Polyherbal and Multimodal Treatments: Kaempferol- and Quercetin-Rich Herbs Alleviate Symptoms of Alzheimer's Disease

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder impairing cognition and memory in the elderly. This disorder has a complex etiology, including senile plaque and neurofibrillary tangle formation, neuroinflammation, oxidative stress, and damaged neuroplasticity. Current treatment options are limited, so alternative treatments such as herbal medicine could suppress symptoms while slowing cognitive decline. We followed PRISMA guidelines to identify potential herbal treatments, their associated medicinal phytochemicals, and the potential mechanisms of these treatments. Common herbs, including Ginkgo biloba, Camellia sinensis, Glycyrrhiza uralensis, Cyperus rotundus, and Buplerum falcatum, produced promising pre-clinical results. These herbs are rich in kaempferol and quercetin, flavonoids with a polyphenolic structure that facilitate multiple mechanisms of action. These mechanisms include the inhibition of Aβ plaque formation, a reduction in tau hyperphosphorylation, the suppression of oxidative stress, and the modulation of BDNF and PI3K/AKT pathways. Using pre-clinical findings from quercetin research and the comparatively limited data on kaempferol, we proposed that kaempferol ameliorates the neuroinflammatory state, maintains proper cellular function, and restores pro-neuroplastic signaling. In this review, we discuss the anti-AD mechanisms of quercetin and kaempferol and their limitations, and we suggest a potential alternative treatment for AD. Our findings lead us to conclude that a polyherbal kaempferol- and quercetin-rich cocktail could treat AD-related brain damage.

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.

Mix of almond baru (Dipteryx alata Vog.) and goat whey modulated intestinal microbiota, improved memory and induced anxiolytic like behavior in aged rats

The objective was to evaluate the effects of the consumption of a mix of baru almond and goat whey on memory performance and anxiety parameters related to the intestinal health of rats treated during aging. The animals were divided into three groups and treated by gavage for 10 weeks (n = 10/each group): Control (CT) - distilled water; Baru almond (BA) - 2000 mg of baru/kg of body weight; and Baru + Whey (BW) - 2000 mg of baru + 2000 mg of goat milk whey/kg of body weight. Anxiety behavior, memory, brain fatty acid profile and fecal microbiota were measured. BA and BW realized less grooming, spent more time in the central area of the open field and the open arms, and realized more head dipping in the elevated plus maze. A higher rate of exploration of the new object in the short and long-term memory was observed in BA and BW. There was an increase in the deposition of MUFAs and PUFAs and oleic acid in the brain of BA and BW. Regarding spatial memory, BA and BW performed better, with an emphasis on BW. There was a beneficial modulation of the fecal microbiota with a reduction of the pathogenic genus Clostridia_UFC-014 in BA and BW and an increase in the abundance of metabolic pathways of interest in the brain-gut axis. Thus, consumption of the mix is efficient in beneficially altering the intestinal microbiota, improving memory and anxiolytic-like behavior in rats during aging.

Honey and Alzheimer's Disease-Current Understanding and Future Prospects

Alzheimer's disease (AD), a leading cause of dementia, has been a global concern. AD is associated with the involvement of the central nervous system that causes the characteristic impaired memory, cognitive deficits, and behavioral abnormalities. These abnormalities caused by AD is known to be attributed by extracellular aggregates of amyloid beta plaques and intracellular neurofibrillary tangles. Additionally, genetic factors such as abnormality in the expression of APOE, APP, BACE1, PSEN-1, and PSEN-2 play a role in the disease. As the current treatment aims to treat the symptoms and to slow the disease progression, there has been a continuous search for new nutraceutical agent or medicine to help prevent and cure AD pathology. In this quest, honey has emerged as a powerful nootropic agent. Numerous studies have demonstrated that the high flavonoids and phenolic acids content in honey exerts its antioxidant, anti-inflammatory, and neuroprotective properties. This review summarizes the effect of main flavonoid compounds found in honey on the physiological functioning of the central nervous system, and the effect of honey intake on memory and cognition in various animal model. This review provides a new insight on the potential of honey to prevent AD pathology, as well as to ameliorate the damage in the developed AD.

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.

