Protective effects of onion-derived quercetin on glutamate-mediated hippocampal neuronal cell death

Neuroprotective mechanisms of luteolin in glutamate-induced oxidative stress and autophagy-mediated neuronal cell death

Neurodegenerative diseases, characterized by progressive neuronal dysfunction and loss, pose significant health challenges. Glutamate accumulation contributes to neuronal cell death in diseases such as Alzheimer's disease. This study investigates the neuroprotective potential of Albizia lebbeck leaf extract and its major constituent, luteolin, against glutamate-induced hippocampal neuronal cell death. Glutamate-treated HT-22 cells exhibited reduced viability, altered morphology, increased ROS, and apoptosis, which were attenuated by pre-treatment with A. lebbeck extract and luteolin. Luteolin also restored mitochondrial function, decreased mitochondrial superoxide, and preserved mitochondrial morphology. Notably, we first found that luteolin inhibited the excessive process of mitophagy via the inactivation of BNIP3L/NIX and inhibited lysosomal activity. Our study suggests that glutamate-induced autophagy-mediated cell death is attenuated by luteolin via activation of mTORC1. These findings highlight the potential of A. lebbeck as a neuroprotective agent, with luteolin inhibiting glutamate-induced neurotoxicity by regulating autophagy and mitochondrial dynamics.

Sanpian decoction ameliorates cerebral ischemia-reperfusion injury by regulating SIRT1/ERK/HIF-1α pathway through in silico analysis and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Cerebral ischemia-reperfusion injury (CIRI) is a complex pathophysiological process involving multiple factors, and becomes the footstone of rehabilitation after ischemic stroke. Sanpian decoction (SPD) has exhibited protective effects against CIRI, migraine, and other cerebral vascular diseases. However, the underlying mechanisms have not been completely elucidated.

AIM OF THE STUDY

This study sought to explore the potential mechanisms underlying the effect of SPD against CIRI.

MATERIALS AND METHODS

High-performance liquid chromatography (HPLC) and ultra-high-performance liquid chromatography (UPLC) were carried out to determine the chemical constituents of SPD. A network pharmacology approach combined with experimental verification was conducted to elucidate SPD's multi-component, multi-target, and multi-pathway mechanisms in CIRI occurrence. The pharmacodynamics of the decoction was evaluated by establishing the rat model of middle cerebral artery occlusion/reperfusion (MCAO/R). In vivo and in vitro experiments were carried out, and the therapeutic effects of SPD were performed using 2,3,5-triphenyltetrazolium chloride (TTC) staining, hematoxylin-eosin (HE) staining, and Nissl staining. We used terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining and flow cytometry to evaluate cortex apoptosis. The quantification of mRNA and corresponding proteins were performed using real-time quantitative reverse transcription polymerase chain reaction (RT-qPCR) and Western blot respectively.

RESULTS

Our research showed that pretreatment with SPD improved neurological function and inhibited CIRI. Network pharmacology revealed that the hypoxia-inducible factor-1 (HIF-1) signaling pathway and mitogen-activated protein kinase (MAPK) signaling pathway-mediated apoptosis may be associated with CIRI. In vivo and in vitro experiments, we confirmed that SPD increased cerebral blood flow, improved neural function, and reduced neural apoptosis via up-regulating the expression of sirtuin 1 (SIRT1) and down-regulating phospho-extracellular regulated protein kinases (p-ERK)/ERK and HIF-1α levels in CIRI rats.

CONCLUSION

Taken together, the present study systematically revealed the potential targets and signaling pathways of SPD in the treatment of CIRI using in silico prediction and verified the therapeutic effects of SPD against CIRI via ameliorating apoptosis by regulating SIRT1/ERK/HIF-1α.

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.

Screening of Anti-carcinogenic Properties of Phytocompounds from Allium ascalonicum for Treating Breast Cancer Through In Silico and In Vitro Approaches

Plants, rich in phytocompounds, have been in usage since time immemorial for treating various diseases, namely, cancer. One such plant species, Allium ascalonicum (Shallot) belonging to Amaryllidaceae family is being studied here for its anti-carcinogenic properties against breast cancer. GC-MS characterization of A. ascalonicum exhibited 48 phytocompounds containing five peak phytocompounds and 13 phytocompounds with anti-carcinogenic properties. These 13 anti-carcinogenic phytocompounds were docked with three hormonal receptors involved in breast cancer malignancy, namely, ERα, PR, and human EGFR with tamoxifen as standard for in silico analysis. The results exhibited three phytocompounds that had better binding scores compared to that of the standard drug, tamoxifen. Lyophilized powder of aqueous A. ascalonicum extract, also referred as ASE, was used for in vitro approaches. Antioxidant study using DPPH assay revealed that the highest percentage of FRSA in ASE, nearly 51%, was observed at 50 µg/ml concentration. Cytotoxicity study on MCF-7 cell line using MTT assay demonstrated IC₅₀ value at 1400 µg/ml and anti-proliferative study using Trypan blue assay for the determination of percentage viability of MCF-7 cells at IC₅₀ concentration was observed to be 49%. Anti-mitotic activity using Vigna radiata seed germination assay revealed clear morphological differences in a dose-dependent manner between the seeds grown at various concentrations of ASE with nearly 56.5% growth inhibition observed at 1500 µg/ml concentration. Hence, this research work proves that Allium ascalonicum has very good anti-carcinogenic properties and this can be confirmed further through in vivo animal model studies and it can also be formulated as a promising drug to treat breast cancer. GC-MS characterization of Allium ascalonicum demonstrated the presence of five peak compounds and thirteen anti-carcinogenic compounds. The thirteen anti-carcinogenic compounds were docked with three target proteins (in silico analysis) involved in breast cancer malignancy and identified the presence of three potential phytocompounds that can be used for treating breast cancer. In vitro approaches also confirmed the presence of anti-carcinogenic properties such as antioxidative potential, cytotoxic, anti-proliferative, and anti-mitotic effects. Hence, Allium ascalonicum can be taken further to in vivo studies so that it can be formulated to treat breast cancer.

