stilbenes and kaempferol

Antioxidant ingredients present in grape have been extensively investigated for their cancer chemopreventive effects. However, much of the work has been done on individual ingredients, especially focusing on resveratrol and quercetin. Phytochemically, whole grape represents a combination of numerous phytonutrients. Limited research has been done on the possible synergistic/additive/antagonistic interactions among the grape constituents. Among these phytochemical constituents of grapes, resveratrol, quercetin, kaempferol, catechin, epicatechin, and anthocyanins (cyanidin and malvidin) constitute more than 70% of the grape polyphenols. Therefore, these have been relatively well studied for their chemopreventive effects against a variety of cancers. While a wealth of information is available individually on cancer chemopreventive/anti-proliferative effects of resveratrol and quercetin, limited information is available regarding the other major constituents of grape. Studies have also suggested that multiple grape antioxidants, when used in combination, alone or with other agents/drugs show synergistic or additive anti-proliferative response. Based on strong rationale emanating from published studies, it seems probable that a combination of multiple grape ingredients alone or together with other agents could impart 'additive synergism' against cancer.

Topics: Animals; Anthocyanins; Anticarcinogenic Agents; Antineoplastic Combined Chemotherapy Protocols; Antioxidants; Catechin; Cell Line, Tumor; Chemoprevention; Disease Models, Animal; Humans; Kaempferols; Neoplasms; Plant Extracts; Polyphenols; Quercetin; Resveratrol; Stilbenes; Vitis

Epithelial-mesenchymal transition (EMT) plays a key role in tumor progression. The cells undergoing EMT upregulate the expression of cell motility-related proteins and show enhanced migration and invasion. The hallmarks of EMT in cancer cells include changed cell morphology and increased metastatic capabilities in cell migration and invasion. Therefore, prevention of EMT is an important tool for the inhibition of tumor metastasis. A novel preventive therapy is needed, such as treatment of natural dietary substances that are nontoxic to normal human cells, but effective in inhibiting cancer cells. Phytoestrogens, such as genistein, resveratrol, kaempferol and 3,3'-diindolylmethane (DIM), can be raised as possible candidates. They are plant-derived dietary estrogens, which are found in tea, vegetables and fruits, and are known to have various biological efficacies, including chemopreventive activity against cancers. Specifically, these phytoestrogens may induce not only anti-proliferation, apoptosis and cell cycle arrest, but also anti-metastasis by inhibiting the EMT process in various cancer cells. There have been several signaling pathways found to be associated with the induction of the EMT process in cancer cells. Phytoestrogens were demonstrated to have chemopreventive effects on cancer metastasis by inhibiting EMT-associated pathways, such as Notch-1 and TGF-beta signaling. As a result, phytoestrogens can inhibit or reverse the EMT process by upregulating the expression of epithelial phenotypes, including E-cadherin, and downregulating the expression of mesenchymal phenotypes, including N-cadherin, Snail, Slug, and vimentin. In this review, we focused on the important roles of phytoestrogens in inhibiting EMT in many types of cancer and suggested phytoestrogens as prominent alternative compounds to chemotherapy.

Topics: Anticarcinogenic Agents; Antineoplastic Agents; Cell Line, Tumor; Epithelial-Mesenchymal Transition; Genistein; Humans; Indoles; Kaempferols; Neoplasm Metastasis; Neoplasms; Phytoestrogens; Resveratrol; Stilbenes

