Comparison between the effects of quercetin on seizure threshold in acute and chronic seizure models

Natural products targeting ferroptosis in depression: Research progress and therapeutic prospects

BACKGROUND

Depression is recognized as a chronic mental illness, also influenced by neurotransmitter homeostasis, with its incidence increasing annually worldwide. This condition inflicts significant physical and psychological harm, severely compromising human health. It exhibits a broad morbidity spectrum, and some current treatments and medications are hindered by short-term efficacy, strong side effects, and other limitations.

PURPOSE

Due to the limitations, it is imperative to explore new treatment approaches and develop targeted drugs. Ferroptosis, a cell death mode dependent on iron, is believed to be intricately linked to the onset of depression. Thus, modulating cellular ferroptosis presents a promising avenue for the targeted therapy of depression.

METHODS

We conducted a comprehensive search of databases such as PubMed, Elsevier ScienceDirect, Google Scholar, and CNKI, using keywords such as "ferroptosis", "depression", "iron death", "safety", "efficacy", and "effectiveness". Our review included original scientific articles, clinical trials, meta-analyses, and review papers published up to February 2025, focusing on studies excluding non-natural products.

RESULTS

Several natural products derived from plant, animal, or microbial sources effectively target ferroptosis, alleviating depressive symptoms and demonstrating unique and favorable outcomes. This review provides an exhaustive overview of the sources, pharmacological actions, mechanisms, efficacy, and safety of these natural products, highlighting their potential clinical benefits and offering a comprehensive perspective on their properties.

CONCLUSION

This study offers concrete ideas and valuable insights for the development and application of these natural products in the targeted treatment of depression.

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

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

Coriandrum sativum and Its Utility in Psychiatric Disorders

The negative impact on worldwide social well-being by the increasing rate of psychiatric diseases has led to a continuous new drug search. Even though the current therapeutic options exert their activity on multiple neurological targets, these have various adverse effects, causing treatment abandonment. Recent research has shown that Coriandrum sativum offers a rich source of metabolites, mainly terpenes and flavonoids, as useful agents against central nervous system disorders, with remarkable in vitro and in vivo activities on models related to these pathologies. Furthermore, studies have revealed that some compounds exhibit a chemical interaction with γ-aminobutyric acid, 5-hydroxytryptamine, and N-methyl-D-aspartate receptors, which are key components in the pathophysiology associated with psychiatric and neurological diseases. The current clinical evaluations of standardized extracts of C. sativum are scarce; however, one or more of its compounds represents an area of opportunity to test the efficacy of the plant as an anxiolytic, antidepressant, antiepileptic, or sleep enhancer. For this, the aim of the review was based on the pharmacological activities offered by the compounds identified and isolated from coriander and the processes involved in achieving their effect. In addition, lines of technological research, like molecular docking and nanoparticles, are proposed for the future development of phytomedicines, based on the bioactive molecules of C. sativum, for the treatment of psychiatric and neurological disorders addressed in the present study.

The effect of quercetin on absence epilepsy in WAG/Rij rats

AIM

In the present study, the effect of quercetin, a powerful antioxidant flavonoid, on genetic absence epilepsy was studied in WAG/Rij rats.

MATERIAL AND METHOD

Tripolar electrodes were implanted into WAG/Rij rats. Basal electrocorticography (ECoG) was recorded following a recovery period. After basal ECoG recording, different doses of quercetin (QRC) (25, 50 and 100 mg/kg) were injected intraperitoneally (i.p.) for 30 days. ECoG recording was continued for 31 days, three hours a day. After recording, the rats were anesthetized and euthanized through cervical dislocation and their brains were excised. Biochemically, TNF-alpha, IL-6 and NO were studied in whole rat brains.

RESULTS

In WAG/Rij rats, low-dose quercetin (25 mg/kg) reduced the number and duration of spike-wave discharges (SWDs) compared to the control group. However, 50 and 100 mg/kg quercetin doses increased SWDs. Duration of SWDs was prolonged only with 100 mg/kg dose. None of the quercetin doses had any effect on average amplitude of SWDs. In addition, it was observed in biochemical analyses that 25 mg/kg quercetin reduced TNF-alpha, IL-6 and NO levels compared to the control group. While TNF-alpha and IL-6 levels in rat brains were not affected by 50 or 100 mg/kg doses, both doses were found to increase NO levels in rat brains.

CONCLUSION

Based on the results of the present study, 25 mg/kg low-dose quercetin may have reduced absence seizures by reducing proinflammatory cytokines and NO, but high-dose quercetin may have increased absence seizures through increasing the NO level. This contrasting effect of quercetin on absence seizures needs to be investigated by advanced mechanisms.

