Specific localization of quercetin-3-O-glucuronide in human brain

Failure of senolytic treatment to prevent cognitive decline in a female rodent model of aging

There are sex differences in vulnerability and resilience to the stressors of aging and subsequent age-related cognitive decline. Cellular senescence occurs as a response to damaging or stress-inducing stimuli. The response includes a state of irreversible growth arrest, the development of a senescence-associated secretory phenotype, and the release of pro-inflammatory cytokines associated with aging and age-related diseases. Senolytics are compounds designed to eliminate senescent cells. Our recent work indicates that senolytic treatment preserves cognitive function in aging male F344 rats. The current study examined the effect of senolytic treatment on cognitive function in aging female rats. Female F344 rats (12 months) were treated with dasatinib (1.2 mg/kg) + quercetin (12 mg/kg) or ABT-263 (12 mg/kg) or vehicle for 7 months. Examination of the estrus cycle indicated that females had undergone estropause during treatment. Senolytic treatment may have increased sex differences in behavioral stress responsivity, particularly for the initial training on the cued version of the watermaze. However, pre-training on the cue task reduced stress responsivity for subsequent spatial training and all groups learned the spatial discrimination. In contrast to preserved memory observed in senolytic-treated males, all older females exhibited impaired episodic memory relative to young (6-month) females. We suggest that the senolytic treatment may not have been able to compensate for the loss of estradiol, which can act on aging mechanisms for anxiety and memory independent of cellular senescence.

Sebacic acid, a royal jelly-containing fatty acid, decreases LPS-induced IL-6 mRNA expression in differentiated human THP-1 macrophage-like cells

Macrophages produce many inflammatory mediators, such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), in innate immune responses. However, excess production of these mediators by activated macrophages triggers deleterious effects, leading to disorders associated with inflammation. Royal jelly (RJ), a milky-white substance secreted by worker bees, contains unique fatty acids, including 10-hydroxy-2-decenoic acid (10H2DA) and sebacic acid (SA). 10H2DA has been reported to have various biological functions, such as anti-inflammation. However, the anti-inflammatory effect of SA is not fully understood. In this study, we investigated the effects of SA on lipopolysaccharide (LPS)-induced cytokine expression using differentiated human THP-1 macrophage-like cells. SA dose-dependently decreased LPS-induced mRNA expression of IL-6, but not TNF-α and IL-1β. SA suppressed the phosphorylation of signal transducers and activators of transcription 1 (STAT1) and STAT3, but hardly affected the activation of JNK, p38, or NF-κB. In addition, SA decreased LPS-induced interferon-β (IFN-β) expression, and the addition of IFN-β restored the inhibition by SA of LPS-induced STAT activation and IL-6 expression. Furthermore, SA suppressed LPS-induced nuclear translocation of interferon regulatory factor 3 (IRF3), a transcription factor responsible for IFN-β expression. Taken together, we conclude that SA selectively decreases LPS-induced expression of IL-6 mRNA through inhibition of the IRF3/IFN-β/STAT axis.

A critical examination of human data for the biological activity of quercetin and its phase-2 conjugates

This critical review examines evidence for beneficial effects of quercetin phase-2 conjugates from clinical intervention studies, volunteer feeding trials, and in vitro work. Plasma concentrations of quercetin-3-O-glucuronide (Q3G) and 3'-methylquercetin-3-O-glucuronide (3'MQ3G) after supplementation may produce beneficial effects in macrophages and endothelial cells, respectively, especially if endogenous deglucuronidation occurs, and lower blood uric acid concentration via quercetin-3'-O-sulfate (Q3'S). Unsupplemented diets produce much lower concentrations (<50 nmol/l) rarely investigated in vitro. At 10 nmol/l, Q3'S and Q3G stimulate or suppress, respectively, angiogenesis in endothelial cells. Statistically significant effects have been reported at 100 nmol/l in breast cancer cells (Q3G), primary neuron cultures (Q3G), lymphocytes (Q3G and3'MQ3G) and HUVECs (QG/QS mixture), but it is unclear whether these translate to a health benefit in vivo. More sensitive and more precise methods to measure clinically significant endpoints are required before a conclusion can be drawn regarding effects at normal dietary concentrations. Future requirements include better understanding of inter-individual and temporal variation in plasma quercetin phase-2 conjugates, their mechanisms of action including deglucuronidation and desulfation both in vitro and in vivo, tissue accumulation and washout, as well as potential for synergy or antagonism with other quercetin metabolites and metabolites of other dietary phytochemicals.

Role of Extracellular Vesicles in Absorption and Functional Mechanisms of Quercetin

SCOPE

Quercetin (QUE), a phytochemical found in various plant foods, has been shown to have a variety of physiological activities in vivo, though biological sites where it has activities and the mechanisms of transport have not been fully elucidated.

METHODS AND RESULTS

In the present study, intracellular uptake of QUE into HT-29 human colon adenocarcinoma cells is found to result in spontaneous release of extracellular vesicles (EVs), which are subsequently embedded with QUE. In addition, QUE-embedded EVs are detected in serum of QUE-administered Sprague-Dawley rats. Interestingly, the rate of cellular uptake of QUE-encapsulated EVs (EV-QUE) into RAW264.7 macrophages is markedly higher than that of free QUE. Moreover, EV-QUE suppresses lipopolysaccharide (LPS)-induced nitric oxide at a lower concentration than free QUE.

CONCLUSION

The present findings suggest that QUE may be embedded in EVs in the gastrointestinal tract, then become absorbed and enter the bloodstream to exhibit biological activities.

Quercetin-3-O-β-d-glucuronide in the Nuciferine Leaf Polyphenol Extract Promotes Neurogenesis Involving the Upregulation of the Tropomyosin Receptor Kinase (Trk) Receptor and AKT/Phosphoinositide 3-Kinase Signaling Pathway

Neurogenesis is crucial during the human lifespan for the maintenance of synaptic plasticity and normal function. The impairment of hippocampal neurogenesis in adults may lead to neurodegenerative disease, such as Alzheimer's disease. Miquelianin (quercetin-3-O-β-d-glucuronide, Q3GA) is a constituent of the nuciferine leaf polyphenol extract (NLPE), and it has protective effects against neurodegeneration. In this study, we examined the effect of the NLPE on neurogenesis and the mechanisms underlying Q3GA on neurogenesis. We fed 24-week-old male C57BL/6 mice with 0.1 or 0.25% NLPE for 2 weeks. NLPE treatment increased small spindle-shaped stem cell numbers in the subgranular zone and the number of doublecortin (DCX)- and neuron-specific nuclear protein (NeuN)-expressing neurons. HT22, a hippocampal cell line, treated with Q3GA revealed significant neurite growth and upregulated TrkR and PI3K/Akt levels. The evidence from a model of retinoic acid-induced SH-SY5Y cell differentiation showed that Q3GA or NLPE increases neurite growth significantly. Taken together, the NLPE containing Q3GA to promote neurogenesis involving the upregulation of TrkR and the PI3K/Akt signaling pathway might be potentiated as an alternative strategy for the treatment of neurodegeneration.

