Antioxidant effects of flavonoids

Regulatory Effects and Molecular Mechanisms of Tea and Its Active Compounds on Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD), the most common chronic liver disease, is a multifactorial disease resulting from the interaction between environment, genetic background, and metabolic stress. Most treatments for NAFLD include dietary intervention and exercise show limited efficacy due to the complex mechanisms involved in NAFLD. Meanwhile, drug therapy is accompanied by serious side effects. The development of high-efficiency natural supplements is a sustainable strategy for the prevention and treatment of NAFLD. As the second most consumed beverage, tea has health benefits that have been widely recognized. Nevertheless, the intervention of tea active compounds in NAFLD has received limited attention. Tea contains abundant bioactive compounds with potential effects on NAFLD, such as catechins, flavonoids, theanine, tea pigments, and tea polysaccharides. We reviewed the intrinsic and environmental factors and pathogenic mechanisms that affect the occurrence and development of NAFLD, and summarized the influences of exercise, drugs, diet, and tea drinking on NAFLD. On this basis, we further analyzed the potential effects and molecular regulatory mechanisms of tea active compounds on NAFLD and proposed future development directions. This review hopes to provide novel insights into the development and application of tea active compounds in the prevention and treatment of NAFLD.

Potential Role of Quercetin Glycosides as Anti-Atherosclerotic Food-Derived Factors for Human Health

Quercetin is a monomeric polyphenol of plant origin that belongs to the flavonol-type flavonoid subclass. Extensive studies using cultured cells and experimental model animals have demonstrated the anti-atherosclerotic effects of dietary quercetin in relation to the prevention of cardiovascular disease (CVD). As quercetin is exclusively present in plant-based foods in the form of glycosides, this review focuses on the bioavailability and bioefficacy of quercetin glycosides in relation to vascular health effects. Some glucose-bound glycosides are absorbed from the small intestine after glucuronide/sulfate conjugation. Both conjugated metabolites and deconjugated quercetin aglycones formed by plasma β-glucuronidase activity act as food-derived anti-atherogenic factors by exerting antioxidant, anti-inflammatory, and plasma low-density lipoprotein cholesterol-lowering effects. However, most quercetin glycosides reach the large intestine, where they are subject to gut microbiota-dependent catabolism resulting in deglycosylated aglycone and chain-scission products. These catabolites also affect vascular health after transfer into the circulation. Furthermore, quercetin glycosides may improve gut microbiota profiles. A variety of human cohort studies and intervention studies support the idea that the intake of quercetin glycoside-rich plant foods such as onion helps to prevent CVD. Thus, quercetin glycoside-rich foods offer potential benefits in terms of cardiovascular health and possible clinical applications.

The Conformations of Isolated Gallic Acid: A Laser-Ablation Rotational Study

The rotational spectrum of laser-ablated gallic acid has been recorded using CP-FTMW spectroscopy. Two rotamers have been detected, and their rotational spectra have been assigned and analyzed to obtain the molecular spectroscopic parameters. The observed rotamers have been unambiguously identified in the light of theoretical computations, based on the comparison of the experimental line intensities and rotational parameters with the rotational constants and electric dipole moments predicted from theoretical calculations. The values of the planar inertial moments confirm that the observed conformers are planar, and their relative stability and population have been determined from relative intensity measurements. The B3LYP-D3/6-311++G(2d,p) level has been shown to be the best method among a series of levels normally used to predict the rotational parameters in rotational spectroscopy. In the observed conformers, the three adjacent OH groups are arranged in a sequential form, and the only difference between them lies in the orientation of the COOH group. Although weak attractive OH···O interactions seem to exist, the analysis of the electron density topology does not show the existence of any critical point corresponding to these interactions.

Alternative Splicing and Its Roles in Plant Metabolism

Plant metabolism, including primary metabolism such as tricarboxylic acid cycle, glycolysis, shikimate and amino acid pathways as well as specialized metabolism such as biosynthesis of phenolics, alkaloids and saponins, contributes to plant survival, growth, development and interactions with the environment. To this end, these metabolic processes are tightly and finely regulated transcriptionally, post-transcriptionally, translationally and post-translationally in response to different growth and developmental stages as well as the constantly changing environment. In this review, we summarize and describe the current knowledge of the regulation of plant metabolism by alternative splicing, a post-transcriptional regulatory mechanism that generates multiple protein isoforms from a single gene by using alternative splice sites during splicing. Numerous genes in plant metabolism have been shown to be alternatively spliced under different developmental stages and stress conditions. In particular, alternative splicing serves as a regulatory mechanism to fine-tune plant metabolism by altering biochemical activities, interaction and subcellular localization of proteins encoded by splice isoforms of various genes.

Neuroregenerative Potential of Prenyl- and Pyranochalcones: A Structure-Activity Study

Loss of neuronal tissue is a hallmark of age-related neurodegenerative diseases. Since adult neurogenesis has been confirmed in the human brain, great interest has arisen in substances stimulating the endogenous neuronal regeneration mechanism based on adult neural stem cells. Medicinal plants are a valuable source of neuroactive small molecules. In the structure-activity study presented here, the activities of prenyl- and pyranochalcones were compared to each other, using a differentiation assay based on the doublecortin promoter sequences. The latter revealed that the pyrano ring is a crucial structural element for the induction of neuronal differentiation of adult neural stem cells, while compounds with a prenyl group show significantly lower activities. Furthermore, a decrease of pro-differentiation activity was observed following structural modifications, such as substitutions on the pyrano ring and on the B-ring of the chalcone. We also initiated the elucidation of the structural characteristics of the newly discovered lead substance xanthohumol C, which correlated with the activation of the doublecortin promoter during neuronal differentiation.

