Tissue distribution and neuroprotective effects of citrus flavonoid tangeretin in a rat model of Parkinson's disease

Much More than Nutrients: The Protective Effects of Nutraceuticals on the Blood-Brain Barrier in Diseases

The dysfunction of the blood-brain barrier (BBB) is well described in several diseases, and is considered a pathological factor in many neurological disorders. This review summarizes the most important groups of natural compounds, including alkaloids, flavonoids, anthocyanidines, carotenoids, lipids, and vitamins that were investigated for their potential protective effects on brain endothelium. The brain penetration of these compounds and their interaction with BBB efflux transporters and solute carriers are discussed. The cerebrovascular endothelium is considered a therapeutic target for natural compounds in diseases. In preclinical studies modeling systemic and central nervous system diseases, nutraceuticals exerted beneficial effects on the BBB. In vivo, they decreased BBB permeability, brain edema, astrocyte swelling, and morphological changes in the vessel structure and basal lamina. At the level of brain endothelial cells, nutraceuticals increased cell survival and decreased apoptosis. From the general endothelial functions, decreased angiogenesis and increased levels of vasodilating agents were demonstrated. From the BBB functions, elevated barrier integrity by tightened intercellular junctions, and increased expression and activity of BBB transporters, such as efflux pumps, solute carriers, and metabolic enzymes, were shown. Nutraceuticals enhanced the antioxidative defense and exerted anti-inflammatory effects at the BBB. The most important signaling changes mediating the increased cell survival and BBB stability were the activation of the WNT, PI3K-AKT, and NRF2 pathways, and inhibition of the MAPK, JNK, ERK, and NF-κB pathways. Nutraceuticals represent a valuable source of new potentially therapeutic molecules to treat brain diseases by protecting the BBB.

Tangeretin offers neuroprotection against colchicine-induced memory impairment in Wistar rats by modulating the antioxidant milieu, inflammatory mediators and oxidative stress in the brain tissue

BACKGROUND

Tangeretin, a flavone compound (O-polymethoxylated) naturally present in tangerine and other citrus peels has demonstrated effectiveness as an anti-inflammatory and neuroprotective agent in several disease model. This study evaluated the impact of tangeretin in mitigating cognitive dysfunction and oxidative stress induced by colchicine in rats, comparing its efficacy with donepezil hydrochloride.

METHODS

Cognitive dysfunction was induced by administering colchicine (15 µg/rat) intracerebroventricularly (ICV) via a stereotaxic apparatus in male Wistar rats. Colchicine resulted in poor memory retention in acquiring and retaining a spatial navigation task, passive avoidance apparatus, and Morris water maze paradigms. Chronic treatment with tangeretin (at doses of 50, 100, and 200 mg/kg, p.o. once daily) and donepezil hydrochloride (at a dose of 10 mg/kg, p.o. daily) for 28 days, starting seven days before colchicine injection, significantly ameliorated colchicine-induced cognitive impairment.

RESULTS

The biochemical analysis showed that chronic administration of tangeretin effectively reversed the colchicine-induced increase in the level/activity of lipid peroxidation, hydrogen peroxide (H2O2), myeloperoxidase (MPO), nitrite, reactive oxygen species (ROS), tumour necrosis factor-α (TNF-α), nuclear factor kappa B (NF-κB), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-10 (IL-10), serotonin, dopamine, glutamate, amyloid beta (Aβ) peptide, and caspase-3. Tangeretin also reversed the colchicine-induced reduction in the level/activity of brain-derived neurotrophic factor (BDNF), amma-aminobutyric acid (GABA), acetylcholinesterase (AChE), glutathione S-Transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR), catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH), and total thiol (T-SH) in rat brains. However, donepezil hydrochloride did not prevent oxidative stress.

CONCLUSIONS

These findings suggest that chronic administration of tangeretin at 50, 100, and 200 mg/kg, p.o. once daily, was protective in mitigating colchicine-induced cognitive impairment and associated oxidative stress. At the same time, donepezil hydrochloride did not demonstrate similar effects.

Identification of non-volatile compounds during the pile fermentation process of Liupao tea using widely targeted metabolomics based on UPLC-QTOF-MS

Pile fermentation plays a crucial role in the formation of the unique flavor of Liupao tea, which can effectively reduce the bitterness of the tea and promote the formation of red tea soup. In this study, the non-volatiles changes of Liupao tea during pile fermentation processing were fully analyzed by UPLC-QTOF-MS/MS. A total of 271 metabolites with significant differences were identified in Liupao tea during pile fermentation(P < 0.01, VIP > 1), and their trends were grouped into 10 subclasses by K-means analysis. Three differential metabolites Choline Alfoscerate, N1-Methyl-4-pyridone-5-carboxamide, and 2-Aminovalienone were shared among the three different pile fermentation periods. The results provided valuable information for understanding the dynamic changes of non-volatile substances during the pile fermentation process of Liupao tea.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-024-06036-7.

Hybrid Lanthanide Metal-Organic Compounds with Flavonoids: Magneto-Optical Properties and Biological Activity Profiles

Lanthanides have seen rapid growth in the pharmaceutical and biomedical field, thus necessitating the development of hybrid metal-organic materials capable of exerting defined biological activities. Ternary hybrid lanthanide compounds were synthesized through reaction systems of Ln(III) (Ln = La, Nd, Eu) involving the antioxidant flavonoid chrysin (Chr) and 1,10-phenanhtroline (phen) under solvothermal conditions, thus leading to pure crystalline materials. The so-derived compounds were characterized physicochemically in the solid state through analytical (elemental analysis), spectroscopic (FT-IR, UV-visible, luminescence, ESI-MS, circular dichroism, 151Eu Mössbauer), magnetic susceptibility, and X-ray crystallographic techniques. The analytical and spectroscopic data corroborate the 3D structure of the mononuclear complex assemblies and are in line with theoretical calculations (Bond Valence Sum and Hirshfeld analysis), with their luminescence suggesting quenching on the flavonoid-phen electronic signature. Magnetic susceptibility data suggest potential correlations, which could be envisioned, supporting future functional sensors. At the biological level, the title compounds were investigated for their (a) ability to interact with bovine serum albumin and (b) antibacterial efficacy against Gram(-) (E. coli) and Gram(+) (S. aureus) bacteria, collectively revealing distinctly configured biological profiles and suggesting analogous applications in cellular (patho)physiologies.

Nobiletin-rich kososan, a Kampo formula, prevents the onset of apathy-like behavior and neuroinflammation in sickness behavior mouse model induced by increasing doses of lipopolysaccharide

Infectious diseases are often concomitant with symptoms of lassitude and emotional disturbances, including depression, the so-called sickness behavior. Kososan, a Kampo (traditional Japanese herbal) formula, has been clinically used for depressive mood, with demonstrated efficacy in stress-induced depressive-like behavior mouse models. Additionally, our previous study has shown that nobiletin-rich kososan (NKS) prevents aging-related depressive-like behaviors and neuroinflammation in mice. Here, we examined whether NKS alleviates depressive-like behavior and neuroinflammation in a mouse model of sickness behavior induced by lipopolysaccharide (LPS). Repeated oral administration of NKS and the positive control antidepressant paroxetine (Paro) significantly prevented this behavior. NKS and Paro significantly increased the anti-inflammatory milieu in the hippocampus and prefrontal cortex (PFC), as well as brain microglia, of LPS-injected mice. The expression of the vascular tight junction protein claudin-5 was also significantly increased by the treatment with NKS, but not with Paro, in the hippocampus and PFC of LPS-injected mice. In vitro analysis using brain microvascular endothelial cells (BMVECs) showed that incubation with 5% serum derived from mice orally administered NKS resulted in a significant increase in the expression of anti-inflammatory heme oxygenase 1 as well as autophagic flux markers. Moreover, the claudin-5 levels in BMVECs were also increased under LPS-stimulated conditions. These results suggest that NKS exerts prophylactic effects against the LPS-induced apathy-like behavior, partly mediated by the increase in the anti-inflammatory milieu and in the levels of tight junction proteins in the brain. This study provides scientific evidence supporting the potential efficacy of NKS in preventing post-infection depression.

