brain function. Polyphenolic compounds, triterpenic acids, and specific phytocompounds like the ones from EGb 761 extract have shown interactions with key enzymes and receptors in the brain, leading to neuroprotective outcomes. However, this review also acknowledges the neurotoxic potential of certain plants, such as the Veratrum species, which contains steroidal alkaloids that can cause DNA damage and disrupt neurological function, or Atropa belladonna, which interfere with the normal functioning of the cholinergic system in the body, leading to a range of symptoms associated with anticholinergic toxicity.

CONSLUSIONS

This review also emphasizes the need for further research to elucidate the complex mechanisms underlying the neuroprotective and neurotoxic effects of plant-derived compounds, as well as to identify novel phytoconstituents with therapeutic potential. Understanding the complex relationship between plants and the human brain is crucial for harnessing the benefits of neuroprotective compounds while mitigating the risks associated with neurotoxic substances. This review provides a comprehensive overview of the knowledge on the neurological properties of plants and highlights the importance of continued research in this field for the development of novel therapeutic strategies targeting brain health and neurological disorders.

Quercetin/Polyethyleneimine Modified Gold Nanoconjugates Inhibit Apoptosis and ROS Production Induced by Hydrogen Peroxide in DRG Sensory Neurons

The basis of most neurological syndromes is the accumulation of free radical molecules. Quercetin is a polyphenolic bioflavonoid molecule and it has a very strong antioxidant effect by maintaining oxidative balance. There are many difficulties in the clinical use of quercetin due to its hydrophobic structure, low solubility, instability, poor oral bioavailability, and limited tissue-barrier penetration. Its synergistic use in complex with gold nanoparticles (AuNPs) could overcome these problems. AuNPs have recently emerged as an attractive candidate for delivery applications of various biomolecules and drugs. The aim of this study was to synthesize two different sized gold nanoparticles (AuNP20 and AuNP50) modified with polyethyleneimine (PEI) and quercetin, evaluate their potential neuroprotective effects on the in vitro oxidative stress model using DRG primary sensory neurons. It was shown that the antioxidant and anti-apoptotic ability of the bioflavonoid was preserved after exposure to the designed quercetin modified AuNPs. The PEI surface coating increased the stability and biocompatibility of the AuNPs in both sizes. It also potentially enables additional surface functionalization. This study indicates that designed nanoparticles (AuNP-Q-PEI) with different sizes could be a useful potential platform for the treatment of neurodegenerative syndromes or cancer diseases.

Extraction Condition Optimization, Quantitative Analysis, and Anti-AD Bioactivity Evaluation of Acorn Polyphenols from Quercus variabilis, Quercus aliena, and Quercus dentata

In the present study, Quercus variabilis (Q. variabilis), Quercus aliena (Q. aliena), and Quercus dentata (Q. dentata) acorn kernels were taken as the research objects, and the free polyphenols and bound polyphenols in acorn kernels were extracted using improved ultrasound-assisted ethanolic and alkaline extraction methods, after which the contents of gallic acid, quercetin, azelaic acid, ellagic acid, and ferulic acid were quantified by LC-MC/MS. The results demonstrated that Q. variabilis and Q. aliena acorns were suitable as raw materials to extract ellagic acid, the contents of ferulic acid and bound gallic acid in them were different, and Q. aliena acorns were more suitable for the research of gallic acid, but not for azelaic acid. Results on APP/PS1 transgenic mice verified that five polyphenols significantly suppressed the progression of AD. This study provides a theoretical basis for the drug development of acorn polyphenols.

Quercetin inhibited LPS-induced cytokine storm by interacting with the AKT1-FoxO1 and Keap1-Nrf2 signaling pathway in macrophages

Cytokine storm (CS) emerges as an exacerbated inflammatory response triggered by various factors such as pathogens and excessive immunotherapy, posing a significant threat to life if left unchecked. Quercetin, a monomer found in traditional Chinese medicine, exhibits notable anti-inflammatory and antiviral properties. This study endeavors to explore whether quercetin intervention could mitigate CS through a combination of network pharmacology analysis and experimental validation. First, common target genes and potential mechanisms affected by quercetin and CS were identified through network pharmacology, and molecular docking experiments confirmed quercetin and core targets. Subsequently, in vitro experiments of Raw264.7 cells stimulated by lipopolysaccharide (LPS) showed that quercetin could effectively inhibit the overexpression of pro-inflammatory mediators and regulate the AKT1-FoxO1 signaling pathway. At the same time, quercetin can reduce ROS through the Keap1-Nrf2 signaling pathway. In addition, in vivo studies of C57BL/6 mice injected with LPS further confirmed quercetin's inhibitory effect on CS. In conclusion, this investigation elucidated novel target genes and signaling pathways implicated in the therapeutic effects of quercetin on CS. Moreover, it provided compelling evidence supporting the efficacy of quercetin in reversing LPS-induced CS, primarily through the regulation of the AKT1-FoxO1 and Keap1-Nrf2 signaling pathways.

Investigating the effects of Thymus vulgaris essential oil, Allium cepa extract, and their active compounds (thymol and quercetin) on expression profile of genes related to Alzheimer's disease in PC12 model cell

Thymus vulgaris and Allium cepa are plants with great medicinal importance. Thymol monoterpene and quercetin, which are present in these plants, have anti-Alzheimer's and antioxidant effects. The objectives of this research were investigating the effects of these compounds on the pathogenesis and progress of Alzheimer's disease in cells modeled by formaldehyde. MTT, flow cytometry, and RT-PCR were used to investigate the toxicity, survival rate and apoptosis of the cells, and the expression level of PP2A, GSK3, NMDAR, BACE1, and APP genes, respectively. Also, the total antioxidant capacity of the modeled cells was measured. The results showed that the two compounds as well as the plants extract and essential oil were able to increase the percentage of cell survival; among them, Thymus vulgaris essential oil had the greatest effect (93.55316 % in 48 h exposure). In addition, quercetin was able to reduce the rate of apoptosis in Alzheimer's cells (4.73 %) which was greater than the effects of other compounds. In general, the essential oil of Thymus vulgaris compared to thymol; and quercetin compared to Allium cepa extract showed more improving effects on the expression of genes involved in the disease. All four compounds increased the antioxidant capacity of the modeled cells compared to the control group, and these effects were almost equal between the compounds. According to the obtained results, both plants, especially Thymus vulgaris can be proposed as candidates to be included in the diet of Alzheimer's patients. In addition, polyphenols thymol and quercetin as derivates from the studied plants can be used in new drugs development for Alzheimer's disease, with greater safety than currently used drugs. These results are significant because most of the drug for Alzheimer's treatments such as cholinesterases (e.g. rivastigmine and donepezil) and memantine are chemically based and have many side effects.

Unveiling the impact of aging on BBB and Alzheimer's disease: Factors and therapeutic implications

Alzheimer's disease (AD) is a highly prevalent neurodegenerative condition that has devastating effects on individuals, often resulting in dementia. AD is primarily defined by the presence of extracellular plaques containing insoluble β-amyloid peptide (Aβ) and neurofibrillary tangles (NFTs) composed of hyperphosphorylated tau protein (P-tau). In addition, individuals afflicted by these age-related illnesses experience a diminished state of health, which places significant financial strain on their loved ones. Several risk factors play a significant role in the development of AD. These factors include genetics, diet, smoking, certain diseases (such as cerebrovascular diseases, obesity, hypertension, and dyslipidemia), age, and alcohol consumption. Age-related factors are key contributors to the development of vascular-based neurodegenerative diseases such as AD. In general, the process of aging can lead to changes in the immune system's responses and can also initiate inflammation in the brain. The chronic inflammation and the inflammatory mediators found in the brain play a crucial role in the dysfunction of the blood-brain barrier (BBB). Furthermore, maintaining BBB integrity is of utmost importance in preventing a wide range of neurological disorders. Therefore, in this review, we discussed the role of age and its related factors in the breakdown of the blood-brain barrier and the development of AD. We also discussed the importance of different compounds, such as those with anti-aging properties, and other compounds that can help maintain the integrity of the blood-brain barrier in the prevention of AD. This review builds a strong correlation between age-related factors, degradation of the BBB, and its impact on AD.