Anticonvulsant effect of quercetin in pentylenetetrazole (PTZ)-induced seizures in male mice: The role of anti-neuroinflammatory and anti-oxidative stress

BACKGROUND

Epilepsy is one of the major neurological disorders. The inflammatory process and oxidative stress are closely related to seizure progression. Quercetin is a flavonoid with anti-inflammatory and antioxidant properties as well as neuroprotective effects. We aimed to evaluate the effect of quercetin on pentylenetetrazole- (PTZ-) induced seizures in male mice focusing on its possible anti-neuroinflammatory and anti-oxidative stress.

METHODS

In this study, 50 male NMRI mice were divided into five groups (n = 10) and given the following treatments: normal saline, quercetin at doses of 10, 20, and 40 mg/kg, and diazepam at a dose of 10 mg/kg. In order to induce seizures, PTZ was administered intravenously. Drugs were administered intravenously 60 min before the seizure induction. The seizure threshold was measured, and finally, malondialdehyde (MDA), total antioxidant capacity (TAC), and the gene expression of IL-1β, TNF-α, NLRP3, and iNOS were determined in the prefrontal cortex.

RESULTS

It was confirmed that quercetin increased the seizure threshold. And quercetin increased TAC, and decreased levels of MDA as well as gene expression of TNF- α, NLRP3, IL-1β, and iNOS in the prefrontal cortex at the time of seizure induction.

CONCLUSION

It was suggested that the anticonvulsant effect of quercetin in PTZ-induced seizures in mice may be due to the reduction of inflammatory responses and oxidative stress in the prefrontal cortex.

Influence of methadone on the anticonvulsant efficacy of valproate sodium gabapentin against maximal electroshock seizure in mice by regulation of brain MDA TNF-α

Methadone is the most frequently used opioid therapy worldwide, with controversial effects on oxidative stress homeostasis. This study investigated the effects of intraperitoneal (i.p.) co-administration of methadone (0.1, 0.3, 1, and 3 mg/kg) and valproate sodium (300 mg/kg) or gabapentin (50 mg/kg) in the mice maximal electroshock (MES)-induced seizure model. The adverse effect of drugs was assessed using the chimney test. The levels of tumor necrosis factor-alpha (TNF-α) and malondialdehyde (MDA) contents were measured in mice brains after a single seizure. Administration of methadone alone resulted in a significant reduction in the duration of hind limb extension (HLE) than that in the control group. Methadone pretreatment at doses of 0.1 and 0.3 mg/kg i.p. decreased, and at doses of 1 and 3 mg/kg i.p. had an increasing effect on anticonvulsant efficacy of gabapentin. Pretreatment with all doses of methadone significantly decreased the valproate anticonvulsive efficacy. At doses of 1 and 3 mg/kg i.p. methadone per se increased brain MDA levels after MES-induced seizure. Administration of methadone (0.3 mg/kg i.p.) enhanced and at 3 mg/kg decreased gabapentin effect on brain MDA level, but their co-treatment did not lead to further increase in MDA. Methadone at 0.3–3 mg/kg enhanced the effect of sodium valproate on MDA levels in the brain, but at all doses significantly potentiated its effect on brain TNF-α levels. The drugs did not produce any side effects on motor coordination in experimental animals. In conclusion, methadone showed different effects on anticonvulsant actions of gabapentin and valproate through regulation of brain levels of MDA and TNF-α.

HPLC and GC-MS based metabolic profiles and in vivo anticonvulsant, sedative, and antinociceptive potentials of truffles Tirmania nivea and Tirmania pinoyi hydromethanolic extracts in mice

GC-MS and HPLC analyses of the hydromethanolic extracts of the truffles Tirmania nivea (TN) and Tirmania pinoyi (TP) revealed the presence of 18 metabolites and 11 polyphenols, respectively. In vivo, TP extract protected against subcutaneous pentylenetetrazole (scPTZ) and maximal electric shock (MES)-induced convulsions faster than TN. TP (100 and 300 mg/kg) showed 100% protection and longer duration than TN in the scPTZ test. Similarly, at 300 mg/kg, TP demonstrated a quicker start (75%) and longer duration of action (100%) than TN in MES test. In scPTZ test, ED₅₀ of TP demonstrated greater anticonvulsant efficacy than TN. In mice given TP and TN treatments, the brain GABA levels were noticeably increased. TP (100 and 300mg/kg) produced a notable sedative effect in open field test, whereas TN (100 or 300 mg/kg) and TP (300 mg/kg) reduced sleep latency by 79, 52, and 45%, respectively. In writhing test, TN (100 or 300mg/kg) significantly enhanced analgesic efficacy by 50 and 87%, respectively. Comparatively, in formalin test, TP and TN at a dosage of 300 mg/kg decreased the length of the licking by 34 and 59%, respectively. For the first time, this study explains the anticonvulsant, sedative, central, and peripheral analgesic activities of truffle extracts.