Flavonoid quercetin and its glucuronide and sulfate conjugates bind to 67-kDa laminin receptor and prevent neuronal cell death induced by serum starvation

Quercetin, a dietary flavonoid, has been shown to protect against various neurodegenerative diseases with mechanisms largely unknown. After oral administration, quercetin is rapidly conjugated, and the aglycone is not detectable in the plasma and brain. However, its glucuronide and sulfate conjugates are present only at low nanomolar concentrations in the brain. Since quercetin and its conjugates have limited antioxidant capability at low nanomolar concentrations, it is crucial to determine whether they induce neuroprotection by binding to high-affinity receptors. Previously we found that (-)-epigallocatechin-3-gallate (EGCG), a polyphenol from green tea, induces neuroprotection by binding to the 67-kDa laminin receptor (67LR). Therefore, in this study, we determined whether quercetin and its conjugates bind 67LR to induce neuroprotection and compared their ability with EGCG. Based on the quenching of intrinsic tryptophan fluorescence of peptide G (residues 161-180 in 67LR), we found quercetin, quercetin-3-O-glucuronide, and quercetin-3-O-sulfate bind to this peptide with a high affinity comparable to EGCG. Molecular docking using the crystal structure of 37-kDa laminin receptor precursor supported the high-affinity binding of all these ligands to the site corresponding to peptide G. A pretreatment with quercetin (1-1000 nM) did not effectively protect Neuroscreen-1 cells from death induced by serum starvation. Contrarily, a pretreatment with low concentrations (1-10 nM) of quercetin conjugates better protected these cells than quercetin and EGCG. The 67LR-blocking antibody substantially prevented neuroprotection by all these agents, suggesting the role of 67LR in this process. Collectively, these studies reveal that quercetin induces neuroprotection primarily through its conjugates via high affinity binding to 67LR.

Polyphenols and Their Impact on the Prevention of Neurodegenerative Diseases and Development

It is well known that neurodegenerative diseases' development and progression are accelerated due to oxidative stress and inflammation, which result in impairment of mitochondrial function, cellular damage, and dysfunction of DNA repair systems. The increased consumption of antioxidants can postpone the development of these disorders and improve the quality of patients' lives who have already been diagnosed with neurodegenerative diseases. Prolonging life span in developed countries contributes to an increase in the incidence ratio of chronic age-related neurodegenerative disorders, such as PD (Parkinson's disease), AD (Alzheimer's disease), or numerous forms of age-related dementias. Dietary supplementation with neuroprotective plant-derived polyphenols might be considered an important element of healthy aging. Some polyphenols improve cognition, mood, visual functions, language, and verbal memory functions. Polyphenols bioavailability differs greatly from one compound to another and is determined by solubility, degree of polymerization, conjugation, or glycosylation resulting from chemical structure. It is still unclear which polyphenols are beneficial because their potential depends on efficient transport across the BBB (blood-brain barrier), bioavailability, and stability in the CNS (central nervous system). Polyphenols improve brain functions by having a direct impact on cells and processes in the CNS. For a direct effect, polyphenolic compounds must be able to overcome the BBB and accumulate in brain tissue. In this review, the latest achievements in studies (animal models and clinical trials) on the effect of polyphenols on brain activity and function are described. The beneficial impact of plant polyphenols on the brain may be summarized by their role in increasing brain plasticity and related cognition improvement. As reversible MAO (monoamine oxidase) inhibitors, polyphenols are mood modulators and improve neuronal self-being through an increase in dopamine, serotonin, and noradrenaline amounts in the brain tissue. After analyzing the prohealth effects of various eating patterns, it was postulated that their beneficial effects result from synergistic interactions between individual dietary components. Polyphenols act on the brain endothelial cells and improve the BBB's integrity and reduce inflammation, thus protecting the brain from additional injury during stroke or autoimmune diseases. Polyphenolic compounds are capable of lowering blood pressure and improving cerebral blood flow. Many studies have revealed that a nutritional model based on increased consumption of antioxidants has the potential to ameliorate the cognitive impairment associated with neurodegenerative disorders. Randomized clinical trials have also shown that the improvement of cognitive functions resulting from the consumption of foods rich in flavonoids is independent of age and health conditions. For therapeutic use, sufficient quantities of polyphenols must cross the BBB and reach the brain tissue in active form. An important issue in the direct action of polyphenols on the CNS is not only their penetration through the BBB, but also their brain metabolism and localization. The bioavailability of polyphenols is low. The most usual oral administration also conflicts with bioavailability. The main factors that limit this process and have an effect on therapeutic efficacy are: selective permeability across BBB, gastrointestinal transformations, poor absorption, rapid hepatic and colonic metabolism, and systemic elimination. Thus, phenolic compounds have inadequate bioavailability for human applications to have any beneficial effects. In recent years, new strategies have been attempted in order to exert cognitive benefits and neuroprotective effects. Converting polyphenols into nanostructures is one of the theories proposed to enhance their bioavailability. The following nanoscale delivery systems can be used to encapsulate polyphenols: nanocapsules, nanospheres, micelles, cyclodextrins, solid lipid nanoparticles, and liposomes. It results in great expectations for the wide-scale and effective use of polyphenols in the prevention of neurodegenerative diseases. Thus far, only natural polyphenols have been studied as neuroprotectors. Perhaps some modification of the chemical structure of a given polyphenol may increase its neuroprotective activity and transportation through the BBB. However, numerous questions should be answered before developing neuroprotective medications based on plant polyphenols.

Comparative Serum and Brain Pharmacokinetics of Quercetin after Oral and Nasal Administration to Rats as Lyophilized Complexes with β-Cyclodextrin Derivatives and Their Blends with Mannitol/Lecithin Microparticles

Quercetin (Que) is one of the most studied flavonoids with strong antioxidant properties ascribed to its ability to bind free radicals and inactivate them. However, the low solubility of the compound along with its inadequate absorption after oral administration limit its beneficial effects. Que's complexation with two different cyclodextrin (CD) derivatives (hydroxypropyl-β-CD and methyl-β-CD) via the neutralization/lyophilization method has been found to improve its physicochemical properties. Moreover, blends of the lyophilized powders with mannitol/lecithin microparticles (MLMPs) have been proposed as candidates for intranasal (IN) administration after in vitro and ex vivo evaluations. In this context, a comparative pharmacokinetic (PK) study of the IN vs oral administration of Que lyophilized powders and their blends with MLMPs (75:25 w/w) was performed on Wistar rats. The PK parameters estimated by a non-compartmental analysis using the sparse data methodology in Phoenix® 8.3 (Certara, Princeton, NJ, USA) illustrated the effectiveness of IN administration either in brain targeting or in reaching the bloodstream. Significant levels of the compound were achieved at both sites, compared to those after oral delivery which were negligible. These results favor the potential application of the prepared Que nasal powders for systemic and nose-to-brain delivery for the prevention and/or treatment of neuroinflammatory degenerative conditions, such as Parkinson's and Alzheimer's disease.