Emerging phosphodiesterase inhibitors for treatment of neurodegenerative diseases

Neurodegenerative diseases (NDs) cause progressive loss of neuron structure and ultimately lead to neuronal cell death. Since the available drugs show only limited symptomatic relief, NDs are currently considered as incurable. This review will illustrate the principal roles of the signaling systems of cyclic adenosine and guanosine 3',5'-monophosphates (cAMP and cGMP) in the neuronal functions, and summarize expression/activity changes of the associated enzymes in the ND patients, including cyclases, protein kinases, and phosphodiesterases (PDEs). As the sole enzymes hydrolyzing cAMP and cGMP, PDEs are logical targets for modification of neurodegeneration. We will focus on PDE inhibitors and their potentials as disease-modifying therapeutics for the treatment of Alzheimer's disease, Parkinson's disease, and Huntington's disease. For the overlapped but distinct contributions of cAMP and cGMP to NDs, we hypothesize that dual PDE inhibitors, which simultaneously regulate both cAMP and cGMP signaling pathways, may have complementary and synergistic effects on modifying neurodegeneration and thus represent a new direction on the discovery of ND drugs.

Mechanistic insights into the potential role of dietary polyphenols and their nanoformulation in the management of Alzheimer's disease

Alzheimer's disease (AD) is a very common neurodegenerative disorder associated with memory loss and a progressive decline in cognitive activity. The two major pathophysiological factors responsible for AD are amyloid plaques (comprising amyloid-beta aggregates) and neurofibrillary tangles (consisting of hyperphosphorylated tau protein). Polyphenols, a class of naturally occurring compounds, are immensely beneficial for the treatment or management of various disorders and illnesses. Naturally occurring sources of polyphenols include plants and plant-based foods, such as fruits, herbs, tea, vegetables, coffee, red wine, and dark chocolate. Polyphenols have unique properties, such as being the major source of anti-oxidants and possessing anti-aging and anti-cancerous properties. Currently, dietary polyphenols have become a potential therapeutic approach for the management of AD, depending on various research findings. Dietary polyphenols can be an effective strategy to tackle multifactorial events that occur with AD. For instance, naturally occurring polyphenols have been reported to exhibit neuroprotection by modulating the Aβ biogenesis pathway in AD. Many nanoformulations have been established to enhance the bioavailability of polyphenols, with nanonization being the most promising. This review comprehensively provides mechanistic insights into the neuroprotective potential of dietary polyphenols in treating AD. It also reviews the usability of dietary polyphenol as nanoformulation for AD treatment.

Focused ultrasound-mediated cerium-based nanoreactor against Parkinson's disease via ROS regulation and microglia polarization

Neuronal damage caused by oxidative stress and inflammatory microenvironment dominated by microglia are the main obstacles in the treatment of Parkinson's disease (PD). In this study, we developed an integrated nanoreactor Q@CeBG by encapsulating CeO2 nanozyme and quercetin (Que) into glutathione-modified bovine serum albumin, and then selected focused ultrasound (FUS) to temporarily open the blood-brain barrier (BBB) to enhance the accumulation level of Q@CeBG in the brain. Q@CeBG exhibited superior multi-ROS scavenging activity. Under the assistance of FUS, Q@CeBG nanoreactor can penetrate the BBB and act on neurons as well as microglia, reducing the neuron's oxidative stress level and polarizing microglia's phenotype from proinflammatory M1 to anti-inflammatory M2. In vitro and In vivo experiments demonstrated that Q@CeBG nanoreactor with good biocompatibility exhibit outstanding neuroprotection and immunomodulatory effects. In short, this dual synergetic nanoreactor will become a reliable platform against PD.

Natural Phenolic Compounds with Neuroprotective Effects

Neurodegenerative disorders are characterized by mitochondrial dysfunction and subsequently oxidative stress, inflammation, and apoptosis that contribute to neuronal cytotoxicity and degeneration. Huntington's (HD), Alzheimer's (AD), and Parkinson's (PD) diseases are three of the major neurodegenerative diseases. To date, researchers have found various natural phytochemicals that could potentially be used to treat neurodegenerative diseases. Particularly, the application of natural phenolic compounds has gained significant traction in recent years, driven by their various biological activities and therapeutic efficacy in human health. Polyphenols, by modulating different cellular functions, play an important role in neuroprotection and can neutralize the effects of oxidative stress, inflammation, and apoptosis in animal models. This review focuses on the current state of knowledge on phenolic compounds, including phenolic acids, flavonoids, stilbenes, and coumarins, as well as their beneficial effects on human health. We further provide an overview of the therapeutic potential and mechanisms of action of natural dietary phenolics in curing neurodegenerative diseases in animal models.

Insights on Quercetin Therapeutic Potential for Neurodegenerative Diseases and its Nano-technological Perspectives

The neurodegeneration process begins in conjunction with the aging of the neurons. It manifests in different parts of the brain as Aβ plaques, neurofibrillary tangles, Lewy bodies, Pick bodies, and other structures, which leads to progressive loss or death of neurons. Quercetin (QC) is a flavonoid compound found in fruits, tea, and other edible plants have antioxidant effects that have been studied from subcellular compartments to tissue levels in the brain. Also, quercetin has been reported to possess a neuroprotective role by decreasing oxidative stress-induced neuronal cell damage. The use of QC for neurodegenerative therapy, the existence of the blood-brain barrier (BBB) remains a significant barrier to improving the clinical effectiveness of the drug, so finding an innovative solution to develop simultaneous BBB-crossing ability of drugs for treating neurodegenerative disorders and improving neurological outcomes is crucial. The nanoparticle formulation of QC is considered beneficial and useful for its delivery through this route for the treatment of neurodegenerative diseases seems necessary. Increased QC accumulation in the brain tissue and more significant improvements in tissue and cellular levels are among the benefits of QC-involved nanostructures.

Oxidative damage in neurodegeneration: roles in the pathogenesis and progression of Alzheimer disease

Alzheimer disease (AD) is associated with multiple etiologies and pathological mechanisms, among which oxidative stress (OS) appears as a major determinant. Intriguingly, OS arises in various pathways regulating brain functions, and it seems to link different hypotheses and mechanisms of AD neuropathology with high fidelity. The brain is particularly vulnerable to oxidative damage, mainly because of its unique lipid composition, resulting in an amplified cascade of redox reactions that target several cellular components/functions ultimately leading to neurodegeneration. The present review highlights the "OS hypothesis of AD," including amyloid beta-peptide-associated mechanisms, the role of lipid and protein oxidation unraveled by redox proteomics, and the antioxidant strategies that have been investigated to modulate the progression of AD. Collected studies from our groups and others have contributed to unraveling the close relationships between perturbation of redox homeostasis in the brain and AD neuropathology by elucidating redox-regulated events potentially involved in both the pathogenesis and progression of AD. However, the complexity of AD pathological mechanisms requires an in-depth understanding of several major intracellular pathways affecting redox homeostasis and relevant for brain functions. This understanding is crucial to developing pharmacological strategies targeting OS-mediated toxicity that may potentially contribute to slow AD progression as well as improve the quality of life of persons with this severe dementing disorder.

Role of BDNF Signaling in the Neuroprotective and Memory-enhancing Effects of Flavonoids in Alzheimer's Disease

BACKGROUND

Foods rich in flavonoids are associated with a reduced risk of various chronic diseases, including Alzheimer's disease (AD). In fact, growing evidence suggests that consuming flavonoid- rich foods can beneficially affect normal cognitive function. Animal models have shown that many flavonoids prevent the development of AD-like pathology and improve cognitive deficits.

OBJECTIVE

Identifying the molecular causes underlying the memory-enhancing effect of flavonoid-rich foods makes it possible to provide the best diet to prevent cognitive decline associated with aging and Alzheimer's disease. Based on the most recent scientific literature, this review article critically examines the therapeutic role of dietary flavonoids in ameliorating and preventing the progression of AD and enhancement of memory with a focus on the role of the BDNF signaling pathway.