Therapeutic Potential of Quercetin and its Derivatives in Epilepsy: Evidence from Preclinical Studies

Quercetin is a polyphenolic bioactive compound highly enriched in dietary fruits, vegetables, nuts, and berries. Quercetin and its derivatives like rutin and hyperoside are known for their beneficial effects in various neurological conditions including epilepsy. The clinical studies of quercetin and its derivatives in relation to epilepsy are limited. This review provides the evidence of most recent knowledge of anticonvulsant properties of quercetin and its derivatives on preclinical studies. Additionally, the studies demonstrating antiseizure potential of various plants extracts enriched with quercetin and its derivatives has been included in this review. Herein, we have also discussed neuroprotective effect of these bioactive compound and presented underlying mechanisms responsible for anticonvulsant properties in brief. Finally, limitations of quercetin and its derivatives as antiseizure compounds as well as possible strategies to enhance efficacy have also been discussed.

Quercetin Abrogates Oxidative Neurotoxicity Induced by Silver Nanoparticles in Wistar Rats

This study aimed to investigate the oxidative neurotoxicity induced by silver nanoparticles (AgNPs) and assess the neuroprotective effects of quercetin against this toxicity. Forty adult male rats were divided into four equal groups: control, AgNPs (50 mg/kg intraperitoneally), quercetin (50 mg/kg orally), and quercetin + AgNPs. After 30 days, blood and brain tissue samples were collected for further studies. AgNP exposure increased lipid peroxidation and decreased glutathione peroxidase, catalase, and superoxide dismutase activities in brain tissue. AgNPs decreased serum acetylcholine esterase activity and γ-aminobutyric acid concentrations. AgNPs upregulated tumor necrosis factor-α, interleukin-1β, and Bax transcript levels. AgNPs reduced the transcripts of claudin-5, brain-derived neurotrophic factor, paraoxonase, nuclear factor-erythroid factor 2 (Nrf2), and Bcl-2. Histopathologically, AgNPs caused various degenerative changes and neuronal necrosis associated with glial cell reactions. AgNPs increased the immunohistochemical staining of glial fibrillary acidic protein (GFAP) in the cerebrum and cerebellum. Oral treatment with quercetin efficiently counteracted the opposing effects of AgNPs on brain tissue via modulation of tight junction proteins, Nrf2, and paraoxonase, and its positive mechanism in modulating pro-inflammatory cytokines and the downregulation of GFAP expression, and the apoptotic pathway. AgNPs also altered the severity of histopathological lesions and modulated GFAP immunostaining in the examined tissue.

The Genus Alternanthera: Phytochemical and Ethnopharmacological Perspectives

Ethnopharmacological relevance: The genus Alternanthera (Amaranthaceae) comprises 139 species including 14 species used traditionally for the treatment of various ailments such as hypertension, pain, inflammation, diabetes, cancer, microbial and mental disorders.

Aim of the review: To search research gaps through critical assessment of pharmacological activities not performed to validate traditional claims of various species of Alternanthera. This review will aid natural product researchers in identifying Alternanthera species with therapeutic potential for future investigation.

Materials and methods: Scattered raw data on ethnopharmacological, morphological, phytochemical, pharmacological, toxicological, and clinical studies of various species of the genus Alternanthera have been compiled utilizing search engines like SciFinder, Google Scholar, PubMed, Science Direct, and Open J-Gate for 100 years up to April 2021.

Results: Few species of Alternanthera genus have been exhaustively investigated phytochemically, and about 129 chemical constituents related to different classes such as flavonoids, steroids, saponins, alkaloids, triterpenoids, glycosides, and phenolic compounds have been isolated from 9 species. Anticancer, antioxidant, antibacterial, CNS depressive, antidiabetic, analgesic, anti-inflammatory, and immunomodulator effects have been explored in the twelve species of the genus. A toxicity study has been conducted on 3 species and a clinical study on 2 species.

Conclusions: The available literature on pharmacological studies of Alternanthera species reveals that few species have been selected based on ethnobotanical surveys for scientific validation of their traditional claims. But most of these studies have been conducted on uncharacterized and non-standardized crude extracts. A roadmap of research needs to be developed for the isolation of new bioactive compounds from Alternanthera species, which can emerge out as clinically potential medicines.

Quercetin Administration Following Hypoxia-Induced Neonatal Brain Damage Attenuates Later-Life Seizure Susceptibility and Anxiety-Related Behavior: Modulating Inflammatory Response

BACKGROUND

Neonatal seizures commonly caused by hypoxia could lead to brain injury and cognitive deficits. Quercetin could cross the blood brain barrier and exerts neuroprotective effects in many neurological disease settings. In this study, we aim to investigate the role of quercetin in attenuating cognitive impairment following hypoxia-induced neonatal seizure (HINS).