Manipulation of Dietary Intake on Changes in Circulating Testosterone Concentrations

Elevations in the circulating concentration of androgens are thought to have a positive effect on the anabolic processes leading to improved athletic performance. Anabolic-androgenic steroids have often been used by competitive athletes to augment this effect. Although there has been concerted effort on examining how manipulating training variables (e.g., intensity and volume of training) can influence the androgen response to exercise, there has been much less effort directed at understanding how changes in both macronutrient and micronutrient intake can impact the androgen response. Thus, the focus of this review is to examine the effect that manipulating energy and nutrient intake has on circulating concentrations of testosterone and what the potential mechanism is governing these changes.

Possible Effects of Beetroot Supplementation on Physical Performance Through Metabolic, Neuroendocrine, and Antioxidant Mechanisms: A Narrative Review of the Literature

Athletes often seek to use dietary supplements to increase performance during exercise. Among various supplements, much attention has been paid to beetroot in recent years. Beetroot is a source of carbohydrates, fiber, protein, minerals, and vitamins; also, it is a natural source of nitrate and associated with improved sports performance. Nitrates can the modification of skeletal muscle contractile proteins or calcium handling after translation. The time to reach the peak plasma nitrate is between 1 and 3 h after consumption of a single dose of nitrate. Nitrate is metabolized by conversion to nitrite and subsequently nitric oxide. Beetroot can have various effects on athletic performance through nitric oxide. Nitric oxide is an intracellular and extracellular messenger for regulating certain cellular functions and causes vasodilation of blood vessels and increases blood flow. Nitric oxide seems to be effective in improving athletic performance by increasing oxygen, glucose, and other nutrients for better muscle fueling. Nitric oxide plays the main role in anabolic hormones, modulates the release of several neurotransmitters and the major mediators of stress involved in the acute hypothalamic-pituitary-adrenal response to exercise. Beetroot is an important source of compounds such as ascorbic acid, carotenoids, phenolic acids, flavonoids, betaline, and highly active phenolics and has high antioxidant properties. Beetroot supplement provides an important source of dietary polyphenols and due to the many health benefits. Phytochemicals of Beetroot through signaling pathways inhibit inflammatory diseases. In this study, the mechanisms responsible for these effects were examined and the research in this regard was reviewed.

Interaction between olanzapine and human serum albumin and effect of metal ions, caffeine and flavonoids on the binding: A spectroscopic study

In this study, the binding of olanzapine (OLZ) to human serum albumin (HSA) and the influence of metal ions (Ca²⁺, Mg²⁺, Cu²⁺, Zn²⁺, Fe³⁺), caffeine (CAF) and flavonoids (diosmin (DIO), catechin (CAT), quercetin (QUE)), on their affinity, was investigated by fluorescence spectroscopy and UV-vis absorption spectroscopy. Fluorescence experiments suggest that OLZ quench the fluorescence of HSA through the mixed quenching mechanism and non-radiation energy transferring as a result of the HSA-OLZ complex formation. OLZ spontaneously bind in the site I on HSA, and according to thermodynamic parameters, the reaction was spontaneous and mainly driven by hydrogen bonds and van der Waals interactions. The presence of Mⁿ⁺ ions, CAF, DIO and CAT decreased binding affinity between OLZ and HSA which indicates that they could compete against OLZ in the site I. Contrary, in the presence of QUE the binding affinity of the HSA-OLZ system enhanced, which may be explained by conformational changes in HSA (non-competitive interference).

Indomethacin Increases Quercetin Affinity for Human Serum Albumin: A Combined Experimental and Computational Study and Its Broader Implications

Human serum albumin (HSA) is the most abundant carrier protein in the human body. Competition for the same binding site between different ligands can lead to an increased active concentration or a faster elimination of one or both ligands. Indomethacin and quercetin both bind to the binding site located in the IIA subdomain. To determine the nature of the HSA-indomethacin-quercetin interactions, spectrofluorometric, docking, molecular dynamics studies, and quantum chemical calculations were performed. The results show that the indomethacin and quercetin binding sites do not overlap. Moreover, the presence of quercetin does not influence the binding constant and position of indomethacin in the pocket. However, binding of quercetin is much more favorable in the presence of indomethacin, with its position and interactions with HSA significantly changed. These results provide a new insight into drug-drug interactions, which can be important in situations when displacement from HSA or other proteins is undesirable or even desirable. This principle could also be used to deliberately prolong or shorten the xenobiotics' half-life in the body, depending on the desired outcomes.

The Mechanisms Behind the Biological Activity of Flavonoids

Flavonoids are phenolic compounds widely distributed in the human diet. Their intake has been associated with a decreased risk of different diseases such as cancer, immune dysfunction or coronary heart disease. However, the knowledge about the mechanisms behind their in vivo activity is limited and still under discussion. For years, their bioactivity was associated with the direct antioxidant and radical scavenging properties of phenolic compounds, but nowadays this assumption is unlikely to explain their putative health effects, or at least to be the only explanation for them. New hypotheses about possible mechanisms have been postulated, including the influence of the interaction of polyphenols and gut microbiota and also the possibility that flavonoids or their metabolites could modify gene expression or act as potential modulators of intracellular signaling cascades. This paper reviews all these topics, from the classical view as antioxidants in the context of the Oxidative Stress theory to the most recent tendencies related with the modulation of redox signaling pathways, modification of gene expression or interactions with the intestinal microbiota. The use of C. elegans as a model organism for the study of the molecular mechanisms involved in biological activity of flavonoids is also discussed.