Neuroprotective effect of quercetin against rotenone-induced neuroinflammation and alterations in mice behavior

Various studies suggested that neuroinflammation leads to the development of several neurodegenerative disorders like Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD). Rotenone is an organic pesticide and potent inhibitor of complex I of electron transport chain widely used to develop the PD model. Numerous studies reported rotenone toxicity in the dopaminergic system but very few studies are available on rotenone-induced glial cell activation and subsequent neurodegeneration and alterations in various types of behavior. Therefore, the present study was designed to explore the effect of rotenone on neuroinflammation and its deleterious effect on the behavior of mice, and also how these effects can be protected through quercetin. Quercetin, a natural flavonoid having strong antioxidant and anti-inflammatory properties, is found in vegetables and fruits. The finding of the study indicated that rotenone 5 mg/kg body weight for 60 days through oral gavage leads to the release of inflammatory markers in blood serum, astrocytes activation in substantia nigra and hippocampus, and subsequently decreased density of dopaminergic fibers in the striatum. Rotenone also altered the memory of the mice as indicated by decreased spontaneous alteration in Y-maze and T-maze tests and reduction in exploration time in novel object recognition, increased immobility time in the forced swim test and reduced muscular strength. Co-treatment of quercetin 30 mg/kg/day through oral gavage for 60 days along with rotenone significantly reversed all these adverse effects, suggesting that quercetin could reduce neuroinflammation, and improve memory, and cognitive function.

Novel Neuroprotective Potential of Bunchosia armeniaca (Cav.) DC against Lipopolysaccharide Induced Alzheimer’s Disease in Mice

Bunchosia armeniaca (Cav.) DC (Malpighiaceae) is one of the well-known traditionally used remedies worldwide. This study aims to explore the leaves’ metabolome via Quadrupole-Time-of-Flight-Liquid-Chromatography-Mass Spectrometry and to investigate the neuroprotective effect of leaves using lipopolysaccharide (LPS) induced Alzheimer’s disease model. Mice were administered LPS (0.25 mg/kg/day; intraperitoneal) as well as methanolic extract (BME), dichloromethane (BDMF), and butanol (BBF) fractions (each 200 mg/kg/day; oral) for one week. BME and BBF improved behavioral activity on the Y maze test, decreased brain content of inflammatory markers such as nuclear factor kappa B and interleukin 1 beta, and prevented the elevation of cytochrome P450 2E1, and glial fibrillary acidic protein compared to the LPS-administered group. Histopathological examination of several brain parts confirmed the neuroprotective effect of the tested extracts. In addition, BBF exhibited higher activity in all tested in vitro antioxidant and acetylcholinesterase inhibition assays. Metabolic profiling offered tentative identification of 88 metabolites, including mainly flavonoids, phenolic acids, and coumarins. Several detected metabolites, such as quercetin, apigenin, baicalin, vitexin, and resveratrol, had previously known neuroprotective effects. The current study highlighted the possible novel potential of B. armeniaca in preventing memory impairment, possibly through its antioxidant effect and inhibition of acetylcholinesterase, inflammatory and oxidative stress mediators.

Quercetin Exhibits α7nAChR/Nrf2/HO-1-Mediated Neuroprotection Against STZ-Induced Mitochondrial Toxicity and Cognitive Impairments in Experimental Rodents

The objective of the present study was to investigate the α7nAChR-mediated Nrf2-dependant protective activity against streptozotocin (STZ)-induced brain mitochondrial toxicity in Alzheimer's disease (AD)-like rats. STZ (3 mg/kg) was injected through an intracerebroventricular route to induce AD-like dementia. Repeated Quercetin (50 mg/kg, i.p.) administration attenuated cognitive impairments in the STZ-challenged animals during Morris water-maze and Y-maze tests. Quercetin significantly mitigated the STZ-induced increase in cholinergic dysfunction, such as the increase in acetylcholinesterase activity, decrease in acetylcholine level, and activity of choline acetyltransferase, and increase in amyloid-beta aggregation and mitochondrial toxicity in respect of mitochondrial bioenergetics, integrity, and oxidative stress in memory-challenged rat hippocampus, prefrontal cortex and, amygdala. Further, Quercetin significantly attenuated STZ-induced reduction in the α7nAChRs and HO-1 expression levels in the selected rat brain regions. On the contrary, trigonelline (10 mg/kg, i.p.) and methyllycaconitine (2 mg/kg; i.p.) abolished the neuroprotective effects of Quercetin against STZ-induced behavioral, molecular, and biochemical alterations in the AD-like animals. Hence, Quercetin exhibits α7nAChR/Nrf2/HO-1-mediated neuroprotection against STZ-challenged AD-like animals. Thus, Quercetin could be considered as a potential therapeutic option in the management of AD.