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

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

Targeting Protein Aggregates with Natural Products: An Optional Strategy for Neurodegenerative Diseases

Protein aggregation is one of the hallmarks of aging and aging-related diseases, especially for the neurodegenerative diseases (NDs) such as Alzheimer's disease (AD), Parkinson's disease (PD), Huntington's disease (HD), Amyotrophic lateral sclerosis (ALS), and others. In these diseases, many pathogenic proteins, such as amyloid-β, tau, α-Syn, Htt, and FUS, form aggregates that disrupt the normal physiological function of cells and lead to associated neuronal lesions. Protein aggregates in NDs are widely recognized as one of the important targets for the treatment of these diseases. Natural products, with their diverse biological activities and rich medical history, represent a great treasure trove for the development of therapeutic strategies to combat disease. A number of in vitro and in vivo studies have shown that natural products, by virtue of their complex molecular scaffolds that specifically bind to pathogenic proteins and their aggregates, can inhibit the formation of aggregates, disrupt the structure of aggregates and destabilize them, thereby alleviating conditions associated with NDs. Here, we systematically reviewed studies using natural products to improve disease-related symptoms by reducing or inhibiting the formation of five pathogenic protein aggregates associated with NDs. This information should provide valuable insights into new directions and ideas for the treatment of neurodegenerative diseases.

Antiradical Potential of Food Products as a Comprehensive Measure of Their Quality

Antiradical potential (ARP) is an important measure of food safety. In addition, it directly or indirectly affects the rate of occurrence of a number of human pathologies. Using a photocolorimetric analysis of DPPH (2,2-diphenyl-1-picrylhydrazyl) solutions, we estimated the antiradical potential of food raw materials, food concentrates, biologically active substances, and wild plants. We conducted approximately 1500 analyses of almost 100 food products selected from 11 food groups: vegetables, milk, meat, fish, cereals and bread, drinks (including tea and coffee), etc. With a confidence interval (CI) of 95%, the average values for animal products range from 15.87 to 18.70 ascorbic acid equivalents per gram of dry matter. For plant materials, the range is 474.54-501.50 equivalents when wild herbs are included and 385.02-408.83 equivalents without taking herbs into account. The antiradical potential of the biologically active substances we studied ranged from 706.84 to 847.77 equivalents per gram of dry matter, which makes it possible to use some of the components to repair products with low ARP values, for example, bread and baked goods, confectionery, milk and dairy products, carbonated drinks, and juice. In this study, a low ARP value is associated with a reduction in the shelf life of products and a deterioration in their organoleptic properties; therefore, we propose using ARP as an important reference for describing the quality of food products and raw food materials.

Effect of Lipopolysaccharide-Induced Inflammatory Challenge on β-Glucuronidase Activity and the Concentration of Quercetin and Its Metabolites in the Choroid Plexus, Blood Plasma and Cerebrospinal Fluid

Quercetin-3-glucuronide (Q3GA), the main phase II metabolite of quercetin (Q) in human plasma, is considered to be a more stable form of Q for transport with the bloodstream to tissues, where it can be potentially deconjugated by β-glucuronidase (β-Gluc) to Q aglycone, which easily enters the brain. This study evaluates the effect of lipopolysaccharide (LPS)-induced acute inflammation on β-Gluc gene expression in the choroid plexus (ChP) and its activity in blood plasma, ChP and cerebrospinal fluid (CSF), and the concentration of Q and its phase II metabolites in blood plasma and CSF. Studies were performed on saline- and LPS-treated adult ewes (n = 40) receiving Q3GA intravenously (n = 16) and on primary rat ChP epithelial cells and human ChP epithelial papilloma cells. We observed that acute inflammation stimulated β-Gluc activity in the ChP and blood plasma, but not in ChP epithelial cells and CSF, and did not affect Q and its phase II metabolite concentrations in plasma and CSF, except Q3GA, for which the plasma concentration was higher 30 min after administration (p < 0.05) in LPS- compared to saline-treated ewes. The lack of Q3GA deconjugation in the ChP observed under physiological and acute inflammatory conditions, however, does not exclude its possible role in the course of neurodegenerative diseases.

Quercetin-3-O-glucuronide in the Ethanol Extract of Lotus Leaf (Nelumbo nucifera) Enhances Sleep Quantity and Quality in a Rodent Model via a GABAergic Mechanism

Current pharmacological treatments for insomnia carry several and long-term side effects. Therefore, natural products without side effects are warranted. In this study, the sleep-promoting activity of the lotus leaf (Nelumbo nucifera) extract was assessed using ICR mice and Sprague Dawley rats. A pentobarbital-induced sleep test and electroencephalogram analysis were conducted to measure sleep latency time, duration, and sleep architecture. The action mechanism of the extract was evaluated through ligand binding experiments. A high dose (300 mg/kg) of the ethanolic lotus leaf extract significantly increased sleep duration compared to the normal group (p < 0.01). Administration of low (150 mg/kg) and high doses (300 mg/kg) of the extract significantly increased sleep quality, especially the relative power of theta waves (p < 0.05), compared to the normal group. Furthermore, caffeine and lotus leaf extract administration significantly recovered caffeine-induced sleep disruption (p < 0.001), and the sleep quality was similar to that of the normal group. Additionally, ligand binding assay using [3H]-flumazenil revealed that quercetin-3-O-glucuronide contained in the lotus leaf extract (77.27 μg/mg of extract) enhanced sleep by binding to GABAA receptors. Collectively, these results indicated that the lotus leaf extract, particularly quercetin-3-O-glucuronide, exhibits sleep quantity- and quality-enhancing activity via the GABAergic pathway.

Natural products targeting mitochondria: emerging therapeutics for age-associated neurological disorders

Mitochondria are the primary source of energy production in the brain thereby supporting most of its activity. However, mitochondria become inefficient and dysfunctional with age and to a greater extent in neurological disorders. Thus, mitochondria represent an emerging drug target for many age-associated neurological disorders. This review summarizes recent advances (covering from 2010 to May 2020) in the use of natural products from plant, animal, and microbial sources as potential neuroprotective agents to restore mitochondrial function. Natural products from diverse classes of chemical structures are discussed and organized according to their mechanism of action on mitochondria in terms of modulation of biogenesis, dynamics, bioenergetics, calcium homeostasis, and membrane potential, as well as inhibition of the oxytosis/ferroptosis pathway. This analysis emphasizes the significant value of natural products for mitochondrial pharmacology as well as the opportunities and challenges for the discovery and development of future neurotherapeutics.