Targeting Estrogen Signaling in the Radiation-induced Neurodegeneration: A Possible Role of Phytoestrogens

Radiation for medical use is a well-established therapeutic method with an excellent prognosis rate for various cancer treatments. Unfortunately, a high dose of radiation therapy comes with its own share of side effects, causing radiation-induced non-specific cellular toxicity; consequently, a large percentage of treated patients suffer from chronic effects during the treatment and even after the post-treatment. Accumulating data evidenced that radiation exposure to the brain can alter the diverse cognitive-related signaling and cause progressive neurodegeneration in patients because of elevated oxidative stress, neuroinflammation, and loss of neurogenesis. Epidemiological studies suggested the beneficial effect of hormonal therapy using estrogen in slowing down the progression of various neuropathologies. Despite its primary function as a sex hormone, estrogen is also renowned for its neuroprotective activity and could manage radiation-induced side effects as it regulates many hallmarks of neurodegenerations. Thus, treatment with estrogen and estrogen-like molecules or modulators, including phytoestrogens, might be a potential approach capable of neuroprotection in radiation-induced brain degeneration. This review summarized the molecular mechanisms of radiation effects and estrogen signaling in the manifestation of neurodegeneration and highlighted the current evidence on the phytoestrogen mediated protective effect against radiationinduced brain injury. This existing knowledge points towards a new area to expand to identify the possible alternative therapy that can be taken with radiation therapy as adjuvants to improve patients' quality of life with compromised cognitive function.

Phytochemicals from Red Onion, Grown with Eco-Sustainable Fertilizers, Protect Mammalian Cells from Oxidative Stress, Increasing Their Viability

Red onion, a species of great economic importance rich in phytochemicals (bioactive compounds) known for its medicinal properties, was fertilized with sulphur-bentonite enriched with orange residue or olive pomace, with the aim of producing onion enriched in health beneficial compounds. There is a worldwide great demand of minimally processed food or food ingredients with functional properties because of a new awareness of how important healthy functional nutrition is in life. Phytochemicals have the capacity to regulate most of the metabolic processes resulting in health benefits. Red onion bioactive compound quantity and quality can vary according to cultivation practices. The main aims of the current research were to determine the chemical characteristics of the crude extracts from red onion bulbs differently fertilized and to evaluate their biological activity in normal and oxidative stress conditions. The lyophilized onion bulbs have been tested in vitro on two cellular models, i.e., the H9c2 rat cardiomyoblast cell line and primary human dermal fibroblasts, in terms of viability and oxygen radical homeostasis. The results evidenced different phytochemical compositions and antioxidant activities of the extracts obtained from red onions differently fertilized. Sulphur-bentonite fertilizers containing orange waste and olive pomace positively affected the red onion quality with respect to the red onion control, evidencing that sulphur-bentonite-organic fertilization was able to stimulate plant a secondary metabolism inducing the production of phytochemicals with healthy functions. A positive effect of the extracts from red onions treated with fertilizers—in particular, with those containing orange waste, such as the reduction of oxidative stress and induction of cell viability of H9c2 and human fibroblasts—was observed, showing a concentration- and time-dependent profile. The results evidenced that the positive effects were related to the phenols and, in particular, to chlorogenic and p-coumaric acids and to the flavonol kaempferol, which were more present in red onion treated with low orange residue than in the other treated ones.

A Critical Analysis of Quercetin as the Attractive Target for the Treatment of Parkinson's Disease

Parkinson's Disease (PD) is a multifaceted disorder with various factors suggested to play a synergistic pathophysiological role, such as oxidative stress, autophagy, pro-inflammatory events, and neurotransmitter abnormalities. While it is crucial to discover new treatments in addition to preventing PD, recent studies have focused on determining whether nutraceuticals will exert neuroprotective actions and pharmacological functions in PD. Quercetin, a flavonol-type flavonoid, is found in many fruits and vegetables and is recognised as a complementary therapy for PD. The neuroprotective effect of quercetin is directly associated with its antioxidant activity, in addition to stimulating cellular defence against oxidative stress. Other related mechanisms are activating Sirtuins (SIRT1) and inducing autophagy, in addition to induction of Nrf2-ARE and Paraoxonase 2 (PON2). Quercetin, whose neuroprotective activity has been demonstrated in many studies, unfortunately, has a disadvantage because of its poor water solubility, chemical instability, and low oral bioavailability. It has been reported that the disadvantages of quercetin have been eliminated with nanocarriers loaded with quercetin. The role of nanotechnology and nanodelivery systems in reducing oxidative stress during PD provides an indisputable advantage. Accordingly, the present review aims to shed light on quercetin's beneficial effects and underlying mechanisms in neuroprotection. In addition, the contribution of nanodelivery systems to the neuroprotective effect of quercetin is also discussed.