Unusual Bioactive Compounds with Antioxidant Properties in Adjuvant Therapy Supporting Cognition Impairment in Age-Related Neurodegenerative Disorders

Cognitive function decline is strictly related to age, resulting in the loss of the ability to perform daily behaviors and is a fundamental clinical neurodegeneration symptom. It has been proven that an adequate diet, comprehensive nutrition, and a healthy lifestyle may significantly inhibit neurodegenerative processes, improving cognitive functions. Therefore, intensive research has been conducted on cognitive-enhancing treatment for many years, especially with substances of natural origin. There are several intervention programs aimed at improving cognitive functions in elderly adults. Cognitive functions depend on body weight, food consumed daily, the quality of the intestinal microflora, and the supplements used. The effectiveness in the prevention of dementia is particularly high before the onset of the first symptoms. The impact of diet and nutrition on age-associated cognitive decline is becoming a growing field as a vital factor that may be easily modified, and the effects may be observed on an ongoing basis. The paper presents a review of the latest preclinical and clinical studies on the influence of natural antioxidants on cognitive functions, with particular emphasis on neurodegenerative diseases. Nevertheless, despite the promising research results in animal models, the clinical application of natural compounds will only be possible after solving a few challenges.

Quercetin: A Bioactive Compound Imparting Cardiovascular and Neuroprotective Benefits: Scope for Exploring Fresh Produce, Their Wastes, and By-Products

Quercetin, a bioactive secondary metabolite, holds incredible importance in terms of bioactivities, which has been proved by in vivo and in vitro studies. The treatment of cardiovascular and neurological diseases by quercetin has been extensively investigated over the past decade. Quercetin is present naturally in appreciable amounts in fresh produce (fruits and vegetables). However, today, corresponding to the growing population and global demand for fresh fruits and vegetables, a paradigm shift and focus is laid towards exploring industrial food wastes and/or byproducts as a new resource to obtain bioactive compounds such as quercetin. Based on the available research reports over the last decade, quercetin has been suggested as a reliable therapeutic candidate for either treating or alleviating health issues, mainly those of cardiovascular and neurological diseases. In the present review, we have summarized some of the critical findings and hypotheses of quercetin from the available databases foreseeing its future use as a potential therapeutic agent to treat cardiovascular and neurological diseases. It is anticipated that this review will be a potential reference material for future research activities to be undertaken on quercetin obtained from fresh produce as well as their respective processing wastes/byproducts that rely on the circular concept.

Neuropharmacological Effects of Quercetin: A Literature-Based Review

Quercetin (QUR) is a natural bioactive flavonoid that has been lately very studied for its beneficial properties in many pathologies. Its neuroprotective effects have been demonstrated in many in vitro studies, as well as in vivo animal experiments and human trials. QUR protects the organism against neurotoxic chemicals and also can prevent the evolution and development of neuronal injury and neurodegeneration. The present work aimed to summarize the literature about the neuroprotective effect of QUR using known database sources. Besides, this review focuses on the assessment of the potential utilization of QUR as a complementary or alternative medicine for preventing and treating neurodegenerative diseases. An up-to-date search was conducted in PubMed, Science Direct and Google Scholar for published work dealing with the neuroprotective effects of QUR against neurotoxic chemicals or in neuronal injury, and in the treatment of neurodegenerative diseases. Findings suggest that QUR possess neuropharmacological protective effects in neurodegenerative brain disorders such as Alzheimer’s disease, Amyloid β peptide, Parkinson’s disease, Huntington's disease, multiple sclerosis, and amyotrophic lateral sclerosis. In summary, this review emphasizes the neuroprotective effects of QUR and its advantages in being used in complementary medicine for the prevention and treatment o of different neurodegenerative diseases.

Role of natural plant products against Alzheimer's disease

Alzheimer's disease (AD) is one of the major neurodegenerative disorder. Deposition of amyloid fibrils and tau protein are associated with various pathological symptoms. Currently limited medication is available for AD treatment. Most of the drugs are basically cholinesterase inhibitors and associated with various side effects. Natural plant products have shown potential as a therapeutic agent for the treatment of AD symptoms. Variety of secondary metabolites like flavonoids, tannins, terpenoids, alkaloids and phenols are used to reduce the progression of the disease. Plant products have less or no side effect and are easily available. The present review gives a detailed account of the potential of natural plant products against the AD symptoms.