METHOD

Sprague-Dawley rats at P7 were exposed to a premixed gas in a hypoxic chamber to induce brain injury, and then continuously administered with quercetin for 21 days. Pentylenetetrazol kindling was used to induce seizures in the evolution. After the hypoxic lesion was stablished, anxiety-related behavior of rats after HINS was assessed using open field test. Memory impairment of rats after HINS was evaluated using novel object-recognition test and elevated plus maze test. The serum and hippocampal concentrations of TNF-a, iNOS, IL-6 MCP-1, and IL-1β were measured using ELISA. The mRNA expression levels of TNF-a, iNOS, IL-6 in the hippocampus were determined using qRT-PCR. The protein levels of TLR4, NF-κB p65, and p-NF-κB p65 in the hippocampus were determined using Western blot.

RESULTS

Quercetin administration significantly reduced later-life seizure susceptibility, anxiety-related behavior, and memory impairments in the rats following the HINS when compared to the HINS group without treatment. Both serum and hippocampal proinflammatory cytokines levels were significantly elevated in the rat after HINS. TLR4 protein expressions were increased in the HINS group when compared to control group, and decreased in the group of quercetin. The protein level of p-NF-κB p65 was significantly lower in the quercetin group compared to the HINS group.

CONCLUSION

We demonstrated that Quercetin significantly reduced susceptibility to later-life seizures. Quercetin could downregulate inflammatory response through TLR4/ NF-κB pathway, thereby attenuating HINS-induced anxiety, hippocampal memory impairment, and cognitive impairment in later life following HINS.

In Silico and In Vivo: Evaluating the Therapeutic Potential of Kaempferol, Quercetin, and Catechin to Treat Chronic Epilepsy in a Rat Model

Recently, alternative therapies are gaining popularity in the treatment of epilepsy. The present study aimed to find out the antiepileptic potential of quercetin, catechin, and kaempferol. In vivo and in silico experiments were conducted to investigate their therapeutic potential. 25 mg/kg/day of pentylenetetrazole was administered for 4 weeks after epilepsy was induced in the rats; this was followed by the behavioral studies and histological analysis of rat brain slices. Binding affinities of kaempferol, quercetin, and catechin were assessed by performing in silico studies. Kaempferol, quercetin, and catechin were found to have the highest binding affinity with the synaptic vesicle 2A (SV2A) protein, comparable to standard levetiracetam (LEV). The mRNA levels of SV2A, as well as the expression of TNF, IL 6, IL 1 beta, NFkB, IL 1Ra, IL 4, and IL 10, were investigated using qPCR. Our results indicate for the first time that SV2A is also a transporter of understudied phytoflavonoids, due to which a significant improvement was observed in epileptic parameters. The mRNA levels of SV2A were found to be significantly elevated in the PF-treated rats when compared with those of the control rats with epilepsy. Additionally, downregulation of the pro-inflammatory cytokines and upregulation of the anti-inflammatory cytokines were also noted in the PF-treated groups. It is concluded that kaempferol, quercetin, and catechin can effectively decrease the epileptic seizures in our chronic epilepsy rat model to a level that is comparable to the antiepileptic effects induced by levetiracetam drug.

The effects of quercetin on seizure, inflammation parameters and oxidative stress in acute on chronic tramadol intoxication

BACKGROUND

Tramadol is a widely used synthetic opioid for moderate to severe pain. Some studies have shown that tramadol can increase oxidative stress in different tissues of the body. Quercetin is also a substance with various biological effects, including antioxidant, anti-inflammatory, hepatoprotective, nephroprotective, and cardioprotective activities. The current investigation aimed at determining the effects of quercetin, with or without naloxone, on tramadol intoxication.

METHODS

This study was performed on 30 male Wistar rats divided into five groups: Group I) control group: intraperitoneal injections of normal saline 0.9% for 14 days; Group II) tramadol: 25 mg/kg for 14 days, and then a 50 mg/kg acute dose injection on the last day; Group III) acute quercetin (single dose): tramadol injection as with the second group plus 100 mg/kg of quercetin on the last day; Group IV) chronic quercetin: tramadol injection similar to the second group plus quercetin 100 mg/kg for 14 days; Group V) quercetin plus naloxone: tramadol injection similar to the second group plus injection of quercetin 100 mg/kg + intravenous naloxone 2 mg/kg on the last day, followed by a 4 mg/kg/h injection of naloxone for six hours. The rats were monitored for six hours on the last day, relating to the number and severity of seizures. Finally, the samples were prepared for biochemical investigation of the serum level of oxidative stress markers (MDA, SOD, NOx), inflammatory factors (IL-6, TNF-α), biochemical parameters (ALT, AST, creatinine, glucose) and hematological assay. The liver, heart, kidney, cortex, cerebellum, and adrenal tissues were collected to investigate the redox state.