Chronic effects of different quercetin doses in penicillin-induced focal seizure model

AIM

The aim of the present study was to examine the effects of different quercetin pretreatment doses on focal epileptiform activity induced by penicillin in adult male rat cortex.

METHOD

Twenty-eight male Wistar rats weighing 200-235 g were randomly divided into four groups: control (only penicillin-injected group) and penicillin + 25, 50 or 100 mg/kg quercetin doses. All quercetin-treated rats had a daily single dose of 25, 50 or 100 mg/kg intraperitoneally administered quercetin for 21 days, and the last dose was given 30 min before the penicillin injection. Epileptiform activity was induced by a single intracortical (i.c.) microinjection of penicillin (500 units/2.5 μl) into left motor cortex. After penicillin injection ECoG was recorded for the following 180 min.

RESULTS

Quercetin pretreatments of 25, 50 and 100 mg/kg significantly increased the duration of latency (initial spike activity) and decreased spike frequency of the epileptiform activity compared to the control group (p < 0.05). Duration of latency was significantly longer in 25 mg/kg quercetin pretreatment group compared to 100 mg/kg group (p < 0.05). Spike amplitude of epileptiform activity was not different in the study groups (p > 0.05).

CONCLUSION

Quercetin had an anticonvulsant activity in penicillin-induced focal seizure model in the present study. In addition, lower quercetin doses had highest anticonvulsant effect in this model.

Low Molecular Weight (poly)Phenol Metabolites Across the Blood-Brain Barrier: The Underexplored Journey

The world of (poly)phenols arising from dietary sources has been significantly amplified with the discovery of low molecular weight (LMW) (poly)phenol metabolites resulting from phase I and phase II metabolism and microbiota transformations. These metabolites, which are known to reach human circulation have been studied to further explore their interesting properties, especially regarding neuroprotection. Nevertheless, once in circulation, their distribution to target tissues, such as the brain, relies on their ability to cross the blood-brain barrier (BBB), one of the most controlled barriers present in humans. This represents a key step of an underexplored journey towards the brain. Present review highlights the main findings related to the ability of LMW (poly)phenol metabolites to reach the brain, considering different studies: in silico, in vitro, and in vivo. The mechanisms associated with the transport of these LMW (poly)phenol metabolites across the BBB and possible transporters will be discussed. Overall, the transport of these LMW (poly)phenol metabolites is crucial to elucidate which compounds may exert direct neuroprotective effects, so it is imperative to continue dissecting their potential to cross the BBB and the mechanisms behind their permeation.

Hyperglycemic Condition Causes Pro-Inflammatory and Permeability Alterations Associated with Monocyte Recruitment and Deregulated NFκB/PPARγ Pathways on Cerebral Endothelial Cells: Evidence for Polyphenols Uptake and Protective Effect

Hyperglycemia alters the function of cerebral endothelial cells from the blood-brain barrier, increasing the risk of cerebrovascular complications during diabetes. This study evaluated the protective effect of polyphenols on inflammatory and permeability markers on bEnd3 cerebral endothelial cells exposed to high glucose concentration. Results show that hyperglycemic condition increased nuclear factor kappa B (NFκB) activity, deregulated the expression of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-10 (IL-10) and endothelial-leukocyte adhesion molecule (E-selectin) genes, raised MCP-1 secretion and elevated monocyte adhesion and transendothelial migration. High glucose decreased occludin, claudin-5, zona occludens-1 (ZO-1) and zona occludens-2 (ZO-2) tight junctions production and altered the endothelial permeability. Characterized polyphenolic extracts from the French medicinal plants Antirhea borbonica, Ayapana triplinervis, Dodonaea viscosa and Terminalia bentzoe, and their major polyphenols quercetin, caffeic, chlorogenic and gallic acids limited the pro-inflammatory and permeability alterations caused by high glucose. Peroxisome proliferator-activated receptor gamma (PPARγ) agonist also attenuated these damages while PPARγ antagonist aggravated them, suggesting PPARγ protective action. Interestingly, polyphenols improved PPARγ gene expression lowered by high glucose. Moreover, polyphenols were detected at the intracellular level or membrane-bound to cells, with evidence for breast cancer resistance protein (BCRP) efflux transporter role. Altogether, these findings emphasize the ability of polyphenols to protect cerebral endothelial cells in hyperglycemic condition and their relevance for pharmacological strategies aiming to limit cerebrovascular disorders in diabetes.

Metabolism and pharmacokinetics of a novel polyphenol fatty acid ester phloridzin docosahexaenoate in Balb/c female mice

Flavonoids are known to undergo phase II metabolism and produce metabolites with similar or stronger biological effects compared to the parent flavonoids. However, the limited cellular uptake and bioavailability restrict their clinical use. We synthesized phloridzin docosahexaenoate (PZ-DHA), a novel fatty acid ester of polyphenol, through an acylation reaction with the aim of increasing the cellular availability and stability of the parent biomolecules, phloridzin (PZ) and docosahexaenoic acid (DHA). Here, we report metabolites and pharmacokinetic parameters of PZ-DHA, determined using ultra-high-performance liquid chromatography-electrospray ionization tandem mass spectrometry. PZ-DHA was taken-up by human (MDA-MB-231, MDA-MB-468, and MCF-7) and mouse (4T1) mammary carcinoma and human non-malignant mammary epithelial cells (MCF-10A) in cellular uptake assays. Our results suggested that the acylation improves the cellular uptake of PZ and stability of DHA within cells. In mouse hepatic microsomal assays, two major glucuronides of PZ-DHA, PZ-DHA-4-O-glucuronide and PZ-DHA-4'-O-glucuronide (MW = 923.02 g/mol), were detected. One tri-methylated- (4,4',6'-O-trimethyl-PZ-DHA) (MW = 788.88 g/mol) and one di-sulphated- (PZ-DHA-4,4'-O-disulphide) PZ-DHA metabolite (MW = 906.20 g/mol) were also identified. Intraperitoneal injections of PZ-DHA (100 mg/kg) into Balb/c female mice was rapidly absorbed with a serum C_max and T_max of 23.7 µM and 60 min, respectively, and rapidly eliminated (t_1/2 = 28.7 min). PZ-DHA and its metabolites are readily distributed throughout the body (V_d = 57 mL) into many organs. We identified in vitro and in vivo metabolites of PZ-DHA, which could be tested for potential use to treat diseases such as cancer in multiple organ systems.