Polyphenols such as apigenin, kaempferol or resveratrol are typically found in plants, including fruits, vegetables, herbs and spices, which have a wide range of biological functions such as antioxidative, anti-inflammatory, vasodilative, anticoagulative and proapoptotic. Discovering such multifunctional compounds in widely consumed plant-based products - ones that both inhibit the release of TNF-α from tissue macrophages and at the same time enhance the secretion of IL-10 - would be an important signpost in the quest for effective pharmacological treatment of numerous diseases that have an inflammatory etiology. The aim of the study is to investigate the impact of biologically active polyphenols such as apigenin, resveratrol and kaempferol on gene expression and protein secretion of IL-10 and TNF-α in line RAW-264.7. Cells were cultured under standard conditions. IL-10 and TNF-α genes expression were examined using QRT-PCR and to assess cytokines concentration ELISA have been used. Apigenin, kaempferol and resveratrol at a dose 30μM significantly decrease the TNF-α expression and secretion. Apigenin decrease the IL-10 expression and secretion. Furthermore, increase in IL-10 secretion after administration of kaempferol and resveratrol were observed. In the process of administration of tested compounds before LPS, which activate macrophages, decrease of TNF-α secretion after apigenin and kaempferol and increase of IL-10 secretion after resveratrol were observed. The results of present work indicate that 1) apigenin, resveratrol and kaempferol may reduce the intensity of inflammatory processes by inhibiting the secretion of proinflammatory cytokine TNF-α, and resveratrol and kaempferol additionally by increasing the secretion of anti-inflammatory cytokine IL-10 2) the studies indicate the potentially beneficial - anti-inflammatory - impact of diet rich in products including apigenin, resveratrol and kaempferol.

Topics: Animals; Anti-Inflammatory Agents; Apigenin; Cell Line; Cytokines; Gene Expression; Inflammation; Interleukin-10; Kaempferols; Lipopolysaccharides; Macrophages; Mice; RAW 264.7 Cells; Resveratrol; Stilbenes; Tumor Necrosis Factor-alpha

Flavonoids are common polyphenolic compounds widely distributed in fruits and vegetables. These pigments have important pharmacological relevance because emerging research suggests possible anti-cancer and anti-inflammatory properties as well other beneficial health effects. These compounds are relatively hydrophobic molecules, suggesting the role of blood transport proteins in their delivery to tissues. In this study, we assess the binding interactions of four flavonoids (kaempferol, luteolin, quercetin, and resveratrol) with human serum albumin (HSA), the most abundant protein in the blood, and with glutathione S-transferase pi isoform-1 (GSTP1), an enzyme with well-characterized hydrophobic binding sites that plays an important role in detoxification of xenobiotics with reduced glutathione, using a novel Taylor dispersion surface plasmon resonance (SPR) technique. For the first time, HSA sites revealed a high-affinity binding site for flavonoid interactions. Out of the four flavonoids that we examined, quercetin and kaempferol showed the strongest equilibrium binding affinities (K(D)) of 63 ± 0.03 nM and 37 ± 0.07 nM, respectively. GSTP1 displayed lower affinities in the micromolar range towards all of the flavonoids tested. The interactions of flavonoids with HSA and GSTP1 were studied successfully using this novel SPR assay method. The new method is compatible with both kinetic and equilibrium analyses.

Topics: Binding Sites; Flavonoids; Glutathione S-Transferase pi; Humans; Kaempferols; Kinetics; Luteolin; Protein Binding; Quercetin; Resveratrol; Serum Albumin; Stilbenes; Surface Plasmon Resonance

Phytoestrogens are of interest because of their reported beneficial effects on many human maladies including cancer, neurodegeneration, cardiovascular disease and diabetes. As data on phytoestrogens continues to accumulate, it is clear that there is significant overlap in the cellular effects elicited by these various compounds. Here, we show that one mechanism by which a number of phytoestrogens achieve their growth inhibitory and cytoprotective effects is via induction of the mitochondrial manganese superoxide dismutase (MnSOD). Eight phytoestrogens, including resveratrol, coumestrol, kaempferol, genistein, daidzein, apigenin, isoliquirtigenin and glycitin, were tested for their ability to induce MnSOD expression in mouse C2C12 and primary myoblasts. Five of these, resveratrol, coumestrol, kaempferol, genistein and daidzein, significantly increased MnSOD expression, slowed proliferative growth and enhanced stress resistance (hydrogen peroxide LD50) . When siRNA was used to prevent the MnSOD induction by genistein, coumestrol or daidzein, none of these compounds exerted any effect on proliferative growth, and only the effect of coumestrol on stress resistance persisted. The estrogen antagonist ICI182780 prevented the increased MnSOD expression and also the changes in cell growth and stress resistance, indicating that these effects are mediated by estrogen receptors (ER). The absence of effects of resveratrol or coumestrol, but not genistein, in ERβ-null cells further indicated that this ER in particular is important in mediating these effects. Thus, an ER-mediated induction of MnSOD expression appears to underlie the growth inhibitory and cytoprotective activities of multiple phytoestrogens.

