Protective effects of flavonoids against Alzheimer's disease-related neural dysfunctions

Basic approach on the protective effects of hesperidin and naringin in Alzheimer's disease

OBJECTIVES

Alzheimer's disease (AD) is a neurodegenerative disease characterized by cognitive impairment. This situation imposes a great burden on individuals, both economically and socially. Today, an effective method for treating the disease and protective approach to tau accumulation has not been developed yet. Studies have been conducted on the effects of hesperidin and naringin flavonoids found in citrus fruits on many diseases.

METHODS

In this review, the pathophysiology of AD is defined, and the effects of hesperidin and naringin on these factors are summarized.

RESULTS

Studies have shown that both components may potentially affect AD due to their antioxidative and anti-inflammatory properties. Based on these effects of the components, it has been shown that they may have ameliorative effects on Aβ, α-synuclein aggregation, tau pathology, and cognitive functions in the pathophysiology of AD.

DISCUSSION

There are studies suggesting that hesperidin and naringin may be effective in the prevention/treatment of AD. When these studies are examined, it is seen that more studies should be conducted on the subject.

Redox changes and cellular senescence in Alzheimer's disease

The redox process and cellular senescence are involved in a range of essential physiological functions. However, they are also implicated in pathological processes underlying age-related neurodegenerative disorders, including Alzheimer's disease (AD). Elevated levels of reactive oxygen species (ROS) are generated as a result of abnormal accumulation of beta-amyloid peptide (Aβ), tau protein, and heme dyshomeostasis and is further aggravated by mitochondria dysfunction and endoplasmic reticulum (ER) stress. Excessive ROS damages vital cellular components such as proteins, DNA and lipids. Such damage eventually leads to impaired neuronal function and cell death. Heightened oxidative stress can also induce cellular senescence via activation of the senescence-associated secretory phenotype to further exacerbate inflammation and tissue dysfunction. In this review, we focus on how changes in the redox system and cellular senescence contribute to AD and how they are affected by perturbations in heme metabolism and mitochondrial function. While potential therapeutic strategies targeting such changes have received some attention, more research is necessary to bring them into clinical application.

Exploring the mechanisms of kaempferol in neuroprotection: Implications for neurological disorders

Kaempferol, a flavonoid compound found in various fruits, vegetables, and medicinal plants, has garnered increasing attention due to its potential neuroprotective effects in neurological diseases. This research examines the existing literature concerning the involvement of kaempferol in neurological diseases, including stroke, Parkinson's disease, Alzheimer's disease, neuroblastoma/glioblastoma, spinal cord injury, neuropathic pain, and epilepsy. Numerous in vitro and in vivo investigations have illustrated that kaempferol possesses antioxidant, anti-inflammatory, and antiapoptotic properties, contributing to its neuroprotective effects. Kaempferol has been shown to modulate key signaling pathways involved in neurodegeneration and neuroinflammation, such as the PI3K/Akt, MAPK/ERK, and NF-κB pathways. Moreover, kaempferol exhibits potential therapeutic benefits by enhancing neuronal survival, attenuating oxidative stress, enhancing mitochondrial calcium channel activity, reducing neuroinflammation, promoting neurogenesis, and improving cognitive function. The evidence suggests that kaempferol holds promise as a natural compound for the prevention and treatment of neurological diseases. Further research is warranted to elucidate the underlying mechanisms of action, optimize dosage regimens, and evaluate the safety and efficacy of this intervention in human clinical trials, thereby contributing to the advancement of scientific knowledge in this field.

The effects of curcumin-piperine supplementation on inflammatory, oxidative stress and metabolic indices in patients with ischemic stroke in the rehabilitation phase: a randomized controlled trial

BACKGROUND

Stroke is a leading cause of death worldwide, which is associated with a heavy economic and social burden. The purpose of this study was to investigate the effects of supplementation with curcumin-piperine combination in patients with ischemic stroke in the rehabilitation stage.

METHODS

In this randomized controlled trial, 66 patients with stroke were randomized into two groups receiving curcumin-piperine tablets (500 mg curcumin + 5 mg piperine) and matched placebo tablets for 12 weeks. High-sensitivity C-reactive protein (hs-CRP), carotid intima-media thickness (CIMT), thrombosis, total antioxidant capacity (TAC), lipid profile, anthropometric indices, blood pressure, and quality of life were assessed before and after the intervention. Statistical data analysis was done using SPSS22 software.

RESULTS

A total of 56 patients with a mean age of 59.80 ± 4.25 years completed the trial. Based on ANCOVA test, adjusted for baseline values, curcumin-piperine supplementation for 12 weeks resulted in significant reductions in serum levels of hs-CRP (p = 0.026), total cholesterol (TC) (p = 0.009), triglycerides (TG) (p = 0.001), CIMT (p = 0.002), weight (P = 0.001), waist circumference (p = 0.024), and systolic and diastolic blood pressure (p < 0.001), and a significant increase in TAC (p < 0.001) in comparison to the placebo. Pain score significantly increased in both groups; however, its increase was significantly higher in the placebo group compared with the intervention group (p = 0.007). No significant changes were observed between the two groups in terms of serum fibrinogen, low-density lipoprotein (LDL), high-density lipoprotein (HDL), and quality of life indices.

CONCLUSION

Curcumin-piperine supplementation had beneficial effects on CIMT, serum hs-CRP, TC, TG, TAC, and systolic and diastolic blood pressure in patients with ischemic stroke in the rehabilitation stage.

Therapeutic potential of flavonoids in the management of obesity-induced Alzheimer's disease: an overview of preclinical and clinical studies

Obesity is a global epidemic that affects people of all ages, genders, and backgrounds. It can lead to a plethora of disorders, including diabetes mellitus, renal dysfunction, musculoskeletal problems, metabolic syndrome, cardiovascular, and neurodegenerative abnormalities. Obesity has also been linked to neurological diseases such as cognitive decline, dementia, and Alzheimer's disease (AD), caused by oxidative stress, pro-inflammatory cytokines, and the production of reactive oxygen free radicals (ROS). Secretion of insulin hormone is impaired in obese people, leading to hyperglycaemia and increased accumulation of amyloid-β in the brain. Acetylcholine, a key neurotransmitter necessary for forming new neuronal connections in the brain, decreases in AD patients. To alleviate acetylcholine deficiency, researchers have proposed dietary interventions and adjuvant therapies that enhance the production of acetylcholine and assist in the management of AD patients. Such measures include dietary intervention with antioxidant and anti-inflammatory flavonoid-rich diets, which have been found to bind to tau receptors, reduce gliosis, and reduce neuroinflammatory markers in animal models. Furthermore, flavonoids like curcumin, resveratrol, epigallocatechin-3-gallate, morin, delphinidins, quercetin, luteolin, and oleocanthal have shown to cause significant reductions in interleukin-1β, increase BDNF levels, stimulate hippocampal neurogenesis and synapse formation, and ultimately prevent the loss of neurons in the brain. Thus, flavonoid-rich nutraceuticals can be a potential cost-effective therapeutic option for treating obesity-induced AD, but further well-designed, randomized, and placebo-controlled clinical studies are needed to assess their optimal dosages, efficacy, and long-term safety of flavonoids in humans. The main objectives of this review are to underscore the therapeutic potential of different nutraceuticals containing flavonoids that can be added in the daily diet of AD patients to enhance acetylcholine and reduce neuronal inflammation in the brain.

