Neuroprotective effects of citrus flavonoids

Host-Guest Inclusion Systems of Morin Hydrate and Quercetin with Two Bis(β-cyclodextrin)s: Preparation, Characterization, and Antioxidant Activity

The inclusion complexation behaviour of morin hydrate (MH) and quercetin (QCT) with the two amide-bridged bis(β-cyclodextrin (β-CD))s, 1 and 2, was investigated in both solution and the solid state. The inclusion complexations were characterised by proton nuclear magnetic resonance, 2D rotating-frame Overhauser effect spectroscopy, X-ray powder diffraction, infrared spectroscopy and scanning electron microscopy. Ultraviolet titration analysis indicated that 1 and 2 form 1:1 molar stoichiometry inclusion complexes with MH and QCT, and the data obtained showed that 2 with two guests has a higher complex stability constant (KS) when compared with that of 1. Moreover, 1 and 2 were able to solubilize MH and QCT to high levels, up to ~200-fold. Furthermore, the antioxidant activity of MH, QCT and their inclusion compounds were determined by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging. Together, these results showed that the inclusion complexes exhibited a more effective antioxidant activity when compared with free MH. The satisfactory antioxidant activity and high water solubility of the bis(β-CD)s/flavonoid complexes may have potential use as healthcare products and herbal medicine.

Development of Health Products from Natural Sources

BioActive Compounds (BACs) recovered from food or food by-product matrices are useful in maintaining well being, enhancing human health, and modulating immune function to prevent or to treat chronic diseases. They are also generally seen by final consumers as safe, non-toxic and environment-friendly. Despite the complex process of production, chemical characterization, and assessment of health effects, BACs must also be manufactured in stable and bioactive ingredients to be used in pharmaceutical, food and nutraceutical industry. Generally, vegetable derivatives occur as sticky raw materials with pervasive smell and displeasing flavor. Also, they show critical water solubility and dramatic stability behavior over time, involving practical difficulties for industrial use. Therefore, the development of novel functional health products from natural sources requires the design of a suitable formulation to delivery BACs at the site of action, preserve stability during processing and storage, slow down the degradation processes, mask lousy tasting or smell, and increase the bioavailability, while maintaining the BACs functionality. The present review focuses on human health benefits, BACs composition, and innovative technologies or formulation approaches of natural ingredients from some selected foods and by-products from industrial food transformations.

Modulation of ERK1/2 and Akt Pathways Involved in the Neurotrophic Action of Caffeic Acid Alkyl Esters

Neurodegenerative diseases affect millions of human lives all over the world. The number of afflicted patients is rapidly growing, and disease-modifying agents are urgently needed. Caffeic acid, an important member of the hydroxycinnamic acid family of polyphenols, has considerable neurotrophic effects. We have previously shown how caffeate alkyl ester derivatives significantly promote survival and differentiation in neuronal cells. In this study, the mechanisms by which these ester derivatives exert their neurotrophic effects are examined. A series of eight caffeic acid esters with different alkyl chain lengths, ranging from methyl (CAF1) to dodecyl esters (CAF8), were synthesized and studied for their influence on neurotrophic signaling pathways. Caffeate esters did not induce tropomyosin-receptor kinase A (TrkA) phosphorylation, which was assessed by immunoblotting up to a concentration of 25 µM. NIH/3T3 cells overexpressing TrkA were generated to further examine phosphorylation of this receptor tyrosine kinase. None of the esters induced TrkA phosphorylation in these cells either. Assessment of the effect of caffeate derivatives on downstream neurotrophic pathways by immunoblotting showed that the most potent esters, decyl caffeate (CAF7) and dodecyl caffeate (CAF8) caused extracellular signal-regulated kinase (ERK1/2) and Akt serine threonine kinase phosphorylation in PC12 cells at 5 and 25 µM concentrations. In conclusion, this study shows that caffeate esters exert their neurotrophic action by modulation of ERK1/2 and Akt signaling pathways in neuronal cells, and further demonstrates the potential therapeutic implications of these derivatives for neurodegenerative diseases.