Topics: Animals; Cell Cycle; Cell Line; Cell Proliferation; Coumestrol; Cytoprotection; Estradiol; Fulvestrant; Genistein; Isoflavones; Kaempferols; Mice; Myoblasts; Phytoestrogens; Receptors, Estrogen; Resveratrol; Stilbenes; Stress, Physiological; Superoxide Dismutase

Quercetin, kaempferol, and pterostilbene are abundant in berries. The anti-oxidative properties of these constituents may contribute to cancer chemoprevention. However, their precise mechanisms of action and their combinatorial effects are not completely understood. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) regulates anti-oxidative stress enzymes and Phase II drug metabolizing/detoxifying enzymes by binding to antioxidant response element (ARE). This study aimed to investigate the anti-oxidative stress activities of quercetin, kaempferol, and pterostilbene individually and in combination, as well as the involvement of the Nrf2-ARE signaling pathway. Quercetin, kaempferol, and pterostilbene all exhibited strong free-radical scavenging activity in the DPPH assay. The MTS assay revealed that low concentration combinations we tested were relatively non-toxic to HepG2-C8 cells. The results of the DCFH-DA assay and combination index (CI) indicated that quercetin, kaempferol, and pterostilbene attenuated intracellular reactive oxygen species (ROS) levels when pretreated individually and had synergistic effects when used in combination. In addition, the combination treatment significantly induced ARE and increased the mRNA and protein expression of Nrf2-regulated genes. Collectively, our study demonstrated that the berry constituents quercetin, kaempferol, and pterostilbene activated the Nrf2-ARE signaling pathway and exhibited synergistic anti-oxidative stress activity at appropriate concentrations.

Topics: Antioxidant Response Elements; Antioxidants; Cell Survival; Dose-Response Relationship, Drug; Drug Synergism; Fruit; Gene Expression Regulation; Hep G2 Cells; Humans; Kaempferols; NF-E2-Related Factor 2; Oxidative Stress; Phytochemicals; Quercetin; Reactive Oxygen Species; Signal Transduction; Stilbenes

The effect of the intake of antioxidant polyphenols such as resveratrol and others on survival and different parameters of life quality has been a matter of debate in the last years. We have studied here the effects of the polyphenols resveratrol and kaempferol added to the diet in a murine model undergoing long-term hypercaloric diet. Using 50 mice for each condition, we have monitored weight, survival, biochemical parameters such as blood glucose, insulin, cholesterol, triglycerides and aspartate aminotransferase, neuromuscular coordination measured with the rotarod test and morphological aspect of stained sections of liver and heart histological samples. Our data show that mice fed since they are 3-months-old with hypercaloric diet supplemented with any of these polyphenols reduced their weight by about 5-7% with respect to the controls fed only with hypercaloric diet. We also observed that mice fed with any of the polyphenols had reduced levels of glucose, insulin and cholesterol, and better marks in the rotarod test, but only after 1 year of treatment, that is, during senescence. No effect was observed in the rest of the parameters studied. Furthermore, although treatment with hypercaloric diets induced large changes in the pattern of gene expression in liver, we found no significant changes in gene expression induced by the presence of any of the polyphenols. Thus, our data indicate that addition of resveratrol or kaempferol to mice food produces an initial decrease in weight in mice subjected to hypercaloric diet, but beneficial effects in other parameters such as blood glucose, insulin and cholesterol, and neuromuscular coordination, only appear after prolonged treatments.