Over the Counter Supplements for Memory: A Review of Available Evidence

In 2021, the Global Brain Health Supplement Industry Market size was valued at US$7.6 billion. It is predicted to increase to US$15.59 billion by 2030. Memory and its enhancement are a segment of the market that comprised the highest global revenue share in 2021. In the USA alone, dietary supplement sales reached US$18 billion in 2018. The US Food and Drug Administration (FDA) does not have the authority to approve dietary supplements' safety, effectiveness, or labeling before products go on the market. The FDA often does not even review supplements before they go to market. Supplement manufacturers are thus responsible for ensuring their products are safe and that their claims are truthful. An extensive review of current supplements on the market was performed by surveying memory products for sale at local and national pharmacies and grocery stores. A list of 103 supplements was compiled and the ingredients in these memory supplements were reviewed. The 18 most common ingredients in these supplements were identified. Each of the supplements included at least one of the 18 most common ingredients. Scientific data relative to these ingredients and their effect on memory was searched using PubMed and Cochrane library databases. Currently, there is no compelling evidence for use of apoaequorin, coenzyme Q10, coffee extracts, L-theanine, omega-3 fatty acids, vitamin B6, vitamin B9, or vitamin B12 supplementation for memory. On the other hand, there is some current evidence for memory benefit from supplementation with ashwagandha, choline, curcumin, ginger, Lion's Mane, polyphenols, phosphatidylserine, and turmeric. There are current studies with mixed results regarding the benefit of carnitine, gingko biloba, Huperzine A, vitamin D, and vitamin E supplementation for memory. Dietary supplements geared toward improving cognition are a billion-dollar industry that continues to grow despite lacking a solid scientific foundation for their marketing claims. More rigorous studies are needed relative to the long-term use of these supplements in homogenous populations with standardized measurements of cognition. Health care providers need to be aware of any and all supplements their older adult patients may be consuming and be educated about their side effects and interactions with prescription medications. Lastly, the FDA needs to take an active position relative to monitoring marketed supplements regarding safety, purity and claims of efficacy.

Neuroprotective Effects of Hesperidin and Naringin in SK-N-AS Cell as an In Vitro Model for Alzheimer's Disease

Hesperidin and naringin are flavonoids that are found in citrus fruits. Our aim was to create an in vitro model of Alzheimer's disease (AD) and to evaluate the neuroprotective effects of hesperidin and naringin in SK-N-AS and AD model cells.

Aβ_25-35 was used to create an AD model in SK-N-AS cells. The cytotoxicity of hesperidin and naringin was evaluated using MTT. β-amyloid, tau and α-synuclein distributions were analyzed using indirect immunoperoxidase staining to investigate the neuroprotective effects of hesperidin and naringin.

The AD model was created by 1 µM of Aβ_25-35 for 48 hours after ThT staining. The intensity of β-amyloid was reduced through both hesperidin and naringin treatment in AD model cells. Both flavonoids significantly decreased the intensity of α-synuclein in SK-N-AS and AD model cells.

Hesperidin and naringin can be potentially used as neuroprotective agents. Naringin may be more effective than hesperidin in the accumulation of β-amyloid and tau proteins.

The alleviative effect of Calendula officinalis L. extract against Parkinson's disease-like pathology in zebrafish via the involvement of autophagy activation

Introduction

Parkinson's disease (PD) is the second most prevalent neurodegenerative disorder. However, effective preventative or therapeutic agents for PD remain largely limited. Marigold Calendula officinalis L. (CoL) has been reported to possess a wide range of biological activities, but its neuroprotective activity including anti-neurodegenerative diseases is unclear. Here, we aim to investigate whether the extract of CoL (ECoL) has therapeutic activity on PD.

Methods

We identified the chemical composition of flavonoid, an important active ingredient in ECoL, by a targeted HPLC-Q-TOF-MS analysis. Subsequently, we evaluated the anti-PD effect of ECoL by using zebrafish PD model induced by 1-methyl-4-phenyl-1-1,2,3,6-tetrahydropyridine (MPTP). After ECoL+MPTP co-treatments, the changes of dopaminergic neurons, neural vasculature, nervous system, and locomotor activity were examined, respectively. The expressions of genes related to neurodevelopment and autophagy were detected by RT-qPCR. Further, the interaction between autophagy regulators and ECoL flavonoids was predicted using molecular docking method.

Results

As a result, 5 kinds of flavonoid were identified in ECoL, consisting of 121 flavones and flavonols, 32 flavanones, 22 isoflavonoids, 11 chalcones and dihydrochalcones, and 17 anthocyanins. ECoL significantly ameliorated the loss of dopaminergic neurons and neural vasculature, restored the injury of nervous system, and remarkably reversed the abnormal expressions of neurodevelopment-related genes. Besides, ECoL notably inhibited the locomotor impairment in MPTP-induced PD-like zebrafish. The underlying anti-PD effect of ECoL may be implicated in activating autophagy, as ECoL significantly upregulated the expressions of genes related to autophagy, which contributes to the degradation of α-synuclein aggregation and dysfunctional mitochondria. Molecular docking simulation showed the stable interaction between autophagy regulators (Pink, Ulk2, Atg7, and Lc3b) and 10 main compounds of flavonoid in ECoL, further affirming the involvement of autophagy activation by ECoL in anti-PD action.

Conclusion

Our results suggested that ECoL has the anti-PD effect, and ECoL might be a promising therapeutic candidate for PD treatment.

The Neuroprotective Potentiality of Flavonoids on Alzheimer's Disease

Alzheimer's disease (AD), due to its spread, has become a global health priority, and is characterized by senile dementia and progressive disability. The main cause of AD and other neurodegenerations (Huntington, Parkinson, Amyotrophic Lateral Sclerosis) are aggregated protein accumulation and oxidative damage. Recent research on secondary metabolites of plants such as polyphenols demonstrated that they may slow the progression of AD. The flavonoids' mechanism of action in AD involved the inhibition of acetylcholinesterase, butyrylcholinesterase, Tau protein aggregation, β-secretase, oxidative stress, inflammation, and apoptosis through modulation of signaling pathways which are implicated in cognitive and neuroprotective functions, such as ERK, PI3-kinase/Akt, NFKB, MAPKs, and endogenous antioxidant enzymatic systems. This review focuses on flavonoids and their role in AD, in terms of therapeutic potentiality for human health, antioxidant potential, and specific AD molecular targets.

Natural product-based pharmacological studies for neurological disorders

Central nervous system (CNS) disorders and diseases are expected to rise sharply in the coming years, partly because of the world's aging population. Medicines for the treatment of the CNS have not been successfully made. Inadequate knowledge about the brain, pharmacokinetic and dynamic errors in preclinical studies, challenges with clinical trial design, complexity and variety of human brain illnesses, and variations in species are some potential scenarios. Neurodegenerative diseases (NDDs) are multifaceted and lack identifiable etiological components, and the drugs developed to treat them did not meet the requirements of those who anticipated treatments. Therefore, there is a great demand for safe and effective natural therapeutic adjuvants. For the treatment of NDDs and other memory-related problems, many herbal and natural items have been used in the Ayurvedic medical system. Anxiety, depression, Parkinson's, and Alzheimer's diseases (AD), as well as a plethora of other neuropsychiatric disorders, may benefit from the use of plant and food-derived chemicals that have antidepressant or antiepileptic properties. We have summarized the present level of knowledge about natural products based on topological evidence, bioinformatics analysis, and translational research in this review. We have also highlighted some clinical research or investigation that will help us select natural products for the treatment of neurological conditions. In the present review, we have explored the potential efficacy of phytoconstituents against neurological diseases. Various evidence-based studies and extensive recent investigations have been included, which will help pharmacologists reduce the progression of neuronal disease.

Therapeutic Effects and Metabolic Spectrum of Traditional Chinese Medicine Hengqing II Prescription on Alzheimer’s Disease

Alzheimer's disease (AD) seriously damages elders' social and daily abilities around the world. Traditional Chinese medicine (TCM), a rich drug resource bank, could help research AD. In order to explore the role of TCM in AD treatment, 86 AD patients were recruited from the hospital, then treated with Hengqing II prescription and donepezil hydrochloride. The cognitive and serum lipid levels were investigated before and after treatment. The patient's urine was collected after three months of treatment. Metabolites in the urine samples were extracted with methanol and detected on the UHPLC-MS platform. Results proved that Hengqing II can improve cognitive levels and reduce the levels of Hcy, D-D, FIB, Apo B, TC, and LDL-C compared with donepezil hydrochloride (P < 0.05). The results of multivariate statistical analysis revealed that the metabolism of HQII was significantly different compared with Control groups. A total of 66 differential metabolites were found in this comparison (50 were down-regulated and 16 were up-regulated). Four amino acid pathways and one linoleic acid pathway were found through these metabolites. After receiver operating characteristic analysis, it was suggested that palmitic acid, palmitoleic acid, linoleic acid, oleic acid, SAH, and methionine can be used as biomarkers for treating AD, while the effects of daidzein, genistein, and naringenin on the treatment of AD need to be further studied.