Development of Optimized Ultrasound-Assisted Extraction Methods for the Recovery of Total Phenolic Compounds and Anthocyanins from Onion Bulbs

Allium cepa L. is one of the most abundant vegetable crops worldwide. In addition to its versatile culinary uses, onion also exhibits quite interesting medicinal uses. Bulbs have a high content of bioactive compounds that are beneficial for human health. This study intends to develop and optimize two appropriate ultrasound-assisted methods for the extraction of the phenolic compounds and anthocyanins present in red onion. A response surface methodology was employed and, specifically, a Box–Behnken design, for the optimization of the methods. The optimal conditions for the extraction of the phenolic compounds were the follows: 53% MeOH as solvent, pH 2.6, 60 °C temperature, 30.1% amplitude, 0.43 s cycle, and 0.2:11 g sample/mL solvent ratio. On the other hand, the optimal conditions for the anthocyanins were as follows: 57% MeOH as solvent, pH 2, 60 °C temperature, 90% amplitude, 0.64 s cycle, and 0.2:15 g sample/mL solvent ratio. Both methods presented high repeatability and intermediate precision, as well as short extraction times with good recovery yields. These results illustrate that the use of ultrasound-assisted extraction, when properly optimized, is suitable for the extraction and quantification of the compounds of interest to determine and improve the quality of the raw material and its subproducts for consumers.

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.

Flavonoids and cellular stress: a complex interplay affecting human health

Flavonoid consumption has beneficial effects on human health, however, clinical evidence remains often inconclusive due to high interindividual variability. Although this high interindividual variability has been consistently observed in flavonoid research, the potential underlying reasons are still poorly studied. Especially the knowledge on the impact of health status on flavonoid responsiveness is limited and merits more investigation. Here, we aim to highlight the bidirectional interplay between flavonoids and cellular stress. First, the state-of-the-art concerning inflammatory stress and mitochondrial dysfunction is reviewed and a comprehensive overview of recent in vitro studies investigating the impact of flavonoids on cellular stress, induced by tumor necrosis factor α, lipopolysaccharide and mitochondrial stressors, is given. Second, we critically discuss the influence of cellular stress on flavonoid uptake, accumulation, metabolism and cell responses, which has, to our knowledge, never been extensively reviewed before. Next, we advocate the innovative insight that stratification of the general population based on health status can reveal subpopulations that benefit more from flavonoid consumption. Finally, suggestions are given for the development of future cell models that simulate the physiological micro-environment, including interindividual variability, since more mechanistic research is needed to establish scientific-based personalized food recommendations for specific subpopulations.

Metabolic and neurological consequences of the treatment with polyphenols: a systematic review in rodent models of noncommunicable diseases

BACKGROUND

Noncommunicable diseases (NCDs) lead to drastic metabolic alterations with associated energy balance and body weight changes, two related physiological processes regulated by the brain. Polyphenol-based treatments for NCDs have emerged as a promising therapy, which seems to involve the energy balance modulation. However, it remains unclear what the most effective polyphenols-based treatment is to attenuate adverse effects in the energy balance of NCDs.

OBJECTIVES

This systematic review aimed to evaluate the literature on the metabolic and neurological effects of polyphenols-based treatment in rodent models of NCDs.

METHODS

Literature search was carried out in the following databases: CINAHL, Medline/PubMed, SCOPUS, and Web of Science. For title and abstract screening, original papers with polyphenols exposure in rodents were selected. For full-text screening, studies with models of NCDs that reported metabolic and neurological outcomes when treated with polyphenols were selected for inclusion in this review.

RESULTS

23 articles, using individual compound (11 articles) or polyphenols extracts (12 articles), were included in this review: 5 articles using tea polyphenols, 12 articles using grape-derived polyphenols, 3 articles using the polyphenol quercetin, and 3 articles using other polyphenol sources. Most results agree on the beneficial effect of polyphenols in attenuating alterations in energy balance and body weight. Such effects were associated with neuroprotective responses in different brain areas including hippocampus and hypothalamus.

CONCLUSION

In conclusion, this review shows that the treatment with polyphenols, especially resveratrol or quercetin, attenuates the adverse effects of NCDs on energy balance and are associated with neuroprotective effects.

Quercetin alleviates styrene oxide-induced cytotoxicity in cortical neurons in vitro via modulation of oxidative stress and apoptosis

Styrene 7,8-oxide (SO) is the principal metabolite of styrene, an industrial neurotoxic compound which causes various neurodegenerative disorders. The present study aimed to explore the mechanisms of SO cytotoxicity (0.5 - 4 mM) in primary cortical neurons and to evaluate the neuroprotective potential of quercetin (QUER). Our results showed that exposure to SO decreased viability of cortical neurons in a concentration-dependent manner. In the presence of QUER, cell viability was increased significantly. The neuroprotective effects of QUER were associated with the reduction of intracellular Reactive Oxygen Species (ROS), the decrease in calcium overload and the restoration of mitochondrial membrane depolarization caused by SO. Additionally, to evaluate neuronal death mechanisms triggered by SO, cells were incubated with Ac-DEVD-CHO, Calpeptin and Necrostatin-1, pharmacological inhibitors of caspase-3, calpains and necroptosis respectively. The data showed that the three inhibitors reduced cell death induced by SO and suggested the implication of apoptotic, necrotic and necroptotic pathways. However, western blot analysis showed that QUER attenuated the activation of caspase-3 but did not prevent calpain activity. Taken together, these data indicated that the cytotoxicity of SO was mediated by oxidative stress and apoptosis, necrosis and necroptosis mechanisms, while the neuroprotection provided by QUER against SO depended mainly on its anti-apoptotic activity.