Topics: Alanine Transaminase; Animals; Blood Glucose; Body Weight; Cholesterol; Gene Expression Regulation; Insulin; Kaempferols; Liver; Male; Mice, Inbred C57BL; Obesity; Resveratrol; Rotarod Performance Test; Stilbenes; Survival Rate; Triglycerides

The progression of Alzheimer's disease (AD) is accompanied by disturbances of the endosome/lysosome (EL) system and there is accumulation of peptides of the AD-associated amyloid beta (Abeta) type in EL vesicles of affected neurons. EL modulating agents partially ameliorate the Abeta-mediated cell abnormalities. However, no extensive studies on the potential pharmaceutical applications of combinations of such agents and their synergistic effects have been performed. This study shows the beneficial anti-amyloid effects of several combinations of lysosomal modulators and other pharmacological and new nanobiotechnological agents. Some agents potentiated each other's action and some of them facilitated the anti-amyloid actions of memantine, a modifier of Ca2+-permeable channels involved in AD and one of the few drugs used for treatment of AD. Another compound used in nanobiotechnology ameliorated as a nanocarrier the beneficial effects of some of these potential pharmaceutical agents. They may be considered as additional drugs to improve the efficacy of the therapeutic approaches for AD and related neurodegenerative disorders.

Topics: Acetylcarnitine; Alzheimer Disease; Amyloid beta-Peptides; Cell Line, Tumor; Cell Survival; Drug Carriers; Endosomes; Humans; Kaempferols; Lactic Acid; Lysosomes; Memantine; Mifepristone; Nanoparticles; Neuroprotective Agents; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Resveratrol; Stilbenes

Thyroid carcinogenesis is accompanied by loss of thyroid-specific functions and refractory to radioiodine and thyroid stimulating hormone (TSH) suppression therapy. Redifferentiating agents have been shown to inhibit tumor growth and improve the response to conventional therapy. Polyphenol phytochemicals (PPs) in fruits and vegetables have been reported to inhibit cancer initiation, promotion, progression and induce redifferentiation in selected types. In this study we examined PPs induce redifferentiation in thyroid cancer cell lines. We investigated the effects of genistein, resveratrol, quercetin, kaempferol, and resorcinol on the F9 embryonal carcinoma cell differentiation model. The thyroid cancer cell lines, TPC-1, FTC-133, NPA, FRO, and ARO, displayed growth inhibition in response to genistein, resveratrol, quercetin. We further demonstrated that genistein decreased the dedifferention marker CD97 in NPA cells and resveratrol decreased CD97 in FTC-133, NPA, FRO cells and quercetin decreased CD97 in all cell lines. We observed increased expression of differentiation marker NIS in FTC-133 cells in response to genistein, and resveratrol but no change in NPA, FRO, ARO cells. Quercetin increased or induced NIS in FTC-133, NPA, FRO cells. These findings suggest that PPs may provide a useful therapeutic intervention in thyroid cancer redifferentiation therapy.

Topics: Antigens, CD; Antineoplastic Agents; Carcinoma, Embryonal; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Flavonoids; Gene Expression Regulation, Neoplastic; Genistein; Humans; Kaempferols; Models, Biological; Phenols; Polyphenols; Quercetin; Receptors, G-Protein-Coupled; Resorcinols; Resveratrol; Stilbenes; Symporters; Thyroid Neoplasms

Resveratrol and kaempferol are natural chemopreventative agents that are also aryl hydrocarbon receptor (AHR) antagonists and estrogen receptor (ER) agonists. In this study we evaluated the role of ERα in resveratrol- and kaempferol-mediated inhibition of AHR-dependent transcription. Kaempferol or resveratrol inhibited dioxin-induced cytochrome P450 1A1 (CYP1A1) and CYP1B1 expression levels and recruitment of AHR, ERα and co-activators to CYP1A1 and CYP1B1. Both phytochemicals induced the expression and recruitment of ERα to gene amplified in breast cancer 1 (GREB1). RNAi-mediated knockdown of ERα in T-47D cells did not affect the inhibitory action of either phytochemical on AHR activity. Both compounds also inhibited AHR-dependent transcription in ERα-negative MDA-MB-231 and BT-549 breast cancer cells. These data show that ERα does not contribute to the AHR-inhibitory activities of resveratrol and kaempferol.