RESULTS

None of the treatments had positive effects on the number and severity of seizures. Chronic administration of quercetin led to alteration of some blood parameters, including reduced hemoglobin level and elevated platelet counts. Acute on chronic tramadol administration resulted in a significant rise in AST, where different treatments failed to reduce their levels down to the control group.

CONCLUSION

chronic administration of quercetin showed decreased oxidative/nitrosative stress in the liver, kidney, adrenal, and heart tissues. Quercetin plus naloxone decreased oxidative stress in the heart and adrenal tissues, but adverse effects on the brain cortex and hepatic function. Single-dose quercetin reduced cardiac oxidative stress.

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.

The effects of naloxone, diazepam, and quercetin on seizure and sedation in acute on chronic tramadol administration: an experimental study

Background

Tramadol is a widely used synthetic opioid. Substantial research has previously focused on the neurological effects of this drug, while the efficacy of various treatments to reduce the associated side effects has not been well studied. This study aimed to evaluate the protective effects of naloxone, diazepam, and quercetin on tramadol overdose-induced seizure and sedation level in male rats.

Methods

The project was performed with 72 male Wistar rats with an average weight of 200–250 g. The rats were randomly assigned to eight groups. Tramadol was administered intraperitoneally at an initial dose of 25 mg/kg/day. On the 14th day, tramadol was injected at 75 mg/kg, either alone or together with naloxone, diazepam, and quercetin (acute and chronic) individually or in combination. The rats were monitored for 6 h on the last day, and the number, the duration, and the severity of seizures (using the criteria of Racine) were measured over a 6-h observation period. The sedation level was also assessed based on a 4-point criterion, ranging from 0 to 3. Data were analyzed in SPSS software using Kruskal–Wallis, Chi-square, regression analysis, and generalized estimating equation (GEE) tests. The significance level was set at P < 0.05.

Results

The naloxone-diazepam combination reduced the number, severity, and cumulative duration of seizures compared to tramadol use alone and reduced the number of higher-intensity seizures (level 3, 4) to a greater extent than other treatments. Naloxone alone reduced the number and duration of seizures but increased the number of mild seizures (level 2). Diazepam decreased the severity and duration of seizures. However, it increased the number of mild seizures (level 2). In comparison with the tramadol alone group, the acute quercetin group exhibited higher numbers of mild (level 2) and moderate (level 3) seizures. Chronic quercetin administration significantly increased the number of mild seizures. In the GEE model, all groups had higher sedation levels than the saline only group (P < 0.001). None of the protocols had a significant effect on sedation levels compared to the tramadol group.

Conclusion

The combined administration of naloxone and diazepam in acute-on-chronic tramadol poisoning can effectively reduce most seizure variables compared to tramadol use alone. However, none of the treatments improved sedation levels.

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.

The Therapeutic Potential of Quercetin in Parkinson's Disease: Insights into its Molecular and Cellular Regulation

Parkinson's disease (PD) is a chronic and progressive neurodegenerative disorder characterized by the progressive death of dopaminergic neurons in the substantia nigra pars compacta (SNc). PD is a multifactorial disorder, with several different factors being suggested to play a synergistic pathophysiological role, including oxidative stress, autophagy, underlying pro-inflammatory events and neurotransmitters abnormalities. Overall, PD can be viewed as the product of a complex interaction of environmental factors acting on a given genetic background. The importance of this subject has gained more attention to discover novel therapies to prevent as well as treat PD. According to previous research, drugs used to treat PD have indicated significant limitations. Therefore, the role of flavonoids has been extensively studied in PD treatment. Quercetin, a plant flavonol from the flavonoid group, has been considered as a supplemental therapy for PD. Quercetin has pharmacological functions in PD by controlling different molecular pathways. Although few studies intended to evaluate the basis for the use of quercetin in the context of PD have been conducted so far, at present, there is very little evidence available addressing the underlying mechanisms of action. Various principal aspects of these treatment procedures remain unknown. Here, currently existing knowledge supporting the use of quercetin for the clinical management of PD has been reviewed.

Enlightening the neuroprotective effect of quercetin in epilepsy: From mechanism to therapeutic opportunities

Epilepsy is a devastating neurological disorder characterized by the repeated occurrence of epileptic seizures. Epilepsy stands as a global health concern affecting around 70 million people worldwide. The mainstream antiepileptic drugs (AEDs) only exert symptomatic relief and drug-resistant epilepsy occurs in up to 33 percent of patients. Hence, the investigation of novel therapeutic strategies against epileptic seizures that could exert disease modifying effects is of paramount importance. In this context, compounds of natural origin with potential antiepileptic properties have recently gained increasing attention. Quercetin is a plant-derived flavonoid with several pharmacological activities. Emerging evidence has demonstrated the antiepileptic potential of quercetin as well. Herein, based on the available evidence, we discuss the neuroprotective effects of quercetin against epileptic seizures and further analyze the plausible underlying molecular mechanisms. Our review suggests that quercetin might be a potential therapeutic candidate against epilepsy that deserves further investigation, and paves the way for the development of plant-derived antiepileptic treatment approaches.