Eucommia ulmoides Olive Male Flower Extracts Ameliorate Alzheimer's Disease-Like Pathology in Zebrafish via Regulating Autophagy, Acetylcholinesterase, and the Dopamine Transporter

Alzheimer's disease (AD) is the most prevalent neural disorder. However, the therapeutic agents for AD are limited. Eucommia ulmoides Olive (EUO) is widely used as a traditional Chinese herb to treat various neurodegenerative disorders. Therefore, we investigated whether the extracts of EUO male flower (EUMF) have therapeutic effects against AD. We focused on the flavonoids of EUMF and identified the composition using a targeted HPLC-MS analysis. As a result, 125 flavonoids and flavanols, 32 flavanones, 22 isoflavonoids, 11 chalcones and dihydrochalcones, and 17 anthocyanins were identified. Then, the anti-AD effects of the EUMF were tested by using zebrafish AD model. The behavioral changes were detected by automated video-tracking system. Aβ deposition was assayed by thioflavin S staining. Ache activity and cell apoptosis in zebrafish were tested by, Acetylcholine Assay Kit and TUNEL assay, respectively. The results showed that EUMF significantly rescued the dyskinesia of zebrafish and inhibited Aβ deposition, Ache activity, and occurrence of cell apoptosis in the head of zebrafish induced by AlCl₃. We also investigated the mechanism underlying anti-AD effects of EUMF by RT-qPCR and found that EUMF ameliorated AD-like symptoms possibly through inhibiting excessive autophagy and the abnormal expressions of ache and slc6a3 genes. In summary, our findings suggested EUMF can be a therapeutic candidate for AD treatment.

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.

Neuroprotective Effect of Luteolin-7-O-Glucoside against 6-OHDA-Induced Damage in Undifferentiated and RA-Differentiated SH-SY5Y Cells

Luteolin is one of the most common flavonoids present in edible plants and its potential benefits to the central nervous system include decrease of microglia activation, neuronal damage and high antioxidant properties. The aim of this research was to evaluate the neuroprotective, antioxidant and anti-inflammatory activities of luteolin-7-O-glucoside (Lut7). Undifferentiated and retinoic acid (RA)-differentiated SH-SY5Y cells were pretreated with Lut7 and incubated with 6-hydroxydopamine (6-OHDA). Cytotoxic and neuroprotective effects were determined by MTT assay. Antioxidant capacity was determined by DPPH, FRAP, and ORAC assays. ROS production, mitochondrial membrane potential (ΔΨm), Caspase–3 activity, acetylcholinesterase inhibition (AChEI) and nuclear damage were also determined in SH-SY5Y cells. TNF-α, IL-6 and IL-10 release were evaluated in LPS-induced RAW264.7 cells by ELISA. In undifferentiated SH-SY5Y cells, Lut7 increased cell viability after 24 h, while in RA-differentiated SH-SY5Y cells, Lut7 increased cell viability after 24 and 48 h. Lut7 showed a high antioxidant activity when compared with synthetic antioxidants. In undifferentiated cells, Lut7 prevented mitochondrial membrane depolarization induced by 6-OHDA treatment, decreased Caspase-3 and AChE activity, and inhibited nuclear condensation and fragmentation. In LPS-stimulated RAW264.7 cells, Lut7 treatment reduced TNF-α levels and increased IL-10 levels after 3 and 24 h, respectively. In summary, the results suggest that Lut7 has neuroprotective effects, thus, further studies should be considered to validate its pharmacological potential in more complex models, aiming the treatment of neurodegenerative diseases.

An ethnopharmacological review on the therapeutical properties of flavonoids and their mechanisms of actions: A comprehensive review based on up to date knowledge

Flavonoids -a class of low molecular weight secondary metabolites- are ubiquitous and cornucopia throughout the plant kingdom. Structurally, the main structure consists of C6-C3-C6 rings with different substitution patterns so that many sub-classes are obtained, for example: flavonols, flavonolignans, flavonoid glycosides, flavans, anthocyanidins, aurones, anthocyanidins, flavones, neoflavonoids, chalcones, isoflavones, flavones and flavanones. Flavonoids are evaluated to have drug like nature since they possess different therapeutic activities, and can act as cardioprotective, antiviral, antidiabetic, anti-inflammatory, antibacterial, anticancer, and also work against Alzheimer's disease and others. However, information on the relationship between their structure and biological activity is scarce. Therefore, the present review tries to summarize all the therapeutic activities of flavonoids, their mechanisms of action and the structure activity relationship.

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Latest updated ethnopharmacological review of the therapeutic effects of flavonoids.

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Flavonoids are attracting attention because of their therapeutic properties.

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Flavonoids are valuable candidates for drug development against many dangerous diseases.

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This overview summarizes the most important therapeutic effect and mechanism of action of flavonoids.

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General knowledge about the structure activity relationship of flavonoids is summarized.

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Substitution of chemical groups in the structure of flavonoids can significantly change their biological and chemical properties.

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The chemical properties of the basic flavonoid structure should be considered in a drug-based structural program.

Plant-derived nootropics and human cognition: A systematic review

Substances with modulatory capabilities on certain aspects of human cognition have been revered as nootropics from the dawn of time. The plant kingdom provides most of the currently available nootropics of natural origin. Here, in this systematic review, we aim to provide state-of-the-art information regarding proven and unproven effects of plant-derived nootropics (PDNs) on human cognition in conditions of health and disease. Six independent searches, one for each neurocognitive domain (NCD), were performed in parallel using three independent scientific library databases: PubMed, Cochrane and Scopus. Only scientific studies and systematic reviews with humans published between January 2000 and November 2021 were reviewed, and 256 papers were included. Ginkgo biloba was the most relevant nootropic regarding perceptual and motor functions. Bacopa monnieri improves language, learning and memory. Withania somnifera (Ashwagandha) modulates anxiety and social-related cognitions. Caffeine enhances attention and executive functions. Together, the results from the compiled studies highlight the nootropic effects and the inconsistencies regarding PDNs that require further research.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.2021137.

Emerging Role of Flavonoids as the Treatment of Depression

Depression is one of the most frequently observed psychological disorders, affecting thoughts, feelings, behavior and a sense of well-being in person. As per the WHO, it is projected to be the primitive cause of various other diseases by 2030. Clinically, depression is treated by various types of synthetic medicines that have several limitations such as side-effects, slow-onset action, poor remission and response rates due to complicated pathophysiology involved with depression. Further, clinically, patients cannot be given the treatment unless it affects adversely the job or family. In addition, synthetic drugs are usually single targeted drugs. Unlike synthetic medicaments, there are many plants that have flavonoids and producing action on multiple molecular targets and exhibit anti-depressant action by affecting multiple neuronal transmissions or pathways such as noradrenergic, serotonergic, GABAnergic and dopaminergic; inhibition of monoamine oxidase and tropomyosin receptor kinase B; simultaneous increase in nerve growth and brain-derived neurotrophic factors. Such herbal drugs with flavonoids are likely to be useful in patients with sub-clinical depression. This review is an attempt to analyze pre-clinical studies, structural activity relationship and characteristics of reported isolated flavonoids, which may be considered for clinical trials for the development of therapeutically useful antidepressant.