Cellular stress response and neuroprotection of flavonoids in neurodegenerative diseases: Clinical insights into targeted therapy and molecular signaling pathways

Neurodegenerative diseases (NDs) are caused by the gradual decline of neuronal structure and function, which presents significant challenges in treatment. Cellular stress responses significantly impact the pathophysiology of these disorders, often exacerbating neuronal damage. Plant-derived flavonoids have demonstrated potential as neuroprotective agents due to their potent anti-inflammatory, anti-apoptotic, and antioxidant properties. This review provides an in-depth analysis of the molecular processes and clinical insights that cause the neuroprotective properties of flavonoids in NDs. By controlling essential signaling pathways such as Nrf2/ARE, MAPK, and PI3K/Akt, flavonoids can lower cellular stress and improve neuronal survival. The study discusses the challenges of implementing these discoveries in clinical practice and emphasizes the therapeutic potential of specific flavonoids and their derivatives. Flavonoids are identified as potential therapeutic agents for NDs, potentially slowing progression by regulating cellular stress and improving neuroprotection despite their potential medicinal uses and clinical challenges. The study designed a strategy to identify literature published in prestigious journals, utilizing search results from PubMed, Scopus, and WOS. We selected and investigated original studies, review articles, and research reports published until 2024. It suggests future research and therapeutic approaches to effectively utilize the neuroprotective properties of flavonoids.

The Neuroprotective Role of Tangeritin

The prevalence of neurodegenerative diseases has increased with longer life expectancies, necessitating the exploration of novel neuroprotective agents. Tangeretin, a polymethoxylated flavone derived from citrus fruits, has gathered attention for its potential therapeutic effects. This review highlights the neuroprotective properties of tangeretin via its antioxidant and anti-inflammatory mechanisms. Tangeretin demonstrates efficacy in mitigating oxidative stress, neuroinflammation, and neuronal damage across various neurodegenerative conditions, including Alzheimer's disease, Parkinson's disease, cerebral ischemia, and epilepsy. It shows promise in ameliorating cognitive deficits and memory impairments associated with these diseases. Moreover, tangeretin modulates multiple signalling pathways and protects against neuronal apoptosis, underscoring its potential as a therapeutic agent.

Progress of Researches on Pharmacological Effects and Bioavailability of Tangeretin

Tangeretin is one of the most abundant polymethoxyflavones in citrus peel and its pharmacological effects are extremely rich. However, due to its poor solubility, bitter taste and poor oral bioavailability, the oral administration of tangeretin is still limited, which seriously limits its application in industrial production. The establishment of encapsulation and delivery systems to improve bioavailability is an effective method. This paper reviewed the research progress of the structure and properties, pharmacological effects and main methods to improve bioavailability of tangeretin, including emulsion delivery, lipid encapsulation, microencapsulation and other delivery and utilization research and application. The article aims to provide theoretical basis for the high-value application of tangeretin in functional food and pharmaceutical industry.

Citrus Polymethoxyflavones Regulate against Aging-Associated Diseases: Advances in Biological Mechanisms Responsible for Their Regulation

As the proportion of the aging population globally is surging year by year, age-associated diseases, including neurodegenerative, metabolic, and cardiovascular diseases, have recently attracted widespread attention of food scientists and nutritionists. Polymethoxyflavonoids (PMFs), a type of dietary flavonoids, have emerged as potential antiaging candidates owing to their diverse bioactivities, encompassing antioxidant, anti-inflammatory, neuroprotective, and metabolic regulatory effects. Herein, this comprehensive updated review has summarized and discussed the effects of PMFs on aging, and the possible mechanisms that link PMFs-mediated modulation and the prevention or treatment of various aging-related diseases have been elaborated in detail. Furthermore, the biological fate of PMFs have been discussed elaborately from their absorption, distribution, metabolism, and excretion in vivo. Special attention is given to the bioavailability-bioactivity relationship of PMFs, as PMF's biological activity is significantly hampered by poor bioavailability. Overall, all of these conclusions may help in providing a perspective for further study of PMFs on aging.

Tangeretin alleviates inflammation and oxidative response induced by spinal cord injury by activating the Sesn2/Keap1/Nrf2 pathway

Spinal cord injury (SCI) is a severe disabling disease that is characterized by inflammation and oxidative reactions. Tangeretin has been shown to possess significant antioxidant and anti-inflammatory activities. The Keap1/Nrf2 pathway, downstream of the Sesn2 gene, is involved in regulating the inflammation and oxidative response. The main objective of this study was to investigate the effect of tangeretin on SCI and its possible mechanism through cell and animal models. A T9 clamp injury was used for the mouse model and the LPS-induced stimulation of BV-2 cells was used for the cell model. The improvement of motor function after SCI was assessed by open field, swimming, and footprint experiments. The morphological characteristics of mouse spinal cord tissue and the levels of INOS, Sesn2, TNF-α, Keap1, Nrf2, IL-10, and reactive oxygen species (ROS) in vivo and in vitro were measured by several methods including western blotting, qPCR, immunofluorescence, HE, and Nissl staining. In vivo data showed that tangeretin can improve motor function recovery and reduce neuron loss and injury size in mice with SCI. Simultaneously, the in vitro findings suggested that treatment of BV-2 cells with tangeretin after LPS stimulation reduced the production of inflammatory factors and ROS, and could convert BV-2 cells from the M1 to the M2 type. Furthermore, Sesn2 knockout suppressed Keap1/Nrf2, inflammatory factors, ROS levels, and the M1 to M2 transition. Tangeretin can alleviate the inflammation and oxidative response induced by SCI by activating the Sesn2/Keap1/Nrf2 pathway.

Tangeretin Enhances Muscle Endurance and Aerobic Metabolism in Mice via Targeting AdipoR1 to Increase Oxidative Myofibers

Slow oxidative myofibers play an important role in improving muscle endurance performance and maintaining body energy homeostasis. However, the targets and means to regulate slow oxidative myofibers proportion remain unknown. Here, we show that tangeretin (TG), a natural polymethoxylated flavone, significantly activates slow oxidative myofibers-related gene expression and increases type I myofibers proportion, resulting in improved endurance performance and aerobic metabolism in mice. Proteomics, molecular dynamics, cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) investigations revealed that TG can directly bind to adiponectin receptor 1 (AdipoR1). Using AdipoR1-knockdown C2C12 cells and muscle-specific AdipoR1-knockout mice, we found that the positive effect of TG on regulating slow oxidative myofiber related markers expression is mediated by AdipoR1 and its downstream AMPK/PGC-1α pathway. Together, our data uncover TG as a natural compound that regulates the identity of slow oxidative myofibers via targeting the AdipoR1 signaling pathway. These findings further unveil the new function of TG in increasing the proportion of slow oxidative myofibers and enhancing skeletal muscle performance.

