Flavonoid compounds are potent inhibitors of cyclic AMP phosphodiesterase

Indian jujube a potential fruit tree to improve the livelihood

Indian Jujube, also known as Ber or Ziziphus Mauritiana Lam., is a fruit-bearing tree endemic to South Asia, including India, Pakistan, Bangladesh, and Sri Lanka. The tree belongs to the buckthorn family and is known for its fruit, a tiny, round, or oblong-shaped drupe roughly the size of a cherry or a small plum. Indian Jujube has been growing for thousands of years. It is a popular fruit throughout the tropical and subtropical regions of Asia, Africa, and South America. Despite the fruit's delicious flavour and health benefits, it is also known for its therapeutic value. Many studies have suggested that various components of ber trees, such as fruit, seed leaves, roots, and flowers, include bioactive substances that demonstrate the potential for antioxidant activity and have anticancer, antibacterial, and antidiabetic effects. Due to the crop's minimal management requirements, it may slow down climate change and the threat of extreme soil and weather conditions, such as drought resistance, strong winds, erosion, high salt, and floods. The main objectives of the current systematic review are to understand Ber's chemical compositions, health benefits, culinary uses, major nutraceutical features, and its function in fostering livelihoods and climatic tolerance.

Mechanisms Underlying the Antidiabetic Activities of Polyphenolic Compounds: A Review

Polyphenolic compounds are thought to show considerable promise for the treatment of various metabolic disorders, including type 2 diabetes mellitus (T2DM). This review addresses evidence from in vitro, in vivo, and clinical studies for the antidiabetic effects of certain polyphenolic compounds. We focus on the role of cytotoxic human amylin (hA) aggregates in the pathogenesis of T2DM, and how polyphenols can ameliorate this process by suppressing or modifying their formation. Small, soluble amylin oligomers elicit cytotoxicity in pancreatic islet β-cells and may thus cause β-cell disruption in T2DM. Amylin oligomers may also contribute to oxidative stress and inflammation that lead to the triggering of β-cell apoptosis. Polyphenols may exert antidiabetic effects via their ability to inhibit hA aggregation, and to modulate oxidative stress, inflammation, and other pathways that are β-cell-protective or insulin-sensitizing. There is evidence that their ability to inhibit and destabilize self-assembly by hA requires aromatic molecular structures that bind to misfolding monomers or oligomers, coupled with adjacent hydroxyl groups present on single phenyl rings. Thus, these multifunctional compounds have the potential to be effective against the pleiotropic mechanisms of T2DM. However, substantial further research will be required before it can be determined whether a polyphenol-based molecular entity can be used as a therapeutic for type 2 diabetes.

( -)-Epicatechin and cardiometabolic risk factors: a focus on potential mechanisms of action

This review summarizes experimental evidence on the beneficial effects of ( -)-epicatechin (EC) attenuating major cardiometabolic risk factors, i.e., dyslipidemias, obesity (adipose tissue dysfunction), hyperglycemia (insulin resistance), and hypertension (endothelial dysfunction). Studies in humans are revised and complemented with experiments in animal models, and cultured cells, aiming to understand the molecular mechanisms involved in EC-mediated effects. Firstly, an assessment of EC metabolism gives relevance to both conjugated-EC metabolites product of host metabolism and microbiota-derived species. Integration and analysis of results stress the maintenance of redox homeostasis and mitigation of inflammation as relevant processes associated with cardiometabolic diseases. In these processes, EC appears having significant effects regulating NADPH oxidase (NOX)-dependent oxidant production, nitric oxide (NO) production, and energy homeostasis (mitochondrial biogenesis and function). The potential participation of cell membranes and membrane-bound receptors is also discussed in terms of direct molecular action of EC and EC metabolites reaching cells and tissues.

