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

The roles of dietary polyphenols at crosstalk between type 2 diabetes and Alzheimer's disease in ameliorating oxidative stress and mitochondrial dysfunction via PI3K/Akt signaling pathways

Alzheimer's disease (AD) is a fatal neurodegenerative disease in which senile plaques and neurofibrillary tangles are crucially involved in its physiological and pathophysiological processes. Growing animal and clinical studies have suggested that AD is also comorbid with some metabolic diseases, including type 2 diabetes mellitus (T2DM), and therefore, it is often considered brain diabetes. AD and T2DM share multiple molecular and biochemical mechanisms, including impaired insulin signaling, oxidative stress, gut microbiota dysbiosis, and mitochondrial dysfunction. In this review article, we mainly introduce oxidative stress and mitochondrial dysfunction and explain their role and the underlying molecular mechanism in T2DM and AD pathogenesis; then, according to the current literature, we comprehensively evaluate the possibility of regulating oxidative homeostasis and mitochondrial function as therapeutics against AD. Furthermore, considering dietary polyphenols' antioxidative and antidiabetic properties, the strategies for applying them as potential therapeutical interventions in patients with AD symptoms are assessed.

5,7-dihydroxy-3',4',5'-trimethoxyflavone mitigates lead induced neurotoxicity in rats via its chelating, antioxidant, anti-inflammatory and monoaminergic properties

Chronic exposure to lead (Pb) induces neurodegenerative changes in animals and humans. Drugs with strong antioxidant properties are effective against Pb-mediated neurotoxicity. In a prior study, we identified 5,7-dihydroxy-3',4',5'-trimethoxyflavone (TMF) from Ocimum basilicum L. leaves as a potent antioxidant and neuroprotective compound. This research explores TMF's neuroprotective effects against Pb-induced brain toxicity in rats to establish it as a therapeutic agent. Rats received lead acetate (100 mg/kg, orally, once daily) for 30 days to induce brain injury, followed by TMF treatment (5 and 10 mg/kg, oral, once daily) 30 min later. Cognitive and motor functions were assessed using Morris Water Maze and horizontal bar tests. Lead, monoamine oxidase (MAO) A and B enzymes, reduced glutathione (GSH), thiobarbituric acid reactive species (TBARS), Tumor necrosis factor-alpha (TNF-α), and IL-6 levels were measured in the hippocampus and cerebellum. Pb exposure impaired cognitive and motor functions, increased Pb, TBARS, TNF-α, and IL-6 levels, and compromised MAO A & B and GSH levels. TMF reversed Pb-induced memory and motor deficits and normalized biochemical anomalies. TMF's neuroprotective effects against lead involve chelating, antioxidant, anti-inflammatory, and monoaminergic properties, suggesting its potential as a treatment for metal-induced brain injury.

Recent advances in the therapeutic potential of nobiletin against respiratory diseases

BACKGROUND

Nobiletin is a natural polymethoxylated flavonoid widely present in citrus fruit peels. It has been demonstrated to exert the effects of anti-tumor, anti-inflammation, anti-oxidative, anti-apoptotic and improve cardiovascular function. Increasing evidences suggest that nobiletin plays an important role in respiratory diseases (RDs) treatment.

OBJECTIVE

This review aimed to investigate the therapeutic potential of nobiletin against RDs, such as lung cancer, COPD, pulmonary fibrosis, asthma, pulmonary infection, acute lung injury, coronavirus disease 2019, and pulmonary arterial hypertension.

METHODS

We retrieved extensive literature of relevant literatures in English until June 26, 2023 from the database of PubMed, Web of Science, and Scopus databases. The keywords of "nobiletin and lung", "nobiletin and respiratory disease", "nobiletin and chronic respiratory diseases", "nobiletin and metabolites", "nobiletin and pharmacokinetics", "nobiletin and toxicity" were searched in pairs. A total of 298 literatures were retrieved from the above database. After excluding the duplicates and reviews, 53 were included in the current review.

RESULTS

We found that the therapeutic mechanisms are based on different signaling pathways. Firstly, nobiletin inhibited the proliferation and suppressed the invasion and migration of cancer cells by regulating the related pathway or key target, like Bcl-2, PD-L1, PARP, and Akt/GSK3β/β-catenin in lung cancer treatment. Secondly, nobiletin treats COPD and ALI by targeting classical signaling pathway mediating inflammation. Besides, the available findings show that nobiletin exerts the effect of PF treatment via regulating mTOR pathway.