METHODS

The databases of PubMed, Web of Science, Google Scholar, and Scopus were searched up to March 2023 and limited to English language. Search strategies were using the following keywords in titles and abstracts: (Flavonoid-rich foods OR Flavonoids OR Polyphenols); AND (Brain-Derived Neurotrophic Factor OR BDNF OR CREB OR) AND (Alzheimer's disease OR memory OR cognition OR).

RESULTS

Flavonoid-rich foods including green tea, berries, curcumin and pomegranate exert their beneficial effects on memory decline associated with aging and Alzheimer's disease mostly through the direct interaction with BDNF signaling pathway.

CONCLUSION

The neuroprotective effects of flavonoid-rich foods through the CREB-BDNF mechanism have the potential to prevent or limit memory decline due to aging and Alzheimer's disease, so their consumption throughout life may prevent age-related cognitive impairment.

In Silico Prediction of Quercetin Analogs for Targeting Death-Associated Protein Kinase 1 (DAPK1) Against Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder that greatly affects the health and life quality of the elderly population. Existing drugs mainly alleviate symptoms but fail to halt disease progression, underscoring the urgent need for the development of novel drugs. Based on the neuroprotective effects of flavonoid quercetin in AD, this study was designed to identify potential AD-related targets for quercetin and perform in silico prediction of promising analogs for the treatment of AD. Database mining suggested death-associated protein kinase 1 (DAPK1) as the most promising AD-related target for quercetin among seven protein candidates. To achieve better biological effects for the treatment of AD, we devised a series of quercetin analogs as ligands for DAPK1, and molecular docking analyses, absorption, distribution, metabolism, and excretion (ADME) predictions, as well as molecular dynamics (MD) simulations, were performed. The energy for drug-protein interaction was predicted and ranked. As a result, quercetin-A1a and quercetin-A1a1 out of 19 quercetin analogs exhibited the lowest interaction energy for binding to DAPK1 than quercetin, and they had similar dynamics performance with quercetin. In addition, quercetin-A1a and quercetin-A1a1 were predicted to have better water solubility. Thus, quercetin-A1a and quercetin-A1a1 could be promising agents for the treatment of AD. Our findings paved the way for further experimental studies and the development of novel drugs.

Binding mechanism and biological effects of flavone DYRK1A inhibitors for the design of new antidiabetics

The selective inhibition of kinases from the diabetic kinome is known to promote the regeneration of beta cells and provide an opportunity for the curative treatment of diabetes. The effect can be achieved by carefully tailoring the selectivity of inhibitor toward a particular kinase, especially DYRK1A, previously associated with Down syndrome and Alzheimer's disease. Recently DYRK1A inhibition has been shown to promote both insulin secretion and beta cells proliferation. Here, we show that commonly available flavones are effective inhibitors of DYRK1A. The observed biochemical activity of flavone compounds is confirmed by crystal structures solved at 2.06 Å and 2.32 Å resolution, deciphering the way inhibitors bind in the ATP-binding pocket of the kinase, which is driven by the arrangement of hydroxyl moieties. We also demonstrate antidiabetic properties of these biomolecules and prove that they could be further improved by therapy combined with TGF-β inhibitors. Our data will allow future structure-based optimization of the presented scaffolds toward potent, bioavailable and selective anti-diabetic drugs.

Exploring Medicinal Herbs' Therapeutic Potential and Molecular Docking Analysis for Compounds as Potential Inhibitors of Human Acetylcholinesterase in Alzheimer's Disease Treatment

Background and Objectives: Alzheimer's disease (AD) stands as a pervasive neurodegenerative ailment of global concern, necessitating a relentless pursuit of remedies. This study aims to furnish a comprehensive exposition, delving into the intricate mechanistic actions of medicinal herbs and phytochemicals. Furthermore, we assess the potential of these compounds in inhibiting human acetylcholinesterase through molecular docking, presenting encouraging avenues for AD therapeutics. Materials and Methods: Our approach entailed a systematic exploration of phytochemicals like curcumin, gedunin, quercetin, resveratrol, nobiletin, fisetin, and berberine, targeting their capability as human acetylcholinesterase (AChE) inhibitors, leveraging the PubChem database. Diverse bioinformatics techniques were harnessed to scrutinize molecular docking, ADMET (absorption, distribution, metabolism, excretion, and toxicity), and adherence to Lipinski's rule of five. Results: Results notably underscored the substantial binding affinities of all ligands with specific amino acid residues within AChE. Remarkably, gedunin exhibited a superior binding affinity (-8.7 kcal/mol) compared to the reference standard. Conclusions: These outcomes accentuate the potential of these seven compounds as viable candidates for oral medication in AD treatment. Notably, both resveratrol and berberine demonstrated the capacity to traverse the blood-brain barrier (BBB), signaling their aptitude for central nervous system targeting. Consequently, these seven molecules are considered orally druggable, potentially surpassing the efficacy of the conventional drug, donepezil, in managing neurodegenerative disorders.

Exploitation of Quercetin's Antioxidative Properties in Potential Alternative Therapeutic Options for Neurodegenerative Diseases

Oxidative stress (OS) is a condition in which there is an excess of reactive oxygen species (ROS) in the body, which can lead to cell and tissue damage. This occurs when there is an overproduction of ROS or when the body's antioxidant defense systems are overwhelmed. Quercetin (Que) is part of a group of compounds called flavonoids. It is found in high concentrations in vegetables, fruits, and other foods. Over the past decade, a growing number of studies have highlighted the therapeutic potential of flavonoids to modulate neuronal function and prevent age-related neurodegeneration. Therefore, Que has been shown to have antioxidant, anticancer, and anti-inflammatory properties, both in vitro and in vivo. Due to its antioxidant character, Que alleviates oxidative stress, thus improving cognitive function, reducing the risk of neurodegenerative diseases. On the other hand, Que can also help support the body's natural antioxidant defense systems, thus being a potentially practical supplement for managing OS. This review focuses on experimental studies supporting the neuroprotective effects of Que in Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), and epilepsy.

Alzheimer's disease: using gene/protein network machine learning for molecule discovery in olive oil

Alzheimer's disease (AD) poses a profound human, social, and economic burden. Previous studies suggest that extra virgin olive oil (EVOO) may be helpful in preventing cognitive decline. Here, we present a network machine learning method for identifying bioactive phytochemicals in EVOO with the highest potential to impact the protein network linked to the development and progression of the AD. A balanced classification accuracy of 70.3 ± 2.6% was achieved in fivefold cross-validation settings for predicting late-stage experimental drugs targeting AD from other clinically approved drugs. The calibrated machine learning algorithm was then used to predict the likelihood of existing drugs and known EVOO phytochemicals to be similar in action to the drugs impacting AD protein networks. These analyses identified the following ten EVOO phytochemicals with the highest likelihood of being active against AD: quercetin, genistein, luteolin, palmitoleate, stearic acid, apigenin, epicatechin, kaempferol, squalene, and daidzein (in the order from the highest to the lowest likelihood). This in silico study presents a framework that brings together artificial intelligence, analytical chemistry, and omics studies to identify unique therapeutic agents. It provides new insights into how EVOO constituents may help treat or prevent AD and potentially provide a basis for consideration in future clinical studies.

An overview of structure-based activity outcomes of pyran derivatives against Alzheimer's disease

Pyran is a heterocyclic group containing oxygen that possesses a variety of pharmacological effects. Pyran is also one of the most prevalent structural subunits in natural products, such as xanthones, coumarins, flavonoids, benzopyrans, etc. Additionally demonstrating the neuroprotective properties of pyrans is the fact that this heterocycle has recently attracted the attention of scientists worldwide. Alzheimer's Disease (AD) treatment and diagnosis are two of the most critical research objectives worldwide. Increased amounts of extracellular senile plaques, intracellular neurofibrillary tangles, and a progressive shutdown of cholinergic basal forebrain neuron transmission are often related with cognitive impairment. This review highlights the various pyran scaffolds of natural and synthetic origin that are effective in the treatment of AD. For better understanding synthetic compounds are categorized as different types of pyran derivatives like chromene, flavone, xanthone, xanthene, etc. The discussion encompasses both the structure-activity correlations of these compounds as well as their activity against AD. Because of the intriguing actions that were uncovered by these pyran-based scaffolds, there is no question that they are at the forefront of the search for potential medication candidates that could treat Alzheimer's disease.