Topics: Antineoplastic Agents, Phytogenic; Aryl Hydrocarbon Hydroxylases; Aryl Hydrocarbon Receptor Nuclear Translocator; Blotting, Western; Breast Neoplasms; Cell Line, Tumor; Cytochrome P-450 CYP1A1; Cytochrome P-450 CYP1B1; Dose-Response Relationship, Drug; Estradiol; Estrogen Receptor alpha; Fulvestrant; Gene Expression Regulation, Neoplastic; Humans; Kaempferols; Polychlorinated Dibenzodioxins; Receptors, Aryl Hydrocarbon; Resveratrol; Reverse Transcriptase Polymerase Chain Reaction; RNA Interference; RNA, Messenger; Stilbenes; Teratogens; Transcription, Genetic

We hypothesized that the phytochemicals resveratrol, quercetin, and kaempferol would modulate B lymphocyte proliferation, Ig synthesis, and apoptosis after activation. Peripheral blood mononuclear cells (PBMC) were isolated from 12 healthy adult human volunteers and incubated with pokeweed mitogen plus 0, 2, 5, and 10 mumol/L resveratrol, quercetin, or kaempferol. After 6 d, CD19+ B cells were analyzed for proliferation, B cell lymphoma-2 (Bcl-2) expression, and activation of caspase-3 using flow cytometry. After 8 d, cell supernatants were collected and IgM and IgG were measured by ELISA. Resveratrol at a concentration of 5 mumol/L increased the percentage of CD19+ cells compared with mitogen only-stimulated cells (P < 0.01), and a trend for increased proliferation was observed for cells treated with 0, 2, and 5 mumol/L resveratrol (P-trend = 0.01). However, 10 mumol/L resveratrol inhibited proliferation of B lymphocytes (P < 0.01). Expression of Bcl-2 and caspase-3 activation increased in B cells treated with 10 mumol/L resveratrol compared with mitogen alone (P < 0.01), and trends for dose-responsive increases in Bcl-2 expression and caspase-3 activation were observed (P-trend < 0.0001). Differences in IgM and IgG production were not observed for PBMC treated with resveratrol. Kaempferol at 10 mumol/L slightly inhibited proliferative responses (P < 0.05) but did not affect B cell function or apoptosis. Quercetin did not alter B cell proliferation, function, or apoptosis. These data show that human B lymphocyte proliferation and apoptosis are modified by physiological concentrations of resveratrol and suggest that exposure of human B cells to resveratrol may increase survival by upregulating Bcl-2.

Topics: Adolescent; Adult; Antigens, CD19; Antineoplastic Agents, Phytogenic; Apoptosis; B-Lymphocytes; Caspase 3; Cell Proliferation; Dose-Response Relationship, Drug; Female; Gene Expression; Genes, bcl-2; Humans; Immunoglobulin G; Immunoglobulin M; Kaempferols; Lymphocyte Activation; Male; Middle Aged; Plant Extracts; Pokeweed Mitogens; Quercetin; Resveratrol; Stilbenes; Young Adult

Inhibition of angiotensin converting enzyme (ACE) has proved to be beneficial in the treatment of various cardiovascular disorders. The aim of this study was to evaluate ACE inhibitory potential of two polyphenolic compounds with different structures: resveratrol (present in high quantities in French wine) and kaempferol (abundant in greens), using method of liquid chromatography coupled with electrospray ionization mass spectrometry (LC-ESI-MS) for ex vivo measurement of angiotensin I to angiotensin II conversion by ACE in aortic tissue of Wistar-Kyoto rats. In this setting, kaempferol (10-30-100 microM), but not resveratrol (10-30-100 microM) appeared to inhibit dose-dependently conversion of Ang I to Ang II. Although the mechanism of ACE inhibition by kaempferol remains to be elucidated, this observation may help in search or designing of new classes of ACE inhibitors.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Kaempferols; Male; Peptidyl-Dipeptidase A; Rats; Rats, Inbred WKY; Resveratrol; Stilbenes