CONCLUSIONS

With the wide range of pharmacological activities, high efficiency and low toxicity, nobiletin can be used as a potential agent for preventing and treating RDs. These findings will contribute to further research on the molecular mechanisms of nobiletin and facilitate in-depth studies on nobiletin at both preclinical and clinical levels for the treatment of RDs.

Integrated HS-GC-IMS and UPLC-Q-Orbitrap HRMS-based metabolomics revealed the characteristics and differential volatile and nonvolatile metabolites of different citrus peels

Citrus is an important genus in the Rutaceae family, and citrus peels can be used in both food and herbal medicine. However, the bulk of citrus peels are discarded as waste by the fruit processing industry, causing environmental pollution. This study aimed to provide guidelines for the rational and effective use of citrus peels by elucidating the volatile and nonvolatile metabolites within them using metabolomics based on headspace-gas chromatography-ion mobility spectrometry and ultra-high-performance liquid chromatography-Q-Orbitrap high-resolution mass spectrometry. In addition, the antioxidant activities of the citrus peels were evaluated using DPPH radical scavenging, ABTS radical scavenging, and ferric reducing antioxidant power. In total, 103 volatile and 53 nonvolatile metabolites were identified and characterized. Alcohols, aldehydes, and terpenes constituted 87.36% of the volatile metabolites, while flavonoids and carboxylic acids accounted for 85.46% of the nonvolatile metabolites. Furthermore, (Z)-2-penten-1-ol, L-pipecolinic acid, and limonin were identified as characteristic components of Citrus reticulata Blanco cv. Ponkan (PK), C. reticulata 'Unshiu' (CLU), and C. reticulata 'Wo Gan' (WG), respectively. Principal component analysis and partial least squares discriminant analysis indicated that C. reticulata Blanco 'Chun Jian' (CJ), PK, CLU, and C. reticulata 'Dahongpao' (DHP) were clustered together. DHP is a traditional Chinese medicine documented in the Chinese Pharmacopoeia, suggesting that the chemical compositions of CJ, PK, and CLU may also have medicinal values similar to those of DHP. Moreover, DHP, PK, C. reticulata 'Ai Yuan 38'(AY38), CJ, C. reticulata 'Gan Ping'(GP), and C. reticulata 'Qing Jian'(QJ) displayed better antioxidant activities, recommending their use as additives in cosmetics and food. Correlation analysis suggested that some polyphenols including tangeritin, nobiletin, skullcapflavone II, genistein, caffeic acid, and isokaempferide were potential antioxidant compounds in citrus peel. The results of this study deepen our understanding of the differences in metabolites and antioxidant activities of different citrus peel varieties and ultimately provide guidance for the full and rational use of citrus peels.

Neurotrophic Natural Products

Neurotrophins (NGF, BDNF, NT3, NT4) can decrease cell death, induce differentiation, as well as sustain the structure and function of neurons, which make them promising therapeutic agents for the treatment of neurodegenerative disorders. However, neurotrophins have not been very effective in clinical trials mostly because they cannot pass through the blood-brain barrier owing to being high-molecular-weight proteins. Thus, neurotrophin-mimic small molecules, which stimulate the synthesis of endogenous neurotrophins or enhance neurotrophic actions, may serve as promising alternatives to neurotrophins. Small-molecular-weight natural products, which have been used in dietary functional foods or in traditional medicines over the course of human history, have a great potential for the development of new therapeutic agents against neurodegenerative diseases such as Alzheimer's disease. In this contribution, a variety of natural products possessing neurotrophic properties such as neurogenesis, neurite outgrowth promotion (neuritogenesis), and neuroprotection are described, and a focus is made on the chemistry and biology of several neurotrophic natural products.