Inhibition Effect and Molecular Mechanisms of Quercetin on the Aβ42 Dimer: A Molecular Dynamics Simulation Study

Amyloid-β (Aβ) dimer as the smallest oligomer has recently been drawing attention due to its neurotoxicity, transient nature, and heterogeneity. The inhibition of Aβ dimer's aggregation is the key to primary intervention of Alzheimer's disease. Previous experimental studies have reported that quercetin, the widespread polyphenolic constituent of multiple fruits and vegetables, can hamper the formation of Aβ protofibrils and disaggregate Aβ fibrils. However, the molecular mechanisms of quercetin in the suppression of the Aβ(1-42) dimer's conformational changes still remain elusive. In this work, to investigate the inhibitory mechanisms of quercetin molecules on the Aβ(1-42) dimer, an Aβ(1-42) dimer based on monomeric the Aβ(1-42) peptide with enriched coil structures is constructed. The early molecular mechanisms of quercetin molecules on inhibiting the Aβ(1-42) dimer at two different Aβ42-to-quercetin molar ratios (1:5 and 1:10) are explored via all-atom molecular dynamics simulations. The results indicate that quercetin molecules can impede the configurational change of the Aβ(1-42) dimer. The interactions and the binding affinity between the Aβ(1-42) dimer and quercetin molecules in the Aβ42 dimer + 20 quercetin system are stronger in comparison with that in the Aβ42 dimer + 10 quercetin system. Our work may be helpful in developing new drug candidates for preventing the conformational transition and further aggregation of the Aβ dimer.

Signal-Enhanced Electrochemical Determination of Quercetin with Poly(chromotrope fb)-Modified Pencil Graphite Electrode in Vegetables and Fruits

A novel signal-enhanced electrochemical sensing strategy was constructed for quercetin determination with a peculiarly developed poly(chromotrope fb)-modified activated pencil graphite electrode in vegetables and fruits. The oxidation signal of quercetin at 118 mV in an alcoholic solution served as the analytical response. The produced platform, characterized by cyclic voltammetry, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, could detect 1.9 nM of quercetin in the range of 0.01-1.2 μM. The extracted quercetin contents of red onion, red cabbage, cranberry, black mulberry, black raisin, and carob were determined by both the developed method and UV-visible spectroscopy. The results were statistically evaluated at the 95% confidence level, and no significant difference between the results was found.

Environmental toxicants and health adversities: A review on interventions of phytochemicals

Toxicity arising from environmental contaminants has attracted global interest in the last few decades, due to the high morbidity and mortality associated with them. Efforts have been made to combat the consequential outcomes of environmental toxicity in humans through traditional remediation techniques and therapeutic measures which have been hampered by one or more limitations. Consequently, this scenario has triggered interest in the medicinal properties of phytochemicals. Thus, this review gives a succinct and in-depth elucidation of the various environmental contaminants and their toxicity effects on humans. It delves into the various classes of phytochemicals and their intervention roles. The study adopted a desk review of existing literatures from scientific reports and peer reviewed articles through triangulation of data sources. "Phytochemicals" are group of secondary metabolites obtained from plants with medicinal properties. These groups of compounds are included but not limited to flavonoids, tannins, saponins, alkaloids, cardenoloids, terpenoids, and phytosteroids. This review corroborates the prophylactic and therapeutics efficacy of these phytochemicals as anti-metastatic, anti-inflammatory, anti-aging, anti-oxidant, anti-microbial and live saving substances with empirical findings from several laboratory, clinical trials and epidemiologic studies. It conclude that given the wide range of medicinal properties of phytochemicals, there is an urgent need for its full optimization in the pharmaceutical industry and future studies should focus on identifying the bioactive molecules in these compounds and its effectiveness against mixer toxicity.

A. Ali G. Inhibitory effect of Titanium dioxide (Tio2) nanoparticles and their synergistic activity with antibiotics in some types of bacteria

Titanium dioxide nanoparticles (TiO2 NPs) were studied as antibacterial agents at different concentrations against clinical and environmental bacterial isolates without UV or photocatalytic activation. Five TiO2 NPs concentrations (20µg/ml,50µg/ml, 100µg/ml,500µg/ml and 1000µg/ml) were studied against 15 bacterial species:10 clinical isolates and 5 environmental isolates) compared with antibiotics Amikacin(AK)and Levloxacin(LEV).Only500µg/ml concentration of TiO2 NPs was active against 7 bacterial isolates (3 clinical and 4 environmental), and 1000µg/ml concentration of TiO2 NPs was effective against 9 isolates (6 clinical and 3 environmental ). These concentrations were mixed with the antibiotics Levloxacin LEV and Amikacin AK to investigate the possibility of synergistic activity against studied bacteria. Bacterial isolate's response or sensitivity to the antibiotic and TiO2 NPs mixture was varied; AK plus 500µg/ml TiO2 NPs concentration showed increased inhibitory activity against 7 isolates (3 clinical, 4 environmental) and 1000µg/ml TiO2 NPs mixed with AK showed increased inhibition activity against one environmental bacterial isolates, where Ak mixed with 500 and Ak plus 1000 µg/ml showed the same effect as the antibiotic alone or less.LEV antibiotic shows no difference in the effect on all 9 bacteria (7 clinical and 2 environmental), while LEV mixed with 500 µg/ml have increased inhibition zones on 4 bacteria (2 clinical, 2 environmental) , and LEV mixed with 1000µg/ml have higher effect than the antibiotic alone on three isolates (2 clinical,1 environmental). Keywords: antibiotic; titanium nanoparticles dioxide; antibacterial.

The Effects of Momordica charantia on Type 2 Diabetes Mellitus and Alzheimer's Disease

T2DM is a complex metabolic disorder characterized by hyperglycemia and glucose intolerance. It is recognized as one of the most common metabolic disorders and its prevalence continues to raise major concerns in healthcare globally. Alzheimer's disease (AD) is a gradual neurodegenerative brain disorder characterized by the chronic loss of cognitive and behavioral function. Recent research suggests a link between the two diseases. Considering the shared characteristics of both diseases, common therapeutic and preventive agents are effective. Certain bioactive compounds such as polyphenols, vitamins, and minerals found in vegetables and fruits can have antioxidant and anti-inflammatory effects that allow for preventative or potential treatment options for T2DM and AD. Recently, it has been estimated that up to one-third of patients with diabetes use some form of complementary and alternative medicine. Increasing evidence from cell or animal models suggests that bioactive compounds may have a direct effect on reducing hyperglycemia, amplifying insulin secretion, and blocking the formation of amyloid plaques. One plant that has received substantial recognition for its numerous bioactive properties is Momordica charantia (M. charantia), otherwise known as bitter melon, bitter gourd, karela, and balsam pear. M. charantia is utilized for its glucose-lowering effects and is often used as a treatment for diabetes and related metabolic conditions amongst the indigenous populations of Asia, South America, India, and East Africa. Several pre-clinical studies have documented the beneficial effects of M. charantia through various postulated mechanisms. Throughout this review, the underlying molecular mechanisms of the bioactive components of M. charantia will be highlighted. More studies will be necessary to establish the clinical efficacy of the bioactive compounds within M. charantia to effectively determine its pertinence in the treatment of metabolic disorders and neurodegenerative diseases, such as T2DM and AD.