Neuroprotective Effect of Tricyclic Pyridine Alkaloids from Fusarium lateritium SSF2, against Glutamate-Induced Oxidative Stress and Apoptosis in the HT22 Hippocampal Neuronal Cell Line

Excessive glutamate damages neuronal cells via the accumulation of intracellular reactive oxygen species (ROS), calcium ion (Ca²⁺) influx, depolarization of mitochondrial membrane potential, and apoptosis, which may result in the development of chronic neurodegenerative diseases. In this study, we evaluated the effects of 4,6′-anhydrooxysporidinone isolated from endophytic fungus Fusarium lateritium SSF2 on glutamate-induced cytotoxicity, accumulation of intracellular ROS, increases in superoxide anion production, Ca²⁺, depolarization of mitochondrial membrane potential, and apoptotic cell death in hippocampal HT22 cells. 2′,7′-Dichlorofluorescin diacetate (H2DCFDA) staining was used to determine the intracellular reactive oxygen species concentration and dihydroethidine (DHE) staining was used to determine the superoxide radical. Expression of the nuclear factor-erythroid-2–related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) was analyzed by Western blot. Fluo-4 staining was used to determine the intracellular Ca²⁺ levels. In order to explore mitochondrial membrane potential, tetramethylrhodamine methyl ester (TMRM) staining was used. Apoptotic cell death was evaluated using Annexin-V/propidium iodide (PI) staining and TUNEL staining. Expression of the cytochrome c release and cleaved caspase-9, -3 was analyzed by Western blot. Here, we were able to isolate 4,6′-anhydrooxysporidinone from endophytic fungus, Fusarium lateritium SSF2, which was shown to protect HT22 cells from glutamate-induced cytotoxicity, accumulation of intracellular ROS, increases in superoxide anion production, Ca²⁺, and depolarization of mitochondrial membrane potential. In addition, 4,6′-anhydrooxysporidinone enhanced the expressions of Nrf2 and HO-1. It also inhibited the apoptotic cell death through the inhibition of cytochrome c release and cleaved caspase-9, -3 in glutamate-treated HT22 cells. Therefore, our results provide ample evidence of the neuroprotective properties of 4,6′-anhydrooxysporidinone.

Neuroprotective effect of Allium hookeri against H2O2-induced PC12 cell cytotoxicity by reducing oxidative stress

In this study, the anti-oxidative and neuro-protective effects of ethanolic extracts of the dried roots of Allium hookeri were investigated. Total phenolic contents and total flavonoid contents of A. hookeri extract depended on the ethanol concentrations used (50, 70 and 95%). In order to evaluate radical scavenging activity, DPPH and ABTS radical scavenging assays and ferric reducing powers were evaluated. The results showed the 95% ethanol extract of A. hookeri (95AH) had higher phenolic and flavonoid contents, and greater radical scavenging activities than 50 or 70% ethanol extracts of A. hookeri. The neuro-protective effects of 95AH were evaluated using H₂O₂-treated PC12 neuronal cells. Treatment of 95AH increased cell viability and superoxide dismutase and glutathione peroxidase activities, reduced lactate dehydrogenate release, reduced reactive oxygen species production, and increased Bcl-2/Bax ratio. HPLC revealed 95AH was rich in phenolics, especially catechin. These results demonstrate 95AH has substantial anti-oxidative and neuro-protective effects against H₂O₂-induced oxidative stress.

Neuroprotective Activity of Polyphenol-Rich Ribes diacanthum Pall against Oxidative Stress in Glutamate-Stimulated HT-22 Cells and a Scopolamine-Induced Amnesia Animal Model

Ribes diacanthum Pall, a native Mongolian medicinal plant, has been reported to show antioxidant activities due to its polyphenol and flavonoid content, and is especially rich in the ethyl acetate fraction from an 80% methanol extraction (RDP). We assessed the cytoprotective effect of RDP on glutamate-caused oxidative stress and apoptosis in mouse hippocampal neuronal cells (HT-22 cells). Cell viability was significantly recovered by RDP treatment. Also, RDP effectively decreased the glutamate-induced production of intracellular reactive oxygen species (ROS). In flow cytometric analysis, apoptotic cells and the mitochondrial membrane potential were suppressed by RDP. In the Western blotting analysis, we found that RDP not only decreased the release of apoptotic proteins but also recovered anti-apoptotic protein. Additionally, RDP enhanced the antioxidant defense system by regulating the expression of antioxidant enzymes. Furthermore, treatment with RDP activated the BDNF/TrkB pathway. In accordance with the in vitro results, RDP meliorated memory deficit by defending hippocampal neuronal cells against oxidative damage in scopolamine-injected mice. Taken together, our present study showed that RDP exerted antioxidant and neuroprotective actions against oxidative stress. Therefore, RDP might facilitate the development of candidates for functional health foods for neurodegenerative disorders.

Allium Flavonols: Health Benefits, Molecular Targets, and Bioavailability

Allium species are revered worldwide as vegetables, condiments, and spices as well as the therapeutic agents in traditional medicine. The bioactive compounds in alliums mainly include organosulfur compounds, polyphenols, dietary fibers, and saponins. Flavonoids, particularly flavonols from alliums, have been demonstrated to have the antioxidant, anticancer, hypolipidemic, anti-diabetic, cardioprotective, neuroprotective, and antimicrobial activities. However, flavonols are mostly characterized from onions and have not been comprehensively reviewed across different species. This article therefore focuses on flavonol profiles from different Allium species, their health effects, underlying molecular mechanisms, and bioavailability. Intriguingly, the functional health effects of flavonols were mainly ascribed to their antioxidant and anti-inflammatory activities involving a cascade of multiple signaling pathways. Although the Allium-derived flavonols offer tremendous potential in preventing chronic disease risks, in-depth studies are needed to translate their clinical application.