Neuroprotective Effect of Quercetin Against the Detrimental Effects of LPS in the Adult Mouse Brain

Chronic neuroinflammation is responsible for multiple neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Huntington's disease. Lipopolysaccharide (LPS) is an essential component of the gram-negative bacterial cell wall and acts as a potent stimulator of neuroinflammation that mediates neurodegeneration. Quercetin is a natural flavonoid that is abundantly found in fruits and vegetables and has been shown to possess multiple forms of desirable biological activity including anti-inflammatory and antioxidant properties. This study aimed to evaluate the neuroprotective effect of quercetin against the detrimental effects of LPS, such as neuroinflammation-mediated neurodegeneration and synaptic/memory dysfunction, in adult mice. LPS [0.25 mg/kg/day, intraperitoneally (I.P.) injections for 1 week]-induced glial activation causes the secretion of cytokines/chemokines and other inflammatory mediators, which further activate the mitochondrial apoptotic pathway and neuronal degeneration. Compared to LPS alone, quercetin (30 mg/kg/day, I.P.) for 2 weeks (1 week prior to the LPS and 1 week cotreated with LPS) significantly reduced activated gliosis and various inflammatory markers and prevented neuroinflammation in the cortex and hippocampus of adult mice. Furthermore, quercetin rescued the mitochondrial apoptotic pathway and neuronal degeneration by regulating Bax/Bcl2, and decreasing activated cytochrome c, caspase-3 activity and cleaving PARP-1 in the cortical and hippocampal regions of the mouse brain. The quercetin treatment significantly reversed the LPS-induced synaptic loss in the cortex and hippocampus of the adult mouse brain and improved the memory performance of the LPS-treated mice. In summary, our results demonstrate that natural flavonoids such as quercetin can be beneficial against LPS-induced neurotoxicity in adult mice.

Protective effects of citrus based mixture drinks (CBMDs) on oxidative stress and restraint stress

In the current study investigated the protective effects of citrus based mixture drinks (CBMDs) using oxidative stress in human dermal fibroblast (HDF) cells and restraint-stressed rats. The CBMDs contained citrus bioflavonoids including narirutin and hesperidin. The cell viability of HDF cells treated with H₂O₂ was observed at 53.9% but treated with CBMD-1 and CBMD-2 (500 μg/mL) on H₂O₂ exposed HDF cells significantly increased the relative cell viability at 65.0 and 72.2%, respectively. In the treadmill test, the time spent on the electrode plate in the restraint-stressed group was analyzed 24.1 s, but restraint-stressed rats with administered CBMDs (300 mg/kg) had significantly decreased the time at 2.4 (CBMD-1) and 4.7 (CBMD-2) s, respectively. In addition, number of touches the electrode plate in restraint-stressed group was observed at 42.4 ea, but, restraint-stressed rats with administered CBMD-1 and CBMD-2 (300 mg/kg) were significantly decreased at 7.0 and 10.2 ea, respectively.

Anti-Inflammatory and Neuroprotective Constituents from the Peels of Citrus grandis

A series of chromatographic separations performed on the ethanol extracts of the peels of Citrus grandis has led to the characterization of forty compounds, including seventeen coumarins, eight flavonoids, two triterpenoids, four benzenoids, two steroids, one lignan, one amide, and five other compounds, respectively. The chemical structures of the purified constituents were identified on the basis of spectroscopic elucidation, including 1D- and 2D-NMR, UV, IR, and mass spectrometric analysis. Most of the isolated compounds were examined for their inhibition of superoxide anion generation and elastase release by human neutrophils. Among the isolates, isomeranzin (3), 17,18-dihydroxybergamottin (12), epoxybergamottin (13), rhoifolin (19), vitexicarpin (22) and 4-hydroxybenzaldehyde (29) displayed the most significant inhibition of superoxide anion generation and elastase release with IC₅₀ values ranged from 0.54 to 7.57 μM, and 0.43 to 4.33 μM, respectively. In addition, 7-hydroxy-8-(2′-hydroxy-3′-methylbut-3′-enyl)coumarin (8) and 17,18-dihydroxybergamottin (12) also exhibited the protection of neurons against Aβ-mediated neurotoxicity at 50 μM.