The aryl hydrocarbon receptor (AHR) is a cytosolic receptor which upon activation by its agonists, translocates into the nucleus and forms a dimer with ARNT (aryl hydrocarbon nuclear translocator). The AHR/ARNT dimer regulates the expression of its target genes by binding to DNA recognition elements termed dioxin responsive elements (DREs). Many AHR agonists, like the polyaromatic hydrocarbons and polyhalogenated hydrocarbons are known human carcinogens. Human exposure to these compounds is common due to their presence in air pollution and cigarette smoke. Interestingly, many dietary constituents that have chemo preventative properties have been found to also act as antagonists of the AHR pathway. Thus, a chemopreventive approach that may be effective in decreasing the incidences of many human cancers may involve a dietary regimen that includes a number of these naturally occurring AHR antagonists. With this idea in mind, we have assayed the ability of 15 flavonoids to inhibit AHR activated reporter activity and selected kaempferol for further analysis. Kaempferol proved to be capable of inhibiting binding of agonist and agonist-induced formation of the AHR/ARNT DNA-binding complex and upregulation of the AHR target gene, CYP1A1. Using an in vitro paradigm of events that are thought to occur during cigarette-smoke-induced lung cancer, we found that kaempferol also inhibited the ability of cigarette smoke condensate to induce growth of immortalized lung epithelial (BEAS-2B) cells in soft agar. Taken together, these results illustrate the promise associated with the use of flavonoids, that inhibit both AHR signaling and the carcinogenic actions of AHR agonists, for chemopreventive purposes.

Topics: Anticarcinogenic Agents; Carcinoma, Hepatocellular; Cell Line, Tumor; Cell Transformation, Neoplastic; Dimethyl Sulfoxide; Flavanones; Flavones; Flavonoids; Humans; Kaempferols; Liver Transplantation; Luteolin; Receptors, Aryl Hydrocarbon; Resveratrol; Smoking; Stilbenes

Disturbances in energy homeostasis can result in obesity and other metabolic diseases. Here we report a metabolic pathway present in normal human skeletal muscle myoblasts that is activated by the small polyphenolic molecule kaempferol (KPF). Treatment with KPF leads to an approximately 30% increase in skeletal myocyte oxygen consumption. The mechanism involves a several-fold increase in cyclic AMP (cAMP) generation and protein kinase A activation, and the effect of KPF can be mimicked via treatment with dibutyryl cAMP. Microarray and real-time PCR studies identified a set of metabolically relevant genes influenced by KPF including peroxisome proliferator-activated receptor gamma coactivator-1alpha, carnitine palmitoyl transferase-1, mitochondrial transcription factor 1, citrate synthase, and uncoupling protein-3, although KPF itself is not a direct mitochondrial uncoupler. The cAMP-responsive gene for type 2 iodothyronine deiodinase (D2), an intracellular enzyme that activates thyroid hormone (T3) for the nucleus, is approximately threefold upregulated by KPF; furthermore, the activity half-life for D2 is dramatically and selectively increased as well. The net effect is an approximately 10-fold stimulation of D2 activity as measured in cell sonicates, with a concurrent increase of approximately 2.6-fold in the rate of T3 production, which persists even 24 h after KPF has been removed from the system. The effects of KPF on D2 are independent of sirtuin activation and only weakly reproduced by other small polyphenolic molecules such as quercetin and fisetin. These data document a novel mechanism by which a xenobiotic-activated pathway can regulate metabolically important genes as well as thyroid hormone activation and thus may influence metabolic control in humans.