Warfarin and Flavonoids Do Not Share the Same Binding Region in Binding to the IIA Subdomain of Human Serum Albumin

Human serum albumin (HSA) binds a variety of xenobiotics, including flavonoids and warfarin. The binding of another ligand to the IIA binding site on HSA can cause warfarin displacement and potentially the elevation of its free concentration in blood. Studies dealing with flavonoid-induced warfarin displacement from HSA provided controversial results: estimated risk of displacement ranged from none to serious. To resolve these controversies, in vitro study of simultaneous binding of warfarin and eight different flavonoid aglycons and glycosides to HSA was carried out by fluorescence spectroscopy as well as molecular docking. Results show that warfarin and flavonoids do not share the same binding region in binding to HSA. Interactions were only observed at high warfarin concentrations not attainable under recommended dosing regimes. Docking experiments show that flavonoid aglycons and glycosides do not bind at warfarin high affinity sites, but rather to different regions within the IIA HSA subdomain. Thus, the risk of clinically significant warfarin-flavonoid interaction in binding to HSA should be regarded as negligible.

Mitigating effect of chrysin loaded solid lipid nanoparticles against Amyloid β25-35 induced oxidative stress in rat hippocampal region: An efficient formulation approach for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent form of dementia. Amyloid-β25-35 (Aβ25-35), a well-established neurotoxicant, is reported to be involved in the etiology of AD. Chrysin (CN) with its wide range of biological activities in terms of reversing the neuronal damage once induced is limited due to its compromised bioavailability. Solid lipid nanoparticles (SLNs) on the other hand due to its improved protein stability, avoids proteolytic degradation, as well as sustained release of the incorporated molecules could be widely applied as a drug delivery vehicle. Hence, in the present investigation, we prepared CN loaded SLNs (CN-SLNs) and investigated its therapeutic role in alleviating Aβ25-35 administered neuronal damage. All the antioxidant enzymes and non-antioxidant enzyme in hippocampus were reduced significantly (P<0.01) in the Aβ25-35 injected group, whereas lipid peroxidation and acetylcholine esterase were increased significantly (P<0.01). These changes were restored significantly (P<0.01) by CN-SLNs (5mg/kg and 10mg/kg) and (P<0.05) by free CN (50mg/kg and 100mg/kg). Aβ25-35 also resulted in poor memory retention in behavioral tasks and histopathological sections of the hippocampal region showed the extent of neuronal loss which was thereby restored back on treatment with CN-SLNs and free CN. Our findings demonstrate that the therapeutic efficacy of CN could be attained at lower dose and also its oral bioavailability could be increased by encapsulating CN in SLNs. Thus the results suggest that CN-SLNs could be used as a potential therapeutic and a brain targeting strategy to combat the global burden of Alzheimer's disease.

Structural and electronic determinants of flavonoid binding to human serum albumin: an extensive ligand-based study

The most prominent features responsible for binding of flavonoid aglycones to the IIA region of human serum albumin (HSA) were determined based onin vitrofluorescence measurements and density functional theory calculations.

Effects of hydro-alcoholic extract of Launaea acanthodes on serum gonadotropin and testosterone levels and the structure of seminiferous tubules in hyperglycemic rats

OBJECTIVE

To investigate the effects of hydro-alcoholic extract of Launaea acanthodes, a blood glucose lowering plant in folk medicine of Iran, on the structure of seminiferous tubules and serum gonadotropin and testosterone levels in hyperglycemic rats.

METHODS

Twenty-four Wistar rats were randomly allocated into 4 groups (n=6): control, streptozotocin (STZ), STZ + insulin [STZ + Ins, 5 IU/(kg•day)], and STZ + Launaea acanthodes extract [STZ + Ext, 150 mg/(kg•day)]. Blood samples were collected at the 2nd and 4th weeks for detection of testosterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH) with enzyme-linked immuno sorbent assay (ELISA), and the right testes of rats were removed at the 7th week for the evaluation of diameter and wall thickness of seminiferous tubules and number of Leydig cells using unbiased stereological techniques.

RESULTS

In comparison with the control group, at the 2nd week FSH (0.45 vs 0.03, 0.02, 0.02 IU/L in STZ, STZ + Ins and STZ + Ext groups, respectively) and LH (1.02 vs 0.37, 0.2, 0.29 IU/L) showed significant decreases (all P<0.05) and testosterone (4.2 vs 8.37, 7.78, 11.8 ng/mL) showed a remarkable increase (all P<0.05). The levels of these hormones became closer in the STZ + Ext and the STZ + Ins groups to the control at the 4th week. A significant decrease in diameter and wall thickness of seminiferous tubules and number of Leydig cells were observed in the STZ group as compared with the control (P<0.01).

CONCLUSIONS

Administration of Launaea extract demonstrated a beneficial impact on the protection of testis from pathogenic and degenerative effects of hyperglycemia which may be partly due to its potential antioxidative effects.