Citrus consumption and incident dementia in elderly Japanese: the Ohsaki Cohort 2006 Study

Although some experimental biological studies have indicated that citrus may have preventive effects against cognitive impairment, no cohort study has yet examined the relationship between citrus consumption and incident dementia. In a baseline survey, we collected data on daily citrus intake (categorised as ≤2, 3–4 times/week or almost every day) and consumption of other foods using a FFQ, and used a self-reported questionnaire to collect data on other covariates. Data on incident dementia were retrieved from the Japanese Long-term Care Insurance database. A multivariate-adjusted Cox model was used to estimate the hazard ratios (HR) and 95 % CI for incident dementia according to citrus consumption. Among 13 373 participants, the 5·7-year incidence of dementia was 8·6 %. In comparison with participants who consumed citrus ≤2 times/week, the multivariate-adjusted HR for incident dementia among those did so 3–4 times/week and almost every day was 0·92 (95 % CI 0·80, 1·07) and 0·86 (95 % CI 0·73, 1·01), respectively (Ptrend=0·065). The inverse association persisted after excluding participants whose dementia events had occurred in the first 2 years of follow-up. The multivariate HR was 1·00 (reference) for ≤2 times/week, 0·82 (95 % CI 0·69, 0·98) for 3–4 times/week and 0·77 (95 % CI 0·64, 0·93) for almost every day (Ptrend=0·006). The present findings suggest that frequent citrus consumption was associated with a lower risk of incident dementia, even after adjustment for possible confounding factors.

Dietary flavonoid aglycones and their glycosides: Which show better biological significance?

The dietary flavonoids, especially their glycosides, are the most vital phytochemicals in diets and are of great general interest due to their diverse bioactivity. The natural flavonoids almost all exist as their O-glycoside or C-glycoside forms in plants. In this review, we summarized the existing knowledge on the different biological benefits and pharmacokinetic behaviors between flavonoid aglycones and their glycosides. Due to various conclusions from different flavonoid types and health/disease conditions, it is very difficult to draw general or universally applicable comments regarding the impact of glycosylation on the biological benefits of flavonoids. It seems as though O-glycosylation generally reduces the bioactivity of these compounds - this has been observed for diverse properties including antioxidant activity, antidiabetes activity, anti-inflammation activity, antibacterial, antifungal activity, antitumor activity, anticoagulant activity, antiplatelet activity, antidegranulating activity, antitrypanosomal activity, influenza virus neuraminidase inhibition, aldehyde oxidase inhibition, immunomodulatory, and antitubercular activity. However, O-glycosylation can enhance certain types of biological benefits including anti-HIV activity, tyrosinase inhibition, antirotavirus activity, antistress activity, antiobesity activity, anticholinesterase potential, antiadipogenic activity, and antiallergic activity. However, there is a lack of data for most flavonoids, and their structures vary widely. There is also a profound lack of data on the impact of C-glycosylation on flavonoid biological benefits, although it has been demonstrated that in at least some cases C-glycosylation has positive effects on properties that may be useful in human healthcare such as antioxidant and antidiabetes activity. Furthermore, there is a lack of in vivo data that would make it possible to make broad generalizations concerning the influence of glycosylation on the benefits of flavonoids for human health. It is possible that the effects of glycosylation on flavonoid bioactivity in vitro may differ from that seen in vivo. With in vivo (oral) treatment, flavonoid glycosides showed similar or even higher antidiabetes, anti-inflammatory, antidegranulating, antistress, and antiallergic activity than their flavonoid aglycones. Flavonoid glycosides keep higher plasma levels and have a longer mean residence time than those of aglycones. We should pay more attention to in vivo benefits of flavonoid glycosides, especially C-glycosides.

Neuroprotective diets for stroke

Stroke is one of the main causes of death and disability in the elderly. In the last few years, there has been increasing evidence that suggests the influence of the diet on the decrease of stroke risk. Probably, because of the presence of bioactive components with beneficial effects such as antioxidant or anti-inflammatory properties. This article reviews several dietary bioactive compounds from studies in models of cerebral ischemia that have obtained promising results decreasing cerebral damage. We propose that many of these compounds present in diet could be good candidates to test new neuroprotection approaches focused on reducing the damage and protecting the brain before stroke occurs.

Inhibition of Human Monoamine Oxidase: Biological and Molecular Modeling Studies on Selected Natural Flavonoids

Naturally occurring flavonoids display a plethora of different biological activities, but emerging evidence suggests that this class of compounds may also act as antidepressant agents endowed with multiple mechanisms of action in the central nervous system, increasing central neurotransmission, limiting the reabsorption of bioamines by synaptosomes, and modulating the neuroendocrine and GABA_A systems. Due to their presence in foods, food-derived products, and nutraceuticals, we established their role and structure-activity relationships as reversible and competitive human monoamine oxidase (MAO) inhibitors. In addition, molecular modeling studies, which evaluated their modes of MAO inhibition, are presented. These findings could provide pivotal implications in the quest of novel drug-like compounds and for the establishment of harmful drug-dietary supplement interactions commonly reported in the therapy with antidepressant agents.