Antioxidant properties of flavonoid metal complexes and their potential inclusion in the development of novel strategies for the treatment against neurodegenerative diseases

The increased oxidative stress in the acceleration of the aging process and development of the neuronal disorder are the common feature detected in neurodegenerative illness, such as Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. Searching for new treatment against these diseases, the inclusion of exogenous antioxidant agents has shown good results. Flavonoids are polyphenols compounds present in plants, fruits and vegetables that exhibit potent antioxidant and biological properties, which are related to their chemical structure that to confer an excellent radical scavenging ability. The design of metal-flavonoid complexes allows to obtain compounds with improved biological and physicochemical properties, generating important increase of the flavonoid antioxidant properties. This evidence we motive to propose that antioxidant properties of the metal flavonoids compounds can play an important role in the design of potential novel therapeutic strategies. This review presents the structure-activity relationship on the antioxidant properties of three series of metal-flavonoid complexes: M-(quercetin), M-(morin), and M-(rutin). In general, we observed that the coordination sites, the metal ion type used, and the molar ratio metal:flavonoid present in the complexes, are important factors for to increase the antioxidant activity. On these evidences we motive to propose that the development of metal-flavonoid compounds is a potentially viable approach for combating neurodegenerative diseases.

Flavonoid Composition and Pharmacological Properties of Elaeis guineensis Jacq. Leaf Extracts: A Systematic Review

The oil palm tree (Elaeis guineensis Jacq.) originates from West and Central Africa, and it is cultivated in Malaysia for its oil-producing fruits. Malaysia is the world’s second largest palm oil producer and the world’s largest exporter to date. Consequently, the Malaysian oil palm industry constantly generates a huge amount of biomass with the major contributor being the leaves. A large percentage of these leaves remain underutilized, making them a promising source of raw materials that can be converted into value-added products. The present review summarizes and discusses the flavonoid composition, total phenolic and flavonoid content, and the in vitro and in vivo pharmacological properties exhibited by the extracts of the leaves of E. guineensis. The purpose of this systematic review is to highlight the potential of valorizing the leaf extracts of the oil palm tree as pharmaceutical and cosmeceutical agents.

Recent Progress on Biological Activity of Amaryllidaceae and Further Isoquinoline Alkaloids in Connection with Alzheimer's Disease

Alzheimer’s disease (AD) is a progressive age-related neurodegenerative disease recognized as the most common form of dementia among elderly people. Due to the fact that the exact pathogenesis of AD still remains to be fully elucidated, the treatment is only symptomatic and available drugs are not able to modify AD progression. Considering the increase in life expectancy worldwide, AD rates are predicted to increase enormously, and thus the search for new AD drugs is urgently needed. Due to their complex nitrogen-containing structures, alkaloids are considered to be promising candidates for use in the treatment of AD. Since the introduction of galanthamine as an antidementia drug in 2001, Amaryllidaceae alkaloids (AAs) and further isoquinoline alkaloids (IAs) have been one of the most studied groups of alkaloids. In the last few years, several compounds of new structure types have been isolated and evaluated for their biological activity connected with AD. The present review aims to comprehensively summarize recent progress on AAs and IAs since 2010 up to June 2021 as potential drugs for the treatment of AD.

A Comprehensive Review on Varicose Veins: Preventive Measures and Different Treatments

The purpose of this article was to review the different preventive measures and treatments for varicose veins disease. Varicose veins are tortuous, enlarged veins that are usually found in the lower extremities damages blood vessels leading to its painful swelling cause's blood clots, affecting people over increasing prevalence with age and affects the proficiency, productivity, and life quality of a person. Prolonged standing and obesity are the major reason for varicose vein disease. The mechanisms, prevention, risk factors, complications, and treatment of varicose veins are explained in this review. Various types of treatments such as endovascular, surgical, and herbal treatments improve quality of life and reduce the secondary complications of varicose veins. Besides these methods of treatments, varicose vein disease can be prevented by doing regular yoga/exercise and consumption of several fruits and vegetables such as Grapes, blackberries, avocados, ginger, and rosemary. Typically, varicose veins can be a benign process with several problems that can influence the life quality of an individual that can lead to potentially life-threatening complications. However, there are numerous surgical, endovascular, and chemical treatments that improve quality of life and decrease secondary complications of varicose veins. Patients with varicose veins should take an antioxidant medicament from the flavonoid groups to reduce the arterial blood pressure value, risk of atherosclerosis development, prevent thrombotic incidents.Key teaching pointsChronic venous disease is a pathological state of vein circulatory systems of the lower limbsProlonged standing and obesity are the major reason for varicose vein diseaseEndovascular, surgical, and herbal treatments improve quality of life and reduce the secondary complications of varicose veinsVenoactive drugs such as flavonoids, saponins, and others have a therapeutic effect on chronic venous disordersPhlebotropic drugs are semi-synthetic substances widely used in different states of chronic venous insufficiencyFood rich in phytoconstituents are more effective in varicose veins.

Sex-Independent Cognition Improvement in Response to Kaempferol in the Model of Sporadic Alzheimer's Disease

Alzheimer's disease (AD) is associated with neural oxidative stress and inflammation, and it is assumed to affect more women than men with unknown mechanisms. Kaempferol (KMP) as a potent natural antioxidant has been known to exhibit various biological and pharmacological functions, including antioxidant and anti-inflammatory. We aimed here to evaluate the role of gender difference in response to KMP on the rat model of sporadic AD. Forty-six female and male Wistar rats were divided into six groups of sham, streptozotocin (STZ) + saline (SAL), STZ + KMP. Female rats were ovariectomized, and then all animals received an intracerebroventricular bilateral injection of STZ (3 mg/kg) to induce the AD model. KMP (10 mg/kg) was intraperitoneally administered for 21 consecutive days. Afterward, spatial learning and memory were assessed via the Morris water maze task (MWM). Finally, the hippocampus level of superoxide dismutase (SOD), glutathione, and malondialdehyde were measured using calorimetric kits. Data showed a significant cognition deficit in STZ + SAL compared with the sham. To sum up, we reported that chronic KMP treatment increase significantly improved acquisition and retrieval of spatial memory as evident by longer TTS (total time spent) and short-latency to the platform in MWM. In addition, KMP increased the levels of SOD and glutathione in the hippocampus of rats. Also, KMP decreased hippocampal levels of malondialdehyde in both genders. In conclusion, KMP successfully restores spatial memory impairment independent of gender difference. This memory restoration may at least in part be mediated through boosting the hippocampal level of SOD and glutathione.

Brain-Derived Neurotrophic Factor Signaling in the Pathophysiology of Alzheimer's Disease: Beneficial Effects of Flavonoids for Neuroprotection

The function of the brain-derived neurotrophic factor (BDNF) via activation through its high-affinity receptor Tropomyosin receptor kinase B (TrkB) has a pivotal role in cell differentiation, cell survival, synaptic plasticity, and both embryonic and adult neurogenesis in central nervous system neurons. A number of studies have demonstrated the possible involvement of altered expression and action of the BDNF/TrkB signaling in the pathogenesis of neurodegenerative diseases, including Alzheimer’s disease (AD). In this review, we introduce an essential role of the BDNF and its downstream signaling in neural function. We also review the current evidence on the deregulated the BDNF signaling in the pathophysiology of AD at gene, mRNA, and protein levels. Further, we discuss a potential usefulness of small compounds, including flavonoids, which can stimulate BDNF-related signaling as a BDNF-targeting therapy.

Inhibitory mechanism of O-methylated quercetins, highly potent β-secretase inhibitors isolated from Caragana balchaschensis (Kom.) Pojark

ETHNOPHARMACOLOGICAL RELEVANCE

Caragana has a standing history of implementation in Traditional Chinese Medicine (TCM). Most species of this genus have been explored for multi-functional purposes, such as promoting blood circulation and curing neuralgia, fatigue, migraine, arthritis, and vascular hypertension (Meng et al., 2009). Among them, the well-known species C. sinica showed the most promising potential to increase the expression of ADAM10 among 313 tested medicinal plants, which is one of the promising approach for the treatment of Alzheimer's disease (AD). (Schuck et al., 2015).