In Vitro Inhibition of Phosphodiesterase 3B (PDE 3B) by Anthocyanin-Rich Fruit Juice Extracts and Selected Anthocyanins

Phosphodiesterases (PDEs) are essential enzymes for the regulation of pathways mediated by cyclic adenosine monophosphate (cAMP). Secondary plant compounds like anthocyanins (ACs) can inhibit PDE activity and, consequently, may be beneficial for lipid metabolism. This study investigated 18 AC-rich juice extracts and pure reference compounds from red fruits for potential inhibitory effects on PDE 3B activity. Extracts were obtained through adsorption on Amberlite^® XAD 7 resin. Based on this screening, the chokeberry, blueberry, pomegranate, and cranberry extracts were active, with half maximal inhibitory concentrations (IC₅₀) ranging from 163 ± 3 µg/mL to 180 ± 3 µg/mL. The ACs in these extracts, peonidin-3-glucoside and cyanidin-3-arabinoside, were the most active single compounds (IC₅₀ = 56 ± 20 µg/mL, 108 ± 6 µg/mL). All extracts comprised high amounts of phenolic compounds, as determined by the Folin-Ciocalteu assay, ranging from 39.8 ± 1.5 to 73.5 ± 4.8 g gallic acid equivalents (GAE)/100 g extract. Pomegranate and chokeberry extracts exhibited the largest amounts of polyphenols (72.3 ± 0.7 g GAE/100 g, 70.6 ± 4.1 g GAE/100 g, respectively). Overall, our results showed that fruit juice extracts and their ACs can inhibit PDE activity. Any potential health benefits in vivo will be investigated in the future.

2-(3,4-Dihydroxyphenyl)-4-(2-(4-nitrophenyl)hydrazono)-4H-chromene-3,5,7-triol

On the basis of the knowledge from traditional herbal and folk medicine, flavonoids are among the most studied chemical classes of natural compounds for their potential activity as phosphodiesterase 5 (PDE5) inhibitors. We here describe the preparation of a semi-synthetic hydrazone derivative of quercetin, 2-(3,4-dihydroxyphenyl)-4-(2-(4-nitrophenyl)hydrazono)-4H-chromene-3,5,7-triol, that was obtained via a single-step modification of the natural compound. The product was characterized by NMR, mass spectrometry and HPLC. Preliminary molecular modeling studies suggest that this compound could efficiently interact with PDE5.

Anti-Asthmatic Effects of Portulaca Oleracea and its Constituents, a Review

OBJECTIVES

The medicinal plants are believed to enhance the natural resistance of the body to infections. Some of the main constituents of the plant and derived materials such as, proteins, lectins and polysaccharides have anti-inflammatory effects. Portulaca oleracea (P. oleracea) were used traditionally for dietary, food additive, spice and various medicinal purposes. This review article is focus on the anti-asthmatic effects of P. oleracea and its constituents.

METHODS

Various databases, such as the PubMed, Scopus, and Google Scholar, were searched the keywords including "Portulaca oleracea", "Quercetin", "Anti-inflammatory", "Antioxidant", "Cytokines", "Smooth muscle ", and " Relaxant effects " until the end of Jul 2018.

RESULTS

P. oleracea extracts and its constituents increased IFN-γ, IL-2, IFNγ/IL-4 and IL- 10/IL-4 ratio, but decreased secretion of TNF-α, IL-4 and chemokines in both in vitro and in vivo studies. P. oleracea extracts and quercetin also significantly decreased production of NO, stimulated β-adrenoceptor and/or blocking muscarinic receptors in tracheal smooth muscles. Conclusion: P. oleracea extracts and quercetin showed relatively potent anti-asthmatic effects due to decreased production of NO, inflammatory cytokines and chemokines, reduced oxidant while enhanced antioxidant markers, and also showed potent relaxant effects on tracheal smooth muscles via stimulatory on β-adrenoceptor or/and blocking muscarinic receptors.

Is psoriasis a bowel disease? Successful treatment with bile acids and bioflavonoids suggests it is

The gut is the largest lymphoid organ in the body. The human microbiome is composed of trillions of bacteria. The DNA of these bacteria dwarfs the human genome. Diet and ethanol can cause rapid shifts in the number and types of bacteria in the gut. The psoriatic microbiome is similar to that seen in alcoholics; there is a decrease in bacterial diversity and overgrowth of bacteria in the small bowel. Psoriatics often have liver disease and deficiencies in bile acids. Psoriasis is a disease characterized by a leaky gut. All of the comorbidities of this disease are due to systemic endotoxemia. Bacterial peptidoglycans absorbed from the gut have direct toxic effects on the liver and skin. Their absorption, as well as endotoxin absorption, must be eliminated to treat psoriasis successfully. Endotoxin absorption is markedly increased by ethanol and peppers. Bioflavonoids, such as quercetin and citrus bioflavonoids, prevent this absorption. Bile acids, given orally, break up endotoxin in the intestinal lumen. Pathogens, including Helicobacter pylori and Streptococcus pyogenes, must be eliminated with antimicrobial therapy for any treatment to work. A complete protocol for curing psoriasis is provided.