Topics: Animals; Cell Line; Chalcones; Cyclic AMP; Cyclic AMP-Dependent Protein Kinase Type II; Cyclic AMP-Dependent Protein Kinases; Dose-Response Relationship, Drug; Energy Metabolism; Gene Expression Profiling; Gene Expression Regulation; Humans; Iodide Peroxidase; Iodothyronine Deiodinase Type II; Kaempferols; Myoblasts; Oxygen Consumption; Rats; Resveratrol; RNA Interference; Stilbenes; Triiodothyronine

We aimed to determine: 1) the concentration of polyphenols in Spanish red wines, 2) the vasodilatory properties of those wines in relation with their polyphenol concentrations and 3) the vasodilation induced by some of these polyphenols in rat aortic rings. In the wines studied the concentration of rutin and kaempferol was high compared with other polyphenols. All wines relaxed precontracted rat aortic rings and this effect was directly related with the concentration of myricetin and kaempferol in the wines. Kaempferol and rutin also induced endothelium-dependent and independent relaxation, kaempferol was more potent. This relaxation was not inhibited by the estrogen receptor alpha antagonist ICI 182,760. Kaempferol also potentiated the endothelium-dependent relaxation induced by acetylcholine, which was reversed by Nw-nitro-l-arginine methyl ester (l-NAME). These findings show a good correlation between the concentration of polyphenols (especially kaempferol) of Spanish red wines and the vasodilatory effect, which may confer on them unique features in the prevention of cardiovascular disease.

Topics: Analysis of Variance; Animals; Aorta, Thoracic; Catechin; Chromatography, High Pressure Liquid; Dose-Response Relationship, Drug; Endothelium, Vascular; Flavonoids; In Vitro Techniques; Kaempferols; Male; Phenols; Polyphenols; Quercetin; Rats; Rats, Wistar; Resveratrol; Rutin; Spain; Stilbenes; Vasodilation; Vasodilator Agents; Wine

The MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay is a widely used screening method to measure cell viability and proliferation. When testing the effects of kaempferol on breast cancer cell number (crystal violet staining) and viability (MTT tetrazolium assay) conflicting results were obtained. Cell number decreased but MTT formazan formation increased, suggesting a direct interaction of kaempferol with the MTT tetrazolium reduction. Direct reductive potential was observed in a cell-free system for the presumptive phytoestrogens kaempferol and resveratrol, and extracts of Hypericum perforatum L. and Cimicifuga racemosa L. All agents led to instantaneous dark blue formazan formation in the absence of cells. Additionally, antioxidants such as ascorbic acid, vitamin E and N-acetylcysteine interfered with the MTT tetrazolium assay. When MCF7 and HS578 cells treated with kaempferol were washed before addition of MTT tetrazolium, the direct reduction of dye was reduced significantly. These results indicate that the MTT tetrazolium assay may lead to false positive results when testing natural compounds with intrinsic reductive potential.

Topics: Acetylcysteine; Antioxidants; Ascorbic Acid; Breast Neoplasms; Cell Division; Cell Survival; Drug Interactions; Estrogens, Non-Steroidal; Flavonoids; Humans; Isoflavones; Kaempferols; Phytoestrogens; Plant Extracts; Plant Preparations; Plants; Quercetin; Resveratrol; Stilbenes; Tetrazolium Salts; Thiazoles; Tumor Cells, Cultured; Vitamin E