Characterization of phenolic profile by LC-ESI-MS/MS and enzyme inhibitory activities of two wild edible garlic: Allium nigrum L. and Allium subhirsutum L

In our study, Allium nigrum L. and Allium subhirsutum L. were investigated in terms of phenolic profile, acetylcholinesterase (AChE), butyrylcholinesterase (BuChE), and tyrosinase inhibitory potentials. The colorimetric analysis revealed that the highest levels of total phenol (45.6, 15.8 mg GAE/g extract, respectively) and total flavonoid contents (8.2, 5.7 mg QE/g extract, respectively) were found in the bulbs of both plants. About 30 compounds were determined by LC-ESI-MS/MS with validated method and 3-hydroxybenzoic acid (2,188.4 μg/g extract) and p-coumaric acid (1,700.8 μg/g extract) were major phenolic acids. (-)-Epigallocatechin gallate (998.3 µg/g extract) and genistein (159.3 μg/g extract) which are neuroprotective compounds were the predominant flavonoids for A. nigrum and A. subhirsutum, respectively. Enzyme inhibitory activities of samples were performed by spectrophotometrically with 96-well microplate reader. All samples showed anti-AChE, anti-BuChE, and anti-tyrosinase activities and the aerial part of A. nigrum was the most potent (IC₅₀ 6.1, 3.27, 22.31 µg/ml, respectively). PRACTICAL APPLICATIONS: Many Allium species, especially those cultivated, are consumed in different countries as food in different ways. In the literature, studies on these species have generally focused on organosulfur compounds of the species. In our present study, phenolic compounds having a wide range of biological activities were determined in different parts of the two Allium species consumed as food. We also investigated in vitro cholinesterases and tyrosinase inhibition activities of these species. A correlation was observed between phenolic compounds and enzyme inhibition activities. These results were further explored and confirmed by principal component analysis (PCA). PCA revealed that samples were discriminated from each other according to phenolic compounds and enzyme inhibitory potencies. Conclusively, this study determines that the chemical profiles and biological activities of A. nigrum and A. subhirsutum.

Quercetin alleviates the injury-induced decrease of protein phosphatase 2A subunit B in cerebral ischemic animal model and glutamate-exposed HT22 cells

Quercetin is a plant flavonoid that has anti-oxidant, anti-inflammatory, anti-cancer, and anti-ischemic properties. Moreover, quercetin exerts neuroprotective effects against focal cerebral ischemia. Protein phosphatase 2A (PP2A) is a form of serine/threonine phosphatase that modulates various biological functions. Among PP2A subunit types, subunit B exists abundantly in brain tissue and plays an essential function in nervous system. We previously reported the decrease of PP2A subunit B in focal cerebral animal model. This study explored the change of PP2A subunit B expression by quercetin treatment in cerebral ischemic animal model and glutamate-treated hippocampal-derived (HT22) cell culture. Quercetin (10 mg/kg) or vehicle was injected intraperitoneally into male rats before 30 min of middle cerebral artery occlusion (MCAO), and cerebral cortices were isolated 24 hr after MCAO. MCAO induced the neurological behavioral deficit and increased infarct volume. However, quercetin treatment attenuated the increase of neurological deficit and infarction. We detected the alleviation of MCAO-induced the decrease in PP2A subunit B by quercetin treatment using a proteomic approach. Reverse-transcription PCR and Western blot analyses confirmed lower PP2A subunit B expression levels in MCAO group with vehicle. However, quercetin treatment attenuated MCAO-induced this reduction. We also observed the neuroprotective effect of quercetin and the change of PP2A subunit B expression in glutamate-exposed HT22 cells. Glutamate exposure dramatically reduced cell viability and PP2A subunit B expression, and quercetin treatment significantly improved these decreases. We clearly showed that quercetin performs a neuroprotective function and modulates down-regulation of PP2A subunit B against MCAO injury and glutamate toxicity. Thus, our finding suggests that the regulation of PP2A subunit B by quercetin contributes to neuroprotective function in ischemic brain injury.

Protective Effect of Water Extracted Spirulina maxima on Glutamate-induced Neuronal Cell Death in Mouse Hippocampal HT22 Cell

Introduction:

Spirulina maxima was used as important nutritional source in the Aztec civilization because it is rich in proteins and vitamins. It contains various antioxidants such as phycocyanin and flavonoids. Based on abundant antioxidants, S. maxima is known to possess anti-inflammatory effect, especially on neuronal cells.

Materials and Methods:

S. maxima was extracted in water and contain of phycocyanin was identified by high-performance liquid chromatography. Cell viability test was performed with treatment of S. maxima extract. After, oxidative stress-related mechanisms were evaluated by detecting the accumulation of reactive oxygen species (ROS) and Ca²⁺ influx, and decrease of mitochondrial membrane potential (MMP) level. Then, the glutathione (GSH) related assays were conducted.

Results:

The water extracted S. maxima exerted the neuroprotective activity by attenuating the ROS and Ca²⁺ formation, maintaining the MMP level, and protecting the activity of the antioxidant enzymes by increasing reduced GSH against oxidative stress compared to control.