Inhibition of Cyclic Adenosine Monophosphate-Specific Phosphodiesterase by Various Food Plant-Derived Phytotherapeutic Agents

Background: Phosphodiesterases (PDEs) play a major role in the regulation of cyclic adenosine monophosphate (cAMP)- and cyclic guanosine monophosphate (cGMP)-mediated pathways. Their inhibitors exhibit anti-inflammatory, vasodilatory and antithrombotic effects. Therefore, consumption of foods with PDE-inhibiting potential may possess beneficial influence on the risk of cardiovascular diseases. Methods: Four plant extracts (Arbutus unedo, Camellia sinensis, Cynara scolymus, Zingiber officinale) with promising ingredient profiles and physiological effects were tested for their ability to inhibit cAMP-specific PDE in vitro in a radioactive assay. Results: Strawberry tree fruit (Arbutus unedo) and tea (Camellia sinensis) extracts did not inhibit PDE markedly. Alternatively, artichoke (Cynara scolymus) extract had a significant inhibitory influence on PDE activity (IC₅₀ = 0.9 ± 0.1 mg/mL) as well as its flavone luteolin (IC₅₀ = 41 ± 10 μM) and 3,4-dicaffeoylquinic acid (IC₅₀ > 1.0 mM). Additionally, the ginger (Zingiber officinale) extract and one of its constituents, [6]-gingerol, significantly inhibited PDE (IC₅₀ = 1.7 ± 0.2 mg/mL and IC₅₀ > 1.7 mM, respectively). Crude fractionation of ginger extract showed that substances responsible for PDE inhibition were in the lipoid fraction (IC₅₀ = 455 ± 19 μg/mL). Conclusions: A PDE-inhibitory effect was shown for artichoke and ginger extract. Whether PDE inhibition in vivo can be achieved through ingestion of artichoke or ginger extracts leading to physiological effects concerning cardiovascular health should be addressed in future research.

Ethnopharmacological Approaches for Therapy of Jaundice: Part II. Highly Used Plant Species from Acanthaceae, Euphorbiaceae, Asteraceae, Combretaceae, and Fabaceae Families

In many developing countries, jaundice is the common symptom of hepatic diseases which are a major cause of mortality. The use of natural product-based therapies is very popular for such hepatic disorders. A great number of medicinal plants have been utilized for this purpose and some facilitated the discovery of active compounds which helped the development of new synthetic drugs against jaundice. However, more epidemiological studies and clinical trials are required for the practical implementation of the plant pharmacotherapy of jaundice. The focus of this second part of our review is on several of the most prominent plants used against jaundice identified in the analysis performed in the first part of the review viz. Andrographis paniculata (Burm.f.) Nees, Silybum marianum (L.) Gaertn., Terminalia chebula Retz., Glycyrrhiza glabra L. and some species of genus Phyllanthus. Furthermore, we discuss their physiological effects, biologically active ingredients, and the potential mechanisms of action. Some of the most important active ingredients were silybin (also recommended by German commission), phyllanthin and andrographolide, whose action leads to bilirubin reduction and normalization of the levels of relevant serum enzymes indicative for the pathophysiological status of the liver.

A comprehensive review on the potential therapeutic benefits of phosphodiesterase inhibitors on cardiovascular diseases

Phosphodiesterases are a group of enzymes that hydrolyze cyclic nucleotides, which assume a key role in directing intracellular levels of the second messengers' cAMP and cGMP, and consequently cell function. The disclosure of 11 isoenzyme families and our expanded knowledge of their functions at the cell and molecular level stimulate the improvement of isoenzyme selective inhibitors for the treatment of various diseases, particularly cardiovascular diseases. Hence, future and new mechanistic investigations and carefully designed clinical trials could help reap additional benefits of natural/synthetic PDE inhibitors for cardiovascular disease in patients. This review has concentrated on the potential therapeutic benefits of phosphodiesterase inhibitors on cardiovascular diseases.