Carbon tetrachloride-induced hepatic and renal damages in rat: inhibitory effects of cacao polyphenol

Here, we investigated the protective effect of cacao polyphenol extract (CPE) on carbon tetrachloride (CCl4)-induced hepato-renal oxidative stress in rats. Rats were administered CPE for 7 days and then received intraperitoneal injection of CCl4. Two hours after injection, we found that CCl4 treatment significantly increased biochemical injury markers, lipid peroxides (phosphatidylcholine hydroperoxide (PCOOH) and malondialdehyde (MDA)) and decreased glutathione peroxidase activity in kidney rather than liver, suggesting that kidney is more vulnerable to oxidative stress under the present experimental conditions. CPE supplementation significantly reduced these changes, indicating that this compound has antioxidant properties against CCl4-induced oxidative stress. An inhibitory effect of CPE on CCl4-induced CYP2E1 mRNA degradation may provide an explanation for CPE antioxidant property. Together, these results provide quantitative evidence of the in vivo antioxidant properties of CPE, especially in terms of PCOOH and MDA levels in the kidneys of CCl4-treated rats.

Evaluation on Antioxidant Effect of Xanthohumol by Different Antioxidant Capacity Analytical Methods

Several assays have been frequently used to estimate antioxidant capacities includingABTS•+, DPPH, and FRAP assays. Xanthohumol (XN), the major prenylated flavonoid contained in beer, witnessed various reports on its antioxidant capacity. We systematically evaluated the antioxidant activity of XN using three systems, 2,2,-azino-bis-3-ethylbenzthiazoline-6-sulphonic acid (ABTS•+) scavenging assays, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical assays, and ferric reducing antioxidant power (FRAP) assays. The results are expressed as Trolox equivalent antioxidant capacity (TEAC). The TEAC of XN was0.32±0.09 μmol·l−1by the ABTS assay and0.27±0.04 μmol·l−1by the FRAP. Meanwhile, the XN did not show obviously scavenging effect on DPPH radical reaction system. These results showed that different methods in the evaluation of compound antioxidant capicity, there may be a different conclusion.

The antioxidant activity of daidzein metabolites, O‑desmethylangolensin and equol, in HepG2 cells

Daidzein and its glycoside form daidzin, are known to have potential health benefits and are metabolized to O‑desmethylangolensin (O‑DMA) and equol following consumption. In the current study, the antioxidant activity and cytotoxicity of O‑DMA, equol, daidzein and daidzin was investigated and their effects on HepG2 human hepatocelluar carcinoma cells were compared. For cytotoxicity assays, lactose dehydrogenase (LDH) release and 3‑(4,5‑dimethylthiazol‑2‑yl)‑2,5‑diphenyltetrazolium bromide‑based cell viability, cells were exposed to various concentrations of each compound (5‑200 µM) for 24, 48 or 72 h. O‑DMA and equol did not affect LDH release, but higher concentrations (<75 µM) showed inhibition of cell growth. By contrast, daidzein and daidzin (200 µM) increased LDH release and cell growth. All compounds stimulated catalase and total superoxide dismutase (SOD) (CuZn‑ and Mn‑SOD) activity, and mRNA and protein expression. This phenomenon was most pronounced for O‑DMA and equol, as their effects were similar. These data suggested that O‑DMA and equol possess greater antioxidant properties compared with daidzein and may, thus, be beneficial for human health.

Robustaside B and para‑hydroxyphenol: phenolic and antioxidant compounds purified from Cnestis ferruginea D.C induced membrane permeability transition in rat liver mitochondria

The antioxidant properties of robustaside B and para‑hydroxyphenol isolated from Cnestis ferruginea were measured as the rate of inhibition of thiobarbituric acid reactive substance (TBARS) production in the Fe2+/ascorbate system. The modulatory effects of the compounds on mitochondrial membrane permeability transition (MMPT) were monitored spectrophotometrically as decreases in light scattering at 540 nm. The varying concentrations of robustaside B and para‑hydroxyphenol (0.05, 0.1, 0.2, 0.25, 0.5, 0.75 and 1 mM) significantly reduced (P<0.05) the amount of TBARS generated by the Fe2+/ascorbate system by 85.3, 86.4, 86.0, 86.1, 86.0, 86.0 and 86.0% and 86.7, 81.3, 81.3, 80, 80, 82.6 and 83.1%, respectively. Similarly, quercetin, a standard antioxidant, was found to induce an 80% reduction in the amount of TBARS produced. The same IC50 value of 0.025 mM was observed for robustaside B, para‑hydroxyphenol and quercetin. Pre‑incubation of varying concentrations of robustaside B (0.125, 0.2, 0.5 and 1 mM) with succinate‑energized mitochondria induced MMPT pore opening by 0, ‑33.3, ‑59.3 and ‑218.5%, compared with control mitochondria. Para‑hydroxyphenol at 0.1, 0.2, 0.25 and 0.5 mM induced MMPT pore opening in a concentration‑dependent manner up to 0.25 mM by ‑21, ‑54.4 and ‑107.0%, respectively. Quercetin at 0.05, 0.1, 0.25, 0.5, 0.75 and 1 mM also induced MMPT pore opening in the absence of calcium in a concentration‑dependent manner by 5, 3.7, ‑42.6, ‑81.5, ‑187 and ‑161.1%, respectively. The current observations confirm the antioxidant properties of robustaside B and para‑hydroxyphenol, and indicate a potential therapeutic use of the compounds for the treatment of diseases requiring the induction of cell death, including cancer.

Antioxidant properties of phytoestrogens

The oxidation of lipids is an autocatalytic process consisting of a number of well-defined interrelated chemical reactions. Its importance has long been recognized in the food and polymer industry, and recent advances in the understanding of vascular diseases have shown that lipid peroxidation also contributes to human disease. The various chemical stages of the reaction offer several therapeutic targets for inhibition, and from the structural characteristics of phytoestrogens it is anticipated that they should exhibit antioxidant properties. Alone, it is not sufficient for compounds such as the phytoestrogens to exhibit biological activity as antioxidants; the criteria that should be satisfied for this mechanism to be relevant biologically are discussed.