Ameliorating effect of quercetin on epilepsy by inhibition of inflammation in glial cells

Epilepsy is a prevalent neurological disorder and it is a significant health risk, affecting >50 million people worldwide. The development of novel and appropriate strategies is required for ameliorating the progression and/or limiting the detrimental consequences of epilepsy. In the current study, kainic acid (KA), a neurotoxin, was used to induce seizures in mice. The flavonoid quercetin has recently been reported to have neuroprotective effects. Therefore, the effects of quercetin on KA-induced epilepsy and the potential underlying molecular mechanisms were examined. It was noted that quercetin attenuated the KA-induced seizure score and proinflammatory cytokine production, including tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), and activation of nuclear factor κB (NF-κB) in mice. Quercetin attenuated KA-induced proinflammatory cytokine (TNF-α and IL-1β) release from microglia cells, as well as activation of NF-κB and ionized calcium binding adapter molecule 1 in microglia cells. Therefore, quercetin inhibited KA-induced epilepsy by microglia cell inactivation and the production of NF-κB, TNF-α and IL-1β.

Fabrication and evaluation of novel quercetin-conjugated Fe3O4-β-cyclodextrin nanoparticles for potential use in epilepsy disorder

BACKGROUND

Despite the numerous pharmacological activities of quercetin, its biomedical application has been hampered, because of poor water solubility and low oral bioavailability. In the present study, we fabricated a novel form of quercetin-conjugated Fe3O4-β-cyclodextrin (βCD) nanoparticles (NPs), and the effect of these prepared NPs was evaluated in a chronic model of epilepsy.

METHODS

Quercetin-loaded NPs were prepared using an iron oxide core coated with βCD and pluronic F68 polymer. The chronic model of epilepsy was developed by intraperitoneal injection of pentylenetetrazole (PTZ) at dose of 36.5 mg/kg every second day. Quercetin or its nanoformulation at doses of 25 or 50 mg/kg were administered intraperitoneally 10 days before PTZ injections and their applications continued 1 hour before each PTZ injection. Immunostaining was performed to evaluate the neuronal density and astrocyte activation of hippocampi.

RESULTS

Our data showed successful fabrication of quercetin onto Fe3O4-βCD NPs. In comparison to free quercetin, quercetin NPs markedly reduced seizure behavior, neuronal loss, and astrocyte activation in a PTZ-induced kindling model.

CONCLUSION

Overall, quercetin-Fe3O4-βCD NPs might be regarded as an ideal therapeutic approach in epilepsy disorder.

Quercetin Reduces Cortical GABAergic Transmission and Alleviates MK-801-Induced Hyperactivity

An imbalance between neuronal excitation and inhibition represents a core feature in multiple neuropsychiatry disorders, necessitating the development of novel strategies to calibrate the excitatory–inhibitory balance of therapeutics. Here we identify a natural compound quercetin that reduces prefrontal cortical GABAergic transmission and alleviates the hyperactivity induced by glutamatergic N-methyl-d-aspartate receptor antagonist MK-801. Quercetin markedly reduced the GABA-activated currents in a noncompetitive manner in cultured cortical neurons, and moderately inhibited spontaneous and electrically-evoked GABAergic inhibitory postsynaptic current in mouse prefrontal cortical slices. Notably, systemic and prefrontal-specific delivery of quercetin reduced basal locomotor activity in addition to alleviated the MK-801-induced hyperactivity. The effects of quercetin were not exclusively dependent on α5-subunit-containing A type GABA receptors (GABA_ARs), as viral-mediated, region-specific genetic knockdown of the α5-subunit in prefrontal cortex improved the MK-801-evoked psychotic symptom but reserved the pharmacological responsivity to quercetin. Both interventions together completely normalized the locomotor activity. Together, quercetin as a negative allosteric GABA_AR modulator exerted antipsychotic activity, facilitating further therapeutic development for the excitatory–inhibitory imbalance disorders.

Anti-inflammatory Effects of Quercetin and Vitexin on Activated Human Peripheral Blood Neutrophils: - The effects of quercetin and vitexin on human neutrophils

Objectives

Polymorphonuclear neutrophils (PMNs) constitute the first line of defense against invading microbial pathogens. Early events in inflammation involve the recruitment of neutrophils to the site of injury or damage where changes in intracellular calcium can cause the activation of pro-inflammatory mediators from neutrophils including superoxide generation, degranulation and release of myeloperoxidase (MPO), productions of interleukin (IL)-8 and tumor necrosis factor α (TNF-α), and adhesion to the vascular endothelium. To address the anti-inflammatory role of flavonoids, in the present study, we investigated the effects of the flavonoids quercetin and vitexin on the stimulus-induced nitric oxide (NO), TNF-α, and MPO productions in human neutrophils.