Therapeutic potentials of natural compounds acting on cyclic nucleotide phosphodiesterase families

Intracellular cyclic AMP and/or cyclic GMP are characterized in the 1960th. These second messengers, hydrolysed specifically by cyclic nucleotide phosphodiesterase (PDE), play a major role in intracellular signalling. Natural products have been a rich source of drug discovery, Theophylline and Methylxanthine originated from tea leaves used for asthma treatment, whereas, Papaverine, a natural isoquinolein originated from Papaver somniferum traditionally used in impotency, altogether as caffeine where firstly described as PDE-inhibiting compounds. Since that time, the knowledge in PDE field has been drastically increased, allowing the design and development of new therapeutic drugs acting against different pathologies in the nanomolar range. During this period some natural compounds have been identified as PDE inhibitors and used in that context to investigate their therapeutic potential effects. The aim of this literature review is to point out the reported data and demonstrating the contribution of natural characterized molecules as PDE inhibitors in various pathologies that can open new fields of research for drug discovery, notably in epigenetic regulation.

Dissection of the Effects of Quercetin on Mouse Myocardium

Quercetin is a plant flavonoid with several biological activities. This study aimed to describe quercetin effects on contractile and electrophysiological properties of the cardiac muscle as well as on calcium handling. Quercetin elicited positive inotropism that was significantly reduced by propranolol indicating an involvement of the sympathetic nervous system. In cardiomyocytes, 30 μM quercetin increased I_Ca,L at 0 mV from -0.95 ± 0.01 A/F to -1.21 ± 0.08 A/F. The membrane potential at which 50% of the channels are activated (V_0.5 ) shifted towards more negative potentials from -13.06 ± 1.52 mV to -19.26 ± 1.72 mV and did not alter the slope factor. Furthermore, quercetin increased [Ca²⁺ ]_i transient by 28% when compared to control. Quercetin accelerated [Ca²⁺ ]_i transient decay time, which could be attributed to SERCA activation. In resting cardiomyocytes, quercetin did not change amplitude or frequency of Ca²⁺ sparks. In isolated heart, quercetin increased heart rate and decreased PRi, QTc and duration of the QRS complex. Thus, we showed that quercetin activates β-adrenoceptors, leading to increased L-type Ca²⁺ current and cell-wide intracellular Ca²⁺ transient without visible changes in Ca²⁺ sparks.

Oral supplementation of trans-cinnamaldehyde reduces uropathogenic Escherichia coli colonization in a mouse model

Urinary tract infections (UTIs) in the United States result in more than 7 million hospital visits per year. Uropathogenic Escherichia coli (UPEC) is responsible for more than 80% of UTIs. Although antibiotics are the drug of choice to control UTIs, their repeated use has resulted in the emergence of antibiotic-resistant UPEC. Thus, there is a need for effective alternate strategies to control UPEC infections. This study investigated the efficacy of trans-cinnamaldehyde (TC), a food-grade molecule present in cinnamon, in reducing UPEC colonization and pathogenesis in the lower UTI. Female C57BL/6 mice (6-8 weeks old) were fed ad libitum with 0, 0·1, 0·2 and 0·4% TC containing mouse chow for 10 days. Following TC supplementation, animals were experimentally infected with UPEC by transurethral catheterization. Mice were euthanized on days 1, 2 and 4 postinfection, and the bladder, urethra and urine were collected for bacterial enumeration. Prophylactic TC supplementation significantly (P ≤ 0·05) reduced UPEC colonization in the urinary bladder and urethra compared to the control. Results indicate that TC could potentially be used as an oral supplement to control UPEC-associated lower UTIs, however, follow-up clinical trials are warranted.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this study, we have demonstrated that oral supplementation of trans-cinnamaldehyde (TC) reduced uropathogenic Escherichia coli (UPEC)-associated lower urinary tract infection (UTI) in mice. Specifically, in-feed supplementation of TC significantly decreased UPEC populations in the urethra and bladder, thereby reducing the infectious load. These findings are particularly significant given the increase in incidence and prevalence of antibiotic-resistant UTIs. Our study offers new insights into the potential use of natural antimicrobials including TC, the active ingredient in cinnamon, as a nonantibiotic-based natural dietary intervention in the prophylaxis of lower UTIs.

Effects of aqueous extracts from Ceratonia siliqua L. pods on small intestinal motility in rats and jejunal permeability in mice

The current study was performed to assess the effects of carob pod aqueous extracts (CPAE, pulp, seeds or mixture) on gastrointestinal transit (GIT) and intestinal epithelium permeability.