Conclusion:

The results suggested that water extracted S. maxima showed powerful neuroprotective effect through the mechanism related to antioxidant activity, able to preventing the radical-mediated cell death.

SUMMARY

Water extracted Spirulina maxima contains C-phycocyanin

Water extracted Spirulina maxima exerts neuroprotective effect on HT22 cell

To investigate the protective mechanisms, reactive oxygen species, Ca²⁺, mitochondrial membrane potential, Glutathione-related assays were performed.

Abbreviations used: ROS: Reactive oxygen species; MMP: Mitochondrial membrane potential; GSH: Glutathione; GSSG: Glutathione disulfide, oxidized glutathione; GPx: Glutathione peroxidase; GR: Glutathione reductase; DMEM: Dulbecco's modified Eagle's medium; FBS: Fetal bovine serum; DCF-DA: 2',7'-dichlorofluorescein diacetate; PBS: Phosphate buffered serum; Rho 123: Rhodamine 123; NADPH: Nicotinamide adenine dinucleotide phosphate; DTNB: 5,5'-dithiobis-2-nitrobenzoic acid, Ellman's reagent; GSSG-R: Glutathione disulfide reductase; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; DMSO: Dimethyl sulfoxide; HPLC: High-performance liquid chromatography.

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 prevents spinal motor neuron degeneration induced by chronic excitotoxic stimulus by a sirtuin 1-dependent mechanism

Background

Excitotoxicity is a mechanism of foremost importance in the selective motor neuron degeneration characteristic of motor neuron disorders. Effective therapeutic strategies are an unmet need for these disorders. Polyphenols, such as quercetin and resveratrol, are plant-derived compounds that activate sirtuins (SIRTs) and have shown promising results in some models of neuronal death, although their effects have been scarcely tested in models of motor neuron degeneration.

Methods

In this work we investigated the effects of quercetin and resveratrol in an in vivo model of excitotoxic motor neuron death induced by the chronic infusion of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) into the rat spinal cord tissue. Quercetin and resveratrol were co-infused with AMPA and motor behavior and muscle strength were assessed daily for up to ten days. Then, animals were fixed and lumbar spinal cord tissue was analyzed by histological and immunocytological procedures.

Results

We found that the chronic infusion of AMPA [1 mM] caused a progressive motor neuron degeneration, accompanied by astrogliosis and microgliosis, and motor deficits and paralysis of the rear limbs. Quercetin infusion ameliorated AMPA-induced paralysis, rescued motor neurons, and prevented both astrogliosis and microgliosis, and these protective effects were prevented by EX527, a very selective SIRT1 inhibitor. In contrast, neither resveratrol nor EX527 alone improved motor behavior deficits or reduced motor neuron degeneration, albeit both reduced gliosis.

Conclusions

These results suggest that quercetin exerts its beneficial effects through a SIRT1-mediated mechanism, and thus SIRT1 plays an important role in excitotoxic neurodegeneration and therefore its pharmacological modulation might provide opportunities for therapy in motor neuron disorders.

Electronic supplementary material

The online version of this article (10.1186/s40035-017-0102-8) contains supplementary material, which is available to authorized users.

The Glycosidase Treatment of Gentianae Scabrae Radix Converts Trifloroside into Deglucosyltrifloroside with an Enhancement of Antioxidative Effects

Herbal medicines were subjected to enzyme reaction by using a commercial glycosidase AMG-300L, and were evaluated for enhancement of their antioxidative activities. The methanolic extract of Gentianae Scabrae Radix (GSR) showed the most dramatic changes after enzyme reaction, as seen in the high-performance liquid chromatography profiles and an increase in the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging effect. Trifloroside (1, TF) was identified as being significantly decreased by enzyme reaction, whereas deglucosyltrifloroside (2, DTF) increased. The optimal reaction time to induce DTF was 24 h at 30°C. The content increased from 1.00 ± 0.29 mg/g of extract (g_ex) to 2.80 ± 0.85 mg/g_ex after 24 h of enzyme reaction. DTF showed better antioxidative effect than TF in the DPPH, Trolox equivalent antioxidant capacity, and reactive oxygen species (ROS) in HT22 cell assays. In addition, when HT22 cells were stressed by 5 mM glutamate, 50 μM of DTF significantly inhibited the glutamate-induced lactate dehydrogenase leakage, Ca²⁺ influx, lipid peroxidation, and intracellular ROS production. These data demonstrated that the enzyme-treated GSR and its increased level of antioxidant DTF could be useful as a starting point in the discovery of functional foods to prevent various oxidative stresses, especially neurodegenerative disorders.

Modulating Oxidative Stress Relieves Stress-Induced Behavioral and Cognitive Impairments in Rats

Background

Persistent psychological stress often leads to anxiety disorders and depression. Benzodiazepines and selective serotonin reuptake inhibitors are popular treatment options but have limited efficacy, supporting the need for alternative treatment. Based on our recent preclinical work suggesting a causal link between neurobehavioral deficits and elevated oxidative stress, we hypothesized that interventions that mitigate oxidative stress can attenuate/overcome neurobehavioral deficits.

Methods

Here, we employed the rat social defeat model of psychological stress to determine whether increasing antioxidant levels using grape powder would prevent and/or reverse social defeat-induced behavioral and cognitive deficits. Furthermore, a hippocampal-derived HT22 cell culture model of oxidative stress was employed to identify the individual beneficial constituent(s) of grape powder and the underlying mechanism(s) of action.