Anti-Inflammatory Effects of Flavonoids in Common Neurological Disorders Associated with Aging

Aging reduces homeostasis and contributes to increasing the risk of brain diseases and death. Some of the principal characteristics are chronic and low-grade inflammation, a general increase in the secretion of proinflammatory cytokines, and inflammatory markers. Aging-related diseases include focal ischemic stroke and neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Flavonoids are the most common class of polyphenols and are abundantly found in plant-based foods and beverages. A small group of individual flavonoid molecules (e.g., quercetin, epigallocatechin-3-gallate, and myricetin) has been used to explore the anti-inflammatory effect in vitro studies and in animal models of focal ischemic stroke and AD and PD, and the results show that these molecules reduce the activated neuroglia and several proinflammatory cytokines, and also, inactivate inflammation and inflammasome-related transcription factors. However, the evidence from human studies has been limited. In this review article, we highlight the evidence that individual natural molecules can modulate neuroinflammation in diverse studies from in vitro to animal models to clinical studies of focal ischemic stroke and AD and PD, and we discuss future areas of research that can help researchers to develop new therapeutic agents.

Neuropharmacological interventions of quercetin and its derivatives in neurological and psychological disorders

Quercetin is a naturally occurring bioactive flavonoid abundant in many plants and fruits. Quercetin and its derivatives have shown an array of pharmacological activities in preclinical tests against various illnesses and ailments. Owing to its protective role against oxidative stress and neuroinflammation, quercetin is a possible therapeutic choice for the treatment of neurological disorders. Quercetin and its derivatives can modulate a variety of signal transductions, including neuroreceptor, neuroinflammatory receptor, and redox signaling events. The research on quercetin and its derivatives in neurology-related illnesses mainly focused on the targets, such as redox stress, neuroinflammation, and signaling pathways; however, the function of quercetin and its derivatives on specific molecular targets, such as nuclear receptors and proinflammatory mediators are yet to be explored. Findings showed that various molecular targets of quercetin and its derivatives have therapeutic potential against psychological and neurodegenerative disorders.

Diet's Role in Modifying Risk of Alzheimer's Disease: History and Present Understanding

Diet is an important nonpharmacological risk-modifying factor for Alzheimer's disease (AD). The approaches used here to assess diet's role in the risk of AD include multi-country ecological studies, prospective and cross-sectional observational studies, and laboratory studies. Ecological studies have identified fat, meat, and obesity from high-energy diets as important risk factors for AD and reported that AD rates peak about 15-20 years after national dietary changes. Observational studies have compared the Western dietary pattern with those of the Dietary Approaches to Stop Hypertension (DASH), Mediterranean (MedDi), and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets. Those studies identified AD risk factors including higher consumption of saturated and total fats, meat, and ultraprocessed foods and a lower risk of AD with higher consumption of fruits, legumes, nuts, omega-3 fatty acids, vegetables, and whole grains. Diet-induced factors associated with a significant risk of AD include inflammation, insulin resistance, oxidative stress, elevated homocysteine, dietary advanced glycation end products, and trimethylamine N-oxide. The molecular mechanisms by which dietary bioactive components and specific foods affect risk of AD are discussed. Given most countries' entrenched food supply systems, the upward trends of AD rates would be hard to reverse. However, for people willing and able, a low-animal product diet with plenty of anti-inflammatory, low-glycemic load foods may be helpful.

Phytochemical Compounds and Nanoparticles as Phytochemical Delivery Systems for Alzheimer's Disease Management

Alzheimer's disease remains one of the most widespread neurodegenerative reasons for dementia worldwide and is associated with considerable mortality and morbidity. Therefore, it has been considered a priority for research. Indeed, several risk factors are involved in the complexity of the therapeutic ways of this pathology, including age, traumatic brain injury, genetics, exposure to aluminum, infections, diabetes, vascular diseases, hypertension, dyslipidemia, and obesity. The pathophysiology of Alzheimer's disease is mostly associated with hyperphosphorylated protein in the neuronal cytoplasm and extracellular plaques of the insoluble β-amyloid peptide. Therefore, the management of this pathology needs the screening of drugs targeting different pathological levels, such as acetylcholinesterase (AchE), amyloid β formation, and lipoxygenase inhibitors. Among the pharmacological strategies used for the management of Alzheimer's disease, natural drugs are considered a promising therapeutic strategy. Indeed, bioactive compounds isolated from different natural sources exhibit important anti-Alzheimer effects by their effectiveness in promoting neuroplasticity and protecting against neurodegeneration as well as neuroinflammation and oxidative stress in the brain. These effects involve different sub-cellular, cellular, and/or molecular mechanisms, such as the inhibition of acetylcholinesterase (AchE), the modulation of signaling pathways, and the inhibition of oxidative stress. Moreover, some nanoparticles were recently used as phytochemical delivery systems to improve the effects of phytochemical compounds against Alzheimer's disease. Therefore, the present work aims to provide a comprehensive overview of the key advances concerning nano-drug delivery applications of phytochemicals for Alzheimer's disease management.

Potential implications of polyphenolic compounds in neurodegenerative diseases

Neurodegenerative diseases are common chronic diseases related to progressive damage to the nervous system. Current neurodegenerative diseases present difficulties and despite extensive research efforts to develop new disease-modifying therapies, there is still no effective treatment for halting the neurodegenerative process. Polyphenols are biologically active organic compounds abundantly found in various plants. It has been reported that plant-derived dietary polyphenols may improve some disease states and promote health. Emerging pieces of evidence indicate that polyphenols are associated with neurodegenerative diseases. This review aims to overview the potential neuroprotective roles of polyphenols in most common neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, epilepsy, and ischemic stroke.

Quercetin Is An Active Agent in Berries against Neurodegenerative Diseases Progression through Modulation of Nrf2/HO1

Berries are well-known fruits for their antioxidant effects due to their high content of flavonoids, and quercetin is one of the potent bioactive flavonoids. Although oxidative stress is an inevitable outcome in cells due to energy uptake and metabolism and other factors, excessive oxidative stress is considered a pivotal mediator for the cell death and leads to the progression of neurodegenerative diseases (NDDs). Furthermore, oxidative stress triggers inflammation that leads to neuronal cell loss. Alzheimer's, Parkinson's, Huntington's disease, amyotrophic lateral sclerosis, multiple sclerosis, and so on are the main neurodegenerative diseases. Hence, AD and PD are the most affected NDDs and cause the most lethality without any effective cure. Since AD and PD are the most common NDDs, therefore, in this study, we will describe the effect of oxidative stress on AD and PD. Targeting oxidative stress could be a very effective way to prevent and cure NDDs. Thus, the nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO1) are potent endogenous antioxidant modulatory pathways, which also show cytoprotective activities. Modulation of Nrf2/HO1 signaling pathways through a biological approach could be an effective way to treat with NDDs. Quercetin is a natural polyphenol, which protects neurodegeneration, remarkably by suppressing oxidative stress and inflammation. Thus, quercetin could be a very effective agent against NDDs. We will discuss the benefits and challenges of quercetin to treat against NDDs, focusing on molecular biology.

Quercetin improves contrast-induced acute kidney injury through the HIF-1α/lncRNA NEAT1/HMGB1 pathway

CONTEXT

The risk of contrast-induced acute kidney injury (CI-AKI) is increasing and the harm is great. Quercetin is the main active component in Abelmoschus manihot (L.) Medik (Malvaceae) and was reported to reduce the expression of HIF-1α.

OBJECTIVE

We investigate whether quercetin improves the CI-AKI through the HIF-1α/lncRNA NEAT1/HMGB1 pathway.

MATERIALS AND METHODS

HK-2 cells were treated with iohexol (200 mg/mL) for 6 h to establish a CI-AKI model. Quercetin (20 μM) was administered to CI-AKI cells cultured in dishes for 24 h. Cell morphology was observed by a fluorescence microscope. MTT and TUNEL assays were used to detect cell survival rate and apoptosis. Relative mRNA levels were measured by qRT-PCR. Protein levels were detected using western blotting. IL-6 and TNF-α protein levels were tested by Elisa assay. Targeting binding sites of HIF-1α and lncRNA NEAT1 were detected by luciferase assay.