(Myrtaceae) grown in Algeria

Guava (Psidium guajava L.) is a fruit tree largely used in folk medicine in tropical and subtropical areas. This exotic species was introduced in a botanical garden in the northeast of Algeria in the 1950’s. The aim of this study is to estimate, for the first time, the antioxidant and anticholinesterase activities of chloroform, ethyl acetate and n-butanol extracts of P. guajava growing in Algeria. Six antioxidant assays were tested, results showed very important efficiency in free radical scavenging, reducing power and β-carotene bleaching of tested extracts. Values of IC50 or A0.5 of some samples were lower than those of standards. With regard to anticholinesterase activity, the inhibitory of both acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) was investigated. The extracts exhibited interesting capacity to inhibit these enzymes with low values of IC50 and even less than that of galanthamine. These activities were correlated with total phenolic content which was more important compared to the one found in extracts from trees growing in tropical and subtropical region. This could be due to resistance and adaptation of P. guajava grown in Algeria. The data obtained suggest the use of bioactive compounds from P. guajava leaves as antioxidant and drugs for symptomatic treatment of Alzheimer disease.

Arbutin reduces cognitive deficit and oxidative stress in animal model of Alzheimer's disease

Objectives: Recent evidences have shown the beneficial effects of natural products for treating of Alzheimer's disease (AD). Arbutin is derived from Pyrus biossieriana and exerts a wide range of pharmacological activities including anti-inflammatory and anti-oxidant effects. The present study was designed to examine the protective effects of arbutin on streptozotocin (STZ)-induced neurotoxicity in rats. Materials and methods: The spatial memory impairment was induced by intracerebroventricular (i.c.v) microinjection of STZ (3 mg/kg, 10 μL). Animals received the pretreatment of arbutin (50 mg/kg) for 21 days before STZ injection. The Morris Water maze (MWM) task was used to study the spatial learning and memory. The levels of oxidative stress markers including malondialdehyde (MDA), nitrite and carbonyl were measured in serum and hippocampus samples. In addition, antioxidant level was assessed by ferric reducing antioxidant power (FRAP) test. Results: The obtained result indicated that administration of STZ is led to memory impairment and increases the levels of oxidative stress markers in the hippocampus tissues. Conversely, arbutin improves spatial memory and reduces oxidative and nitrosative stress, as evidenced by a significant decrease in the amount of MDA and nitrite in the serum and hippocampus. In addition, an increase in FRAP levels of hippocampus was observed in arbutin receiving animals. The protein carbonyl content was not reduced in arbutin receiving animals. Conclusion: It could be concluded that arbutin protects the brain against STZ-induced memory impairment and oxidative damage in the hippocampus. The neuroprotective effect of arbutin might be mediated through its antioxidant and free radical scavenging effects.

Neuroprotective Effect of Quercetin Against the Detrimental Effects of LPS in the Adult Mouse Brain

Chronic neuroinflammation is responsible for multiple neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. Lipopolysaccharide (LPS) is an essential component of the gram-negative bacterial cell wall and acts as a potent stimulator of neuroinflammation that mediates neurodegeneration. Quercetin is a natural flavonoid that is abundantly found in fruits and vegetables and has been shown to possess multiple forms of desirable biological activity including anti-inflammatory and antioxidant properties. This study aimed to evaluate the neuroprotective effect of quercetin against the detrimental effects of LPS, such as neuroinflammation-mediated neurodegeneration and synaptic/memory dysfunction, in adult mice. LPS [0.25 mg/kg/day, intraperitoneally (I.P.) injections for 1 week]-induced glial activation causes the secretion of cytokines/chemokines and other inflammatory mediators, which further activate the mitochondrial apoptotic pathway and neuronal degeneration. Compared to LPS alone, quercetin (30 mg/kg/day, I.P.) for 2 weeks (1 week prior to the LPS and 1 week cotreated with LPS) significantly reduced activated gliosis and various inflammatory markers and prevented neuroinflammation in the cortex and hippocampus of adult mice. Furthermore, quercetin rescued the mitochondrial apoptotic pathway and neuronal degeneration by regulating Bax/Bcl2, and decreasing activated cytochrome c, caspase-3 activity and cleaving PARP-1 in the cortical and hippocampal regions of the mouse brain. The quercetin treatment significantly reversed the LPS-induced synaptic loss in the cortex and hippocampus of the adult mouse brain and improved the memory performance of the LPS-treated mice. In summary, our results demonstrate that natural flavonoids such as quercetin can be beneficial against LPS-induced neurotoxicity in adult mice.