Results

Grape powder treatment prevented and reversed social defeat-induced behavioral and cognitive deficits and also decreased social defeat-induced increase in plasma corticosterone and 8-isoprostane (systemic and oxidative stress markers, respectively). And grape powder treatment replenished social defeat-induced depleted pool of key antioxidant enzymes glyoxalase-1, glutathione reducatse-1, and superoxide dismutase. Grape powder constituents, quercetin and resveratrol, were most effective in preventing oxidative stress-induced decreased cellular antioxidant capacity. Grape powder protected oxidative stress-induced cell death by preventing calcium influx, mitochondrial dysfunction, and release of cytochrome c.

Conclusions

Grape powder treatment by increasing antioxidant pool and preventing cell damage and death prevented and reversed social defeat-induced behavioral and cognitive deficits in rats. Quercetin and resveratrol are the major contributors towards beneficial effects of grape powder.

Chemical constituents from a Gynostemma laxum and their antioxidant and neuroprotective activities

Background

A few bioactivities of constituents from Gynostemma laxum, which has been collected in Vietnam, have been reported until now. There is no report about the effects of constituents from G. laxum although the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated heme oxygenase-1 (HO-1) antioxidant defense system is involved in neuroprotection in the brain. Therefore, we investigated whether quercetin (2), benzoic acid (10) and their analogues (1, 3–9 and 11) from G. laxum have the antioxidant and neuroprotective activities and also their underlying mechanism.

Methods

To examine their neuroprotective and antioxidant activities, oxytosis, total oxidant scavenging capacity (TOSC), 2,7-dichlorofluorescein (DCFDA), dihydroethidium (DHE), antioxidant response element (ARE)-luciferase reporter gene assays, Western blot analysis, real time-PCR, immunocytochemistry and in silico 3D molecular docking simulation were performed.

Results

The study of constituents using chromatographic techniques and spectroscopic analysis showed that G. laxum contained an abundance of quercetin (2), benzoic acid (10) and their analogues (1, 3–9 and 11). Our data demonstrated that quercetin (2) and its analogue (4) among the constituents from G. laxum showed the strongest neuroprotective effect against oxytosis triggered by the excessive amount of glutamate. Compounds 2, 4, 6 and 11 exhibited reactive oxygen species (ROS) inhibitory and ARE transcriptional activities in immortalized hippocampal HT22 cell line. Among them, compound 4, a second active compound, induced Nrf2/HO-1 activation. They were also fit stable onto the Tramtrack and Bric-à-Brac (BTB) domain of Kelch-like ECH-associated protein 1 (Keap1), a known Nrf2 inhibitor protein, based on the results of docking and interaction energies. Overall, these data suggest that –OH and –OCH₃ groups of quercetin and its analogues are responsible for their neuroprotective effect.

Conclusions

In summary, the major constituents of G. laxum had strong antioxidant and neuroprotective activities so that they could consider as a natural antioxidant supplement. Furthermore, G. laxum might be used beneficially in reducing oxidative complications with the further deep investigation in vivo.

Electronic supplementary material

The online version of this article (doi:10.1186/s13020-017-0136-y) contains supplementary material, which is available to authorized users.

Detoxification effects of phytonutrients against environmental toxicants and sharing of clinical experience on practical applications

According to the Food and Health Bureau and Trade and Industry Department of the Hong Kong Government, 90 % of the total food supply in Hong Kong was imported from the Mainland China. In addition, the hidden or illegal use of prohibited pesticides, food adulteration (e.g., using industrial salt in food processing, using gutter oil as cooking oil), and pollutions were periodically reported by the media. Excessive exposure to toxic heavy metals or persistent organic pollutants (POPs) from diet or environmental is inevitable amid industrialization and pollution. Understanding of the detoxification ability among nutrients in plant-based food (i.e., phytonutrients in green tea, onion, garlic, coriander, and turmeric) offers therapeutic and preventive effects against the poisoning effects due to these pollutants. Oxidative stress and pro-inflammatory actions are the common mechanisms for heavy metals or POPs toxicities, while phytonutrients counteracts these cellular insults by anti-oxidation, upregulation of anti-inflammatory pathways, and chelation.

Chemical Composition and Biological Activity of Allium cepa L. and Allium × cornutum (Clementi ex Visiani 1842) Methanolic Extracts

Here, we report a comparative study of the phytochemical profile and the biological activity of two onion extracts, namely Allium cepa L. and Allium × cornutum (Clementi ex Visiani 1842), members of the family Amaryllidaceae. The identification of flavonoids and anthocyanins, and their individual quantities, was determined by high-performance liquid chromatography (HPLC). The potency of both extracts to scavenge free radicals was determined by the DPPH (2,2'-diphenyl-1-picrylhydrazyl) radical-scavenging activity and oxygen radical absorbance capacity (ORAC) methods. The DNA protective role was further tested by the single-cell gel electrophoresis (COMET) assay and by Fenton's reagent causing double-strand breaks on the closed circular high copy pUC19 plasmid isolated from Escherichia coli. In the presence of both extracts, a significant decrease in DNA damage was observed, which indicates a protective role of Allium cepa and Allium × cornutum on DNA strand breaks. Additionally, cytotoxicity was tested on glioblastoma and breast cancer cell lines. The results showed that both extracts had antiproliferative effects, but the most prominent decrease in cellular growth was observed in glioblastoma cells.