Xanthohumol-induced presynaptic reduction of glutamate release in the rat hippocampus

This study examined whether xanthohumol, a hop-derived prenylated flavonoid present in beer, affects glutamate release in the rat hippocampus. In the rat hippocampal nerve terminals (synaptosomes), xanthohumol inhibited the release of 4-aminopyridine (4-AP)-evoked glutamate and the elevation of cytosolic Ca(2+) concentration, whereas it had no effect on 4-AP-mediated depolarization. The inhibitory effect of xanthohumol on the evoked glutamate release was prevented by removing extracellular Ca(2+), using the Cav2.2 (N-type) and Cav2.1 (P/Q-type) channel blocker ω-CgTX MVIIC, the calmodulin antagonists W7 and calmidazolium, and the protein kinase A inhibitor H89; however, no such effect was observed when the G-protein inhibitor N-ethylmaleimide was used. In addition, immunocytochemical data demonstrated that GABAA receptors are present in the hippocampal synaptosomes and that the xanthohumol effect on evoked glutamate release was antagonized by the GABAA receptor antagonist SR95531. Furthermore, in slice preparations, xanthohumol reduced the frequency of miniature excitatory postsynaptic currents without affecting their amplitude. We conclude that xanthohumol acts at GABAA receptors present in the hippocampal nerve terminals to decrease the Ca(2+) influx through N- and P/Q-type Ca(2+) channels, which subsequently suppresses the Ca(2+)-calmodulin/PKA cascade to decrease the evoked glutamate release.

Neurodegenerative Diseases: Might Citrus Flavonoids Play a Protective Role?

Neurodegenerative diseases (ND) result from the gradual and progressive degeneration of the structure and function of the central nervous system or the peripheral nervous system or both. They are characterized by deterioration of neurons and/or myelin sheath, disruption of sensory information transmission and loss of movement control. There is no effective treatment for ND, and the drugs currently marketed are symptom-oriented, albeit with several side effects. Within the past decades, several natural remedies have gained attention as potential neuroprotective drugs. Moreover, an increasing number of studies have suggested that dietary intake of vegetables and fruits can prevent or delay the onset of ND. These properties are mainly due to the presence of polyphenols, an important group of phytochemicals that are abundantly present in fruits, vegetables, cereals and beverages. The main class of polyphenols is flavonoids, abundant in Citrus fruits. Our review is an overview on the scientific literature concerning the neuroprotective effects of the Citrus flavonoids in the prevention or treatment of ND. This review may be used as scientific basis for the development of nutraceuticals, food supplements or complementary and alternative drugs to maintain and improve the neurophysiological status.

Converting citrus wastes into value-added products: Economic and environmently friendly approaches

Citrus fruits, including oranges, grapefruits, lemons, limes, tangerines, and mandarins, are among the most widely cultivated fruits around the globe. Its production is increasing every year due to rising consumer demand. Citrus-processing industries generate huge amounts of wastes every year, and citrus peel waste alone accounts for almost 50% of the wet fruit mass. Citrus waste is of immense economic value as it contains an abundance of various flavonoids, carotenoids, dietary fiber, sugars, polyphenols, essential oils, and ascorbic acid, as well as considerable amounts of some trace elements. Citrus waste also contains high levels of sugars suitable for fermentation for bioethanol production. However, compounds such as D-limonene must be removed for efficient bioethanol production. The aim of the present article was to review the latest advances in various popular methods of extraction for obtaining value-added products from citrus waste/byproducts and their potential utility as a source of various functional compounds.