Nutritional flavonoids impact on nuclear and extranuclear estrogen receptor activities

Flavonoids are a large group of nonnutrient compounds naturally produced from plants as part of their defence mechanisms against stresses of different origins. They emerged from being considered an agricultural oddity only after it was observed that these compounds possess a potential protective function against several human degenerative diseases. This has led to recommending the consumption of food containing high concentrations of flavonoids, which at present, especially as soy isoflavones, are even available as overthecounter nutraceuticals. The increased use of flavonoids has occurred even though their mechanisms are not completely understood, in particular those involving the flavonoid impact on estrogen signals. In fact, most of the human health protective effects of flavonoids are described either as estrogenmimetic, or as antiestrogenic, while others do not involve estrogen signaling at all. Thus, the same molecule is reported as an endocrine disruptor, an estrogen mimetic or as an antioxidant without estrogenic effects. This is due in part to the complexity of the estrogen mechanism, which is conducted by different pathways and involves two different receptor isoforms. These pathways can be modulated by flavonoids and should be considered for a reliable evaluation of flavonoid, both estrogenicity and antiestrogenicity, and for a correct prediction of their effects on human health.

Dietary phenolic acids act as effective antioxidants in membrane models and in cultured cells, exhibiting proapoptotic effects in leukaemia cells

Caffeic, syringic, and protocatechuic acids are phenolic acids derived directly from food intake or come from the gut metabolism of polyphenols. In this study, the antioxidant activity of these compounds was at first evaluated in membrane models, where caffeic acid behaved as a very effective chain-breaking antioxidant, whereas syringic and protocatechuic acids were only retardants of lipid peroxidation. However, all three compounds acted as good scavengers of reactive species in cultured cells subjected to exogenous oxidative stress produced by low level of H(2)O(2). Many tumour cells are characterised by increased ROS levels compared with their noncancerous counterparts. Therefore, we investigated whether phenolic acids, at low concentrations, comparable to those present in human plasma, were able to decrease basal reactive species. Results show that phenolic acids reduced ROS in a leukaemia cell line (HEL), whereas no effect was observed in normal cells, such as HUVEC. The compounds exhibited no toxicity to normal cells while they decreased proliferation in leukaemia cells, inducing apoptosis. In the debate on optimal ROS-manipulating strategies in cancer therapy, our work in leukaemia cells supports the antioxidant ROS-depleting approach.

Natural Flavonoids Interact with Dinitrobenzene System in Aprotic Media: An Electrochemical Probing

Three structurally related natural flavonoids (FlOH), quercetin (Q), rutin (R) and morin (M), were investigated by cyclic voltammetry to probe their interactions with hazardous 1,4-dinitrobenzene (1,4-DNB) using a glassy carbon electrode. Scavenging of 1,4-DNB by FlOH was inferred from a positive shift in reduction potential, decrease in anodic peak current, and irreversible electrochemical behavior of 1,4-DNB on increasing the flavonoid concentration. The homogeneous bi-molecular rate constant (k2) was determined using the Nicholson-Shain equation and found to be higher for the dianion. Morin posed a comparatively higher k2 value for its interaction with the 1,4-DNB electrochemical system owing to its more acidic nature and least intramolecular hydrogen bonding. The cyclic voltammetric (CV) results were further supported by HyperchemPM3 quantum mechanical semi-empirical calculations, which point towards ErCi interactions between flavonoids and 1,4-DNB. The present investigation is biologically significant in terms of natural flavonoidal scavenging activity toward toxins such as dinitroaromatics.

Phenolic profile of edible honeysuckle berries (genus lonicera) and their biological effects

The current status of research on polyphenolic compounds in the berries of edible honeysuckle and their biological effects, including recommended utilization, are reviewed. The major classes of phenolic compounds in the blue berried honeysuckle are flavonols (quercetin, rutin, quercitrin) and flavanes (proanthocyanidins, catechins) and anthocyanins. Cyanidin-3-glucoside and cyanidin-3-rutinoside are considered as major anthocyanidins in edible honeysuckle berries. Such a high level of antioxidant activity in the berries of different species of the genus Lonicera is especially due to the high level of polyphenolic compounds, especially anthocyanins. These berries seem to be prospective sources of health-supporting phytochemicals that exhibit beneficial anti-adherence and chemo-protective activities, thus they may provide protection against a number of chronic conditions, e.g., cancer, diabetes mellitus, tumour growth or cardiovascular and neurodegenerative diseases.