RESULTS

The IC₅₀ value of quercetin was 163.25 μM. The expression levels of HIF-1α, lncRNA NEAT1 and HMGB1 were upregulated in the CI-AKI cell model. Quercetin diminished cell injury and apoptosis via inhibiting HIF-1α. Silencing of HIF-1α targeting lncRNA MEAT1 diminished cell injury and apoptosis. Silencing lncRNA NEAT1 has the same effect via suppressing HMGB1 expression. Collectively, quercetin diminished cell injury and apoptosis in CI-AKI cell model via the inhibition of HIF-1α on lncRNA NEAT1/HMGB1 signalling pathway.

DISCUSSION AND CONCLUSIONS

Quercetin diminished cell injury and apoptosis in CI-AKI cell mode via the inhibition of HIF-1α on the lncRNA NEAT1/HMGB1 signalling pathway, offering a potential novel therapeutic target for CI-AKI therapy.

Temporal Pattern of Neuroinflammation Associated with a Low Glycemic Index Diet in the 5xFAD Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is associated with brain amyloid-β (Aβ) peptide accumulation and neuroinflammation. Currants, a low glycemic index dried fruit, and their components display pleiotropic neuroprotective effects in AD. We examined how diet containing 5% Corinthian currant paste (CurD) administered in 1-month-old 5xFAD mice for 1, 3, and 6 months affects Aβ levels and neuroinflammation in comparison to control diet (ConD) or sugar-matched diet containing 3.5% glucose/fructose (GFD). No change in serum glucose or insulin levels was observed among the three groups. CurD administered for 3 months reduced brain Aβ42 levels in male mice as compared to ConD and GFD, but after 6 months, Aβ42 levels were increased in mice both on CurD and GFD compared to ConD. CurD for 3 months also reduced TNFα and IL-1β levels in male and female mouse cortex homogenates compared to ConD and GFD. However, after 6 months, TNFα levels were increased in cortex homogenates of mice both on CurD and GFD as compared to ConD. A similar pattern was observed for TNFα-expressing cells, mostly co-expressing the microglial marker CD11b, in mouse hippocampus. IL-1β levels were similarly increased in the brain of all groups after 6 months. Furthermore, a time dependent decrease of secreted TNFα levels was found in BV2 microglial cells treated with currant phenolic extract as compared to glucose/fructose solution. Overall, our findings suggest that a short-term currant consumption reduces neuroinflammation in 5xFAD mice as compared to sugar-matched or control diet, but longer-term intake of currant or sugar-matched diet enhances neuroinflammation.

Exploring the Inhibition of Quercetin on Acetylcholinesterase by Multispectroscopic and In Silico Approaches and Evaluation of Its Neuroprotective Effects on PC12 Cells

This study investigated the inhibitory mechanism of quercetin in acetylcholinesterase (AChE) and its neuroprotective effects on β-amyloid_25-35-induced oxidative stress injury in PC12 cells. Quercetin inhibited AChE in a reversible mixed manner with an IC₅₀ of 4.59 ± 0.27 µM. The binding constant of quercetin with AChE at 25 °C was (5.52 ± 0.05) × 10⁴ L mol^-1. Hydrogen bonding and van der Waals forces were the main interactions in forming the stable quercetin-AChE complex. Computational docking revealed that quercetin was dominant at the peripheral aromatic site in AChE and induced enzymatic allosterism; meanwhile, it extended deep into the active center of AChE and destabilized the hydrogen bond network, which caused the constriction of the gorge entrance and prevented the substrate from entering the enzyme, thus resulting in the inhibition of AChE. Molecular dynamics (MD) simulation emphasized the stability of the quercetin-AChE complex and corroborated the previous findings. Interestingly, a combination of galantamine hydrobromide and quercetin exhibited the synergistic inhibition effect by binding to different active sites of AChE. In a β-amyloid_25-35-induced oxidative stress injury model in PC12 cells, quercetin exerted neuroprotective effects by increasing the glutathione level and reducing the malondialdehyde content and reactive oxygen species levels. These findings may provide novel insights into the development and application of quercetin in the dietary treatment of Alzheimer's disease.

Mechanistic Insights into the Neuroprotective Potential of Sacred Ficus Trees

Ficus religiosa (Bo tree or sacred fig) and Ficus benghalensis (Indian banyan) are of immense spiritual and therapeutic importance. Various parts of these trees have been investigated for their antioxidant, antimicrobial, anticonvulsant, antidiabetic, anti-inflammatory, analgesic, hepatoprotective, dermoprotective, and nephroprotective properties. Previous reviews of Ficus mostly discussed traditional usages, photochemistry, and pharmacological activities, though comprehensive reviews of the neuroprotective potential of these Ficus species extracts and/or their important phytocompounds are lacking. The interesting phytocompounds from these trees include many bengalenosides, carotenoids, flavonoids (leucopelargonidin-3-O-β-d-glucopyranoside, leucopelargonidin-3-O-α-l-rhamnopyranoside, lupeol, cetyl behenate, and α-amyrin acetate), flavonols (kaempferol, quercetin, myricetin), leucocyanidin, phytosterols (bergapten, bergaptol, lanosterol, β-sitosterol, stigmasterol), terpenes (α-thujene, α-pinene, β-pinene, α-terpinene, limonene, β-ocimene, β-bourbonene, β-caryophyllene, α-trans-bergamotene, α-copaene, aromadendrene, α-humulene, alloaromadendrene, germacrene, γ-cadinene, and δ-cadinene), and diverse polyphenols (tannin, wax, saponin, leucoanthocyanin), contributing significantly to their pharmacological effects, ranging from antimicrobial action to neuroprotection. This review presents extensive mechanistic insights into the neuroprotective potential, especially important phytochemicals from F. religiosa and F. benghalensis. Owing to the complex pathophysiology of neurodegenerative disorders (NDDs), the currently existing drugs merely alleviate the symptoms. Hence, bioactive compounds with potent neuroprotective effects through a multitarget approach would be of great interest in developing pharmacophores for the treatment of NDDs.

Neuroprotective Effects of Natural Antioxidants Against Branched-Chain Fatty Acid-Induced Oxidative Stress in Cerebral Cortex and Cerebellum Regions of the Rat Brain

Valproic acid (VPA) is short branched-chain fatty acid (BCFA) derived from valeric acids which are naturally produced by Valeriana officinalis (flowering plant). Neurotoxicity caused by BCFA-like VPA may be mediated by oxidative stress, according to research involving the cerebral cortex and cerebellum. In the present study, we explored the possible protective effect of different antioxidants such as melatonin, quercetin, and piperine on VPA exposure by using a supernatant preparation of the cerebral cortex and cerebellum regions of the rat brain. The present study revealed that melatonin, quercetin, and piperine significantly prevented VPA-induced oxidative stress in the cerebral cortex and cerebellum regions. VPA was also observed to lower the level of reduced glutathione, and this effect was significantly mitigated by these antioxidants. Melatonin, quercetin, and piperine also ameliorated and altered the activities of AChE, Na⁺, K⁺ATPase, and MAO in the cerebral cortex and cerebellum. Results of this study also suggest that prior treatment of antioxidants like melatonin, quercetin, and piperine helps in combating the oxidative stress induced by VPA in the cerebral cortex and cerebellum region of the rat brain. Thus, sufficient dietary intake of these antioxidants by individuals at high risk of VPA exposure could prove beneficial in combating the adverse effect of VPA.