Chokeberry anthocyanins and their metabolites ability to cross the blood-cerebrospinal fluid barrier

The aim of this study was to determine whether anthocyanins and their phase II metabolites permeate the blood-cerebrospinal fluid barrier (B-CSF-B) of sheep and to profile these compounds in sheep biofluids after chokeberry intraruminal administration. Anthocyanins were analyzed using micro-HPLC-MS/MS. After chokeberry administration, anthocyanins were absorbed and occurred in body fluids mainly in the form of methylated, glucuronidated, and sulfated derivatives (in total, 21 derivatives were identified). The study showed that anthocyanins penetrated the B-CSF-B and their change in profile and concentration in the cerebrospinal fluid (CSF) resulted from fluctuations in concentrations of these compounds in blood plasma, although the presence of various cyanidin derivatives in CSF also depended on their chemical structure. The biological fate of chokeberry anthocyanins, from absorption into blood to penetration into CSF, was tracked to facilitate the design of further experimental procedures to determine the biological properties of these compounds, including potentially neuroprotective activities.

The Blood-Cerebrospinal Fluid Barrier Is Selective for Red Cabbage Anthocyanins and Their Metabolites

The study aim was to determine whether strongly bioactive hydrophilic red cabbage anthocyanins possess the ability to cross the blood-cerebrospinal fluid barrier (blood-CSF barrier) and whether there is a selectivity of this barrier toward these compounds. To fulfill objectives, red cabbage preparation, containing nonacylated and acylated anthocyanins, was administered to 16 sheep with implanted cannulas into the brain third ventricle, and next, within 10 h, blood, urine, and the cerebrospinal fluid (CSF) were collected and analyzed with HPLC-MS/MS. Though, in blood plasma and urine after red cabbage intake, both, acylated and nonacylated anthocyanins and their metabolites occurred, but only nonacylated derivatives were present in the CSF, and their changes in the profile and concentration in the CSF resulted from the fluctuation of these pigments' concentration and profile in blood, their different abilities to permeate via the blood-CSF barrier, and their transformations in this barrier. Results indicate that the blood-CSF barrier is selective for red cabbage anthocyanins.

Anti-stress effects of polyphenols: animal models and human trials

Polyphenols, a category of plant compounds that contain multiple phenol structural units, are widely distributed throughout the plant kingdom and have multiple benefits for human health including anti-obesity, anti-hyperglycemic, and anti-hyperlipidemic effects. Additionally, polyphenols have recently gained attention for their anti-stress effects. In this review article, we summarize physiological responses against exposure to stressors and discuss biomarkers for exposure to stressors that are widely used in animal studies and human trials. We also review commonly used animal models for evaluating anti-stress effects. Finally, we discuss recent findings related to the anti-stress effects of polyphenols evaluated in animal models and human trials, and their putative mechanisms. These emerging data require further investigation in scientific studies and human trials to evaluate the anti-stress effects of polyphenols and their potential use for the prevention of stress-related health problems.

Potential Therapeutic Targets of Quercetin and Its Derivatives: Its Role in the Therapy of Cognitive Impairment

Quercetin (QC) is a flavonoid and crucial bioactive compound found in a variety of vegetables and fruits. In preclinical studies, QC has demonstrated broad activity against several diseases and disorders. According to recent investigations, QC is a potential therapeutic candidate for the treatment of nervous system illnesses because of its protective role against oxidative damage and neuroinflammation. QC acts on several molecular signals, including ion channels, neuroreceptors, and inflammatory receptor signaling, and it also regulates neurotrophic and anti-oxidative signaling molecules. While the study of QC in neurological disorders has focused on numerous target molecules, the role of QC on certain molecular targets such as G-protein coupled and nuclear receptors remains to be investigated. Our analysis presents several molecular targets of QC and its derivatives that demonstrate the pharmacological potential against cognitive impairment. Consequently, this article may guide future studies using QC and its analogs on specific signaling molecules. Finding new molecular targets of QC and its analogs may ultimately assist in the treatment of cognitive impairment.

Application of quercetin in neurological disorders: from nutrition to nanomedicine

Quercetin is a polyphenolic flavonoid, which is frequently found in fruits and vegetables. The antioxidant potential of quercetin has been studied from subcellular compartments, that is, mitochondria to tissue levels in the brain. The neurodegeneration process initiates alongside aging of the neurons. It appears in different parts of the brain as Aβ plaques, neurofibrillary tangles, Lewy bodies, Pick bodies, and others, which leads to Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and other diseases. So far, no specific treatment has been identified for these diseases. Despite common treatments that help to prevent the development of disease, the condition of patients with progressive neurodegenerative diseases usually do not completely improve. Currently, the use of flavonoids, especially quercetin for the treatment of neurodegenerative diseases, has been expanded in animal models. It has also been used to treat animal models of neurodegenerative diseases. In addition, improvements in behavioral levels, as well as in cellular and molecular levels, decreased activity of antioxidant and apoptotic proteins, and increased levels of antiapoptotic proteins have been observed. Low bioavailability of quercetin has also led researchers to construct various quercetin-involved nanoparticles. The treatment of animal models of neurodegeneration using quercetin-involved nanoparticles has shown that improvements are observed in shorter periods and with use of lower concentrations. Indeed, intranasal administration of quercetin-involved nanoparticles, constructing superparamagnetic nanoparticles, and combinational treatment using nanoparticles such as quercetin and other drugs are suggested for future studies.

Overcoming the Blood–Brain Barrier. Challenges and Tricks for CNS Drug Delivery

Treatment of certain central nervous system disorders, including different types of cerebral malignancies, is limited by traditional oral or systemic administrations of therapeutic drugs due to possible serious side effects and/or lack of the brain penetration and, therefore, the efficacy of the drugs is diminished. During the last decade, several new technologies were developed to overcome barrier properties of cerebral capillaries. This review gives a short overview of the structural elements and anatomical features of the blood–brain barrier. The various in vitro (static and dynamic), in vivo (microdialysis), and in situ (brain perfusion) blood–brain barrier models are also presented. The drug formulations and administration options to deliver molecules effectively to the central nervous system (CNS) are presented. Nanocarriers, nanoparticles (lipid, polymeric, magnetic, gold, and carbon based nanoparticles, dendrimers, etc.), viral and peptid vectors and shuttles, sonoporation and microbubbles are briefly shown. The modulation of receptors and efflux transporters in the cell membrane can also be an effective approach to enhance brain exposure to therapeutic compounds. Intranasal administration is a noninvasive delivery route to bypass the blood–brain barrier, while direct brain administration is an invasive mode to target the brain region with therapeutic drug concentrations locally. Nowadays, both technological and mechanistic tools are available to assist in overcoming the blood–brain barrier. With these techniques more effective and even safer drugs can be developed for the treatment of devastating brain disorders.