1. Resveratrol, a polyphenolic compound present in grape and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. Resveratrol is sulphated, and the hepatic and duodenal sulphation might limit the bioavailability of this compound. The aim of this study was to see whether natural flavonoids present in wine, fruits and vegetables inhibit the sulphation of resveratrol in the human liver and duodenum. 2. In the liver, IC50 for the inhibition of resveratrol sulphation was 12+/-2 pM (quercetin), 1.0+/-0.04 microM (fisetin), 1.4+/-0.1 microM (myricetin), 2.2+/-0.1 microM (kaempferol) and 2.8+/-0.2 microM (apigenin). Similarly, in the duodenum, IC50 was 15+/-2 pM (quercetin), 1.3+/-0.1 microM (apigenin), 1.3+/-0.5 microM (fisetin), 2.3+/-0.1 microM (kaempferol) and 2.5+/-0.3 microM (myricetin). 3. The type of inhibition of quercetin on resveratrol sulphation was studied in three liver samples and was determined to be non-competitive and mixed in nature. Km (mean+/-SD; microM) was 0.23+/-0.07 (control), 0.40+/-0.08 (5 pM quercetin) and 0.56+/-0.09 (10 pM quercetin). Vmax (mean+/-SD; pmol min(-1) x mg(-1)) was 99+/-11 (control), 73+/-15 (5 pM quercetin) and 57 +/- 10 (10 pM quercetin). Kj and Kies estimates (mean+/-SD) were 3.7+/-1.8 pM and 12.1+/-1.7 pM respectively (p = 0.010). 4. Chrysin was a substrate for the sulphotransferase(s) and an assay was developed for measuring the chrysin sulphation rate in human liver. The enzyme followed Michaelis-Menten kinetics and Km and Vmax (mean+/-SD) measured in four livers were 0.29+/-0.07 microM and 43.1+/-1.9 pmol x min(-1) x mg(-1) respectively. 5. Catechin was neither an inhibitor of resveratrol sulphation nor a substrate of sulphotransferase. 6. These results are consistent with the view that many, but not all, flavonoids inhibit the hepatic and duodenal sulphation of resveratrol, and such inhibition might improve the bioavailability of this compound.

Topics: Aged; Apigenin; Biological Availability; Duodenum; Female; Flavonoids; Flavonols; Fruit; Humans; Kaempferols; Kinetics; Liver; Male; Middle Aged; Quercetin; Resveratrol; Stilbenes; Substrate Specificity; Sulfates; Sulfotransferases; Vegetables; Wine

1. Resveratrol, a polyphenolic compound present in grape and wine, has beneficial effects against cancer and protective effects on the cardiovascular system. It has been shown that the compound is sulphated in human liver and the aims of the present investigation were to study resveratrol glucuronidation in human liver microsomes and to determine whether flavonoids inhibit resveratrol glucuronidation. 2. A simple and reproducible radiometric assay for resveratrol glucuronidation was developed. The assay employed uridine-5'-diphosphoglucuronic acid-[14C] and unlabelled resveratrol. Resveratrol-glucuronide was isolated by TLC. The intra- and interassays variabilities were 1 and 1.5%, respectively. 3. The rate of resveratrol glucuronidation was measured in 10 liver samples. The mean +/- SD and median of resveratrol glucuronidation rate were 0.69 +/- 0.34 and 0.80 nmol/min/mg, respectively. Resveratrol glucuronosyl transferase followed Michaelis-Menten kinetics and the Km and Vmax (mean +/- SD; n = 5) were 0.15 +/- 0.09 mM and 1.3 +/- 0.3 nmol/min/mg, respectively. The intrinsic clearance was 11 +/- 4 x 10(-3) ml/min.mg. 4. The flavonoid quercetin inhibited resveratrol glucuronidation and its IC50 (mean +/- SD; n = 3) was 10 +/- 1 microM. Myricetin, catechin, kaempferol, fisetin and apigenin (all at 20 microM) inhibited resveratrol glucuronidation and the percent of control ranged between 46% (catechin) to 72% (apigenin). 5. The present results show that resveratrol is glucuronated in the human liver. Glucuronidation may reduce the bioavailability of this compound however, flavonoids inhibit resveratrol glucuronidation and such an inhibition might improve the bioavailability of resveratrol.

Topics: Adult; Aged; Apigenin; Catechin; Chromatography, Thin Layer; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Flavonoids; Flavonols; Glucuronic Acid; Humans; Hydrogen-Ion Concentration; Inhibitory Concentration 50; Kaempferols; Kinetics; Liver; Male; Microsomes, Liver; Middle Aged; Quercetin; Reproducibility of Results; Resveratrol; Rosales; Stilbenes; Wine