Patterns of genetic structure and evidence of gene flow among Tunisian Citrus species based on informative nSSR markers

This study investigates the extent of genetic diversity, phylogenetic relationships and the amount of gene flow among Tunisian Citrus species based on a set of 15 informative nuclear SSR molecular markers. Genotyping data highlighted an allelic richness among Tunisian Citrus species and has allowed the detection of 168 alleles among them 104.19 were effective. The partition of the total genetic diversity (HT=0.832) showed that the highest amount of variation within the Citrus species is HS=0.550, while the relative amount of the between-species genetic diversity GST does not exceed 0.338. This pattern of genetic structure was supported by low-to-moderate FST pairwise values and the presence of a gene flow (Nm) among the eight Citrus species. The lowest genetic differentiation was revealed between the species C. sinensis and C. insitorum (FST=0.111, Nm=1.99), while the highest genetic differentiation was recorded between the species C. aurantifolia and C. paradisi (FST=0.367, Nm=0.43). The established Neighbor Joining analysis showed that all genotypes were widely discriminated and clearly pooled according to their species of origin, with minor exceptions.

Citrus bergamia Juice Extract Attenuates β-Amyloid-Induced Pro-Inflammatory Activation of THP-1 Cells Through MAPK and AP-1 Pathways

Flavonoids have been shown to be effective in protecting against age-related cognitive and motor decline in both in vitro and in vivo models. Recently, a flavonoid-rich extract of Citrus bergamia juice (BJe) has been shown to display anti-oxidant and anti-inflammatory properties against LPS-induced activation of human THP-1 monocytes. In the light of these observations, we wondered whether BJe may be beneficial against neuroinflammatory processes, such as those observed in Alzheimer’s disease. To this aim we used THP-1 monocytes to investigate the mechanisms underlying the beneficial potential of BJe against amyloid-beta_1–42 (Aβ₁₋₄₂) -mediated inflammation. Exposure of THP-1 cells to Aβ₁₋₄₂ significantly induced the expression and secretion of IL-6 and IL-1β in THP-1 cells and increased the phosphorylation of ERK 1/2 as well as p46 and p54 members of JNK family. Moreover, Aβ₁₋₄₂ raises AP-1 DNA binding activity in THP-1-treated cells. Interestingly, all these effects were reduced in the presence of BJe. Our data indicate that BJe may effectively counteract the pro-inflammatory activation of monocytes/microglial cells exposed to amyloid fibrils, suggesting a promising role as a natural drug against neuroinflammatory processes.

Bioactive Flavonoids, Antioxidant Behaviour, and Cytoprotective Effects of Dried Grapefruit Peels (Citrus paradisi Macf.)

Grapefruit (Citrus paradisi Macf.) is an important cultivar of the Citrus genus which contains a number of nutrients beneficial to human health. The objective of the present study was to evaluate changes in bioactive flavonoids, antioxidant behaviour, and in vitro cytoprotective effect of processed white and pink peels after oven-drying (45°C–60°C) and freeze-drying treatments. Comparison with fresh grapefruit peels was also assessed. Significant increases in DPPH, FRAPS, and ABTS values were observed in dried grapefruit peel samples in comparison with fresh peels, indicating the suitability of the treatments for use as tools to greatly enhance the antioxidant potential of these natural byproducts. A total of thirteen flavonoids were quantified in grapefruit peel extracts by HPLC-MS/MS. It was found that naringin, followed by isonaringin, was the main flavonoid occurring in fresh, oven-dried, and freeze-dried grapefruit peels. In vivo assay revealed that fresh and oven-dried grapefruit peel extracts (45°C) exerted a strong cytoprotective effect on SH-SY5Y neuroblastoma cell lines at concentrations ranging within 0.1–0.25 mg/mL. Our data suggest that grapefruit (Citrus paradisi Macf.) peel has considerable potential as a source of natural bioactive flavonoids with outstanding antioxidant activity which can be used as agents in several therapeutic strategies.

Lipidomic approach in young adult triathletes: effect of supplementation with a polyphenols-rich juice on neuroprostane and F2-dihomo-isoprostane markers

With adequate training, our juice rich in polyphenolic compounds has been able to influence the excretion values of oxidative stress biomarkers associated with the central nervous system.

Effects of aging on the phytochemical profile and antioxidative activity of Pericarpium Citri Reticulatae ‘Chachiensis’

PCR-Chachiensis stored long-term exhibits higher total phenolics, flavonoid content and superior antioxidant activity, which provide additional health benefits during aging.