Procyanidins Extracted from Lotus Seedpod Ameliorate Amyloid-β-Induced Toxicity in Rat Pheochromocytoma Cells

Alzheimer's disease (AD) is a progressive neurodegenerative disease, which is characterized by extracellular senile plaque deposits, intracellular neurofibrillary tangles, and neuronal apoptosis. Amyloid-β (Aβ) plays a critical role in AD that may cause oxidative stress and downregulation of CREB/BDNF signaling. Anti-Aβ effect has been discussed as a potential therapeutic strategy for AD. This study aimed to identify the amelioration of procyanidins extracted from lotus seedpod (LSPC) on Aβ-induced damage with associated pathways for AD treatment. Rat pheochromocytoma (PC12) cells incubated with Aβ_25–35 serve as an Aβ damage model to evaluate the effect of LSPC in vitro. Our findings illustrated that LSPC maintained the cellular morphology from deformation and reduced apoptosis rates of cells induced by Aβ_25–35. The mechanisms of LSPC to protect cells from Aβ-induced damage were based on its regulation of oxidation index and activation of CREB/BDNF signaling, including brain-derived neurotrophic factor (BDNF) and phosphorylation of cAMP-responsive element-binding (CREB), protein kinase B (also known as AKT), and the extracellular signal-regulated kinase (ERK). Of note, by high-performance liquid chromatography-tandem mass spectroscopy (LC-MS/MS), several metabolites were detected to accumulate in vivo, part of which could take primary responsibility for the amelioration of Aβ-induced damage on PC12 cells. Taken together, our research elucidated the effect of LSPC on neuroprotection through anti-Aβ, indicating it as a potential pretreatment for Alzheimer's disease.

Neuroprotective effects of quercetin 4'-O-β-d-diglucoside on human striatal precursor cells in nutrient deprivation condition

Several investigations have demonstrated neuroprotective effects of quercetin, a polyphenol widely present in nature, against neurotoxic chemicals, as well as in neuronal injury/neurodegenerative disease models. Most of these studies have been performed with quercetin aglycone and its metabolites, while scanty data are available on its glycosides. This study is aimed at investigating the neuroprotective effects of quercetin 3,4'-O-β-d-diglucoside (Q3,4'dG), isolated from the bulbs of the white cultivar (Allium cepa L.), using an in vitro model of human striatal precursor cells (HSPs), a primary culture isolated from the striatal primordium and previously characterized. To study the effect of Q3,4'dG on cell survival, HSPs were exposed to nutrient deprivation created by replacing culture medium with phosphate buffer saline (PBS). Our findings showed that Q3,4'dG treatment significantly promoted cell survival and strongly decreased apoptosis induced by nutrient deprivation, as evaluated by cell proliferation/death analyses. In addition, since the adhesive capacities of cells are essential for cell survival, the expression of some adhesion molecules, such as pancadherin and focal adhesion kinase, was evaluated. Interestingly, PBS exposure significantly decreased the expression of both molecules, while in the presence of Q3,4'dG this effect was prevented. This study provides evidence of a neuroprotective role exerted by Q3,4'dG and suggests its possible implication in sustaining neuronal survival for prevention and treatment of neurodegenerative disorders.

Quercetin inhibits okadaic acid-induced tau protein hyperphosphorylation through the Ca2+‑calpain‑p25‑CDK5 pathway in HT22 cells

Alzheimer's disease (AD) is a common neurodegenerative disorder characterized by aberrant tau protein hyperphosphorylation, which eventually leads to the formation of neurofibrillary tangles. Hyperphosphorylated tau protein is considered as a vital factor in the development of AD and is highly associated with cognitive impairment. Therefore, it is recognized to be a potential therapeutic target. Quercetin (QUE) is a naturally occurring flavonoid compound. In the present study, the inhibitory effect of QUE on okadaic acid (OA)-induced tau protein hyperphosphorylation in HT22 cells was explored. Western blotting results indicated that QUE significantly attenuated OA‑induced tau protein hyperphosphorylation at the Ser396, Ser199, Thr231 and Thr205 sites. Further experiments demonstrated that QUE inhibited the activity of cyclin‑dependent kinase 5 (CDK5), a key enzyme in the regulation of tau protein, and blocked the Ca2+‑calpain‑p25‑CDK5 signaling pathway. These observations indicate the ability of QUE to decrease tau protein hyperphosphorylation and thereby attenuate the associated neuropathology. In conclusion, these results support the potential of QUE as a therapeutic agent for AD and other neurodegenerative tauopathies.

Blood-brain barrier transport and neuroprotective potential of blackberry-digested polyphenols: an in vitro study

PURPOSE

Epidemiological and intervention studies have attempted to link the health effects of a diet rich in fruits and vegetables with the consumption of polyphenols and their impact in neurodegenerative diseases. Studies have shown that polyphenols can cross the intestinal barrier and reach concentrations in the bloodstream able to exert effects in vivo. However, the effective uptake of polyphenols into the brain is still regarded with some reservations. Here we describe a combination of approaches to examine the putative transport of blackberry-digested polyphenols (BDP) across the blood-brain barrier (BBB) and ultimate evaluation of their neuroprotective effects.

METHODS

BDP was obtained by in vitro digestion of blackberry extract and BDP major aglycones (hBDP) were obtained by enzymatic hydrolysis. Chemical characterization and BBB transport of extracts were evaluated by LC-MSⁿ. BBB transport and cytoprotection of both extracts was assessed in HBMEC monolayers. Neuroprotective potential of BDP was assessed in NT2-derived 3D co-cultures of neurons and astrocytes and in primary mouse cerebellar granule cells. BDP-modulated genes were evaluated by microarray analysis.

RESULTS

Components from BDP and hBDP were shown to be transported across the BBB. Physiologically relevant concentrations of both extracts were cytoprotective at endothelial level and BDP was neuroprotective in primary neurons and in an advanced 3D cell model. The major canonical pathways involved in the neuroprotective effect of BDP were unveiled, including mTOR signaling and the unfolded protein response pathway. Genes such as ASNS and ATF5 emerged as novel BDP-modulated targets.

CONCLUSIONS

BBB transport of BDP and hBDP components reinforces the health benefits of a diet rich in polyphenols in neurodegenerative disorders. Our results suggest some novel pathways and genes that may be involved in the neuroprotective mechanism of the BDP polyphenol components.

Factors modulating bioavailability of quercetin-related flavonoids and the consequences of their vascular function

Nowadays dietary flavonoids attract much attention in the prevention of chronic diseases. Epidemiological and intervention studies strongly suggest that flavonoid intake has beneficial effects on vascular health. It is unlikely that flavonoids act as direct antioxidants, although oxidative stress profoundly contributes to vascular impairment leading to cardiovascular diseases. Instead, flavonoids may exert their function by tuning the cellular redox state to an adaptive response or tolerable stress. However, the optimum intake of flavonoids from supplements or diet has not been clarified yet, because a number of exogenous and endogenous factors modulating their bioavailability affect their vascular function. This review will focus on the current knowledge of the bioavailability and vascular function of quercetin as a representative of antioxidative flavonoids. Current intervention studies imply that intake of quercetin-rich onion improves vascular health. Onion may be superior to quercetin supplement from the viewpoint of quercetin bioavailability, probably because the food matrix enhances the intestinal absorption of quercetin. α-Glucosylation increases its bioavailability by elevating the accessibility to the absorptive cells. Prenylation may enhance bioaccumulation at the target site by increasing the cellular uptake. However, these chemical modifications do not guarantee health benefits to the vascular system. Dietary quercetin is exclusively present as their conjugated form in the blood stream. Quercetin may exert its vascular function as an aglycone within macrophage cells after inflammation-induced deconjugation and as conjugated metabolites by targeting endothelial cells. The relationship between the bioavailability and bio-efficacy should be clarified, to evaluate the vascular function of a wide variety of dietary flavonoids.