AIM OF THIS STUDY

The aim of this work is to explore β-secretase inhibitory activity of compounds isolated from the aerial part of endemic Caragana balchaschensis (Kom.) Pojark. We provided a full characterization of their inhibitory mechanisms, binding affinities, and binding modes.

MATERIALS AND METHODS

The isolation of quercetin derivatives was accomplished by various chromatographical approaches and their structures were annotated by spectroscopic analysis. The detailed kinetic behavior of β-secretase inhibitors was determined by estimation of kinetic parameters (K_m, V_max, K_I, and K_IS). Binding affinities (K_SV) and binding modes of inhibitors were elucidated by fluorescence quenching and molecular docking studies, respectively.

RESULTS

O-methylated quercetins (2-7) were significantly effective in β-secretase inhibition with IC₅₀ ranging from 1.2 to 6.5 μM. The most active one (6) was 20-fold effective than the mother skeleton, quercetin. The O-methyl motif was a critical factor in β-secretase inhibition: tri-O-methylated (1.2 μM) > di-O-methylated (3.5 μM) > mono-O-methylated (6.5 μM) > quercetin (25.2 μM). In the kinetic study, all quercetins (1-7) showed a noncompetitive inhibition, but glucoside ones (8 and 9) were mixed type I inhibitors. The binding affinities (K_SV) were agreed with inhibitory potencies. The O-methylated quercetins were annotated as the most natural abundant metabolites in the aerial part by LC-ESI-TOF/MS. Binding modes of inhibitors to enzyme were elucidated by molecular docking experiments.

CONCLUSION

This study disclosed that most of the major phenolic metabolites of the aerial part of C. balchaschensis are O-methylated quercetins, which have a significant inhibitory effect on β-secretase, which is a critical factor for AD.

Green-synthesized zinc oxide nanoparticles, anti-Alzheimer potential and the metabolic profiling of Sabal blackburniana grown in Egypt supported by molecular modelling

Nowadays, the biosynthesis of metal nanoparticles, particularly from plants, has been gaining interest. In the present work, the methanolic extracts of leaves, fruits, and the pollen grains of Sabal blackburniana were used for the green synthesis of ZnO nanoparticles, which were early detected by the formation of precipitate and further confirmed by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) spectroscopy and zeta potential (ZP) studies. TEM analysis has shown different shapes, predominantly irregular small spherical narrow particles included in hexagonal structures with size ranging from 2.23 to 49.56 nm. The XRD pattern confirmed that all synthesized ZnO nanoparticles have wurtzite hexagonal structure with crystalline nature. The average particle crystallite sizes were 47.21, 47.67 and 47.8 nm. The UV-visible spectra showed λ max in the range of 354-368 nm, which indicated the presence of ZnO nanoparticles. The FT-IR analysis identifies the characteristic functional groups present on the surface of ZnO nanoparticles. The ZP determination demonstrated that all representative selected synthesized ZnONPs exhibited acceptable ZP values of -30.8 to -45.9 mV, which indicated their good stability. In addition, the anti-Alzheimer potential of the selected extracts and ZnONPs was evaluated by assessing acetylcholinesterase inhibitory activity in vitro according to the improved Ellman method. The results indicated that the selected extracts have acetylcholinesterase inhibitory activity, and highlighted the promising inhibitory potential of green-synthesized ZnONPs using pollen grains, fruits and leaves extracts; they exhibited a potent inhibitory effect with IC50 values 63.78 ± 1.04651, 81.985 ± 3.075 and 117.95 ± 6.858 ng ml-1 respectively in comparison to donepezil as standard (IC50 = 50.7 ± 5.769 ng ml-1). Dereplication analysis of the selected extracts was performed using LC-MS; metabolic profiling revealed the presence of 41 compounds belonging to various chemical classes: flavonoids, steroidal saponins, terpenoids, alkaloids, lignans, sterols and fatty acids. Docking these dereplicated metabolites against the human AChE showed that the non-glycosylated flavonoid class of compounds was able to achieve interesting binding modes inside the AChE active site; they are suggested to be associated with the observed anti-AChE activity of Sabal extracts. This study is the first report to shed light on the acetylcholinesterase inhibitory activity of green-synthesized ZnO nanoparticles of S. blackburniana metabolites.

The flavonoids of okra insulates against oxidative stress, neuroinflammation and restores BDNF levels in Aβ1-42 induced mouse model of Alzheimer's disease

Okra (Abelmoschus esculentus [L.] Moench.) has been used as a natural drug in East or West Africa for many centuries, as well as consumed in most areas of the world as a tropical vegetable. The study aimed to evaluate whether the flavonoids of okra fruit (FOF) administration influence Aβ_1-42-induced learning and memory impairment, and explore the underlying mechanisms. The Y-maze task and the Morris water maze test were used for evaluating cognition processes. The levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and glutathione peroxidase (GSH-Px) were detected by ELISA kits. The expressions of nuclear factor kappa-light chain-enhancer of activated B (NF-κB), brain-derived neurotrophic factor (BDNF), cAMP-response element-binding protein (CREB), extracellular signal-regulated kinase (ERK), phosphatidylinositol 3 kinase (PI3K), protein kinase B (AKT), glycogen synthase kinase-3β (GSK-3β) were studied by western blot. Histopathological changes were observed by H.E. straining. The results showed that intracerebroventricular injection of Aβ_1-42 was effective in producing memory deficits in mice. Besides, Aβ_1-42 exposure could significantly increase the levels of NF-κB, TNF-α, IL-1β, and decreased T-AOC, the activities of SOD and GSH-Px in the hippocampus and cortex. Furthermore, the level of BDNF was also reduced, accompanied by down-regulated CREB/ERK and PI3K/AKT/GSK-3β signaling pathways in the hippocampus and cortex. Nevertheless, chronic administration of FOF (100 or 300 mg/kg, i.g.) significantly prevented Aβ_1-42-induced behavioral and biochemical alterations. It also suggested that FOF could improve the cognitive deficits in AD-like model mice, which might be mediated by regulation of BDNF levels in cortex and hippocampus and up-regulating of CREB/ERK and PI3K/AKT/GSK3β pathways, as well as alleviation of oxidative stress and neuroinflammation.

Recent Research on Flavonoids and their Biomedical Applications

Flavonoids, commonly found in various plants, are a class of polyphenolic compounds having a basic structural unit of 2-phenylchromone. Flavonoid compounds have attracted much attention due to their wide biological applications. In order to facilitate further research on the biomedical application of flavonoids, we surveyed the literature published on the use of flavonoids in medicine during the past decade, documented the commonly found structures in natural flavonoids, and summarized their pharmacological activities as well as associated mechanisms of action against a variety of health disorders including chronic inflammation, cancer, cardiovascular complications and hypoglycemia. In this mini-review, we provide suggestions for further research on the biomedical applications of flavonoids.

Important Flavonoids and Their Role as a Therapeutic Agent

Flavonoids are phytochemical compounds present in many plants, fruits, vegetables, and leaves, with potential applications in medicinal chemistry. Flavonoids possess a number of medicinal benefits, including anticancer, antioxidant, anti-inflammatory, and antiviral properties. They also have neuroprotective and cardio-protective effects. These biological activities depend upon the type of flavonoid, its (possible) mode of action, and its bioavailability. These cost-effective medicinal components have significant biological activities, and their effectiveness has been proved for a variety of diseases. The most recent work is focused on their isolation, synthesis of their analogs, and their effects on human health using a variety of techniques and animal models. Thousands of flavonoids have been successfully isolated, and this number increases steadily. We have therefore made an effort to summarize the isolated flavonoids with useful activities in order to gain a better understanding of their effects on human health.