Analysis of cerebrospinal fluid metabolites affected by WenDanTang based on ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry

WenDanTang (WDT) is a Chinese herbal formula used to treat various diseases, including neurodegenerative diseases. However, the neuroprotective metabolic pathways and the components involved in this process are not fully understood. In this study, we examined the neuroprotective metabolic pathways of WDT in rat brains using cerebrospinal fluid metabolomics and ultra-high-performance liquid chromatography-high-resolution mass spectrometry. Twelve rats were randomly divided into a WDT (administrated with WDT solution) and a control group. The ultra-high-performance liquid chromatography technique was used to explore the components of the WDT solution and cerebrospinal fluid, and secondary mass spectra of cerebrospinal fluid were used to identify possible brain-incorporating components after WDT. The results of the differential metabolism analysis showed that eight metabolites were typically altered (all p < 0.05). By comparing the secondary mass spectra of the cerebrospinal fluid of rats and WDT solution, two possible brain-incorporating components of WDT, stachydrine and α-methoxyphenylacetic acid, were identified. The data also suggested that WDT affects nucleotide metabolism, glutathione metabolism, and B-vitamin metabolic pathways, the central differential metabolic pathways. These data suggest that WDT protects neurons through its active components, such as stachydrine, and regulates biochemical metabolism to affect the brain's energy metabolism and antioxidant capacity.

Tangeretin's Anti-apoptotic Signaling Mechanisms in Oral Cancer Cells: In Vitro Anti-cancer Activity

Introduction Citrus fruit peels contain Tangeretin, a natural chemical flavonoid that reinforces plant cell walls and serves as a defense mechanism. Apoptosis, growth inhibition, anti-oxidant, anti-diabetic, and anti-cancer activities are only a few of its many qualities. Tangeretin's principal function is to shield healthy cells or tissues from the harmful effects of chemotherapy. The purpose of this study was to investigate the apoptotic activity of Tangeretin's impact on KB (oral cancer cells) cell lines. Materials and method This study employed Tangeritin, in investigating its effects on oral cancer cells. Oral cancer cells were cultured in Dulbecco's modified Eagle's medium (DMEM), with 10% fetal bovine serum at 37°C in a 5% CO2 environment. Cell viability was assessed by seeding oral cancer cells in 96-well plates, exposing them to varying Tangeritin concentrations (50 µM, 100 µM, and 200 µM) with growth inhibition of KB cell viability in 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and morphological changes in cells were observed under an inverted light microscope at 10x magnification. The results were reported as mean ± standard error mean (SEM) using one-way analysis of variance through IBM SPSS Statistics for Windows, Version 23 (Released 2015; IBM Corp., Armonk, New York, United States). Result MTT assay showed a significant reduction in KB cell viability when treated with Tangeretin. With a significant decrease in mRNA levels of the anti-apoptotic genes Bcl-2 and Bcl-xL. At 50 µM, 100 µM, and 200 µM, the levels of Bcl-2 were 0.85 ± 0.09, 0.62 ± 0.05, and 0.67 ± 0.05, respectively. Similarly, the mRNA expression of Bcl-xL was 0.82 ± 0.07 for 50 µM, 0.7 ± 0.06 for 100 µM, and 0.77 ± 0.06for 200 µM. The mRNA expression levels of Bax were 1.1 ± 0.09 for 50 µM, 1.4 ± 0.12for 100 µM, and 1.3 ± 0.11 for 200 µM, respectively. Conclusion Tangeretin showed a promising apoptotic activity in KB cells suggesting its utility as an anti-cancer compound. It prevented the growth and proliferation of cancer cells by acting on pro-apoptotic and anti-apoptotic genes. However, this conclusion is mostly based on the in vitro study. Therefore in vivo animal studies were needed to confirm the findings.

The miR-34b-5p-negative target Gnai2 aggravates fluorine combined with aluminum-induced apoptosis of rat offspring hippocampal neurons and NG108-15 cells

It is known that fluorine and aluminum are commonly found in the environment and that long-term overexposure can adversely affect the organism's nervous system, damaging the structure and function of brain tissue. Our previous study showed that fluorine combined with aluminum (FA) could trigger apoptosis in vitro and cause spatial learning and memory impairment and differentially expressed miRNAs (including miR-34b-5p) in the hippocampi in vivo. However, the detailed mechanism is unclear. Learning memory damage is implicated in excessive hippocampal neuron apoptosis, and miR-34b-5p participates in regulating the hippocampal neuron apoptosis. Thus, in the current research, Sprague-Dawley (SD) rats were subjected to FA, and NG108-15 control cells and NG108-15 cells pretransfected with miR-34b-5p agomir or antagomir were exposed to FA. We found that FA triggered apoptosis of rat hippocampal neurons and NG108-15 cells, increased miR-34b-5p expression, and decreased Gnai2, PKA, ERK and CREB expression. Inhibition of miR-34b-5p alleviated FA-induced NG108-15 cell apoptosis and further increased Gnai2, PKA, ERK, and CREB expression, and vice versa. Furthermore, miR-34b-5p modulated the level of Gnai2 by directly targeting its 3'-untranslated region (UTR), as verified through the dual Luciferase reporter assay. These outcomes suggested that miR-34b-5p participated in FA-induced neuronal apoptosis by targeting Gnai2 negatively, thereby inhibiting the PKA/ERK/CREB signaling pathway.