Modulation of neurotrophic signaling pathways by polyphenols

Polyphenols are an important class of phytochemicals, and several lines of evidence have demonstrated their beneficial effects in the context of a number of pathologies including neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. In this report, we review the studies on the effects of polyphenols on neuronal survival, growth, proliferation and differentiation, and the signaling pathways involved in these neurotrophic actions. Several polyphenols including flavonoids such as baicalein, daidzein, luteolin, and nobiletin as well as nonflavonoid polyphenols such as auraptene, carnosic acid, curcuminoids, and hydroxycinnamic acid derivatives including caffeic acid phentyl ester enhance neuronal survival and promote neurite outgrowth in vitro, a hallmark of neuronal differentiation. Assessment of underlying mechanisms, especially in PC12 neuronal-like cells, reveals that direct agonistic effect on tropomyosin receptor kinase (Trk) receptors, the main receptors of neurotrophic factors including nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) explains the action of few polyphenols such as 7,8-dihydroxyflavone. However, several other polyphenolic compounds activate extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Akt pathways. Increased expression of neurotrophic factors in vitro and in vivo is the mechanism of neurotrophic action of flavonoids such as scutellarin, daidzein, genistein, and fisetin, while compounds like apigenin and ferulic acid increase cyclic adenosine monophosphate response element-binding protein (CREB) phosphorylation. Finally, the antioxidant activity of polyphenols reflected in the activation of Nrf2 pathway and the consequent upregulation of detoxification enzymes such as heme oxygenase-1 as well as the contribution of these effects to the neurotrophic activity have also been discussed. In conclusion, a better understanding of the neurotrophic effects of polyphenols and the concomitant modulations of signaling pathways is useful for designing more effective agents for management of neurodegenerative diseases.

Synthesis and Evaluation of Neuroprotective Selenoflavanones

The physicochemical properties and antioxidant activity of a molecule could be improved by the substitution of an oxygen atom in a molecule with selenium. We synthesized selenoflavanones and flavanones to evaluate their neuroprotective effects. The selenoflavanones showed improved physicochemical properties, suggestive of the ability to pass through the blood-brain barrier (BBB). They showed in vitro antioxidant effects against hydrogen peroxide, and did not result in severe cytotoxicity. Moreover, infarction volumes in a transient ischemia mouse model were significantly reduced by the selenoflavanone treatments.

The Distribution of Coumarins and Furanocoumarins in Citrus Species Closely Matches Citrus Phylogeny and Reflects the Organization of Biosynthetic Pathways

Citrus plants are able to produce defense compounds such as coumarins and furanocoumarins to cope with herbivorous insects and pathogens. In humans, these chemical compounds are strong photosensitizers and can interact with medications, leading to the "grapefruit juice effect". Removing coumarins and furanocoumarins from food and cosmetics imply additional costs and might alter product quality. Thus, the selection of Citrus cultivars displaying low coumarin and furanocoumarin contents constitutes a valuable alternative. In this study, we performed ultra-performance liquid chromatography coupled with mass spectrometry analyses to determine the contents of these compounds within the peel and the pulp of 61 Citrus species representative of the genetic diversity all Citrus. Generally, Citrus peel contains larger diversity and higher concentrations of coumarin/furanocoumarin than the pulp of the same fruits. According to the chemotypes found in the peel, Citrus species can be separated into 4 groups that correspond to the 4 ancestral taxa (pummelos, mandarins, citrons and papedas) and extended with their respective secondary species descendants. Three of the 4 ancestral taxa (pummelos, citrons and papedas) synthesize high amounts of these compounds, whereas mandarins appear practically devoid of them. Additionally, all ancestral taxa and their hybrids are logically organized according to the coumarin and furanocoumarin pathways described in the literature. This organization allows hypotheses to be drawn regarding the biosynthetic origin of compounds for which the biogenesis remains unresolved. Determining coumarin and furanocoumarin contents is also helpful for hypothesizing the origin of Citrus species for which the phylogeny is presently not firmly established. Finally, this work also notes favorable hybridization schemes that will lead to low coumarin and furanocoumarin contents, and we propose to select mandarins and Ichang papeda as Citrus varieties for use in creating species devoid of these toxic compounds in future breeding programs.