An Update on the Potential of Tangeretin in the Management of Neuroinflammation-Mediated Neurodegenerative Disorders

Neuroinflammation is the major cause of neurodegenerative disorders such as Alzheimer's and Parkinson's disease. Currently available drugs present relatively low efficacy and are not capable of modifying the course of the disease or delaying its progression. Identifying well-tolerated and brain-penetrant agents of plant origin could fulfil the pressing need for novel treatment techniques for neuroinflammation. Attention has been drawn to a large family of flavonoids in citrus fruits, which may function as strong nutraceuticals in slowing down the development and progression of neuroinflammation. This review is aimed at elucidating and summarizing the effects of the flavonoid tangeretin (TAN) in the management of neuroinflammation-mediated neurodegenerative disorders. A literature survey was performed using various resources, including ScienceDirect, PubMed, Google Scholar, Springer, and Web of Science. The data revealed that TAN exhibited immense neuroprotective effects in addition to its anti-oxidant, anti-diabetic, and peroxisome proliferator-activated receptor-γ agonistic effects. The effects of TAN are mainly mediated through the inhibition of oxidative and inflammatory pathways via regulating multiple signaling pathways, including c-Jun N-terminal kinase, phosphoinositide 3-kinase, mitogen-activated protein kinase, nuclear factor erythroid-2-related factor 2, extracellular-signal-regulated kinase, and CRE-dependent transcription. In conclusion, the citrus flavonoid TAN has the potential to prevent neuronal death mediated by neuroinflammatory pathways and can be developed as an auxiliary therapeutic agent in the management of neurodegenerative disorders.

Dietary Cocoa Flavanols Do Not Alter Brain Excitability in Young Healthy Adults

The ingestion of dietary cocoa flavanols acutely alters functions of the cerebral endothelium, but whether the effects of flavanols permeate beyond this to alter other brain functions remains unclear. Based on converging evidence, this work tested the hypothesis that cocoa flavanols would alter brain excitability in young healthy adults. In a randomised, cross-over, double-blinded, placebo-controlled design, transcranial magnetic stimulation was used to assess corticospinal and intracortical excitability before as well as 1 and 2 h post-ingestion of a beverage containing either high (695 mg flavanols, 150 mg (-)-epicatechin) or low levels (5 mg flavanols, 0 mg (-)-epicatechin) of cocoa flavanols. In addition to this acute intervention, the effects of a short-term chronic intervention where the same cocoa flavanol doses were ingested once a day for 5 consecutive days were also investigated. For both the acute and chronic interventions, the results revealed no robust alteration in corticospinal or intracortical excitability. One possibility is that cocoa flavanols yield no net effect on brain excitability, but predominantly alter functions of the cerebral endothelium in young healthy adults. Future studies should increase intervention durations to maximize the acute and chronic accumulation of flavanols in the brain, and further investigate if cocoa flavanols would be more effective at altering brain excitability in older adults and clinical populations than in younger adults.

Effect of Flavonoids against Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder. It is characterized by the depletion of striatal dopamine content and aggregation of alphasynuclein in the substantia nigra (SN). It is possible to treat the symptoms of PD with a variety of medications, but they often result in complications and are not able to cure or stop the progression of the disease. Flavonoids (the phytocomponents present in almost all fruits and vegetables) are the class of secondary metabolites that have generated a peak of interest because of their medicinal properties, including a reduction in the risk of PD. Several flavonoids such as quercetin, kaempferol, hesperitin, anthocyanin and many more have been reported for their anti- Parkinson's effect. This review deals with the neuroprotective benefits of different classes of flavonoids against PD.

Review of Phytochemical Potency as a Natural Anti-Helicobacter pylori and Neuroprotective Agent

Phytochemicals are plant secondary metabolites that show health benefits for humans due to their bioactivity. There is a huge variety of phytochemicals that have already been identified, and these compounds can act as antimicrobial and neuroprotection agents. Due to their anti-microbial activity and neuroprotection, several phytochemicals might have the potency to be used as natural therapeutic agents, especially for Helicobacter pylori infection and neurodegenerative disease, which have become a global health concern nowadays. According to previous research, there are some connections between H. pylori infection and neurodegenerative diseases, especially Alzheimer's disease. Hence, this comprehensive review examines different kinds of phytochemicals from natural sources as potential therapeutic agents to reduce H. pylori infection and improve neurodegenerative disease. An additional large-scale study is needed to establish the connection between H. pylori infection and neurodegenerative disease and how phytochemicals could improve this condition.

Hirami lemon (Citrus reticulata var. depressa) modulates the gut-brain axis in a chronic mild stress-induced depression mouse model

Citrus reticulata var. depressa, commonly known as Hirami lemon, is a native citrus species found in Taiwan and Okinawa islands of Japan. While several Citrus species are known to possess antidepressant activity by modulating the gut microbiota, the antidepressant effect of Hirami lemon and its underlying mechanisms have not been thoroughly investigated. In this study, we explored the potential antidepressant efficacy of the fruit extract (CD) and the essential oil (CDE) from Hirami lemon peel using a chronic mild stress (CMS)-induced mouse model and analyzed the association of gut microbiome changes. Our findings revealed that mice subjected to CMS exhibited anxiety- and depression-like behaviors as assessed by elevated plus-maze and forced swimming tests, respectively. Significantly, oral administration of CDE and CD notably reversed CMS-induced depression- and anxiety-like behaviors in CMS-induced mice. Moreover, compared to the non-stressed group, CMS significantly altered the gut microbiome, characterized by highly diverse bacterial communities, reduced Bacteroidetes, and increased Firmicutes. However, oral administration of CDE and CD restored gut microbiota dysbiosis. We also performed a qualitative analysis of CD and CDE using UPLC-MS and GC-MS, respectively. The CD contained 25 compounds, of which 3 were polymethoxy flavones and flavanones. Three major compounds, nobiletin, tangeretin and hesperidin, accounted for 56.88% of the total relative peak area. In contrast, the CDE contained 11 terpenoids, of which 8 were identified as major compounds, with D-limonene (45.71%) being the most abundant, followed by γ-terpinene (34.65%), linalool (6.46%), p-cymene (2.57%), α-terpineol (2.04%), α-pinene (1.89%), α-terpinolene (1.46%), and β-pinene (1.16%), accounting for 95.94% of the total oil. In conclusion, our study demonstrated the potential of Hirami lemon as a source of natural antidepressant agents for the prevention and treatment of major depressive disorders.

Diet and lifestyle impact the development and progression of Alzheimer's dementia

Dementia is a growing public health concern, with an estimated prevalence of 57 million adults worldwide. Alzheimer's disease (AD) accounts for 60-80% of the cases. Clinical trials testing potential drugs and neuroprotective agents have proven futile, and currently approved drugs only provide symptomatic benefits. Emerging epidemiological and clinical studies suggest that lifestyle changes, including diet and physical activity, offer an alternative therapeutic route for slowing and preventing cognitive decline and dementia. Age is the single most common risk factor for dementia, and it is associated with slowing cellular bioenergetics and metabolic processes. Therefore, a nutrient-rich diet is critical for optimal brain health. Furthermore, type 2 diabetes (T2D) is a risk factor for AD, and diets that reduce the risk of T2D may confer neuroprotection. Foods predominant in Mediterranean, MIND, and DASH diets, including fruits, leafy green vegetables, fish, nuts, and olive oil, may prevent or slow cognitive decline. The mechanisms by which these nutrients promote brain health, however, are not yet completely understood. Other dietary approaches and eating regimes, including ketogenic and intermittent fasting, are also emerging as beneficial for brain health. This review summarizes the pathophysiology, associated risk factors, and the potential neuroprotective pathways activated by several diets and eating regimes that have shown promising results in promoting brain health and preventing dementia.