Nobiletin protects retinal ganglion cells in models of ocular hypertension in vivo and hypoxia in vitro

Glaucoma, a common cause of blindness, is characterized by the progressive loss of retinal ganglion cells (RGCs). Growing evidence suggests that nobiletin (NOB) is a promising neuroprotective drug; however, its effects on glaucomatous neurodegeneration remain unknown. Using rat models of microbead occlusion in vivo and primary RGCs model of hypoxia in vitro, we first demonstrate that NOB reduces RGC apoptosis by a TUNEL assay, Hoechst 33342 staining and FluoroGold (FG) retrograde labeling. This effect does not depend on intraocular pressure (IOP) lowering. Additionally, NOB partially restored the functional and structural damage of inner retinas, attenuated Müller glial activation and oxidative stress caused by ocular hypertension. At 2 weeks after IOP elevation, NOB further enhanced Nrf2/HO-1 pathway in RGCs to withstand the cumulative damage of ocular hypertension. With the administration of HO-1 inhibitor tin-protoporphyrin IX (SnPP), the protective effect of NOB was attenuated. Overall, these results indicate that NOB exerts an outstanding neuroprotective effect on RGCs of glaucomatous neurodegeneration. Besides, interventions to enhance activation of Nrf2/HO-1 pathway can slow the loss of RGCs and are viable therapies for glaucoma.

Activation of Extracellular Signal-Regulated Kinase 2 and cAMP Response Element-Binding Protein in Cultured Neurons by the Macrocyclic Ellagitannin Oenothein B

(1) Background: The findings of our recent in vivo study indicated that the oral administration of oenothein B, a unique macrocyclic ellagitannin, activated extracellular signal-regulated kinase (ERK) 2 and cAMP response element-binding protein (CREB) in the mouse brain. A large hydrophilic oenothein B is unable to reach the brain, suggesting that any metabolite(s) of oenothein B might function in the brain. (2) Results: The addition of oenothein B to the culture medium of rat cortical neurons induced the prompt and significant activation of ERK2 and CREB. (3) Conclusions: The activation of ERK2 and CREB is crucial for synaptic transmission and learning/memory formation in the brain. The present results suggest oenothein B exerts neurotrophic/neuroprotective effects in the brain through the modulation of neuronal signaling pathways, if it reaches the brain.

Perilla frutescens seed oil combined with Anredera cordifolia leaf powder attenuates age-related cognitive decline by reducing serum triglyceride and glucose levels in healthy elderly Japanese individuals: a possible supplement for brain health

We have shown that Anredera cordifolia extract improves learning and memory in a senescence-accelerated mouse model, and that α-linolenic acid (ALA)-rich Perilla frutescens seed oil (PO) improves brain function in healthy Japanese adults and elderly individuals. Herein, we present a 12-month, randomised, double-blind, parallel-armed intervention trial examining the effects of PO supplementation alone or in combination with A. cordifolia leaf powder on brain function in healthy elderly Japanese individuals. Participants were randomly divided into two groups: the PO group received 1.47 mL PO (0.88 g ALA) daily via soft gelatine capsules, and the POAC group received 1.47 mL PO and 1.12 g A. cordifolia leaf powder (1.46 mg vitexin and 1.12 mg adenosine) daily. After 12 months of intervention, the POAC group showed generally higher cognitive index scores than the PO group. The beneficial effects of combined supplementation on cognitive function were associated with increased ALA and eicosapentaenoic acid levels in red blood cell plasma membranes, increased serum biological antioxidant potential, and decreased serum triglyceride, glucose, and N-(epsilon)-carboxymethyl-lysine (CML), an advanced glycation end-product and biochemical marker of oxidative stress levels. The effects of combined supplementation on cognitive function also showed a significant negative correlation with serum CML levels after 12 months of intervention. Our findings suggest that combined long-term supplementation with PO and A. cordifolia more effectively ameliorates age-related cognitive decline than PO alone. These findings may serve as a basis for the development of new supplements for brain health. Clinical Trial Registry, UMIN000040863.