Pharmacological Potential of the Standardized Methanolic Extract of Prunus armeniaca L. in the Haloperidol-Induced Parkinsonism Rat Model

Parkinson's disease (PD) is a complex, age-related neurodegenerative disease that causes neuronal loss and dysfunction over time. An imbalance of redox potential of oxidative stress in the cell causes neurodegenerative diseases and dysfunction of neurons. Plants are a rich source of bioactive substances that attenuate oxidative stress in a variety of neurological disorders. The aim of the present study was to evaluate the Prunus armeniaca L. methanolic extract (PAME) for anti-Parkinson activity in rats. PD was induced with haloperidol (1 mg/kg, IP). The PAME was administered orally at 100, 300, and 800 mg/kg dose levels for 21 days. Behavioral studies (catalepsy test, hang test, open-field test, narrow beam walk, and hole-board test), oxidative stress biomarkers (SOD, CAT, GSH, and MDA) levels, neurotransmitters (dopamine, serotonin, and noradrenaline) levels, and acetylcholinesterase activity were quantified in the brain homogenate. Liver function tests (LFTs), renal function tests (RFTs), complete blood count (CBC), and lipid profiles were measured in the blood/serum samples to note the side effects of PAME at the selected doses. Histopathological analysis was performed on the brain (anti-PD study), liver, heart, and kidney (to check the toxicity of PAME on these vital organs). Motor functions were improved in the behavioral studies. Dopamine, serotonin, and noradrenaline levels were significantly increased (P < 0.001), whereas the level of acetylcholinesterase was decreased significantly (P < 0.001). The levels of superoxide dismutase (SOD), catalase (CAT), and reduced glutathione (GSH) were increased, while malondialdehyde (MDA) and nitrite levels were decreased in the PAME-treated groups significantly compared with the disease control group, hence reducing oxidative stress. The incidence of toxicity was determined by biochemical analysis of LFT and RFT biomarkers testing. The histopathological analysis indicated that neurofibrillary tangles and plaques decreased in a dose-dependent manner in the PAME-treated groups. Based on the data, it is concluded that PAME possessed good anti-Parkinson activity, rationalizing the plant's traditional use as a neuroprotective agent.

Forest Biomass as a Promising Source of Bioactive Essential Oil and Phenolic Compounds for Alzheimer's Disease Therapy

Alzheimer’s disease (AD) is the most common neurodegenerative disorder affecting elderly people worldwide. Currently, there are no effective treatments for AD able to prevent disease progression, highlighting the urgency of finding new therapeutic strategies to stop or delay this pathology. Several plants exhibit potential as source of safe and multi-target new therapeutic molecules for AD treatment. Meanwhile, Eucalyptus globulus extracts revealed important pharmacological activities, namely antioxidant and anti-inflammatory properties, which can contribute to the reported neuroprotective effects. This review summarizes the chemical composition of essential oil (EO) and phenolic extracts obtained from Eucalyptus globulus leaves, disclosing major compounds and their effects on AD-relevant pathological features, including deposition of amyloid-β (Aβ) in senile plaques and hyperphosphorylated tau in neurofibrillary tangles (NFTs), abnormalities in GABAergic, cholinergic and glutamatergic neurotransmission, inflammation, and oxidative stress. In general, 1,8-cineole is the major compound identified in EO, and ellagic acid, quercetin, and rutin were described as main compounds in phenolic extracts from Eucalyptus globulus leaves. EO and phenolic extracts, and especially their major compounds, were found to prevent several pathological cellular processes and to improve cognitive function in AD animal models. Therefore, Eucalyptus globulus leaves are a relevant source of biological active and safe molecules that could be used as raw material for nutraceuticals and plant-based medicinal products useful for AD prevention and treatment.

Suitability of Banana and Plantain Fruits in Modulating Neurodegenerative Diseases: Implicating the In Vitro and In Vivo Evidence from Neuroactive Narratives of Constituent Biomolecules

Active principles in plant-based foods, especially staple fruits, such as bananas and plantains, possess inter-related anti-inflammatory, anti-apoptotic, antioxidative, and neuromodulatory activities. Neurodegenerative diseases affect the functionality of the central and peripheral nervous system, with attendant cognitive deficits being hallmarks of these conditions. The dietary constitution of a wide range of bioactive compounds identified in this review further iterates the significance of the banana and plantain in compromising, halting, or preventing the pathological mechanisms of neurological disorders. The neuroprotective mechanisms of these biomolecules have been identified by using protein expression regulation and specific gene/pathway targeting, such as the nuclear and tumor necrosis factors, extracellular signal-regulated and mitogen-activated protein kinases, activator protein-1, and the glial fibrillary acidic protein. This review establishes the potential double-edged neuro-pharmacological fingerprints of banana and plantain fruits in their traditionally consumed pulp and less utilized peel component for human nutrition.

Quercetin binding accelerates prion fibrillation into proteinase sensitive and loosely structured amyloids

Amyloidoses are caused by the deposition of amyloid fibrils ascribed to protein misfolding. In this study, we examined the antiamyloidogenic and antioxidative activities of quercetin, a plant flavonol from the flavonoid group of polyphenols, on mouse prion protein (moPrP) with biophysical approaches. As the results show, quercetin binds to the C-terminal region of moPrP, and quercetin binding does not affect the structure of moPrP. However, quercetin binding accelerates moPrP fibrillation and changes the structure of moPrP fibrils. Unlike typical prion fibrils, quercetin-bound fibrils are sensitive to proteinase K and are loosely structured. Moreover, due to high antioxidant activity of flavonoid, quercetin-bound fibrils lack imbalance of free radicals and, therefore, they are nontoxic towards neuroblastoma cells. The quercetin shows its uniqueness from typical antiamyloidogenic drugs which either suppress the development of amyloid or eliminate formed amyloids. Quercetin binding converts moPrP into protease-sensitive and non-cytotoxic fibrils. This work provides a powerful resolution in the advancement of antiamyloidogenic treatment.

Quercitrin improved cognitive impairment through inhibiting inflammation induced by microglia in Alzheimer's disease mice

OBJECTIVE

Diets rich in quercitrin show a neuroprotective effect, but the mechanism is not very clear at present. The objective of this study is to explore the effect and mechanism of quercitrin in the treatment of alzheimer's disease (AD).

METHODS

5XFAD transgenic mice were fed with a diet supplemented with quercitrin for three consecutive months. Behavioral experiments were conducted to assess the cognitive ability, luminex liquid chip technology was used to assess the production of proinflammatory cytokines and immunohistochemistry was used to elucidate the activation of microglia.

RESULTS

Quercitrin increased the frequency in exploring new objects, shortened the escape latency and increased the frequency crossing the platform in AD model mice. Quercitrin inhibited the activation and proliferation of microglia, inhibited the secretion of inflammatory cytokines and chemokines and reduced the accumulation of amyloid-β plaques in AD model mice.

CONCLUSION

Quercitrin improved mice cognitive impairment through alleviating the intensity of inflammatory response and is a promising medicinal plant extract in the treatment of AD.

The Potential Benefits of Dietary Polyphenols for Peripheral Nerve Regeneration

Peripheral nerves are frequently affected by lesions caused by trauma (work accidents, car incidents, combat injuries) and following surgical procedures (for instance cancer resection), resulting in loss of motor and sensory function with lifelong impairments. Irrespective of the intrinsic capability of the peripheral nervous system for regeneration, spontaneous or surgically supported regeneration is often unsatisfactory with the limited functional success of nerve repair. For this reason, many efforts have been made to improve the regeneration process. Beyond innovative microsurgical methods that, in certain cases, are necessary to repair nerve injuries, different nonsurgical treatment approaches and adjunctive therapies have been investigated to enhance nerve regeneration. One possibility could be taking advantage of a healthy diet or lifestyle and their relation with proper body functions. Over the years, scientific evidence has been obtained on the benefits of the intake of polyphenols or polyphenol-rich foods in humans, highlighting the neuroprotective effects of these compounds in many neurodegenerative diseases. In order to improve the available knowledge about the potential beneficial role of polyphenols in the process of peripheral nerve regeneration, this review assessed the biological effects of polyphenol administration in supporting and promoting the regenerative process after peripheral nerve injury.