UPLC-Orbitrap HRMS metabolic profiling of Cymbopogon citratus cultivated in Egypt; neuroprotective effect against AlCl3-induced neurotoxicity in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Cymbopogon citratus (lemongrass) is commonly used in teas, soups and treat inflammatory-based ailments, vascular and nervous disorders.

AIM OF THE STUDY

The study aimed to evaluate the neuroprotective effect of Cymbopogon citratus leaves through scientific protocol. The effect of aqueous (AE) and ethanolic (EE) extracts was evaluated against AlCl₃-induced Alzheimer's disease (AD) in rats. Metabolic profiling of the plant, isolation of bioactive compounds and standardization of the active fraction were investigated.

MATERIALS AND METHODS

AE of Cymbopogon citratus leaves was prepared as per traditional method (infusion), EE was prepared by repeated maceration in 90% ethanol, bioactive fraction (BAEE) was obtained from EE and the active compounds thereof were obtained by column chromatography. Metabolic profiling of Cymbopogon citratus was performed by UPLC-Orbitrap HRMS and HPLC was used for standardization. AlCl₃-induced Alzheimer's rats were used to assess neuroprotective effect of the extracts. Neuroprotective mechanism(s) of Cymbopogon citratus extracts was clarified through histopathological examination of brain tissues, estimation of AD biochemical markers, oxidative stress and neuroinflammation in brain homogenates. In addition, antioxidant (using DPPH assay) and anticholinesterase (using modified Ellman's method) activities were investigated.

RESULTS

AlCl₃-treated rats (17 mg/kg/day) showed histopathological alteration in brain tissues together with elevated levels of Aβ, tau proteins, MDA, NF-kB and IL-6. However, treatment with AE and EE of Cymbopogon citratus leaves prevented the pathological changes and maintained the levels of oxidative stress and inflammatory markers. In addition, BAEE significantly inhibited acetylcholinesterase enzyme (2.11 ± 0.11 mg/ml) and exhibited a strong antioxidant activity (24.99 ± 0.00 μg/ml). UPLC-MS of Cymbopogon citratus leaves showed peaks for twenty-eight compounds, twenty-one of them were identified. Three flavonoids; isoorientin, isoschaftoside and luteolin-7-O-neohesperidoside were isolated from BAEE as major constituents. The powdered leaves of Cymbopogon citratus was found to contain remarkable amounts of caffeic acid (3.49 mg/g dry wt.) and isoorientin (7.37 mg/g dry wt.) as determined by HPLC.

CONCLUSION

Cymbopogon citratus ethanolic extract attenuates AlCl₃-induced neurotoxicity in rats through inhibition of oxidative stress and inflammatory markers. This effect could possibly attributed, in part to its high content of phenolic acids and flavonoids. Accordingly, we recommend Cymbopogon citratus leaves for protection against AD.

Plant-Derived Antioxidants Protect the Nervous System From Aging by Inhibiting Oxidative Stress

Alzheimer's disease (AD) has become a major disease contributing to human death and is thought to be closely related to the aging process. The rich antioxidant substances in plants have been shown to play a role in delaying aging, and in recent years, significant research has focused on also examining their potential role in AD onset and progression. Many plant-derived antioxidant research studies have provided insights for the future treatment and prevention of AD. This article reviews various types of plant-derived antioxidants with anti-aging effects on neurons. Also it distinguishes the different types of active substances that exhibit different degrees of protection for the nervous system and summarizes the mechanism thereof. Plant-derived antioxidants with neuroprotective functions can protect various components of the nervous system in a variety of ways and can have a positive impact on interventions to prevent and alleviate AD. Furthermore, when considering neuroprotective agents, glial cells also contribute to the defense of the nervous system and should not be ignored.

Role of antioxidants and a nutrient rich diet in Alzheimer's disease

The joint attack on the body by metabolic acidosis and oxidative stress suggests that treatment in degenerative diseases, including Alzheimer's disease (AD), may require a normalizing of extracellular and intracellular pH with simultaneous supplementation of an antioxidant combination cocktail at a sufficiently high dose. Evidence is also accumulating that combinations of antioxidants may be more effective, taking advantage of synergistic effects of appropriate antioxidants as well as a nutrient-rich diet to prevent and reverse AD. This review focuses on nutritional, nutraceutical and antioxidant treatments of AD, although they can also be used in other chronic degenerative and neurodegenerative diseases.

Combined Black Rice Germ, Bran Supplement and Exercise Intervention Modulate Aging Biomarkers and Improve Physical Performance and Lower-Body Muscle Strength Parameters in Aging Population

Aging is a time-dependent functional decline in muscle mass and strength, which is reflected in poor physical performances, hormonal imbalance, and development of chronic low-grade inflammation. This study aimed to assess the effectiveness of black rice germ, bran supplement, and exercise program either alone or in combination for 24 weeks on the aging biomarkers (C-reactive protein, Interleukin-6, Insulin-like growth factor-1, and CD4:CD8 T cell ratio) physical performance, muscle strength parameters (walking speed, sit-to-stand time, grip strength) among Thai aging population. A total of 120 healthy volunteers aged 65-74 years were assigned to the exercise group (EX), black rice germ, and bran supplement (BR) group or the combination of BR and EX group (BR + EX). Over the course of the 24-week intervention, compared with baseline data (T0), the combined BR + EX intervention significantly decreased the inflammatory biomarkers (C-reactive protein and interleukin-6 levels, both p < 0.05 vs. T0) and significantly increased the insulin-like growth factor-1 levels (p < 0.001 vs. T0). Significant improvement in physical performance and muscle strength were also observed in the combined BR + EX group (decrease in sit-to-stand time and gait speed over the 24-week intervention, both p < 0.05 vs. T0, and trend toward grip strength improvement at p = 0.088 vs. T0). Overall, our results indicated a synergistic effect towards the combined intervention with the sustainable improvement in physical performances, lower-body muscle strength, and the modulation of both inflammatory and endocrine biomarkers. This study could encourage older adults to change their lifestyles to improve healthy aging and longevity.

Chemical Fingerprint of Free Polyphenols and Antioxidant Activity in Dietary Fruits and Vegetables Using a Non-Targeted Approach Based on QuEChERS Ultrasound-Assisted Extraction Combined with UHPLC-PDA

Fruits and vegetables are considered a good source of antioxidants, which are beneficial in protecting the human body against damage induced by free radicals and other reactive oxygen (ROS) and nitrogen (RNS) species. In this work, we aimed to evaluate the integral antioxidant activity (AOA) and determine individual polyphenols in fruits and vegetables of frequent consumption. For this purpose, an innovative and high throughput analytical approach based on original QuEChERS assisted by ultrasound extraction (USAE), instead of the manual agitation used in the classical procedure, was optimized and implemented for the isolation of polyphenols. The total phenolic content (TPC), flavonoids, anthocyanins, and betalains were evaluated using different spectrophotometric assays. In addition, free radical scavenging by methods 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and 2,2'-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) were used to estimate the AOA of the investigated fruit and vegetable extracts. Red onion, tamarillo, and beetroot were the samples with the highest AOA. The quantification and identification of free low molecular weight polyphenols from QuEChERS-USAE extracts was carried out by ultra-high-pressure liquid chromatography equipped with a photodiode array detection system (UHPLC-PDA). Catechin was the most abundant polyphenol, followed by gentisic and ferulic acids, mainly in the watercress sample. In relation to flavonols, quercetin and kaempferol were found mostly in onion samples, and in small quantities in tomato and watercress. The improved analytical approach, QuEChERS-USAE/UHPLC-PDA, offers an attractive alternative for the analysis of polyphenols from fruit and vegetable samples, providing several advantages over traditional extraction techniques, in terms of reproducibility, simplicity, low cost, analysis speed, and analytical performance.

Effects of the soy isoflavones, genistein and daidzein, on male rats' skin

Introduction

Genistein and daidzein are typical soy isoflavones with known estrogenic properties to provide protection against skin ageing in postmenopausal women and female rats. However their effect on male skin was very rarely studied.