Flavonoid Nobiletin Attenuates Cyclophosphamide-Induced Cystitis in Mice through Mechanisms That Involve Inhibition of IL-1β Induced Connexin 43 Upregulation and Gap Junction Communication in Urothelial Cells

Bladder inflammatory diseases cause various urinary symptoms, such as urinary frequency and painful urination, that impair quality of life. In this study, we used a mouse model of cyclophosphamide (CYP)-induced bladder inflammation and immortalized human urothelial (TRT-HU1) cells to explore the preventive potential of nobiletin (NOB), a polymethoxylated flavone enriched in citrus fruit peel, and investigate its mechanism of action in the bladder. Prophylaxis with PMF90 (60% NOB) attenuated the development of bladder inflammation and urinary symptoms in CYP-treated mice. PMF90 also reduced the upregulation of connexin 43 (Cx43), a major component of gap junction channels, in the bladder mucosa of CYP-treated mice. Stimulation of TRT-HU1 cells with the pro-inflammatory cytokine IL-1β increased Cx43 mRNA and protein expression and enhanced gap junction coupling-responses that were prevented by pre-treatment with NOB. In urothelium-specific Cx43 knockout (uCx43KO) mice, macroscopic signs of bladder inflammation and changes in voiding behavior induced by CYP treatment were significantly attenuated when compared to controls. These findings indicate the participation of urothelial Cx43 in the development of bladder inflammation and urinary symptoms in CYP-treated mice and provide pre-clinical evidence for the preventive potential of NOB through its anti-inflammatory effects on IL-1β signaling and urothelial Cx43 expression.

A Narrative Review of the Effects of Citrus Peels and Extracts on Human Brain Health and Metabolism

As life expectancy increases, age-associated diseases such as Alzheimer's disease (AD) become a major health problem. The onset of AD involves neurological dysfunction due to amyloid-β accumulation, tau hyperphosphorylation, oxidative stress, and neuroinflammation in the brain. In addition, lifestyle-related diseases-such as dyslipidemia, diabetes, obesity, and vascular dysfunction-increase the risk of developing dementia. The world population ages, prompting the development of new strategies to maintain brain health and prevent the onset of dementia in older and preclinical patients. Citrus fruits are abundant polymethoxylated flavone and flavanone sources. Preclinical studies reported that these compounds have neuroprotective effects in models of dementia such as AD. Interestingly, clinical and epidemiological studies appear to support preclinical evidence and show improved cognitive function and reduced associated disease risk in healthy individuals and/or patients. This review summarizes the recent evidence of the beneficial effects of citrus peels and extracts on human cognition and related functions.

Phlomis fruticosa L. exerts in vitro antineurodegenerative and antioxidant activities and induces prooxidant effect in glioblastoma cell line

Despite the significant advances in drug development we are witnessing the inability of health systems to combat both neurodegenerative diseases and cancers, especially glioblastoma. Hence, natural products are comprehensively studied in order to provide novel therapeutic options. This study aimed to explore anti-neurodegenerative and anti-glioblastoma potential of extract of Phlomis fruticosa L. using in vitro model systems. It was found that the methanol extract of P. fruticosa was able to efficiently reduce activities of enzymes linked to neurodegenerative disease including acetylcholinesterase, butyrylcholinesterase and tyrosinase. Furthermore, P. fruticosa extract has shown excellent antioxidant potential, as evidenced by six different methods. Analysis of cytotoxic effect of P. fruticosa extract on A172 glioblastoma cell line revealed that the concentration of the extract necessary for 50 % inhibition of A172 growth (IC₅₀) was 710 μg/mL. The extract did not induce changes in proliferation and morphology of A172 glioblastoma cells. On the other side, production of ROS was increased in A172 cells treated with the extract. Observed cytotoxic effect of P. fruticosa extract might be based on increase in ROS generation upon treatment. Quantitative chemical analysis revealed the presence of twelve different polyphenols with the cis 3-O-caffeoylquinic acid being the most abundant. This study provided scientific evidence for further exploration of P. fruticosa as a promising natural anti-neurodegenerative therapeutic option.