Methods

Human peripheral blood neutrophils were isolated, and their viabilities were determined by using the Trypan Blue exclusion test. The polymorphonuclear leukocyte (PMNL) preparations contained more than 98% neutrophils as determined by morphological examination with Giemsa staining. The viabilities of cultured neutrophils with various concentrations of quercetin and vitexin (1 – 100 μM) were studied using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assays. Neutrophils were cultured in complete Roswell Park Memorial Institute (RPMI) medium, pre-incubated with or without quercetin and vitexin (25 μM) for 45 min, and stimulated with phorbol 12-myristate 13-acetate (PMA) (10⁻⁷ M). NO production was carried out through nitrite determination by using the Griess method. Also, the TNF-α and the MPO productions were measured using enzyme-linked immunosorbent assay (ELISA) kits and MPO assay kits.

Results

Neutrophil viability was not affected up to a concentration of 100 μM of quercetin or vitexin. Both quercetin and vitexin significantly inhibited TNF-α, NO, and MPO productions in human neutrophils (P < 0.001).

Conclusion

The present study showed that both quercetin and vitexin had significant anti-inflammatory effects. Thus, treatment with either quercetin or vitexin may be considered as a therapeutic strategy for treating patients with neutrophil-mediated inflammatory diseases.

Influence of the dual combination of silymarin and (-)-epigallocatechin gallate, natural dietary flavonoids, on the pharmacokinetics of oxcarbazepine in rats

Considering the potential of flavonoids in reversing the P-glycoprotein (P-gp)-mediated multidrug resistance, this work aimed to assess the combined effects of silymarin and (-)-epigallocatechin gallate (EPG) on the pharmacokinetics of the P-gp substrates oxcarbazepine (OXC) and licarbazepine (LIC). Rats were pre-treated intraperitoneally with silymarin (25 mg/kg), EPG (25 mg/kg), silymarin/EPG (12.5/12.5 mg/kg; 6.25/18.75 mg/kg; 18.75/6.25 mg/kg) or verapamil (25 mg/kg, reference P-gp inhibitor) before the intraperitoneal administration of OXC (50 mg/kg). Pre-treatment with dual silymarin/EPG combinations originated peak plasma concentrations of OXC and LIC (pharmacologically active metabolite of OXC) similar to those achieved in the presence of verapamil (positive control). Moreover, the effects promoted by silymarin/EPG combinations on the magnitude of systemic drug exposure to OXC and LIC were also reflected in the corresponding drug levels attained in the brain (biophase). These findings evidence the synergistic effect of silymarin and EPG in enhancing the degree of systemic exposure to OXC and LIC in rats, which occurred in a comparable extent to that observed with verapamil. Hence, our findings support the combination of flavonoid-type P-gp inhibitors and P-gp substrate antiepileptic drugs as a potential therapeutic strategy for the management of pharmacoresistant epilepsy.

The effects of quercetin on the gene expression of the GABAA receptor α5 subunit gene in a mouse model of kainic acid-induced seizure

The flavonoid quercetin has recently been reported to have neuroprotective effects, and the role of the gamma-aminobutyric acid A alpha 5 subunit (GABAA α5) receptor has been determined in some nervous system disorders. The aim of this study was to identify the molecular mechanism of the effect of quercetin administered at anticonvulsive doses on the expression of the GABAA α5 receptor gene in kainic acid (KA)-induced seizures in mice. The experimental animals were divided into four groups: control, KA, and KA + quercetin at 50 or 100 mg/kg, respectively. The results showed a dose-dependent reduction in the behavioral seizure score with quercetin pre-treatment in the KA mouse model. Two hours after the end of the 7-day treatment regimen, expression of the GABAA α5 receptor gene in the hippocampus was found to be increased in the KA group, but this increase was reduced in the KA + quercetin 50 or 100 mg/kg treatment groups. These results suggest that expression of the GABAA α5 receptor could be a mechanism for reducing seizure severity or may be a marker of seizure severity. Further studies are necessary to clarify quercetin's mechanism of action and the relation of GABAA α5 receptor gene expression to seizure severity.

Modulation of the Expression of the GABAA Receptor β1 and β3 Subunits by Pretreatment with Quercetin in the KA Model of Epilepsy in Mice: -The Effect of Quercetin on GABAA Receptor Beta Subunits

Objectives:

Quercetin is a flavonoid and an important dietary constituent of fruits and vegetables. In recent years, several pharmacological activities of quercetin, such as its neuroprotective activity and, more specifically, its anti-convulsant effects in animal models of epilepsy, have been reported. This study evaluated the role of quercetin pretreatment on gene expression of γ-amino butyric acid type A (GABAA) receptor beta subunits in kainic acid (KA)-induced seizures in mice.