Investigation into the effects of antioxidant-rich extract of Tamarindus indica leaf on antioxidant enzyme activities, oxidative stress and gene expression profiles in HepG2 cells

The leaf extract of Tamarindus indica L. (T. indica) had been reported to possess high phenolic content and showed high antioxidant activities. In this study, the effects of the antioxidant-rich leaf extract of the T. indica on lipid peroxidation, antioxidant enzyme activities, H₂O₂-induced ROS production and gene expression patterns were investigated in liver HepG2 cells. Lipid peroxidation and ROS production were inhibited and the activity of antioxidant enzymes superoxide dismutase, catalase and glutathione peroxidase was enhanced when the cells were treated with the antioxidant-rich leaf extract. cDNA microarray analysis revealed that 207 genes were significantly regulated by at least 1.5-fold (p < 0.05) in cells treated with the antioxidant-rich leaf extract. The expression of KNG1, SERPINC1, SERPIND1, SERPINE1, FGG, FGA, MVK, DHCR24, CYP24A1, ALDH6A1, EPHX1 and LEAP2 were amongst the highly regulated. When the significantly regulated genes were analyzed using Ingenuity Pathway Analysis software, “Lipid Metabolism, Small Molecule Biochemistry, Hematological Disease” was the top biological network affected by the leaf extract, with a score of 36. The top predicted canonical pathway affected by the leaf extract was the coagulation system (P < 2.80 × 10⁻⁶) followed by the superpathway of cholesterol biosynthesis (P < 2.17 × 10⁻⁴), intrinsic prothrombin pathway (P < 2.92 × 10⁻⁴), Immune Protection/Antimicrobial Response (P < 2.28 × 10⁻³) and xenobiotic metabolism signaling (P < 2.41 × 10⁻³). The antioxidant-rich leaf extract of T. indica also altered the expression of proteins that are involved in the Coagulation System and the Intrinsic Prothrombin Activation Pathway (KNG1, SERPINE1, FGG), Superpathway of Cholesterol Biosynthesis (MVK), Immune protection/antimicrobial response (IFNGR1, LEAP2, ANXA3 and MX1) and Xenobiotic Metabolism Signaling (ALDH6A1, ADH6). In conclusion, the antioxidant-rich leaf extract of T. indica inhibited lipid peroxidation and ROS production, enhanced antioxidant enzyme activities and significantly regulated the expression of genes and proteins involved with consequential impact on the coagulation system, cholesterol biosynthesis, xenobiotic metabolism signaling and antimicrobial response.

Hesperidin inhibits glutamate release and exerts neuroprotection against excitotoxicity induced by kainic acid in the hippocampus of rats

The citrus flavonoid hesperidin exerts neuroprotective effects and could cross the blood-brain barrier. Given the involvement of glutamate neurotoxicity in the pathogenesis of neurodegenerative disorders, this study was conducted to evaluate the potential role of hesperidin in glutamate release and glutamate neurotoxicity in the hippocampus of rats. In rat hippocampal nerve terminals (synaptosomes), hesperidin inhibited the release of glutamate and elevation of cytosolic free Ca(2+) concentration evoked by 4-aminopyridine (4-AP), but did not alter 4-AP-mediated depolarization. The inhibitory effect of hesperidin on evoked glutamate release was prevented by chelating the extracellular Ca(2+) ions and blocking the activity of Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels or protein kinase C. In hippocampal slice preparations, whole-cell patch clamp experiments showed that hesperidin reduced the frequency of spontaneous excitatory postsynaptic currents without affecting their amplitude, indicating the involvement of a presynaptic mechanism. In addition, intraperitoneal (i.p.) injection of kainic acid (KA, 15 mg/kg) elevated the extracellular glutamate levels and caused considerable neuronal loss in the hippocampal CA3 area. These KA-induced alterations were attenuated by pretreatment with hesperidin (10 or 50 mg/kg, i.p.) before administering the KA. These results demonstrate that hesperidin inhibits evoked glutamate release in vitro and attenuates in vivo KA-induced neuronal death in the hippocampus. Our findings indicate that hesperidin may be a promising candidate for preventing or treating glutamate excitotoxicity related brain disorders such as neurodegenerative diseases.

Effects of Kaixinjieyu, a Chinese herbal medicine preparation, on neurovascular unit dysfunction in rats with vascular depression

BACKGROUND

Kaixinjieyu (KJ), derived from Kaixin and Sini powder, is an effective Chinese herbal medicine preparation used in the treatment of vascular depression (VD). We hypothesize that broad antidepressant effect of KJ results from the improved neurovascular unit (NVU) function via neurogenesis, permeability of blood-brain barrier (BBB) and balance of the fibrinolytic system.