Comparative flavonoid profile of orange (Citrus sinensis) flavedo and albedo extracted by conventional and emerging techniques using UPLC-IMS-MS, chemometrics and antioxidant effects

Introduction

Citrus fruits are one of the most frequently counterfeited processed products in the world. In the juice production alone, the peels, divided into flavedo and albedo, are the main waste product. The extracts of this by-product are enriched with many bioactive substances. Newer extraction techniques generally have milder extraction conditions with simultaneous improvement of the extraction process.

Methods

This study presents a combinatorial approach utilizing data-independent acquisition-based ion mobility spectrometry coupled to tandem mass spectrometry. Integrating orthogonal collision cross section (CCS) data matching simultaneously improves the confidence in metabolite identification in flavedo and albedo tissues from Citrus sinensis. Furthermore, four different extraction approaches [conventional, ultrasonic, High Hydrostatic Pressure (HHP) and Pulsed Electric Field (PEF)] with various optimized processing conditions were compared in terms of antioxidant effects and flavonoid profile particularly polymethoxy flavones (PMFs).

Results

A total number of 57 metabolites were identified, 15 of which were present in both flavedo and albedo, forming a good qualitative overlapping of distributed flavonoids. For flavedo samples, the antioxidant activity was higher for PEF and HHP treated samples compared to other extraction methods. However, ethyl acetate extract exhibited the highest antioxidant effects in albedo samples attributed to different qualitative composition content rather than various quantities of same metabolites. The optimum processing conditions for albedo extraction using HHP and PEF were 200 MPa and 15 kJ/kg at 10 kV, respectively. While, HHP at medium pressure (400 MPa) and PEF at 15 kJ/kg/3 kV were the optimum conditions for flavedo extraction.

Conclusion

Chemometric analysis of the dataset indicated that orange flavedo can be a valid source of soluble phenolic compounds especially PMFs. In order to achieve cross-application of production, future study should concentrate on how citrus PMFs correlate with biological engineering techniques such as breeding, genetic engineering, and fermentation engineering.

A Scientometric Study to a Critical Review on Promising Anticancer and Neuroprotective Compounds: Citrus Flavonoids

Flavonoids derived from citrus plants are favored by phytomedicinal researchers due to their wide range of biological activities, and relevant studies have been sustained for 67 years (since the first paper published in 1955). In terms of a scientometric and critical review, the scientometrics of related papers, chemical structures, and pharmacological action of citrus flavonoids were comprehensively summarized. The modern pharmacological effects of citrus flavonoids are primarily focused on their anticancer activities (such as breast cancer, gastric cancer, lung cancer, and liver cancer), neuroprotective effects (such as anti-Alzheimer’s disease, Parkinson’s disease), and metabolic diseases. Furthermore, the therapeutic mechanism of cancers (including inducing apoptosis, inhibiting cell proliferation, and inhibiting cancer metastasis), neuroprotective effects (including antioxidant and anti-inflammatory), and metabolic diseases (such as non-alcoholic fatty liver disease, type 2 diabetes mellitus) were summarized and discussed. We anticipate that this review could provide an essential reference for anti-cancer and neuroprotective research of citrus flavonoids and provide researchers with a comprehensive understanding of citrus flavonoids.

Anti-Inflammatory Effects of Flavonoids in Common Neurological Disorders Associated with Aging

Aging reduces homeostasis and contributes to increasing the risk of brain diseases and death. Some of the principal characteristics are chronic and low-grade inflammation, a general increase in the secretion of proinflammatory cytokines, and inflammatory markers. Aging-related diseases include focal ischemic stroke and neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD). Flavonoids are the most common class of polyphenols and are abundantly found in plant-based foods and beverages. A small group of individual flavonoid molecules (e.g., quercetin, epigallocatechin-3-gallate, and myricetin) has been used to explore the anti-inflammatory effect in vitro studies and in animal models of focal ischemic stroke and AD and PD, and the results show that these molecules reduce the activated neuroglia and several proinflammatory cytokines, and also, inactivate inflammation and inflammasome-related transcription factors. However, the evidence from human studies has been limited. In this review article, we highlight the evidence that individual natural molecules can modulate neuroinflammation in diverse studies from in vitro to animal models to clinical studies of focal ischemic stroke and AD and PD, and we discuss future areas of research that can help researchers to develop new therapeutic agents.

Analysis of phenolic compounds in Parkinson's disease: a bibliometric assessment of the 100 most cited papers

Objective

The aim of this study was to identify and characterize the 100 most cited articles on Parkinson's disease (PD) and phenolic compounds (PCs).

Methods

Articles were selected in the Web of Science Core Collection up to June 2022 based on predetermined inclusion criteria, and the following bibliometric parameters were extracted: the number of citations, title, keywords, authors, year, study design, tested PC and therapeutic target. MapChart was used to create worldwide networks, and VOSviewer software was used to create bibliometric networks. Descriptive statistical analysis was used to identify the most researched PCs and therapeutic targets in PD.

Results

The most cited article was also the oldest. The most recent article was published in 2020. Asia and China were the continent and the country with the most articles in the list (55 and 29%, respectively). In vitro studies were the most common experimental designs among the 100 most cited articles (46%). The most evaluated PC was epigallocatechin. Oxidative stress was the most studied therapeutic target.

Conclusion

Despite the demonstrations in laboratorial studies, the results obtained point to the need for clinical studies to better elucidate this association.

Neuroprotective Potential of Thinned Peaches Extracts Obtained by Pressurized Liquid Extraction after Different Drying Processes

Genetic, environmental and nutritional factors are suggested as primary factors of Alzheimer’s disease (AD), and secondary metabolites such as polyphenols present in thinned peaches are considered as good candidates for AD prevention. Thinned peaches are usually dried to avoid putrefaction, but the effects of the drying method and the extraction process on the polyphenol composition and the neuroprotective potential have never been addressed. In this work, a pressurized liquid extraction (PLE) method was optimized and applied to thinned peaches dried under different conditions, and their neuroprotective potential was evaluated in vitro. In addition, the PLE extracts were characterized via HPLC-Q-TOF-MS/MS, and a permeability assay was performed to evaluate the ability of the identified metabolites to cross the blood–brain barrier (BBB). The PLE extracts obtained from freeze-dried (FD) samples with 50% ethanol in water at 180 °C showed the best neuroprotective potential. Finally, among the 81 metabolites identified, isoferulic acid, 4-methyldaphnetin, coniferyl aldehyde and 3,4-dihydroxyacetophenone were found at higher concentrations in FD extracts. These metabolites are able to cross the BBB and are positively correlated with the neuroprotective potential, suggesting FD together with PLE extraction as the best combination to exploit the neuroprotective capacity of thinned peaches.