Phytotherapeutic Approaches to the Prevention of Age-Related Changes and the Extension of Active Longevity

Maintaining quality of life with an increase in life expectancy is considered one of the global problems of our time. This review explores the possibility of using natural plant compounds with antioxidant, anti-inflammatory, anti-glycation, and anti-neurodegenerative properties to slow down the onset of age-related changes. Age-related changes such as a decrease in mental abilities, the development of inflammatory processes, and increased risk of developing type 2 diabetes have a significant impact on maintaining quality of life. Herbal preparations can play an essential role in preventing and treating neurodegenerative diseases that accompany age-related changes, including Alzheimer’s and Parkinson’s diseases. Medicinal plants have known sedative, muscle relaxant, neuroprotective, nootropic, and antiparkinsonian properties. The secondary metabolites, mainly polyphenolic compounds, are valuable substances for the development of new anti-inflammatory and hypoglycemic agents. Understanding how mixtures of plants and their biologically active substances work together to achieve a specific biological effect can help develop targeted drugs to prevent diseases associated with aging and age-related changes. Understanding the mechanisms of the biological activity of plant complexes and mixtures determines the prospects for using metabolomic and biochemical methods to prolong active longevity.

The Effects of Matcha and Decaffeinated Matcha on Learning, Memory and Proteomics of Hippocampus in Senescence-Accelerated (SAMP8) Mice

Although the benefits of the consumption of green tea and its components, including catechins and theanine, regarding aging, memory impairment and age-related cognitive decline have been investigated in senescence-accelerated prone mice (SAMP8), studies that simultaneously measured the kinds of proteins that vary in their expression due to the administration of green tea and its extracts were not found. In this study, the effect of dietary and decaffeinated matcha on protein expression in the hippocampus of SAMP 8 was examined comprehensively, mainly using proteomics. Although improvements in memory and the hair appearance of the back coat were limited upon administering the samples, the following regulations were observed in some of the proteins involved in neuron degeneration, Parkinson’s and Alzheimer’s diseases, synapse transmission and nerve cell plasticity, antioxidation, glutamate transport and metabolism, GABA (γ-amino butyric acid) formation and transport and excitatory amino acid transporters: proteins downregulated upon sample intake (p < 0.05): brain acid-soluble protein 1, microtubule-associated protein tau, synapsin-2, sodium- and chloride-dependent GABA transporter; proteins that tended to decrease upon sample intake (0.05 < p < 0.10): Parkinson’s disease (autosomal recessive and early-onset) 7 and synapsin-1; proteins upregulated upon sample intake (p > 0.95): glutathione S-transferase Mu 1, tubulin alpha-1A chain, dynamin-2, calcium/calmodulin-dependent protein kinase type II subunit gamma and tyrosine 3-monooxygenase/tyrosine 5-monooxygenase activation protein epsilon polypeptide; proteins that tended to increase upon sample intake (0.95 > p > 0.90): glutathione S-transferase Mu7 and soluble carrier family 1 (glial high-affinity glutamate transporter); proteins that tended to decrease: sodium- and chloride-dependent GABA transporter 3. These results indicate that matcha and decaffeinated matcha could reduce aging and cognitive impairment by regulating the expression of these proteins. Furthermore, these proteins could be used as markers for the evaluation of food and its available components for reducing aging and cognitive impairment.

Nobiletin as a chemopreventive natural product against cancer, a comprehensive review

As a leading cause of death, second only to heart disease, cancer has always been one of the burning topics in medical research. When targeting multiple signal pathways in tumorigenesis chemoprevention, using natural or synthetic anti-cancer drugs is a vital strategy to reduce cancer damage. However, toxic effects, multidrug resistance (MDR) as well as cancer stem cells (CSCs) all prominently limited the clinical application of conventional anticancer drugs. With low side effects, strong biological activity, unique mechanism, and wide range of targets, natural products derived from plants are considered significant sources for new drug development. Nobiletin is one of the most attractive compounds, a unique flavonoid primarily isolated from the peel of citrus fruits. Numerous studies in vitro and in vivo have suggested that nobiletin and its derivatives possess the eminent potential to become effective cancer chemoprevention agents through various cellular and molecular levels. This article aims to comprehensively review the anticancer efficacy and specific mechanisms of nobiletin, enhancing our understanding of its chemoprevention properties and providing the latest research findings. At the end of this review, we also give some discussion and future perspectives regarding the challenges and opportunities in nobiletin efficient exploitation.