Polyphenols Beyond Barriers: A Glimpse into the Brain

BACKGROUND

Ageing can be simply defined as the process of becoming older, which is genetically determined but also environmentally modulated. With the continuous increase of life expectancy, quality of life during ageing has become one of the biggest challenges of developed countries. The quest for a healthy ageing has led to the extensive study of plant polyphenols with the aim to prevent age-associated deterioration and diseases, including neurodegenerative diseases. The world of polyphenols has fascinated researchers over the past decades, and in vitro, cell-based, animal and human studies have attempted to unravel the mechanisms behind dietary polyphenols neuroprotection.

METHODS

In this review, we compiled some of the extensive and ever-growing research in the field, highlighting some of the most recent trends in the area.

RESULTS

The main findings regarding polypolyphenols neuroprotective potential performed using in vitro, cellular and animal studies, as well as human trials are covered in this review. Concepts like bioavailability, polyphenols biotransformation, transport of dietary polyphenols across barriers, including the blood-brain barrier, are here explored.

CONCLUSION

The diversity and holistic properties of polypolyphenol present them as an attractive alternative for the treatment of multifactorial diseases, where a multitude of cellular pathways are disrupted. The underlying mechanisms of polypolyphenols for nutrition or therapeutic applications must be further consolidated, however there is strong evidence of their beneficial impact on brain function during ageing. Nevertheless, only the tip of the iceberg of nutritional and pharmacological potential of dietary polyphenols is hitherto understood and further research needs to be done to fill the gaps in pursuing a healthy ageing.

Quercetin and derivatives: useful tools in inflammation and pain management

Inflammation represents a very frequent condition in humans; it is often underestimated, making the problem an increasingly alarming phenomenon. For these reasons, conventional therapies are losing their effectiveness, leaving room for innovative therapies. In this field, natural products showed their efficacy in various diseases; and flavonoids, in particular quercetin, is known for its broad range of activities. In this review, we have highlighted its efficacy in various models of inflammation, focusing also on the activity of its semisynthetic derivatives, and those naturally present in plant extracts. Finally, the analgesic property of quercetin, intrinsically linked to its anti-inflammatory action, has been also evaluated, to investigate about an innovative approach to this interesting natural compound, such as analgesic remedial.

Effect of the oral administration of nanoencapsulated quercetin on a mouse model of Alzheimer's disease

Quercetin has been identified as a promising compound with a neuroprotective potential against age-related neurodegenerative diseases such as Alzheimer's disease (AD). Nevertheless, the clinical application of quercetin is hampered by its low oral bioavailability. The aim of this work was to evaluate the capability of nanoencapsulated quercetin in zein nanoparticles (NPQ), that significantly improves the oral absorption and bioavailability of the flavonoid, as potential oral treatment for AD. For this purpose, SAMP8 mice were orally treated for two months with either NPQ (25mg/kg every 48h) or a solution of quercetin (Q; 25mg/kg daily). NPQ displayed a size of 260nm and a payload of about 70μg/mg. For Q, no significant effects were observed in animals. On the contrary, the oral administration of NPQ improved the cognition and memory impairments characteristics of SAMP8 mice. These observations appeared to be related with a decreased expression of the hippocampal astrocyte marker GFAP. Furthermore, significant levels of quercetin were quantified in the brain of mice treated with nanoparticles. These findings highlight the potential of zein nanoparticles to promote the oral absorption of quercetin as well as the therapeutic potential of this flavonoid in AD pathogenesis.

Pharmacokinetic comparison between quercetin and quercetin 3-O-β-glucuronide in rats by UHPLC-MS/MS

Quercetin is a natural flavonoid widely distributed in human diet and functional foods. Quercetin 3-O-β-glucuronide (Q3G) is present in wine and some medicinal plants. Quercetin and Q3G may be metabolized from each other in vivo. While quercetin has been the subject of many studies, the pharmacokinetic profiles of quercetin and Q3G (in animals) have not yet been compared. Herein, we prepared a column-based method for rapid isolation of Q3G from Nelumbo nucifera. Then, we developed an UHPLC-MS/MS method to compare the pharmacokinetics of quercetin and Q3G. Our results showed that the plasma concentration-time curves of quercetin and Q3G show two maxima (T_max1 ≈ 0.75 h, T_max2 ≈ 5 h). After oral administration of 100 mg/kg quercetin or 100 mg/kg Q3G in rats, predominantly Q3G was detected in plasma with AUC at 39529.2 ± 6108.2 mg·h·L⁻¹ or 24625.1 ± 1563.8 mg·h·L⁻¹, 18-fold higher than quercetin with AUC at 1583.9 ± 583.3 mg·h·L⁻¹ or 1394.6 ± 868.1 mg·h·L⁻¹, respectively. After intravenous injection of 10 mg/kg in rats, Q3G showed extensive tissue uptake in kidney (409.2 ± 118.4 ng/g), liver (166.1 ± 52.9 ng/g), heart (97.7 ± 22.6 ng/g), and brain (5.8 ± 1.2 ng/g). In conclusion, we have shown that Q3G is a major active component in plasma and tissue for oral administration of quercetin or Q3G.

Enhancement of flavonoid ability to cross the blood-brain barrier of rats by co-administration with α-tocopherol

Vitamin E and polyphenols could exhibit a therapeutic role in the treatment of oxidative stress-induced neurodegenerative diseases. Therefore, their ability to cross the blood-brain barrier (BBB) represents an important issue to be explored by different diet combinations. In this study, we have evaluated the ability of α-tocopherol to support epigallocatechin-3-gallate (EGCG), quercetin and rutin to cross the BBB, following oral administration. Eighteen rats were fed a standard diet (C), a diet supplemented with α-tocopherol (A), with a mixture of EGCG, quercetin and rutin (P); or with a mixture of α-tocopherol and the three flavonoids (AP). Flavonoids and their conjugated derivatives were assayed in brain and plasma by HPLC-MS, whereas α-tocopherol was detected by RP-HPLC. The oxidative damage, due to the potential pro-oxidant activity of flavonoids, was evaluated by the presence of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in hippocampal Cornus Ammonis, one of the most vulnerable sites in the brain. Our results indicate that α-tocopherol is able to promote quercetin transport across the BBB. The mixture of rutin and quercetin seems to favour the accumulation of quercetin and/or its conjugated derivatives in the brain. In contrast, α-tocopherol does not affect EGCG transport across the BBB. The densitometric analysis of 8-OHdG immunoreactivity does not reveal any difference of oxidative damage among the experimental groups. Our results suggest that α-tocopherol may promote quercetin transport across the BBB, leading to a significant increase of α-tocopherol and quercetin concentration in the brain.