Neuroprotective effects of Bergenia ciliata on NMDA induced injury in SH-SY5Y cells and attenuation of cognitive deficits in scopolamine induced amnesia in rats

Bergenia ciliata (Haw) Sternb. possess immunomodulatory, anti-inflammatory, antioxidant, anti-urolithiatic, wound healing, anti-malarial, anti-diabetic and anti-cancer properties. Moreover, the methanolic extracts of the rhizomes of the plant were found to demonstrate beneficial neuroprotective effects in the intracerebroventricular streptozotocin-induced model in rats. Thus, the present study was undertaken to further explore the neuroprotective potential of the aqueous (BA) and methanolic extracts (BM) of B. ciliata through various in-vitro and in-vivo studies. Both the extracts at all tested concentrations i.e. 50-50,000 ng/mL did not cause any significant reduction of cell viability of SH-SY5Y cells when tested for 48 h when assessed through MTT and resazurin metabolism- based cell viability assays. The pre-treatment with the extracts could confer significant (p < 0.001) and dose-dependent protective effects against NMDA induced injury in SH-SY5Y cells. BM [IC₅₀: 5.7 and 5.19 μg/mL for acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) respectively] led to more potent inhibition of both the enzymes as compared to BA (IC₅₀: 227.12 and 23.25 μg/mL for AChE and BuChE respectively). BM also proved to be a 1.85-fold better scavenger of the DPPH free radicals as compared to BA. Thus, BM was taken further for the evaluation of the beneficial effects of 14-day pre-treatment in rats in the scopolamine (2 mg/kg, i.p.) induced amnesia model at 125, 250 and 500 mg/kg, p.o. BM pre-treatment at 250 and 500 mg/kg could significantly ameliorate the cognitive impairment (p < 0.001), inhibit AChE (p < 0.001) and BuChE (p < 0.05) activity, restore GSH levels (p < 0.05) in serum and brain homogenates and recover the morphology of hippocampal neurons back to normal. Moreover, the BM administration at 500 mg/kg also showed beneficial effects through the significant (p < 0.05) reduction of Aβ_1-42, phosphorylated tau (p-tau) and GSK-3β immunoreactivity in the brain homogenates of the intracerebroventricularly streptozotocin (ICV STZ) injected rats as observed from the results of the ELISA assays. The outcomes of the study unveiled that BM exerts its beneficial effects through prevention of NMDA induced excitotoxic cell death, dual cholinesterase inhibition, antioxidant activity coupled with the reduction of the immunoreactivity for the Aβ_1-42, p-tau and GSK-3β indicating its potential to be screened further for various other models to determine the exact mechanism of action.

Bioactive effects of quercetin in the central nervous system: Focusing on the mechanisms of actions

Quercetin, a ubiquitous flavonoid that is widely distributed in plants is classified as a cognitive enhancer in traditional and oriental medicine. The protective effects of quercetin for the treatment of neurodegenerative disorders and cerebrovascular diseases have been demonstrated in both in vitro and in vivo studies. The free radical scavenging activity of quercetin has been well-documented, wherein quercetin has been observed to exhibit protective effects against oxidative stress mediated neuronal damage by modulating the expression of NRF-2 dependent antioxidant responsive elements, and attenuation of neuroinflammation by suppressing NF-κB signal transducer and activator of transcription-1 (STAT-1). Several in vitro and in vivo studies have also shown that quercetin destabilizes and enhances the clearance of abnormal protein such as beta- amyloid peptide and hyperphosphorlyated tau, the key pathological hallmarks of Alzheimer's disease. Quercetin enhances neurogenesis and neuronal longevity by modulating a broad number of kinase signaling cascades such as phophoinositide 3- kinase (P13-kinase), AKT/PKB tyrosine kinase and Protein kinase C (PKC). Quercetin has also been well reported for its ability to reverse cognitive impairment and memory enhancement during aging. The current review focuses on summarizing the recent findings on the neuroprotective effect of quercetin, its mechanism of action and its possible roles in the prevention of neurological disorders.

Myricetin protects hippocampal CA3 pyramidal neurons and improves learning and memory impairments in rats with Alzheimer's disease

There is currently no treatment for effectively slowing the progression of Alzheimer's disease, so early prevention is very important. Numerous studies have shown that flavonoids can improve memory impairment. The present study investigated the effects of myricetin, a member of the flavonoids, on intracerebroventricular streptozotocin induced neuronal loss and memory impairment in rat models of Alzheimer's disease. Myricetin at 5 or 10 mg/kg was intraperitoneally injected into rats over 21 days. Control rats were treated with 10 mL/kg saline. Behavioral test (the shuttle box test) was performed on day 22 to examine learning and memory in rats. Immediately after that, hematoxylin-eosin staining was performed to observe the morphological change in hippocampal CA3 pyramidal neurons. Myricetin greatly increased the number of hippocampal CA3 pyramidal neurons and improved learning and memory impairments in rats with Alzheimer's disease. These findings suggest that myricetin is beneficial for treatment of Alzheimer's disease.