Aim

This study was designed to evaluate the effect of a mixture of genistein and daidzein on male rats’ skin.

Material and methods

Male rats were administered this mixture in a dose of 2 or 20 mg/kg body weight (bw) per day for 5 days weekly mixed with regular rat chow, from prenatal life until sexual maturity. The female and male rats of the control group received regular rat chow. The skin epidermis thickness, number of fibroblasts in the dermis and diameter of collagen fibers in the dermis were measured using morphometric assay. The isoflavone effects on activities of antioxidant enzymes, lipid peroxides, and glutathione concentration in the skin were measured with commercially available kits.

Results

The thickness of the skin epidermis and collagen fibers in the dermis and amount of elastic fibers were significantly greater in the isoflavone-treated groups. Isoflavones significantly decreased catalase activity in the skin homogenates and at a higher dose inhibited lipid peroxides formation.

Conclusions

Our results provide further support for the contribution of isoflavones to defence mechanisms against oxidative stress in the skin and suggest that genistein and daidzein supplementation may provide protection against skin ageing in males.

Flavonoids as positive allosteric modulators of α7 nicotinic receptors

The use of positive allosteric modulators (PAM) of α7 nicotinic receptors is a promising therapy for neurodegenerative, inflammatory and cognitive disorders. Flavonoids are polyphenolic compounds showing neuroprotective, anti-inflammatory and pro-cognitive actions. Besides their well-known antioxidant activity, flavonoids trigger intracellular pathways and interact with receptors, including α7. To reveal how the beneficial actions of flavonoids are linked to α7 function, we evaluated the effects of three representative flavonoids -genistein, quercetin and the neoflavonoid 5,7-dihydroxy-4-phenylcoumarin- on whole-cell and single-channel currents. All flavonoids increase the maximal currents elicited by acetylcholine with minimal effects on desensitization and do not reactivate desensitized receptors, a behaviour consistent with type I PAMs. At the single-channel level, they increase the duration of the open state and produce activation in long-duration episodes with a rank order of efficacy of genistein > quercetin ≥ neoflavonoid. By using mutant and chimeric α7 receptors, we demonstrated that flavonoids share transmembrane structural determinants with other PAMs. The α7-PAM activity of flavonoids results in decreased cell levels of reactive oxygen species. Thus, allosteric potentiation of α7 may be an additional mechanism underlying neuroprotective actions of flavonoids, which may be used as scaffolds for designing new therapeutic agents.

The Role of Nutrition in Cognitive Function and Brain Ageing in the Elderly

PURPOSE OF REVIEW

The purposes of this review were to examine literature published over the last 5 years and to evaluate the role of nutrition in cognitive function and brain ageing, focussing on the Mediterranean diet (MeDi), Dietary Approaches to Stop Hypertension (DASH), and Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diets.

RECENT FINDINGS

Results suggest that higher adherence to a healthy dietary pattern is associated with preservation of brain structure and function as well as slower cognitive decline, with the MIND diet substantially slowing cognitive decline, over and above the MeDi and DASH diets. Whilst results to-date suggest adherence to a healthy diet, such as the MeDi, DASH, or MIND, is an important modifiable risk factor in the quest to develop strategies aimed at increasing likelihood of healthy brain ageing, further work is required to develop dietary guidelines with the greatest potential benefit for public health; a research topic of increasing importance as the world's population ages.

Flavonols and 4-thioflavonols as potential acetylcholinesterase and butyrylcholinesterase inhibitors: Synthesis, structure-activity relationship and molecular docking studies

To explore new scaffolds for the treat of Alzheimer's disease appears to be an inspiring goal. In this context, a series of varyingly substituted flavonols and 4-thioflavonols have been designed and synthesized efficiently. All the newly synthesized compounds were characterized unambiguously by common spectroscopic techniques (IR, ¹H-, ¹³C NMR) and mass spectrometry (EI-MS). All the derivatives (1-24) were evaluated in vitro for their inhibitory potential against cholinesterase enzymes. The results exhibited that these derivatives were potent selective inhibitors of acetylcholinesterase (AChE), except the compound 11 which was selective inhibitor of butyrylcholinesterase (BChE), with varying degree of IC₅₀ values. Remarkably, the compounds 20 and 23 have been found the most potent almost dual inhibitors of AChE and BChE amongst the series with IC₅₀ values even less than the standard drug. The experimental results in silico were further validated by molecular docking studies in order to find their binding modes with the active pockets of AChE and BChE enzymes.

Flavonoids as Prospective Neuroprotectants and Their Therapeutic Propensity in Aging Associated Neurological Disorders

Modern research has revealed that dietary consumption of flavonoids and flavonoids-rich foods significantly improve cognitive capabilities, inhibit or delay the senescence process and related neurodegenerative disorders including Alzheimer’s disease (AD). The flavonoids rich foods such as green tea, cocoa, blue berry and other foods improve the various states of cognitive dysfunction, AD and dementia-like pathological alterations in different animal models. The mechanisms of flavonoids have been shown to be mediated through the inhibition of cholinesterases including acetylcholinesterase (AChE), and butyrylcholinesterase (BChE), β-secretase (BACE1), free radicals and modulation of signaling pathways, that are implicated in cognitive and neuroprotective functions. Flavonoids interact with various signaling protein pathways like ERK and PI3-kinase/Akt and modulate their actions, thereby leading to beneficial neuroprotective effects. Moreover, they enhance vascular blood flow and instigate neurogenesis particularly in the hippocampus. Flavonoids also hamper the progression of pathological symptoms of neurodegenerative diseases by inhibiting neuronal apoptosis induced by neurotoxic substances including free radicals and β-amyloid proteins (Aβ). All these protective mechanisms contribute to the maintenance of number, quality of neurons and their synaptic connectivity in the brain. Thus flavonoids can thwart the progression of age-related disorders and can be a potential source for the design and development of new drugs effective in cognitive disorders.

Therapeutic potential of natural compounds in inflammation and chronic venous insufficiency

The term varicose vein refers to the twisted and swollen vein visible under the skin surface which occurs most commonly in the leg. Epidemiological studies report a varying percentage of incidences from 2 to 56% in men and <1-60% in women. Venous insufficiency is most often caused by the damage to the valves and walls of the veins. The mechanism of varicose vein formation is complex. It is, however, based on hypotensive blood vessels, hypoxia, and other mechanisms associated with inflammation. This work describes mechanisms related to the formation and development of the varicose vein. It discusses risk factors, pathogenesis of chronic venous disease, markers of the epithelial and leukocyte activation, state of hypoxia and inflammation, reactive oxygen species (ROS) generation, and oxidative stress. Additionally, this paper describes substances of plant origin used in the treatment of venous insufficiency. It also considers the structure of the molecules, their properties, and their mechanisms of action, the structure-activity relationship and chemical properties of flavonoids and other substances. The flavonoids include quercetin derivatives, micronized purified flavonoid fraction (Daflon), natural pine bark extract (Pycnogenol), and others such as triterpene saponine, extracts from Ruscus aculeatus and Centella asiatica, Ginkgo biloba extract, coumarin dereivatives that are used in chronic venous insufficiency. Flavonoids are natural substances found in plants, including fruits, vegetables, flowers, and others. They are important to the circulatory system and critical to blood vessels and the blood flow. Additionally, they have antioxidant, antiinflammatory properties.