Quercetin and the mitochondria: A mechanistic view

Quercetin is an important flavonoid that is ubiquitously present in the diet in a variety of fruits and vegetables. It has been traditionally viewed as a potent antioxidant and anti-inflammatory molecule. However, recent studies have suggested that quercetin may exert its beneficial effects independent of its free radical-scavenging properties. Attention has been placed on the effect of quercetin on an array of mitochondrial processes. Quercetin is now recognized as a phytochemical that can modulate pathways associated with mitochondrial biogenesis, mitochondrial membrane potential, oxidative respiration and ATP anabolism, intra-mitochondrial redox status, and subsequently, mitochondria-induced apoptosis. The present review evaluates recent evidence on the ability of quercetin to interact with the abovementioned pathways, and critically analyses how, such interactions can exert protection against mitochondrial damage in response to toxicity induced by several exogenously and endogenously-produced cellular stressors, and oxidative stress in particular.

The mechanisms of action of flavonoids in the brain: Direct versus indirect effects

The projected increase in the incidence of dementia in the population highlights the urgent need for a more comprehensive understanding of how different aspects of lifestyle, in particular exercise and diet, may affect neural function and consequent cognitive performance throughout the life course. In this regard, flavonoids, found in a variety of fruits, vegetables and derived beverages, have been identified as a group of promising bioactive compounds capable of influencing different aspects of brain function, including cerebrovascular blood flow and synaptic plasticity, both resulting in improvements in learning and memory in mammalian species. However, the precise mechanisms by which flavonoids exert these actions are yet to be fully established, although accumulating data indicate an ability to interact with neuronal receptors and kinase signaling pathways which are key to neuronal activation and communication and synaptic strengthening. Alternatively or concurrently, there is also compelling evidence derived from human clinical studies suggesting that flavonoids can positively affect peripheral and cerebrovascular blood flow, which may be an indirect effective mechanism by which dietary flavonoids can impact on brain health and cognition. The current review examines the beneficial effects of flavonoids on both human and animal brain function and attempts to address and link direct and indirect actions of flavonoids and their derivatives within the central nervous system (CNS).

Quercetin and isorhamnetin aglycones are the main metabolites of dietary quercetin in cerebrospinal fluid

SCOPE

Reports on the protective effect of certain foods on brain functions are numerous; however, the permeability of the brain barriers by food components is still hardly recognised. There have been in vitro studies aimed at demonstrating this possibility, but not much is known about this phenomenon in in vivo systems. The objective of the study was to determine the metabolites of dietary quercetin (Q) in urine, blood plasma and cerebrospinal fluid (CSF) after intra-rumen administration of Q rich onion dry skin in an animal model.

METHODS AND RESULTS

Eleven sheep had permanently implanted cannulas in the third ventricle of the brain as the means for CSF collection. The animals were administered Q at the dose of 10 mg/kg bwt. For 12 h the concentration of Q metabolites was measured in urine, blood plasma, and CSF. It was demonstrated that while in blood plasma Q and isorhamnetin mono-glucuronides or mono-sulphates were the main metabolites (80%), in CSF their aglycones were the dominating ones (88%).

CONCLUSION

Q and IR aglycones are the main Q metabolites present in CSF after dietary Q intake. Their passive transport through blood-CSF barrier or a de-conjugating mechanism within that barrier may be involved.

Inhibition of microglial activation by elderberry extracts and its phenolic components

AIMS

Elderberry (Sambucus spp.) is one of the oldest medicinal plants noted for its cardiovascular, anti-inflammatory, and immune-stimulatory properties. In this study, we investigated the anti-inflammatory and anti-oxidant effects of the American elderberry (Sambucus nigra subsp. canadensis) pomace as well as some of the anthocyanins (cyanidin chloride and cyanidin 3-O-glucoside) and flavonols (quercetin and rutin) in bv-2 mouse microglial cells.

MAIN METHODS

The bv-2 cells were pretreated with elderberry pomace (extracted with ethanol or ethyl acetate) or its anthocyanins and flavonols and stimulated by either lipopolysaccharide (LPS) or interferon-γ (IFNγ). Reactive oxygen species (ROS) and nitric oxide (NO) production (indicating oxidative stress and inflammatory response) were measured using the ROS detection reagent DCF-DA and the Griess reaction, respectively.

KEY FINDINGS

Analysis of total monomeric anthocyanin (as cyanidin 3-O-glucoside equivalents) indicated five-fold higher amount in the freeze-dried ethanol extract as compared to that of the oven-dried extract; anthocyanin was not detected in the ethyl acetate extracts. Elderberry ethanol extracts (freeze-dried or oven-dried) showed higher anti-oxidant activities and better ability to inhibit LPS or IFNγ-induced NO production as compared with the ethyl acetate extracts. The phenolic compounds strongly inhibited LPS or IFNγ-induced ROS production, but except for quercetin, they were relatively poor in inhibiting NO production.

SIGNIFICANCE

These results demonstrated differences in anti-oxidative and anti-inflammatory effects of elderberry extracts depending on solvents used. Results further identified quercetin as the most active component in suppressing oxidative stress and inflammatory responses on microglial cells.

Quercetin and related polyphenols: new insights and implications for their bioactivity and bioavailability

The physiological functions and mechanisms of action of quercetin and its related polyphenols are highlighted, including their effects on brain, blood vessels, muscle, and intestinal microflora.

Immunochemical authentication of manuka honey using a monoclonal antibody specific to a glycoside of methyl syringate

Leptosperin, a novel glycoside of methyl syringate, is exclusively present in manuka honey derived from the Leptospermum species Leptospermum scoparium. Quantification of leptosperin might thus be applicable for authentication of honey. The concentration of leptosperin has high linearity with antibacterial activity. We established a monoclonal antibody to leptosperin and characterized the antibody in detail by a competitive enzyme-linked immunosorbent assay (ELISA), comparing the results with those of the high-performance liquid chromatography (HPLC) method for validation. The antigen in manuka honey was confirmed as leptosperin by HPLC fractionation with quantitation by an ELISA. Leptosperin contents of 50 honey samples were analyzed by an established ELISA, which can handle 20 samples (duplicate) on one 96-well plate. Significant coincidence with the chemical quantitation was observed. Immunochemical quantitation of leptosperin would be an economical and facile method for the possible authentication of manuka honey, allowing many honey samples to be processed and analyzed by an ELISA simultaneously.