A synthetic naringenin derivative, 5-hydroxy-7,4'-diacetyloxyflavanone-N-phenyl hydrazone (N101-43), induces apoptosis through up-regulation of Fas/FasL expression and inhibition of PI3K/Akt signaling pathways in non-small-cell lung cancer cells

Naringenin, a well-known naturally occurring flavonone, demonstrates cytotoxicity in a variety of human cancer cell lines; its inhibitory effects on tumor growth have spurred interest in its therapeutic application. In this study, naringenin was derivatized to produce more effective small-molecule inhibitors of cancer cell proliferation, and the anticancer effects of its derivative, 5-hydroxy-7,4'-diacetyloxyflavanone-N-phenyl hydrazone (N101-43), in non-small-cell lung cancer (NSCLC) cell lines NCI-H460, A549, and NCI-H1299 were investigated. Naringenin itself possesses no cytotoxicity against lung cancer cells. In contrast, N101-43 inhibits proliferation of both NCI-H460 and A549 cell lines; this capacity is lost in p53-lacking NCI-H1299 cells. N101-43 induces apoptosis via sub-G1 cell-cycle arrest in NCI-H460 and via G0/G1 arrest in A549 cells. Expression of apoptosis and cell-cycle regulatory factors is altered: Cyclins A and D1 and phospho-pRb are down-regulated, but expression of CDK inhibitors such as p21, p27, and p53 is enhanced by N101-43 treatment; N101-43 also increases expression levels of the extrinsic death receptor Fas and its binding partner FasL. Furthermore, N101-43 treatment diminishes levels of cell survival factors such as PI3K and p-Akt dose-dependently, and N101-43 additionally induces cleavage of the pro-apoptotic factors caspase-3, caspase-8, and poly ADP-ribose polymerase (PARP). Cumulatively, these investigations show that the naringenin derivative N101-43 induces apoptosis via up-regulation of Fas/FasL expression, activation of caspase cascades, and inhibition of PI3K/Akt survival signaling pathways in NCI-H460 and A549 cells. In conclusion, these data indicate that N101-43 may have potential as an anticancer agent in NSCLC.

The protective effect of Malva sylvestris on rat kidney damaged by vanadium

Background

The protective effect of the common mallow (Malva sylvestris) decoction on renal damages in rats induced by ammonium metavanadate poisoning was evaluated. On the one hand, vanadium toxicity is associated to the production of reactive oxygen species, causing a lipid peroxidation and an alteration in the enzymatic antioxidant defence. On the other hand, many medicinal plants are known to possess antioxidant and radical scavenging properties, thanks to the presence of flavonoids. These properties were confirmed in Malva sylvestris by two separate methods; namely, the Diphenyl-2-picrylhydrazyl assay and the Nitroblue Tetrazolium reduction assay.

Results

In 80 rats exposed to ammonium metavanadate (0.24 mmol/kg body weight in drinking water) for 90 days, lipid peroxidation levels and superoxide dismutase, catalase and glutathione peroxidase activities were measured in kidney. A significant increase in the formation of free radicals and antioxidant enzyme activities was noticed. In addition, a histological examination of kidney revealed a structural deterioration of the renal cortical capsules and a shrinking of the Bowman space. In animals intoxicated by metavanadate but also given a Malva sylvestris decoction (0.2 g dry mallow/kg body weight), no such pathologic features were observed: lipid peroxidation levels, antioxidant enzyme activities and histological features appeared normal as compared to control rats.

Conclusion

Malva sylvestris is proved to have a high antioxidative potential thanks to its richness in phenolic compounds.

Neuroprotective herbs and foods from different traditional medicines and diets

Plant secondary metabolites include an array of bioactive constituents form both medicinal and food plants able to improve human health. The exposure to these phytochemicals, including phenylpropanoids, isoprenoids and alkaloids, through correct dietary habits, may promote health benefits, protecting against the chronic degenerative disorders mainly seen in Western industrialized countries, such as cancer, cardiovascular and neurodegenerative diseases. In this review, we briefly deal with some plant foods and herbs of traditional medicines and diets, focusing on their neuroprotective active components. Because oxidative stress and neuroinflammation resulting from neuroglial activation, at the level of neurons, microglial cells and astrocytes, are key factors in the etiopathogenesis of both neurodegenerative and neurological diseases, emphasis will be placed on the antioxidant and anti-inflammatory activity exerted by specific molecules present in food plants or in remedies prescribed by herbal medicines.

Design, synthesis, and examination of neuron protective properties of alkenylated and amidated dehydro-silybin derivatives

A series of C7-O- and C20-O-amidated 2,3-dehydrosilybin (DHS) derivatives ((+/-)-1a-f and (+/-)-2), as well as a set of alkenylated DHS analogues ((+/-)-4a-f), were designed and de novo synthesized. A diesteric derivative of DHS ((+/-)-3) and two C23 esterified DHS analogues ((+/-)-5a and (+/-)-5b) were also prepared for comparison. The cell viability of PC12 cells, Fe(2+) chelation, lipid peroxidation (LPO), free radical scavenging, and xanthine oxidase inhibition models were utilized to evaluate their antioxidative and neuron protective properties. The study revealed that the diether at C7-OH and C20-OH as well as the monoether at C7-OH, which possess aliphatic substituted acetamides, demonstrated more potent LPO inhibition and Fe(2+) chelation compared to DHS and quercetin. Conversely, the diallyl ether at C7-OH and C20-OH was more potent in protection of PC12 cells against H(2)O(2)-induced injury than DHS and quercetin. Overall, the more lipophilic alkenylated DHS analogues were better performing neuroprotective agents than the acetamidated derivatives. The results in this study would be beneficial for optimizing the therapeutic potential of lignoflavonoids, especially in neurodegenerative disorders such as Alzheimer's and Parkinson's disease.