Elucidating polypharmacological mechanisms of polyphenols by gene module profile analysis

Due to the diverse medicinal effects, polyphenols are among the most intensively studied natural products. However, it is a great challenge to elucidate the polypharmacological mechanisms of polyphenols. To address this challenge, we establish a method for identifying multiple targets of chemical agents through analyzing the module profiles of gene expression upon chemical treatments. By using FABIA algorithm, we have performed a biclustering analysis of gene expression profiles derived from Connectivity Map (cMap), and clustered the profiles into 49 gene modules. This allowed us to define a 49 dimensional binary vector to characterize the gene module profiles, by which we can compare the expression profiles for each pair of chemical agents with Tanimoto coefficient. For the agent pairs with similar gene expression profiles, we can predict the target of one agent from the other. Drug target enrichment analysis indicated that this method is efficient to predict the multiple targets of chemical agents. By using this method, we identify 148 targets for 20 polyphenols derived from cMap. A large part of the targets are validated by experimental observations. The results show that the medicinal effects of polyphenols are far beyond their well-known antioxidant activities. This method is also applicable to dissect the polypharmacology of other natural products.

Dietary polyphenols regulate endothelial function and prevent cardiovascular disease

Vascular endothelial cell (EC) dysfunction strongly induces development of cardiovascular and cerebrovascular diseases. Epidemiologic studies demonstrated a preventative effect of dietary polyphenols toward cardiovascular disease. In studies using cultured vascular ECs, polyphenols were recognized to regulate nitric oxide and endothelin-1 (ET-1) production. Furthermore, epigallocatechin-3-gallate inhibited the expression of adhesion molecules by a signaling pathway that is similar to that of high-density lipoprotein and involves induction of Ca(2+)/calmodulin-dependent kinase II, liver kinase B, and phosphatidylinositol 3-kinase expression. The effects of polyphenols on ECs include antioxidant activity and enhancement of the expression of several protective proteins, including endothelial nitric oxide synthase and paraoxonase 1. However, the observed effects of dietary polyphenols in vitro do not always translate to an in vivo setting. As such, there are many questions concerning their physiological mode of action. In this review, we discuss research on the effect of dietary polyphenols on cardiovascular disease and their protective effect on EC dysfunction.

Cissus quadrangularis augments IGF system components in human osteoblast like SaOS-2 cells

Osteoporosis is a public health problem which is associated with significant morbidity and mortality. Growth factors are produced locally in the bone and control cellular events such as induction of bone growth. Signaling through the Insulin-like growth factor (IGF)-I receptor (IGF-IR) by locally synthesized IGF - I or IGF-II in osteoblast is considered crucial for normal development and for bone remodeling. Traditional use of Cissus quadrangularis (C. quadrangularis) in the treatment of bone disorders have been documented, however its regulatory effects on IGF system components remain largely unknown. The present study is employed to delineate the effects of ethanolic extract of C. quadrangularis on the regulation of IGF system components in human osteoblast like SaOS-2 cells. RT-PCR analysis revealed an increase in the mRNA expression of IGF-I, IGF-II, IGF-IR in cells treated with C. quadrangularis when compared with control cells. The mRNA expression of IGF binding protein-3 (IGFBP-3) did not differ significantly between control and C. quadrangularis treated cells. Immunoradiometric analysis revealed increased levels of IGF-I, IGF-II and IGFBP-3 in the conditioned medium of C. quadrangularis treated cultures when compared with control. Western blotting analysis revealed increase in protein levels of IGF-IR in cells treated with C. quadrangularis. These results indicate positive regulation of C. quadrangularis on the IGF system components of human osteoblast like SaOS-2 cells.

Effect of flavonoids on basal and insulin-stimulated 2-deoxyglucose uptake in adipocytes

SCOPE

The adipose tissue is a major site of insulin action and contributes substantially to energy homeostasis. Insulin increases the extraction of glucose from circulation into adipose tissue by recruiting the glucose transporter GLUT4 to the plasma membrane. It has been proposed that dietary flavonoids may interfere with glucose transport processes.

METHODS AND RESULTS

We have used murine 3T3-L1 adipocytes and isolated mature human adipocytes to assess the interaction of selected flavonoids with glucose uptake, both in the basal state and after insulin stimulation. Kinetic characterization of 2-deoxyglucose uptake in the basal state revealed in both cell types an apparent K(m) of around 8 mM with no change in affinity but a significant increase in maximal influx in the presence of insulin. A screening of representative flavonoids of different structural classes revealed the flavanone naringenin and the isoflavone daidzein to affect glucose transport significantly with half-maximal inhibition at concentrations of around 60-80 μM for basal and 70-110 μM for insulin-stimulated glucose uptake in both 3T3-L1 adipocytes and mature human adipocytes.