Presence and risks of polycyclic aromatic hydrocarbons, dioxins and dioxin-like PCBs in dietary plant supplements as elucidated by a combined DR CALUX® bioassay and GC-HRMS based approach

Plant-based dietary supplements may contain undesirable contaminants such as polycyclic aromatic hydrocarbons, dioxins and dioxin-like polychlorinated biphenyls (dl-PCBs) due to the sources of raw materials or processing methods used. The presence of these contaminants in a series of herbal supplements sold on the Ghanaian market for improving sexual performance was examined using the DR CALUX^® bioassay in combination with GC-HRMS analysis. Overall, cell responses at 4 and 48 h exposure to extracts prepared without an acid-silica clean-up were relatively higher than the responses obtained from extracts prepared with an acid-silica clean-up. This indicated that the 40 supplements contained only low levels of stable aryl hydrocarbon receptor (AhR) agonists like polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and dl-PCBs, while some contained substantial amounts of less stable AhR-agonists. Ten supplements selected for confirmation with GC-HRMS analysis contained PCDD/Fs and dl-PCBs at levels ranging from 0.01 to 0.19 pg toxic equivalent (TEQ)/g only, while the level of the sum of 4 polycyclic aromatic hydrocarbons (Σ4PAHs) representing less stable AhR agonists, ranged from not detected (ND) to 25.5 ng/g. These concentrations were in line with the responses observed in the DR CALUX^® bioassay. The concentration of PCDD/Fs and dl-PCBs corresponded to estimated daily intakes (EDIs) ranging from 0.01 to 1.20 pg TEQ/day, or 0.001 to 0.12 pg TEQ/kg bw/week for a 70 kg bw consumer, which was below the established tolerable weekly intake (TWI) of 2 pg TEQ/kg bw/week, thus indicating low concern for consumers' health. Similarly, the EDIs based on the detected Σ4PAHs in supplements ranged from 7.2 to 111 ng/day, or 0.1 to 1.6 ng/kg bw/day, which corresponded to MOE values above 10,000, indicating a low health concern.

Cyrcadian Rhythm, Mood, and Temporal Patterns of Eating Chocolate: A Scoping Review of Physiology, Findings, and Future Directions

This paper discusses the effect of chrononutrition on the regulation of circadian rhythms; in particular, that of chocolate on the resynchronization of the human internal biological central and peripheral clocks with the main external synchronizers, light-dark cycle and nutrition-fasting cycle. The desynchronization of internal clocks with external synchronizers, which is so frequent in our modern society due to the tight rhythms imposed by work, social life, and technology, has a negative impact on our psycho-physical performance, well-being, and health. Taking small amounts of chocolate, in the morning at breakfast at the onset of the active phase, helps speed up resynchronization time. The high flavonoid contents in chocolate promote cardioprotection, metabolic regulation, neuroprotection, and neuromodulation with direct actions on brain function, neurogenesis, angiogenesis, and mood. Although the mechanisms of action of chocolate compounds on brain function and mood as well as on the regulation of circadian rhythms have yet to be fully understood, data from the literature currently available seem to agree in suggesting that chocolate intake, in compliance with chrononutrition, could be a strategy to reduce the negative effects of desynchronization. This strategy appears to be easily implemented in different age groups to improve work ability and daily life.

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.

Aryl Hydrocarbon Receptor in Oxidative Stress as a Double Agent and Its Biological and Therapeutic Significance

The aryl hydrocarbon receptor (AhR) has long been implicated in the induction of a battery of genes involved in the metabolism of xenobiotics and endogenous compounds. AhR is a ligand-activated transcription factor necessary for the launch of transcriptional responses important in health and disease. In past decades, evidence has accumulated that AhR is associated with the cellular response to oxidative stress, and this property of AhR must be taken into account during investigations into a mechanism of action of xenobiotics that is able to activate AhR or that is susceptible to metabolic activation by enzymes encoded by the genes that are under the control of AhR. In this review, we examine various mechanisms by which AhR takes part in the oxidative-stress response, including antioxidant and prooxidant enzymes and cytochrome P450. We also show that AhR, as a participant in the redox balance and as a modulator of redox signals, is being increasingly studied as a target for a new class of therapeutic compounds and as an explanation for the pathogenesis of some disorders.

Blueberry juice augments exercise-induced neuroprotection in a Parkinson's disease model through modulation of GDNF levels

Exercise and consumption of plant-based foods rich in polyphenols are attractive therapeutic approaches for the prevention and treatment of Parkinson's disease (PD). Few studies, however, have examined the neuroprotective efficacy of combining these treatment modalities against PD. Therefore we investigated whether combining voluntary running and consumption of blueberry juice (BBJ) was more efficacious against 6-hydroxydopamine (6-OHDA) toxicity than either treatment alone. Four weeks of running before and after intrastriatal 6-OHDA reduced amphetamine-induced rotational behavior and loss of substantia nigra dopamine (DA) neurons. BBJ consumption alone had no ameliorative effects, but when combined with exercise, behavioral deficits and nigrostriatal DA neurodegeneration were reduced to a greater extent than exercise alone. The neuroprotection observed with exercise alone was associated with an increase in striatal glial cell-lined derived neurotrophic factor (GDNF), whereas combining exercise and BBJ was associated with an increase in nigral GDNF. These results suggest that polyphenols may potentiate the protective effects of exercise and that differential regulation of GDNF expression underlies protection observed with exercise alone versus combined treatment with consumption of BBJ.

Influence of Tangeretin on the Exponential Regression of Inflammation and Oxidative Stress in Streptozotocin-Induced Diabetic Nephropathy

Diabetes is an amalgamation of metabolic disorders marked by hyperglycemia. Over time diabetes brings up several other complications with it like cardiovascular disease, retinopathy, neuropathy, and nephropathy. among which diabetic nephropathy (DN) is the one we are concerned about in the present study. Diabetes management requires following a healthy lifestyle with proper medication. Most of the anti-diabetic drugs available at present come with adverse side effects. Nature has provided us with several components that are anti-diabetic in nature which has fewer or no side effects and tangeretin is one among them. Tangeretin is a natural flavonoid abundantly present in orange peel and tangerines. Our study is designed to evaluate tangeretin, as an anti-diabetic medication especially for patients suffering from diabetic nephropathy. The procured healthy rats were first divided into four groups: the group I was maintained as healthy control and the others were subjected to the induction of diabetes by i.p. injection of streptozotocin (STZ) at the concentration of 55mg/kg b.wt .Then, the diabetic rats were further divided into three groups: group II was used as the diabetic control rats and the group III and group IV were administered with tangeretin (25mg/kg b.wt) and positive control drug metformin (150mg/kg b.wt) for 8 weeks. The body weight, blood glucose, and serum insulin levels were estimated at week 0 and week 8. Reactive oxygen species (ROS) inhibitory effect, antioxidant, antilipidemic, nephroprotective, and anti-inflammatory effects of tangeretin on the diabetic-induced rats were evaluated at the end of week 8 in addition to the histopathological assessment of the sections of the kidneys of the experimental rats. All the test results concluded that tangeretin was able to significantly decelerate the progression of DN in STZ-induced diabetic rats.