Protective activity of plicatin B against human LDL oxidation induced in metal ion-dependent and -independent processes. Experimental and theoretical studies

Oxidation of low-density lipoproteins (LDL) is thought to be a major factor in the pathophysiology of atherosclerosis. Natural antioxidants have been shown to protect LDL from oxidation and to inhibit atherogenic developments in animals. Structurally related prenylated pterocarpans, erybraedin C and bitucarpin A, and the prenylchalcone plicatin B were examined for their ability to inhibit LDL oxidation in vitro. The kinetic profile of peroxidation is characterized by the lag time of oxidation (t(lag)), the maximal rate of oxidation (V(max)) and the maximal accumulation of oxidation products (OD(max)). Specific variation of the set of kinetic parameters by antioxidants may provide important information about the mechanism of inhibitory action of a given compound. At equimolar concentrations (1 microM) the prenylated derivatives tested were found to inhibit 1 microM copper sulphate-induced oxidation of LDL (50 microg protein/ml) in accordance with the following order of activity: plicatin B>erybraedin Cbitucarpin A. Structural aspects, such as hydrogen-donating substituents, their number and arrangement in the aromatic ring moieties, and the prenyl and methoxy substituents, were investigated in order to explain the findings obtained. It is well known that the antioxidant activity of flavonoids is believed to be caused by a combination of transition metal chelation and free-radical-scavenging activities. To investigate these differences we comparatively studied the protective mechanism of plicatin B in copper-dependent or -independent LDL oxidation. The latter was mediated by 2,2'-azo-bis-(2-amidinopropane) dihydrochloride (ABAP). We measured the formation of conjugated dienes (OD(234 nm)). Plicatin B (0.2-1.5 microM) delayed the Cu(2+) (1 microM) promoted oxidation as conjugate diene formation (t(lag)) of the LDL by 45.2-123.5 min and reduced V(max) by 0.46-0.29 microM/min. In the ABAP (0.2mM) promoted LDL oxidation t(lag) increased by 67.2-110.2 min through plicatin B (0.5-2.5 microM). In experiments in which Cu(2+) concentrations increased (0.5 - 3 microM) and the amount of plicatin B (1 microM) was maintained constant, a significant decrease in t(lag) and an increase in V(max) was observed. In this study plicatin B appeared to exhibit a mixed mechanism, interfering with the formation of the radicals by chelating copper involved in the initiation/propagation reaction, but also by scavenging free hydroperoxyl radicals resulting from ABAP thermolysis. In addition, theoretical analysis indicated that plicatin B preferentially established the chelating complex with Cu(2+), because its affinity value is notably higher (by a factor of 5) than that for Cu(+).

Antioxidant effects of xanthohumol and functional impact on hepatic ischemia-reperfusion injury

Therapeutic effects of dietary flavonoids have been attributed mainly to their antioxidant capacity. Xanthohumol (1), a prominent flavonoid of the hop plant, Humulus lupulus, was investigated for its antioxidant potential and for its effect on NF-kappaB activation. To examine the biological relevance of 1, a hepatic ischemia/reperfusion model was chosen as a widely accepted model of oxidative stress generation. The impact of 1 on endogenous antioxidant systems, on the NF-kappaB signal transduction pathway as well as on apoptotic parameters, and on hepatic tissue damage was evaluated. Compound 1 markedly decreased the level of reactive oxygen species in vitro. Furthermore, levels of enzymatic and nonenzymatic antioxidants were restored after pretreatment in postischemic hepatic tissue, and lipid peroxidation was attenuated. NF-kappaB activity was reduced in vitro as well as in hepatic tissue after ischemia/reperfusion upon pretreatment with 1. In addition, the phosphorylation of Akt was markedly inhibited. Surprisingly, 1 decreased the expression of the antiapoptotic protein Bcl-X and increased caspase-3 like-activity, a proapoptotic parameter. Moreover, hepatic tissue damage as well as TNF-alpha levels increased in xanthohumol-pretreated liver tissue after ischemia/reperfusion. In summary, xanthohumol did not protect against ischemia/reperfusion injury in rat liver, despite its antioxidant and NF-kappaB inhibitory properties.

Acetyl derivate of quercetin increases the sensitivity of human leukemia cells toward apoptosis

The hydroxyl groups of flavonoids are important for their bioactive functions and also prone to oxidation to quinones. To block the potential oxidation of quercetin, and generate a stronger bioactive compound, we synthesized acetyl and methyl derivatives of quercetin, 3,7,3',4'-O-tetraacetylquercetin (4Ac-Q) and 3,7,3',4'-O-tetramethylquercetin (4Me-Q), which substituted the hydroxyl groups of quercetin with acetyl or methyl groups at the 3,7,3',4' positions of quercetin, and then evaluated the ability to cause cell proliferation inhibition and apoptosis in HL-60 cells. The results revealed that 4Ac-Q and quercetin, but not 4Me-Q, significantly inhibit cell proliferation by caspase-mediated apoptosis when characterized by DNA fragmentation, activation of caspase-3 and PARP cleavage while 4Me-Q lost this ability. Interestingly, 4Ac-Q revealed stronger apoptotic activity than parent quercetin via a ROS-independent pathway. These findings provide a valuable strategy to increase the sensitivity of human leukemia HL-60 cells toward apoptosis by modifying quercetin structure.

Bioactivity of Grape Chemicals for Human Health

Grapevine ( Vitis vinifera) products, grape and grape juice, represent a valuable source of bioactive phytochemicals, synthesized by three secondary metabolic pathways (phenylpropanoid, isoprenoid and alkaloid biosynthetic routes) and stored in different plant tissues. In the last decades, compelling evidence suggested that regular consumption of these products may contribute to reducing the incidence of chronic illnesses, such as cancer, cardiovascular diseases, ischemic stroke, neurodegenerative disorders and aging, in a context of the Mediterranean dietary tradition. The health benefits arising from grape product intake can be ascribed to the potpourri of biologically active chemicals occurring in grapes. Among them, the recently discovered presence of melatonin adds a new element to the already complex grape chemistry. Melatonin, and its possible synergistic action with the great variety of polyphenols, contributes to further explaining the observed health benefits associated with regular grape product consumption.