The Therapeutic and Prophylactic Potential of Quercetin against COVID-19: An Outlook on the Clinical Studies, Inventive Compositions, and Patent Literature

Quercetin is a phenolic flavonol compound with established antioxidant, anti-inflammatory, and immuno-stimulant properties. Recent studies demonstrate the potential of quercetin against COVID-19. This article highlighted the prophylactic/therapeutic potential of quercetin against COVID-19 in view of its clinical studies, inventions, and patents. The literature for the subject matter was collected utilizing different databases, including PubMed, Sci-Finder, Espacenet, Patentscope, and USPTO. Clinical studies expose the potential of quercetin monotherapy, and also its combination therapy with other compounds, including zinc, vitamin C, curcumin, vitamin D3, masitinib, hydroxychloroquine, azithromycin, and ivermectin. The patent literature also examines claims that quercetin containing nutraceuticals, pharmaceuticals, and dietary supplements, alone or in combination with other drugs/compounds, including favipiravir, remdesivir, molnupiravir, navitoclax, dasatinib, disulfiram, rucaparib, tamarixin, iota-carrageenan, and various herbal extracts (aloe, poria, rosemary, and sphagnum) has potential for use against COVID-19. The literature reveals that quercetin exhibits anti-COVID-19 activity because of its inhibitory effect on the expression of the human ACE2 receptors and the enzymes of SARS-CoV-2 (MPro, PLPro, and RdRp). The USFDA designated quercetin as a “Generally Recognized as Safe” substance for use in the food and beverage industries. It is also an inexpensive and readily available compound. These facts increase the possibility and foreseeability of making novel and economical drug combinations containing quercetin to prevent/treat COVID-19. Quercetin is an acidic compound and shows metabolic interaction with some antivirals, antibiotics, and anti-inflammatory agents. Therefore, the physicochemical and metabolic drug interactions between quercetin and the combined drugs/compounds must be better understood before developing new compositions.

Biological Effect of Quercetin in Repairing Brain Damage and Cerebral Changes in Rats: Molecular Docking and In Vivo Studies

This study examined the protective effect of quercetin against high-altitude-induced brain damage in rats. A molecular docking study was performed to investigate the potential effect of quercetin in reducing brain damages through its ability to target the oxidative stress enzymes. Biomarker assessment screening assays were also performed then followed by in vivo studies. Three groups of rats were divided into the control group, an untreated animal model group with induced brain damage, and finally, the quercetin treated group that received quercetin dose equal to 20 mg/kg of their body weights. Molecular docking studies and biomarker assessment screening assays proved the potential effect of quercetin to affect the level of representative biomarkers glutathione (GSH), glutathione reductase (GR), glutathione-S-transferase (GST), glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA). Additionally, the protective effect of quercetin against high altitude, low pressure, and low oxygen was also investigated by exploring the brain histopathology of experimental rats. Brain damage was observed in the untreated animal model group. After treatment with quercetin, the cerebral edema in the brain tissues was improved significantly, confirming the protective effects of quercetin. Therefore, quercetin can be used as a natural food additive to protect from the highaltitude-induced brain damage.

Quercetin: an effective polyphenol in alleviating diabetes and diabetic complications

Various studies, especially in recent years, have shown that quercetin has beneficial therapeutic effects in various human diseases, including diabetes. Quercetin has significant anti-diabetic effects and may be helpful in lowering blood sugar and increasing insulin sensitivity. Quercetin appears to affect many factors and signaling pathways involved in insulin resistance and the pathogenesis of type 2 of diabetes. TNFα, NFKB, AMPK, AKT, and NRF2 are among the factors that are affected by quercetin. In addition, quercetin can be effective in preventing and ameliorating the diabetic complications, including diabetic nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy, and affects the key mechanisms involved in the pathogenesis of these complications. These positive effects of quercetin may be related to its anti-inflammatory and anti-oxidant properties. In this article, after a brief review of the pathogenesis of insulin resistance and type 2 diabetes, we will review the latest findings on the anti-diabetic effects of quercetin with a molecular perspective. Then we will review the effects of quercetin on the key mechanisms of pathogenesis of diabetes complications including nephropathy, cardiovascular complications, neuropathy, delayed wound healing, and retinopathy. Finally, clinical trials investigating the effect of quercetin on diabetes and diabetes complications will be reviewed.

Potential of flavonoids as anti-Alzheimer's agents: bench to bedside

Developing therapies for neurodegenerative diseases are challenging because of the presence of blood-brain barrier and Alzheimer being one of the commonest and uprising neurodegenerative disorders possess the need for developing novel therapies. Alzheimer's is attributed to be the sixth leading cause of death in the USA and the number of cases is estimated to be increased from 58 million in 2021 to 88 million by 2050. Natural drugs have benefits of being cost-effective, widely available, fewer side effects, and immuno-booster can be useful in managing Alzheimer. Flavonoids can slow the neuronal degeneration as they have shown activity in central nervous system and are able to cross the blood-brain barrier. These can be easily extracted from fruits, vegetable, and plants. In Alzheimer disease, flavonoids scavenges the reactive oxygen species and reduces the production of amyloid beta protein. Agents from sub-classes of flavonoids such as flavanones, flavanols, flavones, flavonols, anthocyanins, and isoflavones having pharmacological action in treating Alzheimer disease are discussed in this review.

A focus on natural products for preventing and cure of mitochondrial dysfunction in Parkinson's disease

Mitochondria are considered the only source of energy production within cells. This organelle is vital for neural function and survival by producing energy (adenosine triphosphate (ATP)) and regulating intracellular calcium. Mitochondrial dysfunction, which significantly contributes to both idiopathic and familial types of Parkinson's disease (PD), depletes cellular energy, disrupts homeostasis, and induces oxidative stress, leading to cell death. In recent years several natural products have been discovered to be protective against mitochondrial dysfunction. This review discusses the role of mitochondria in the progression of PD to define the path for using natural products to prevent and/or cure PD.

Dietary Polyphenols as Therapeutic Intervention for Alzheimer’s Disease: A Mechanistic Insight

Dietary polyphenols encompass a diverse range of secondary metabolites found in nature, such as fruits, vegetables, herbal teas, wine, and cocoa products, etc. Structurally, they are either derivatives or isomers of phenol acid, isoflavonoids and possess hidden health promoting characteristics, such as antioxidative, anti-aging, anti-cancerous and many more. The use of such polyphenols in combating the neuropathological war raging in this generation is currently a hotly debated topic. Lately, Alzheimer’s disease (AD) is emerging as the most common neuropathological disease, destroying the livelihoods of millions in one way or another. Any therapeutic intervention to curtail its advancement in the generation to come has been in vain to date. Using dietary polyphenols to construct the barricade around it is going to be an effective strategy, taking into account their hidden potential to counter multifactorial events taking place under such pathology. Besides their strong antioxidant properties, naturally occurring polyphenols are reported to have neuroprotective effects by modulating the Aβ biogenesis pathway in Alzheimer’s disease. Thus, in this review, I am focusing on unlocking the hidden secrets of dietary polyphenols and their mechanistic advantages to fight the war with AD and related pathology.

Quercetin Alleviates Demyelination Through Regulating Microglial Phenotype Transformation to Mitigate Neuropsychiatric Symptoms in Mice with Vascular Dementia

Cerebral hypoperfusion plays a pivotal role in the ictus and development of vascular dementia (VaD) with neuropsychiatric symptoms. To date, few pharmacological interventions for neuropsychiatric symptoms are available in the VaD patients with neuropsychiatric impairments. Here, our results demonstrated that the extent of demyelination was dramatically deteriorated and the thickness of myelin sheath was evidently decreased in the presence of cerebral hypoperfusion, whereas Quercetin possessed the potential of abrogating these effects at least in part, then relieving anxiety and depression-like behavior when mice exposed to bilateral carotid artery stenosis (BCAS)/chronic restraint stress (CRS). The underlying mechanism was that Quercetin facilitated secretion of anti-inflammatory cytokines (IL-4 and IL-10) and in turn decreased production of pro-inflammatory factors (TNF-α and IL-1β) due to regulating microglial phenotype transformation, thereafter enhancing the microglial engulfment ability of myelin fragments in vitro and in vivo. Collectively, the results demonstrated that that Quercetin mediated microglial transformation into anti-inflammatory phenotype to reduce demyelination in ventral hippocampus (vHIP), thereafter mitigating neuropsychiatric deficits (including anxiety and depression). The present research broadens the therapeutic scope of Quercetin in central nervous system (CNS) disorders with presence of white matter damage and/or the insufficient activation of anti-inflammatory microglia, particularly for vascular dementia with/without neuropsychiatric symptoms.