Bidirectional Responses of Eight Neuroinflammation-Related Transcriptional Factors to 64 Flavonoids in Astrocytes with Transposable Insulated Signaling Pathway Reporters

Neuroinflammation is implicated in a variety of pathologies and is mechanistically linked to hyperactivation of glial cells in the central nervous system (CNS), predominantly in response to external stimuli. Multiple dietary factors were reported to alter neuroinflammation, but their actions on the relevant transcription factors in glia are not sufficiently understood. Here, an in vitro protocol employing cultured astroglial cells, which carry reporters of multiple signaling pathways associated with inflammation, was developed for screening environmental factors and synthetic drugs. Immortalized rat astrocyte line DI TNC1 was stably transfected with piggyBac transposon vectors containing a series of insulated reporters for the transcriptional activity of NF-κB, AP-1, signal transducer and activator of transcription 1 (STAT1), signal transducer and activator of transcription 3 (STAT3), aromatic hydrocarbon receptor (AhR), Nrf2, peroxisome proliferator-activated receptor γ (PPARγ), and HIF-1α, which is quantified via luciferase assay. Concatenated green fluorescent protein (GFP) expression was employed for simultaneous evaluation of cellular viability. Responses to a set of 64 natural and synthetic monomeric flavonoids representing six main structural classes (flavan-3-ols, flavanones, flavones, flavonols, isoflavones, and anthocyan(id)ins) were obtained at 10 and 50 μM concentrations. Except for HIF-1α, the activity of NF-κB and other transcription factors (TFs) in astrocytes was predominantly inhibited by flavan-3-ols and anthocyan(id)ins, while flavones and isoflavones generally activated these TFs. In addition, we obtained dose-response profiles for 11 flavonoids (apigenin, baicalein, catechin, cyanidin, epigallocatechin gallate, genistein, hesperetin, kaempferol, luteolin, naringenin, and quercetin) within the 1-100 μM range and in the presence of immune-stimulants and immune-suppressors. The flavonoid concentration profiles for TF-activation reveal biphasic response curves from the astrocytes. Apart from epigallocatechin gallate (EGCG), flavonoids failed to inhibit the NF-κB activation by proinflammatory agents [lipopolysaccharide (LPS), cytokines], but most of the tested polyphenols synergized with STAT3 inhibitors (stattic, ruxolitinib) against the activation of this TF in the astrocytes. We conclude that transposable insulated reporters of transcriptional activation represent a convenient neurochemistry tool in screening for activators/inhibitors of signaling pathways.

Tangeretin Inhibits BACE1 Activity and Attenuates Cognitive Impairments in AD Model Mice

Tangeretin (TAN) exhibits many bioactivities, including neuroprotective effects. However, the efficacy of TAN in Alzheimer's disease (AD) has not been sufficiently investigated. In the present study, we integrated behavioral tests, pathology assessment, and biochemical analyses to elucidate the antidementia activity of TAN in APPswe/PSEN1dE9 transgenic (Tg) mice. At supplementation levels of 100 mg/kg body weight per day, TAN significantly attenuated the cognitive impairment of Tg mice in behavioral tests. These effects were associated with less synaptic impairments and fewer β-amyloid accumulations after TAN administration. Furthermore, our study revealed that TAN possessed powerful inhibitory activity against β-secretase both in vitro and in vivo, which played a crucial role in the process of Aβ generation. These findings indicate that TAN is a potential drug for preventing AD pathology. The key mechanism underlying the antidementia effect of TAN may include its inhibitory activity against β-secretase.

Exosome-like nanoparticles from Mulberry bark prevent DSS-induced colitis via the AhR/COPS8 pathway

Bark protects the tree against environmental insults. Here, we analyzed whether this defensive strategy could be utilized to broadly enhance protection against colitis. As a proof of concept, we show that exosome-like nanoparticles (MBELNs) derived from edible mulberry bark confer protection against colitis in a mouse model by promoting heat shock protein family A (Hsp70) member 8 (HSPA8)-mediated activation of the AhR signaling pathway. Activation of this pathway in intestinal epithelial cells leads to the induction of COP9 Constitutive Photomorphogenic Homolog Subunit 8 (COPS8). Utilizing a gut epithelium-specific knockout of COPS8, we demonstrate that COPS8 acts downstream of the AhR pathway and is required for the protective effect of MBELNs by inducing an array of anti-microbial peptides. Our results indicate that MBELNs represent an undescribed mode of inter-kingdom communication in the mammalian intestine through an AhR-COPS8-mediated anti-inflammatory pathway. These data suggest that inflammatory pathways in a microbiota-enriched intestinal environment are regulated by COPS8 and that edible plant-derived ELNs may hold the potential as new agents for the prevention and treatment of gut-related inflammatory disease.

The Role of AhR in the Hallmarks of Brain Aging: Friend and Foe

In recent years, aryl hydrocarbon receptor (AhR), a ligand-activated transcription factor, has been considered to be involved in aging phenotypes across several species. This receptor is a highly conserved biosensor that is activated by numerous exogenous and endogenous molecules, including microbiota metabolites, to mediate several physiological and toxicological functions. Brain aging hallmarks, which include glial cell activation and inflammation, increased oxidative stress, mitochondrial dysfunction, and cellular senescence, increase the vulnerability of humans to various neurodegenerative diseases. Interestingly, many studies have implicated AhR signaling pathways in the aging process and longevity across several species. This review provides an overview of the impact of AhR pathways on various aging hallmarks in the brain and the implications for AhR signaling as a mechanism in regulating aging-related diseases of the brain. We also explore how the nature of AhR ligands determines the outcomes of several signaling pathways in brain aging processes.

Flavonoid and cannabinoid impact on the ocular surface

PURPOSE OF REVIEW

To evaluate the impact of flavonoids and cannabinoids as anti-inflammatory and antiallergic treatments on the anterior surface of the eye.

RECENT FINDINGS

Allergic conjunctivitis and dry eye syndrome are common ocular surface diseases that have been treated with traditional pharmacological measures, e.g. corticosteroids, antihistamines. Given the side-effect profiles of these medications and the growing interest in complementary treatment modalities as part of integrative medical interventions, well known flavonoids, such as quercetin and catechin, are under investigation for topical and systemic application methods for relief. As flavonoid derivatives, pycnogenol and epigallocatechin gallate have alleviated dry eye symptoms, including lacrimal gland inflammation, tear secretion, and the stability of the tear film. Research on ocular cannabinoid receptors and response to synthetic cannabinoids are also being considered for therapy of anterior ocular disorders. The expansion of herbal formulations provides a framework for future treatment regimens for ocular surface disorders.

SUMMARY

Flavonoids and cannabinoids show promise as potential complementary treatment for allergic diseases because of their anti-inflammatory and antiallergic properties. Several studies implementing ocular and systemic application of these compounds show potential in becoming adjuvant treatment strategies for improving quality of life while also managing ocular surface disease processes.

Pharmacological Potentiality of Bioactive Flavonoid against Ketamine Induced Cell Death of PC 12 Cell Lines: An In Vitro Study

During the past few years, there has been exponential growth in the field of ethnopharmacology in the treatment of different human ailments, including neurological disorders. In our previous study, we isolated, characterized, and reported a novel bioactive compound with therapeutic efficacy in vivo, which was used in the current study. This study was designed to investigate the pharmacological effect and therapeutic mechanism of the natural plant compound 3-(3,4-dimethoxy phenyl)-1-(4-methoxy phenyl)prop-2-en-1-one against ketamine-induced toxicity in PC 12 cell lines. Cell death was induced in PC 12 cell lines by incubating with ketamine, and the protection offered by the compound at different concentrations was studied during pretreatment. The therapeutic efficacy was screened through MTT assay, LDH assay, DCF-DA assay, clonogenic assay, RT-PCR, and densitometric analysis. The bioactive compound caused a significant elevation in cell viability up to approximately 80%, down-regulation of cell damage, reduction in free radical damage caused by intracellular reactive oxygen species, and up-regulation of cell survival ability, which was dysregulated during ketamine induction. In addition, RT-PCR analysis of DOPA-related genes suggests that the compound exerted significant inhibition in the expression of these genes, which were overexpressed during ketamine induction. The current findings provide new insight into the neuroprotective mediation of bioactive factors as a prospective therapy for neurological disorders.

Tangeretin as an adjuvant and chemotherapeutic sensitizer against various types of cancers: a comparative overview

OBJECTIVES

Cancer is a leading cause of disabling morbidities and death worldwide. Although there are various strategies for the management of cancer, the severe adverse effects negatively impact the patient's quality of life. In addition, the development of resistance limits the efficacy of many chemotherapeutics. Many natural agents are capable of reducing the adverse effects associated with chemotherapy and improving the therapeutic outcome. Tangeretin, a polymethoxy flavone, is one of the promising natural anticancer agents.