Methods:

The animals were divided into four groups: one saline group, one group in which seizures were induced by using KA (10 mg/kg) without quercetin pretreatment and two groups pretreated with quercetin (50 and 100 mg/kg) prior to seizures being induced by using KA. Next, the messenger ribonucleic acid (mRNA) levels of the GABAA receptor β subunits in the hippocampus of each animal were assessed at 2 hours and 7 days after KA administration. Quantitative real-time polymerase chain reaction (RT-PCR) assay was used to detect mRNA content in hippocampal tissues.

Results:

Pretreatments with quercetin at doses of 50 and 100 mg/kg prevented significant increases in the mRNA levels of the β₁ and the β₃ subunits of the GABAA receptor at 2 hours after KA injection. Pretreatment with quercetin (100 mg/kg) significantly inhibited β₁ and β₃ gene expression in the hippocampus at 7 days after KA injection. But, this inhibitory effect of quercetin at 50 mg/kg on the mRNA levels of the β₃ subunit of the GABAA receptor was not observed at 7 days after KA administration.

Conclusion:

These results suggest that quercetin (100 mg/kg) modulates the expression of the GABAA receptor β₁ and β₃ subunits in the KA model of epilepsy, most likely to prevent compensatory responses. This may be related to the narrow therapeutic dose range for the anticonvulsant activities of quercetin.

Selective potentiation of alpha 1 glycine receptors by ginkgolic acid

Glycine receptors (GlyRs) belong to the superfamily of pentameric cys-loop receptor-operated channels and are involved in numerous physiological functions, including movement, vision, and pain. In search for compounds performing subunit-specific modulation of GlyRs we studied action of ginkgolic acid, an abundant Ginkgo biloba product. Using patch-clamp recordings, we analyzed the effects of ginkgolic acid in concentrations from 30 nM to 25 μM on α1–α3 and α1/β, α2/β configurations of GlyR and on GABA_ARs expressed in cultured CHO-K1 cells and mouse neuroblastoma (N2a) cells. Ginkgolic acid caused an increase in the amplitude of currents mediated by homomeric α1 and heteromeric α1/β GlyRs and provoked a left-shift of the concentration-dependent curves for glycine. Even at high concentrations (10–25 μM) ginkgolic acid was not able to augment ionic currents mediated by α2, α2/β, and α3 GlyRs, or by GABA_AR consisting of α1/β2/γ2 subunits. Mutation of three residues (T59A/A261G/A303S) in the α2 GlyR subunit to the corresponding ones from the α1 converted the action of ginkgolic acid to potentiation with a distinct decrease in EC₅₀ for glycine, suggesting an important role for these residues in modulation by ginkgolic acid. Our results suggest that ginkgolic acid is a novel selective enhancer of α1 GlyRs.

Effect of quercetin and rutin in some acute seizure models in mice

Quercetin is one of the most widely occurring flavonoid which is also often present in plants as glycosidic form - rutin. These compounds are ingredients of plant diet and are also present in numerous pharmaceutical preparations and diet supplements which are taken by patients suffering from epilepsy and treating with antiepileptic drugs (AEDs). Influence of these compounds on central nervous system-related effects was proved both in experimental and clinical studies. Their influence on anxiety, depression, memory processes and convulsant activity was reported. The aim of the present study was to investigate the effect of quercetin and rutin in some models of seizures, i.e., in the model of psychomotor seizures induced by 6Hz stimulation, in the maximal electroshock seizure threshold and intravenous pentylenetetrazole tests in mice. We also examined a possible mechanism of anticonvulsant activity of quercetin and its influence on action of two AEDs, i.e., valproic acid and levetiracetam, in the 6Hz seizure test. Our results revealed only a weak anticonvulsant potential of the studied flavonoids because they showed anticonvulsant action at doses from 10 to 200mg/kg only in the 6Hz test and did not change seizure thresholds in the remaining tests. Moreover, anticonvulsant action of the studied flavonoids was short-term, noted only at pretreatment time ranging between 30 and 60min. The highest anticonvulsant activity of quercetin was correlated with its high plasma and brain concentration, which was revealed in a pharmacokinetic study. We did not note changes in the anticonvulsant action of the used AEDs combined with quercetin in the model of psychomotor seizures in mice. Neither quercetin and rutin nor combinations of quercetin with the studied AEDs produced any significant impairments of motor coordination (assessed in the chimney test), muscular strength (investigated in the grip-strength test) and long-term memory (evaluated in the passive avoidance test) in mice. The results of the present study suggest that quercetin and rutin have only weak and short-term anticonvulsant potential. These flavonoids seem to be safe for patients with epilepsy because they neither changed activity of the studied AEDs nor produced any adverse effects.