Flavonoids Regulate Lipid Droplets Biogenesis in Drosophila melanogaster

Lipid droplets (LDs), cytosolic fat storage organelles, are emerging as major regulators of lipid metabolism, trafficking, and signaling in various cells and tissues. LDs are altered in cardiovascular and neuronal disorders, inflammation, obesity, and cancer. Flavonoids comprise different classes of molecules, characterized by a well-known antioxidant activity and a beneficial effect in several diseases. However, the cellular mechanism by which different classes of flavonoids improve health is poorly understood, in particular as far as LDs biogenesis is concerned. Here we used Drosophila melanogaster as a model system to investigate the effects of a selected group of flavonoids on larval tissues by examining LDs biogenesis. In our study, fruit flies were grown in xanthohumol-, isoquercetin-, and genistein-enriched food and larval tissues were analyzed using a LD marker. Total mRNA expression of two main enzymes (minotaur and midway) responsible for triacylglycerides synthesis was evaluated after treatments. Among the flavonoids analyzed, xanthohumol and isoquercetin resulted to be potent regulators of LDs biogenesis in a tissue-specific manner, inducing fat storage decrease in fat bodies and accumulation of LDs in nerves. Since LDs have been suggested to play a protective role against intracellular stress in nonadipocyte cells, our data support the hypothesis that some phytochemicals could act as strong modulators of LDs biogenesis in vivo. The knowledge of how different flavonoids act on lipid metabolism in different tissues can help to manage the use of phytochemicals with the aim of selectively ameliorating specific neuronal and metabolic diseases’ manifestations.

Theracurmin Ameliorates Cognitive Dysfunctions in 5XFAD Mice by Improving Synaptic Function and Mitigating Oxidative Stress

As the elderly population is increasing, Alzheimer’s disease (AD) has become a global issue and many clinical trials have been conducted to evaluate treatments for AD. As these clinical trials have been conducted and have failed, the development of new theraphies for AD with fewer adverse effects remains a challenge. In this study, we examined the effects of Theracurmin on cognitive decline using 5XFAD mice, an AD mouse model. Theracurmin is more bioavailable form of curcumin, generated with submicron colloidal dispersion. Mice were treated with Theracurmin (100, 300 and 1,000 mg/kg) for 12 weeks and were subjected to the novel object recognition test and the Barnes maze test. Theracurmin-treated mice showed significant amelioration in recognition and spatial memories compared those of the vehicle-treated controls. In addition, the antioxidant activities of Theracurmin were investigated by measuring the superoxide dismutase (SOD) activity, malondialdehyde (MDA) and glutathione (GSH) levels. The increased MDA level and decreased SOD and GSH levels in the vehicle-treated 5XFAD mice were significantly reversed by the administration of Theracurmin. Moreover, we observed that Theracurmin administration elevated the expression levels of synaptic components, including synaptophysin and post synaptic density protein 95, and decreased the expression levels of ionized calcium-binding adapter molecule 1 (Iba-1), a marker of activated microglia. These results suggest that Theracurmin ameliorates cognitive function by increasing the expression of synaptic components and by preventing neuronal cell damage from oxidative stress or from the activation of microglia. Thus, Theracurmin would be useful for treating the cognitive dysfunctions observed in AD.

Therapeutic potential of mistletoe in CNS-related neurological disorders and the chemical composition of Viscum species

ETHNOPHARMACOLOGICAL RELEVANCE

Viscum album L., commonly known as mistletoe, has been used for centuries in traditional medicine to treat various neurological diseases, including epilepsy, hysteria, nervousness, hysterical psychosis, dizziness and headaches.

AIM OF THE STUDY

The aim of this review is to summarize existing evidence confirming the influence of mistletoe on the central nervous system and to investigate the compounds that may be responsible for this activity.

MATERIALS AND METHODS

Available information from studies of various species of the Viscum L. genus was collected from scientific journals, books, and reports via a library and an electronic data search (Elsevier, Google Scholar, PubMed, Springer, Science Direct, ResearchGate, and ACS).

RESULTS

The main chemical constituents of Viscum L. species are viscotoxins, lectins, flavonoids, phenolic acids, terpenoids, sterols, phenylpropanoids, and alkaloids. Various extracts of Viscum album L. showed central nervous system activity, including antiepileptic, sedative, antipsychotic, anxiolytic, antidepressant and antinociceptive effects in mice and rats. Additionally, the extracts increased the level of brain-derived neurotrophic factor, prevented apoptotic neuronal death induced by amyloid β and weakly inhibited cholinesterase activity.

CONCLUSIONS

Numerous historical references describe the use of mistletoe for the treatment of central nervous system disorders. In recent years, studies have started to confirm the antiepileptic, antipsychotic, sedative and antinociceptive effects of mistletoe. Additionally, mistletoe can be used as a complementary treatment for Alzheimer's disease. The therapeutic effect of mistletoe might be a result of the synergistic interactions of various secondary metabolites, including mistletoe-specific lectins. Further studies of the chemical composition and CNS activity of mistletoe are required. The mechanisms of action, target sites, pharmacokinetics, metabolic mechanisms, adverse effects and interactions of mistletoe with other drugs must also be investigated, as well.

Exploring the efficacy of natural products in alleviating Alzheimer's disease

Alzheimer’s disease (hereafter AD) is a progressive neurodegenerative disorder that affects the central nervous system. There are multiple factors that cause AD, viz., accumulation of extracellular Amyloid-beta 42 plaques, intracellular hyper-phosphorylated Tau tangles, generation of reactive oxygen species due to mitochondrial dysfunction and genetic mutations. The plaques and tau tangles trigger aberrant signaling, which eventually cause cell death of the neurons. As a result, there is shrinkage of brain, cognitive defects, behavioral and psychological problems. To date, there is no direct cure for AD. Thus, scientists have been testing various strategies like screening for the small inhibitor molecule library or natural products that may block or prevent onset of AD. Historically, natural products have been used in many cultures for the treatment of various diseases. The research on natural products have gained importance as the active compounds extracted from them have medicinal values with reduced side effects, and they are bioavailable. The natural products may target the proteins or members of signaling pathways that get altered in specific diseases. Many natural products are being tested in various animal model systems for their role as a potential therapeutic target for AD, and to address questions about how these natural products can rescue AD or other neurodegenerative disorders. Some of these products are in clinical trials and results are promising because of their neuroprotective, anti-inflammatory, antioxidant, anti-amyloidogenic, anticholinesterase activities and easy availability. This review summarizes the use of animal model systems to identify natural products, which may serve as potential therapeutic targets for AD.

Exploring the Mechanism of Flavonoids Through Systematic Bioinformatics Analysis

Flavonoids are the largest class of plant polyphenols, with common structure of diphenylpropanes, consisting of two aromatic rings linked through three carbons and are abundant in both daily diets and medicinal plants. Fueled by the recognition of consuming flavonoids to get better health, researchers became interested in deciphering how flavonoids alter the functions of human body. Here, systematic studies were performed on 679 flavonoid compounds and 481 corresponding targets through bioinformatics analysis. Multiple human diseases related pathways including cancers, neuro-disease, diabetes, and infectious diseases were significantly regulated by flavonoids. Specific functions of each flavonoid subclass were further analyzed in both target and pathway level. Flavones and isoflavones were significantly enriched in multi-cancer related pathways, flavan-3-ols were found focusing on cellular processing and lymphocyte regulation, flavones preferred to act on cardiovascular related activities and isoflavones were closely related with cell multisystem disorders. Relationship between chemical constitution fragment and biological effects indicated that different side chain could significantly affect the biological functions of flavonoids subclasses. Results will highlight the common and preference functions of flavonoids and their subclasses, which concerning their pharmacological and biological properties.

A review on flavonoid-based scaffolds as multi-target-directed ligands (MTDLs) for Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is a multifactorial neurodegenerative disease. The target enzymes inhibition including cholinesterase, beta-secretase, monoamine oxidase and inhibition of amyloid-β aggregation as well as oxidative stress and metal chelation play an important role in the pathogenesis of AD. Chroman-4-one scaffold with benzo-γ-pyrone network is a privileged structure in organic synthesis and drug design. A large number of research has been carried out on modified naturally occurring chromanone scaffolds and/or synthesized new analogues, to obtain effective drugs for AD management. The present review summarizes aspects related to the multi-target-directed ligands (MTDLs) strategy in enzyme targets modulation performed with natural and synthesized chroman-4-one-based structures to look at their potential in the management of multifactorial Alzheimer's disease.