KEY FINDINGS

Tangeretin not only targets various malignancies but also synergizes chemotherapeutic agents and reverses cancer resistance. Hence, the application of tangeretin as an adjuvant in cancer chemotherapy would be a promising strategy.

SUMMARY

This work critically highlighted the proposed anticancer activity of tangeretin and discussed its potential combination with various chemotherapeutic agents. Additionally, it shed light on tangeretin chemical derivatives with improved pharmacokinetic and pharmacodynamic activity. Finally, this review described flavonoid biosynthetic pathways and how bioengineering can be employed to enhance the production yield of tangeretin. Thus, this work paves the way for the rational clinical utilization of tangeretin as a safe and effective adjuvant in chemotherapeutic protocols.

Therapeutic Implications of a Polymethoxylated Flavone, Tangeretin, in the Management of Cancer via Modulation of Different Molecular Pathways

Chemotherapeutics can induce oxidative stress, inflammation, apoptosis, mitochondrial dysfunction, and abnormalities in neurotransmitter metabolism leading to toxicity. Because there have been no therapeutic strategies developed to target inflammation and oxidative stress, there is a continuing need for new and improved therapy. As a result, there has been increasing interest in complementary and alternative medicine with anticancer potential. Studies have shown that the antioxidant activities and anti-inflammatory effects of citrus fruits are promising natural phytochemicals in the development of new anticancer agents. Tangeretin is a naturally polymethoxylated flavone compound extracted from the citrus peel that has shown significant intestinal absorption and adequate bioavailability, with the added benefit of promoting longevity. In addition, tangeretin is known to exhibit considerable selective toxicity to many types of cancer cell proliferation such as ovarian, brain, blood, and skin cancer. Evidence indicates that tangeretin acts through several mechanisms including growth inhibition, induction of apoptosis, autophagy, antiangiogenesis, and estrogenic-like effects. Furthermore, tangeretin works through mitigating levels of inflammatory mediators in the immune system. Using tangeretin in combination with clinically applied anticancer drugs could be a good strategy for increasing the efficiency of these agents and protecting noncancerous cells from damage caused by chemotherapy. The purpose of this review is to highlight the protective effects of a novel natural product, tangeretin against chemotherapeutic-induced toxicity. The development of chemoprevention strategies can lead to significant health care improvement in cancer survivors. Thus, study outcomes may attract more investigators to conduct tangeretin-related research and find out potentially significant impacts on health care of cancer patients and decreased health problems associated with chemotherapeutics-induced toxicity.

The biological fate and bioefficacy of citrus flavonoids: bioavailability, biotransformation, and delivery systems

Citrus fruits are among the most popularly consumed fruits worldwide, including oranges, grapefruits, pomelos and lemons. Citrus flavonoids such as hesperidin, naringin and nobiletin have shown an array of health benefits in cell, animal and clinical studies, including antioxidative, anti-inflammatory, neuroprotective, anticancer, and anti-obesity activities. Citrus flavonoids have limited bioavailability after oral administration, leaving the major part unabsorbed and persisted in the colon. Recent studies have highlighted the important role of the gut microbiota and in vivo biotransformation on the bioactivity of citrus flavonoids. This article discusses the biological fate of citrus flavonoids from the viewpoint of their absorption, distribution, metabolism and excretion in vivo. Many delivery systems have been designed to enhance the oral bioavailability of citrus flavonoids, such as emulsions, self-emulsifying systems, nanoparticles and solid dispersions. The ultimate goal of these delivery systems is to enhance the bioefficacy of citrus flavonoids. Several studies have found that the increased bioavailability leads to enhanced bioefficacy of citrus flavonoids in specific animal models. Regarding the complex dynamics of citrus flavonoids and gut microbiota, the bioavailability-bioactivity relationship is an interesting but under-discussed area. Comprehensively understanding the biological fate and bioefficacy of citrus flavonoids would be helpful to develop functional foods with better health benefits.

[Search for Neuroprotective Compounds -From 4-Methycatechol to Citrus Compounds]

In the 1980s, the authors developed the enzyme immunoassay (EIA) system for mouse nerve growth factor (NGF) to clarify its important physiological roles. Our EIA system was a new and powerful tool for measurement of extremely low levels of NGF in vitro and in vivo, and it contributed to investigation into the regulatory mechanism of NGF synthesis. After that, we demonstrated that the compounds with a low molecular weight, such as 4-methylcatechol, which elicit stimulatory activity toward NGF synthesis, were useful and practical for therapeutic purposes; as NGF has potent activity on neuronal degeneration in both the central nervous system (CNS) and the peripheral nervous system. Since 2008, we have been searching for and isolating neuroprotective component(s) from citrus peels. As a result, our study revealed that 1) 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF) has neuroprotective ability in the CNS by inducing brain-derived neurotrophic factor (BDNF) and by suppressing inflammation; 2) auraptene (AUR) also has neuroprotective ability in the CNS by suppressing inflammation and by probably inducing neurotrophic factor(s). As the content of AUR in the peels of Kawachi Bankan is exceptionally high, 1) we found this peel powder to exert neuroprotective effects in the brain of various pathological model mice; 2) some of the AUR transited from the peel to the juice during the squeezing process to obtain the juice. Therefore, K. Bankan juice, which is enriched in AUR by adding peel paste to the raw juice, was shown to be practical for suppression of cognitive dysfunction of aged healthy volunteers.

Isolation and Characterization of Neuroprotective Components from Citrus Peel and Their Application as Functional Food

The elderly experience numerous physiological alterations. In the brain, aging causes degeneration or loss of distinct populations of neurons, resulting in declining cognitive function, locomotor capability, etc. The pathogenic factors of such neurodegeneration are oxidative stress, mitochondrial dysfunction, inflammation, reduced energy homeostatis, decreased levels of neurotrophic factor, etc. On the other hand, numerous studies have investigated various biologically active substances in fruit and vegetables. We focused on the peel of citrus fruit to search for neuroprotective components and found that: 1) 3,5,6,7,8,3',4'-heptamethoxyflavone (HMF) and auraptene (AUR) in the peel of Kawachi Bankan (Citrus kawachiensis) exert neuroprotective effects; 2) both HMF and AUR can pass through the blood-brain barrier, suggesting that they act directly in the brain; 3) the content of AUR in the peel of K. Bankan was exceptionally high, and consequently the oral administration of the dried peel powder of K. Bankan exerts neuroprotective effects; and 4) intake of K. Bankan juice, which was enriched in AUR by adding peel paste to the raw juice, contributed to the prevention of cognitive dysfunction in aged healthy volunteers. This review summarizes our studies in terms of the isolation/characterization of HMF and AUR in K. Bankan peel, analysis of their actions in the brain, mechanisms of their actions, and trials to develop food that retains their functions.