The transcription factor XBP1 in memory and cognition: Implications in Alzheimer disease

X-box binding protein 1 (XBP1) is a unique basic region leucine zipper transcription factor isolated two decades ago in a search for regulators of major histocompatibility complex class II gene expression. XBP1 is a very complex protein regulating many physiological functions, including immune system, inflammatory responses, and lipid metabolism. Evidence over the past few years suggests that XBP1 also plays important roles in pathological settings since its activity as transcription factor has profound effects on the prognosis and progression of diseases such as cancer, neurodegeneration, and diabetes. Here we provide an overview on recent advances in our understanding of this multifaceted molecule, particularly in regulating synaptic plasticity and memory function, and the implications in neurodegenerative diseases with emphasis on Alzheimer disease.

Morinda citrifolia mitigates rotenone-induced striatal neuronal loss in male Sprague-Dawley rats by preventing mitochondrial pathway of intrinsic apoptosis

OBJECTIVES

Parkinson disease (PD) is a neurodegenerative disorder affecting mainly the motor system, as a result of death of dopaminergic neurons in the substantia nigra pars compacta. The present scenario of research in PD is directed to identify novel molecules that can be administered individually or co-administered with L-Dopa to prevent the L-Dopa-Induced Dyskinesia (LID) like states that arise during chronic L-Dopa administration. Hence, in this study, we investigated whether Morinda citrifolia has therapeutic effects in rotenone-induced Parkinson's disease (PD) with special reference to mitochondrial dysfunction mediated intrinsic apoptosis.

METHODS

Male Sprague-Dawley rats were stereotaxically infused with rotenone (3 µg in both SNPc and VTA) and co-treated with the ethyl acetate extract of Morinda citrifolia and levodopa.

RESULTS

The results revealed that rotenone-induced cell death was reduced by MCE treatment as measured by decline in the levels of pro-apoptotic proteins. Moreover, MCE treatment significantly augmented the levels of anti-apoptotic Bcl2 and blocks the release of cytochrome c, thereby alleviating the rotenone-induced dopaminergic neuronal loss, as evidenced by tyrosine hydroxylase (TH) immunostaining in the striatum.

DISCUSSION

Taken together, the results suggest that Morinda citrifolia may be beneficial for the treatment of neurodegenerative diseases like PD.

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.

Allium cepa Extract and Quercetin Protect Neuronal Cells from Oxidative Stress via PKC-ε Inactivation/ERK1/2 Activation

Oxidative stress plays an important role in the pathophysiology of various neurologic disorders. Allium cepa extract (ACE) and their main flavonoid component quercetin (QCT) possess antioxidant activities and protect neurons from oxidative stress. We investigated the underlying molecular mechanisms, particularly those linked to the antioxidant effects of the ACE. Primary cortical neuronal cells derived from mouse embryos were preincubated with ACE or QCT for 30 min and exposed to L-buthionine sulfoximine for 4~24 h. We found that ACE and QCT significantly decreased neuronal death and the ROS increase induced by L-buthionine-S, R-sulfoximine (BSO) in a concentration-dependent manner. Furthermore, ACE and QCT activated extracellular signal-regulated kinase 1/2 (ERK1/2), leading to downregulation of protein kinase C-ε (PKC-ε) in BSO-stimulated neuronal cells. In addition, ACE and QCT decreased the phosphorylated levels of p38 mitogen-activated protein kinase. Our results provide new insight into the protective mechanism of ACE and QCT against oxidative stress in neuronal cells. The results suggest that the inactivation of PKC-ε induced by phosphorylating ERK1/2 is responsible for the neuroprotective effect of ACE and QCT against BSO-induced oxidative stress.

Synergistic neuroprotection by epicatechin and quercetin: Activation of convergent mitochondrial signaling pathways

In view of evidence that increased consumption of epicatechin (E) and quercetin (Q) may reduce the risk of stroke, we have measured the effects of combining E and Q on mitochondrial function and neuronal survival following oxygen-glucose deprivation (OGD). Relative to mouse cortical neuron cultures pretreated (24h) with either E or Q (0.1-10μM), E+Q synergistically attenuated OGD-induced neuronal cell death. E, Q and E+Q (0.3μM) increased spare respiratory capacity but only E+Q (0.3μM) preserved this crucial parameter of neuronal mitochondrial function after OGD. These improvements were accompanied by corresponding increases in cyclic AMP response element binding protein (CREB) phosphorylation and the expression of CREB-target genes that promote neuronal survival (Bcl-2) and mitochondrial biogenesis (PGC-1α). Consistent with these findings, E+Q (0.1 and 1.0μM) elevated mitochondrial gene expression (MT-ND2 and MT-ATP6) to a greater extent than E or Q after OGD. Q (0.3-3.0μM), but not E (3.0μM), elevated cytosolic calcium (Ca(2+)) spikes and the mitochondrial membrane potential. Conversely, E and E+Q (0.1 and 0.3μM), but not Q (0.1 and 0.3μM), activated protein kinase B (Akt). Nitric oxide synthase (NOS) inhibition with L-N(G)-nitroarginine methyl ester (1.0μM) blocked neuroprotection by E (0.3μM) or Q (1.0μM). Oral administration of E+Q (75mg/kg; once daily for 5days) reduced hypoxic-ischemic brain injury. These findings suggest E and Q activate Akt- and Ca(2+)-mediated signaling pathways that converge on NOS and CREB resulting in synergistic improvements in neuronal mitochondrial performance which confer profound protection against ischemic injury.