Characterization of a Caffeic Acid 8-O-Methyltransferase from Citrus and Its Function in Nobiletin Biosynthesis

Nobiletin (3',4',5,6,7,8-hexamethoxyflavone) is a polymethoxylated flavonoid specifically accumulated in citrus fruit with numerous beneficial effects to human health. In this study, a novel O-methyltransferase (CitOMT2) was isolated from three citrus varieties, Ponkan mandarin (Citrus reticulata Blanco), Nou 6 ("King mandarin" × "Mukaku-kishu"), and Satsuma mandarin (Citrus unshiu Marc.), and its functions were characterized in vitro. The gene expression results showed that CitOMT2 was highly expressed in the two nobiletin abundant varieties of Ponkan mandarin and Nou 6. However, the expression level of CitOMT2 was low in the flavedo of Satsuma mandarin, in which only a small amount of nobiletin was accumulated. Functional analysis suggested that CitOMT2 was a caffeic acid 8-O-methyltransferase, and it catalyzed the O-methylation of 7,8-dihydroxyflavone at 8-OH. As the methylation of flavone at 8-OH was required for nobiletin biosynthesis, the results presented in this study suggested that CitOMT2 was a key gene regulating nobiletin accumulation in citrus fruit.

Perilla seed oil in combination with the nobiletin-rich ponkan powder enhances cognitive function in healthy elderly Japanese individuals: Possible supplement for brain health in the elderly

Perilla (Perilla frutescens) seed oil (PO), rich in α-linolenic acid (ALA), can improve cognitive function in healthy elderly Japanese people. Here, supplements containing either PO alone or PO with nobiletin-rich...

An overview on therapeutic and medicinal potential of poly-hydroxy flavone viz. Heptamethoxyflavone, Kaempferitrin, Vitexin and Amentoflavone for management of Alzheimer's and Parkinson's diseases: a critical analysis on mechanistic insight

Neurodegenerative disorders occur when nerve cells in the brain or peripheral nervous system partial or complete fail in their functions and sometimes even die due to some injuries or aging. Neurodegenerative disorders such as Alzheimer's Disease (AD) and Parkinson's Disease (PD), have been majorly resulted due to degeneration of neurons and neuroinflammation progressively. There are many similarities that correlates both AD and PD on a cellular and sub-cellular level. Therefore, a hope for therapeutic advancement for simultaneous upgradation in both the diseases are directly depending on the discovery of common mechanism at molecular and cellular level. Recent and past evidences from scientific literature supporting the efficacy of plants flavonoids in treatment and protection of both AD and PD. Further, dietary flavones, specially Heptamethoxyflavone, Kaempferitrin, Vitexin and Amentoflavone gains recently much more attention for producing many health beneficiary effects including neuroprotection. Despite of these evidence a detailed updated overview of neuroprotective effects against both AD and PD by Heptamethoxyflavone, Kaempferitrin, Vitexin and Amentoflavone are still missing. In this context several published studies were assessed by using various online electronic search engines/databases to meet the objective from 1981 to 2021 (Approx. 224). Therefore, present review was designed to deliver the detailed description on these flavones including therapeutic benefits in AD, PD and other CNS complications with critical analysis on underlying mechanisms.

Health benefits of dietary chronobiotics: beyond resynchronizing internal clocks

The internal circadian clock in mammals drives whole-body biological activity rhythms. The clock reflects changes in external signals by controlling enzyme functions and the release of hormones involved in metabolic processes. Thus, misalignments between the circadian clock and an individual's daily schedule are recognized to be related to various metabolic diseases, such as obesity and diabetes. Although evidence has shown the existence of a complex relationship between circadian clock regulation and daily food intake, the regulatory effects of phytochemicals on the circadian clock remain unclarified. To better elucidate these relationships/effects, the circadian system components in mammals, circadian misalignment-related metabolic diseases, circadian rhythm-adjusting phytochemicals (including the heterocycles, acids, flavonoids and others) and the potential mechanisms (including the regulation of clock genes/proteins, metabolites of gut microbiota and secondary metabolites) are reviewed here. The bioactive components of functional foods discussed in this review could be considered potentially effective factors for the prevention and treatment of metabolic disorders related to circadian misalignment.