Plant polyphenols and multidrug resistance: Effects of dietary flavonoids on drug transporters in Caco-2 and MDCKII-MDR1 cell transport models

The hypothesis tested was that specific flavonoids such as epicatechin gallate, epigallocatechin gallate, genistein, genistin, naringenin, naringin, quercetin and xanthohumol will modulate cellular uptake and permeability (P(e)) of multidrug-resistant substrates, cyclosporin A (CSA) and digoxin, across Caco-2 and MDCKII-MDR1 cell transport models. (3)H-CSA/(3)H-digoxin transport and uptake experiments were performed with and without co-exposure of the flavonoids. Aglycone flavonoids reduced the P(e) of CSA to a greater extent than glycosylated flavonoids with 30 microM xanthohumol producing the greatest effect (7.2 x 10(-6) to 6.6 x 10(-7) and 17.9 x 10(-6) to 4.02 x 10(-6) cm s(-1) in Caco-2 and MDCKII-MDR1 cells, respectively); while no measurable effects were seen with digoxin. Xanthohumol significantly demonstrated (1) saturable efflux, (2) increased uptake of (3)H-digoxin and (3) decreased uptake of (3)H-CSA in the Caco-2 cells. The transport data suggests that xanthohumol effects transport of CSA in a manner that is distinct from the digoxin efflux pathway and suggests that intestinal transport of these MDR1 substrates is more complex than previously reported.

Induction of apoptotic cell death by synthetic naringenin derivatives in human lung epithelial carcinoma A549 cells

Although flavonoids, which are both qualitatively and quantitatively one of the largest groups of natural products, exhibit a variety of beneficial health effects, the exact molecular mechanism of the cellular activities is still not fully explained and there currently exists a lack of evidence for any relationship between the structure-activity relationship and apoptosis-inducing activity. In order to determine the importance of the OH group or substitution of the 5 or carbon-7 in the diphenylpropane skeleton of flavonoids, we originally synthesized several modified naringenin derivatives, including 7-O-benzyl naringenin (KUF-1) and 7-O-(MeO-L-Leu-D-Pro-carbonylmethyl) naringenin (KUF-7). Treatment with KUF-1 or KUF-7 resulted in significant apoptosis-inducing effects concomitant with chromatin condensation, caspase activation, and intracellular ROS production. Our data indicate that originally synthesized naringenin derivatives, KUF-1 and KUF-7 differentially regulate the apoptosis of A549 cells via intracellular ROS production coupled with the concomitant activation of the caspase cascade signaling pathway, thereby implying that hydroxylation or substitution at Carbon-7 is critical for the apoptosis-inducing activity of flavonoids.

Evaluation of the protective effects of quercetin in the hepatopulmonary syndrome

The hepatopulmonary syndrome (HPS) occurs when intrapulmonary dilatation causes hypoxemia in cirrhosis. The free radicals may play a significant contributory role in the progression of HPS, and flavonoid agents could protect against deleterious effects of free radicals. The flavonoid quercetin was evaluated in an experimental model of biliary cirrhosis induced by bile duct ligation (BDL) in rats. Quercetin was administered at 50mg/kg for 14 days to cirrhotic and non-cirrhotic rats. Bone marrow was extracted from animals to analyze micronuclei. Lung, liver and blood were extracted to detect DNA damage using the comet assay. The results showed that the micronuclei and DNA damages to lung and liver were increased in BDL rats. Quercetin caused no damage to the DNA while decreasing the occurrence of micronucleated cells in bone marrow as well as DNA damage to lung and liver in cirrhotic rats. Quercetin showed antimutagenic activity against hydroperoxides as evaluated by the oxidative stress sensitive bacterial strains TA102 Salmonella typhimurium and IC203 Escherichia coli, suggesting protection by free radical scavenging. In Saccharomyces cerevisie yeast strains lacking mitochondrial or cytosolic superoxide dismutase, these results indicate that quercetin protects cells by induction of antioxidant enzymes. The present study is the first report of genotoxic/antigenotoxic effects of quercetin in a model of animal cirrhosis. In this model, quercetin was not able to induce genotoxicity and, conversely, it increased the genomic stability in the cirrhotic rats, suggesting beneficial effects, probably by its antioxidant properties.

Assessment by Survival Analysis of the Radioprotective Properties of Propolis and Its Polyphenolic Compounds

The radioprotective effects of propolis and polyphenolic compounds from propolis on the radiation-induced mortality of mice exposed to 9 Gy of gamma-irradiation were studied. Intraperitoneal (i.p.) treatment of mice at doses of 100 mg kg(-1) body weight of propolis (water or ethanolic extract; WSDP or EEP) or its polyphenolic compounds (quercetin, naringin caffeic acid, chrysin) consecutively for 3 d before irradiation, delayed the onset of mortality and reduced the symptoms of radiation sickness. All test compounds provided protection against hematopoietic death (death within 30 d after irradiation). The greatest protection was achieved with quercetin; the number of survivors at the termination of the experiment was 63%. According to statistical analyses by the Kaplan-Meier method and the log-rank test, a significant difference between test components and control was found (p<0.001). Treatment with test components after lethal irradiation was ineffective. These results suggest that propolis and its polyphenolic compounds given to mice before irradiation protect mice from the lethal effects of whole-body irradiation.