METHODS

A VD model of rat was established by chronic unpredictable mild stress and separation after ligation of the bilateral common carotid arteries. The rats were treated with KJ and fluoxetine hydrochloride (FLU) for 21 days, respectively. The behavior and cerebral perfusion were investigated and then NVU functions including neurogenesis, permeability of BBB and balance of the fibrinolytic system were studied using a number of biomarkers and TUNEL assay.

RESULTS

KJ significantly increased sucrose preference, moving distance, number of rearing and cortical blood flow. NVU functions measured by brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB) and tissue plasminogen activator (t-PA) proteins and mRNA, zona occludens protein-1 (ZO-1), occludin and claudin-5 proteins increased significantly, whereas, plasminogen activator inhibitor-1 (PAI-1), matrix metalloproteinase-2 (MMP-2) proteins, mRNA and apoptotic rates of neurons decreased significantly with treatment of KJ. FLU has a function similar to KJ in behavior, regulation of BDNF, TrkB, MMP-2, occludin and apoptotic rates of cells.

CONCLUSIONS

KJ has function of reducing depression-like behavior and improving cerebral hypoperfusion, which might be mediated by the up-regulation of neurogenesis and tight junction of BBB, and balance of the fibrinolytic system. The results imply that KJ is better than FLU in improving cerebral hypoperfusion and the fibrinolytic system.

Naringin Attenuates Autophagic Stress and Neuroinflammation in Kainic Acid-Treated Hippocampus In Vivo

Kainic acid (KA) is well known as a chemical compound to study epileptic seizures and neuronal excitotoxicity. KA-induced excitotoxicity causes neuronal death by induction of autophagic stress and microglia-derived neuroinflammation, suggesting that the control of KA-induced effects may be important to inhibit epileptic seizures with neuroprotection. Naringin, a flavonoid in grapefruit and citrus fruits, has anti-inflammatory and antioxidative activities, resulting in neuroprotection in animal models from neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. In the present study, we examined its beneficial effects involved in antiautophagic stress and antineuroinflammation in the KA-treated hippocampus. Our results showed that naringin treatment delayed the onset of KA-induced seizures and decreased the occurrence of chronic spontaneous recurrent seizures (SRS) in KA-treated mice. Moreover, naringin treatment protected hippocampal CA1 neurons in the KA-treated hippocampus, ameliorated KA-induced autophagic stress, confirmed by the expression of microtubule-associated protein light chain 3 (LC3), and attenuated an increase in tumor necrosis factor-α (TNFα) in activated microglia. These results suggest that naringin may have beneficial effects of preventing epileptic events and neuronal death through antiautophagic stress and antineuroinflammation in the hippocampus in vivo.

Apigenin, a natural flavonoid, inhibits glutamate release in the rat hippocampus

The purpose of this study was to examine the effect and mechanism of apigenin, a natural flavonoid, on glutamate release in the rat hippocampus. In rat hippocampal nerve terminals (synaptosomes), apigenin inhibited glutamate release and the elevation of the cytosolic free Ca(2+) concentration evoked by 4-aminopyridine, whereas it had no effect on 4-aminopyridine-mediated depolarization and Na(+) influx. The apigenin-mediated inhibition of evoked glutamate release was prevented by chelating the extracellular Ca(2+) ions and blocking Cav2.2 (N-type) and Cav2.1 (P/Q-type) channel activity. Furthermore, we determined that gamma-aminobutyric acid type A (GABAA) receptors are present in the hippocampal nerve terminals because they are colocalized with the presynaptic marker synaptophysin. However, the effect of apigenin on 4-aminopyridine-evoked glutamate release from synaptosomes was unaffected by the GABAA receptor antagonists SR95531 and bicuculline. Furthermore, in slice preparations, whole-cell patch-clamp experiments showed that apigenin reduced the frequency of spontaneous excitatory postsynaptic currents without affecting their amplitude, suggesting a presynaptic mechanism. On the basis of these results, we suggested that apigenin exerts its presynaptic inhibition probably by reducing Ca(2+) entry mediated by the Cav2.2 (N-type) and Cav2.1 (P/Q-type) channels, thereby inhibiting glutamate release from the rat hippocampal nerve terminals.