Beneficial Effects of Citrus-Derived Polymethoxylated Flavones for Central Nervous System Disorders

The number of patients with central nervous system disorders is increasing. Despite diligent laboratory and clinical research over the past 30 years, most pharmacologic options for the prevention and long-term treatment of central nervous system disorders and neurodegenerative disorders have been unsuccessful. Therefore, the development of drugs and/or functional foods to prevent the onset of neurodegenerative disorders is highly expected. Several reports have shown that polymethoxylated flavones (PMFs) derived from citrus fruit, such as nobiletin, tangeretin, and 3,3',4',5,6,7,8-heptamethoxyflavone, are promising molecules for the prevention of neurodegenerative and neurological disorders. In various animal models, PMFs have been shown to have a neuroprotective effect and improve cognitive dysfunction with regard to neurological disorders by exerting favorable effects against their pathological features, including oxidative stress, neuroinflammation, neurodegeneration, and synaptic dysfunction as well as its related mechanisms. In this review, we describe the profitable and ameliorating effects of citrus-derived PMFs on cognitive impairment and neural dysfunction in various rat and murine models or in several models of central nervous system disorders and identify their mechanisms of action.

Important Flavonoids and Their Role as a Therapeutic Agent

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

The Aryl Hydrocarbon Receptor: A Mediator and Potential Therapeutic Target for Ocular and Non-Ocular Neurodegenerative Diseases

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor, which senses environmental, dietary or metabolic signals to mount a transcriptional response, vital in health and disease. As environmental stimuli and metabolic products have been shown to impact the central nervous system (CNS), a burgeoning area of research has been on the role of the AHR in ocular and non-ocular neurodegenerative diseases. Herein, we summarize our current knowledge, of AHR-controlled cellular processes and their impact on regulating pathobiology of select ocular and neurodegenerative diseases. We catalogue animal models generated to study the role of the AHR in tissue homeostasis and disease pathogenesis. Finally, we discuss the potential of targeting the AHR pathway as a therapeutic strategy, in the context of the maladies of the eye and brain.

Flavonoids with inhibitory activity against SARS-CoV-2 3CLpro

Coronavirus disease 2019 (COVID-19) has been a pandemic disease of which the termination is not yet predictable. Currently, researches to develop vaccines and treatments is going on globally to cope with this disastrous disease. Main protease (3CLpro) from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is one of the good targets to find antiviral agents before vaccines are available. Some flavonoids are known to inhibit 3CLpro from SARS-CoV which causes SARS. Since their sequence identity is 96%, a similar approach was performed with a flavonoid library. Baicalin, herbacetin, and pectolinarin have been discovered to block the proteolytic activity of SARS-CoV-2 3CLpro. An in silico docking study showed that the binding modes of herbacetin and pectolinarin are similar to those obtained from the catalytic domain of SARS-CoV 3CLpro. However, their binding affinities are different due to the usage of whole SARS-CoV-2 3CLpro in this study. Baicalin showed an effective inhibitory activity against SARS-CoV-2 3CLpro and its docking mode is different from those of herbacetin and pectolinarin. This study suggests important scaffolds to design 3CLpro inhibitors to develop antiviral agents or health-foods and dietary supplements to cope with SARS-CoV-2.

Synergistic therapy with tangeretin and 5-fluorouracil accelerates the ROS/JNK mediated apoptotic pathway in human colorectal cancer cell

Synergistic therapy is emerging as a promising strategy for improving the chemotherapeutic efficacy of anticancer drugs. Addition of adjuvants with standard anticancer drugs has shown successful reduction of adverse side effects. The synthetic drug 5-Fluorouracil (5-FU) shows several side effects upon prolonged chemotherapy, thereby restricting its long-term clinical application. Several studies have reported anticancer potential and anti-inflammatory activity of tangeretin (TAN) towards mammalian cells. Therefore, we investigate whether the combination of TAN with 5-FU increases their anticancer potential against colorectal cancer. In this study, we examined the synergistic activity of TAN and 5-FU on the viability of several human cancer and normal cells. Several possible mechanistic pathways were screened, and found that co-exposure of TAN and 5-FU accelerates oxidative-stress and increases endogenous-ROS generation, which sequentially triggers the DNA damage response and activates the apoptotic pathway, by down-regulating autophagy and DNA repair system in HCT-116 cells. TAN and 5-FU co-treatment also remarkably reduces the mitochondrial membrane potential, and sequentially decreases ATPase activity. Collectively, results indicate that combination of TAN and 5-FU significantly accelerates apoptosis via JNK mediated pathway. To our knowledge gained from literature, this study is the first to describe synergistic activity of TAN and 5-FU against colorectal cancer cells.

An evaluation of the genotoxicity and subchronic toxicity of the peel extract of Ponkan cultivar 'Ohta ponkan' (Citrus reticulata Blanco) that is rich in nobiletin and tangeretin with anti-dementia activity

Nobiletin and tangeretin are major components of polymethoxylated flavones in the peels of citrus fruits such as Citrus reticulata. Because nobiletin and tangeretin have attracted attention due to their beneficial health properties, citrus peel extracts, in which they are concentrated, have the potential to serve as a functional food ingredient to prevent diseases. In this study, a series of toxicological studies on the peel extract of Ponkan cultivar 'Ohta ponkan' (Citrus reticulata Blanco), was conducted. No mutagenic activity was observed in a bacterial reverse mutation test, whereas chromosomal aberrations were induced in an in vitro mammalian chromosomal aberration test. No genotoxicity was observed in an in vivo mammalian micronucleus test. In a 90-day study at daily doses of 54, 180, or 540 mg/kg body weight (bw)/day, hyaline droplet nephropathy, which specifically occurs in adult male rats, was observed in males of 540 mg/kg bw/day group. No other adverse effects were observed in the 90-day study. The no adverse effect level in the 90-day study was considered to be 540 mg/kg bw/day for female rats and less than 540 mg/kg bw/day for male rats.

Phenolic composition, antioxidant potential and health benefits of citrus peel

Citrus peel (CP) forms around 40-50% of the total fruit mass but is generally thought to be a waste. However, it is a substantial source of naturally occurring health enhancing compounds, particularly phenolic compounds and carotenoids. Phenolic compounds in CP mainly comprise phenolic acids (primarily caffeic, p-coumaric, ferulic and sinapic acid), flavanones (generally naringin and hesperidin) and polymethoxylated flavones (notably nobiletin and tangeretin). It has also been noted that CP's contain more amounts of these compounds than corresponding edible parts of the fruits. Phenolic compounds present in CP act as antioxidants (by either donation of protons or electrons) and protect cells against free radical damage as well as help in reducing the risk of many chronic diseases. Owing to the more abundance of polyphenols in CP's, their antioxidant activity is also higher than other edible fruit parts. Therefore, peels from citrus fruits can be used as sources of functional compounds and preservatives for the development of newer food products, that are not only safe but also have health-promoting activities. The present review provides in-depth knowledge about the phenolic composition, antioxidant potential and health benefits of CP.

Beneficial Effects of Dark Chocolate for Episodic Memory in Healthy Young Adults: A Parallel-Groups Acute Intervention with a White Chocolate Control

There is good evidence that cocoa flavonoids can acutely improve cognitive function in humans, possibly via mechanisms such as increased cerebral blood flow. To date, much of the evidence is based on measures of executive function with extracts and cocoa-based interventions with a high flavonoid content. The aim of the present study was to explore whether benefits to episodic verbal memory and mood are observed two hours post consumption of a commercially available dark chocolate (DC) bar relative to a 35 g white chocolate bar (WC). Ninety-eight healthy young adults (n = 57 females) aged 18–24 years consumed either a 35 g DC bar or a calorie-matched low flavonoid WC bar. Verbal episodic memory and mood were assessed pre consumption and 2 h post consumption. An ANOVA analysis showed that the DC was associated with better verbal memory performance for several outcome measures of the Rey Auditory Verbal Learning Test relative to the WC, however, there were no effects on mood. These findings lend support to the notion that everyday available portions of dark chocolate can confer benefits to the brain in healthy consumers.