CONCLUSION

Considering attainable plasma concentrations of flavonoids in vivo, we assume that even under physiological conditions naringenin and daidzein could impair glucose removal from plasma, which may pose a risk to patients with diabetes mellitus.

Effects of resveratrol and flavonols on cardiovascular function: Physiological mechanisms

Resveratrol and flavonols are commonly found together in fruits and vegetables and, therefore, consumed in the diet. These two polyphenols share both vasorelaxant and antioxidant activity and may act together to improve cardiovascular function. This review examines the mechanisms by which resveratrol and flavonols influence cardiovascular function and perhaps offer a new approach for the development of therapeutic agents for the prevention and/or treatment of coronary artery disease.

Antibiofilm effect of trans-cinnamaldehyde on uropathogenic Escherichia coli

PURPOSE

Urinary tract infections are the most common hospital acquired infections in humans, caused primarily by uropathogenic Escherichia coli. Indwelling urinary catheters for bladder drainage in humans become encrusted with uropathogenic E. coli biofilms that are resistant to common antibiotics, resulting in chronic infections. We studied the efficacy of the cinnamon ingredient trans-cinnamaldehyde (Sigma) for preventing uropathogenic E. coli biofilm. We also determined the efficacy of trans-cinnamaldehyde as an ingredient in catheter lock solution to inactivate preformed uropathogenic E. coli biofilm.

MATERIALS AND METHODS

Polystyrene plates and urinary catheters inoculated with uropathogenic E. coli (5 to 6.0 log cfu) were treated with trans-cinnamaldehyde (0%, 0.1%, 0.25% or 0.5%) at 37C. Catheters with uropathogenic E. coli biofilm were also treated with lock solution containing trans-cinnamaldehyde (0%, 1%, 1.25% or 1.5%). Uropathogenic E. coli biofilm on control and trans-cinnamaldehyde treated plates and catheters was determined on incubation days 0, 1, 3 and 5. Trans-cinnamaldehyde potential cytotoxity, if any, was determined in HTB-4 bladder epithelial cells (ATCC).

RESULTS

At all concentrations trans-cinnamaldehyde effectively prevented uropathogenic E. coli biofilm on plates and catheters. As a constituent in catheter lock solution, it inactivated uropathogenic E. coli biofilm on catheters. Trans-cinnamaldehyde produced no cytotoxic effects on human bladder epithelial cells at the tested concentrations.

CONCLUSIONS

Results suggest that trans-cinnamaldehyde may be applied as a catheter surface coating or as an ingredient in catheter lock solution to prevent urinary tract infection in humans.

Improvement of inflammatory and toxic stress biomarkers by silymarin in a murine model of type one diabetes mellitus

Type 1 diabetes mellitus (T1DM) is characterized by an impairment of the insulin-secreting beta cells with an immunologic base. Inflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, and free radicals are believed to play key roles in destruction of pancreatic β cells. The present study was designed to investigate the effect of Silybum marianum seed extract (silymarin), a combination of several flavonolignans with immunomodulatory, anti-oxidant, and anti-inflammatory potential on streptozotocin (STZ)-induced T1DM in mouse. Experimental T1DM was induced in male albino mice by IV injection of multiplelow- doses of STZ for 5 days. Seventy-two male mice in separate groups received various doses of silymarin (20, 40, and 80 mg/kg) concomitant or after induction of diabetes for 21 days. Blood glucose and pancreatic biomarkers of inflammation and toxic stress (IL-1β, TNF-α, myeloperoxidase, lipid peroxidation, protein oxidation, thiol molecules, and total antioxidant capacity) were determined. Silymarin treatment reduced levels of inflammatory cytokines such as TNF-α and IL-1β and oxidative stress mediators like myeloperoxidase activity, lipid peroxidation, carbonyl and thiol content of pancreatic tissue in an almost dose dependent manner. No marked difference between the prevention of T1DM and the reversion of this disease by silymarin was found. Use of silymarin seems to be helpful in T1DM when used as pretreatment or treatment. Benefit of silymarin in human T1DM remains to be elucidated by clinical trials.

The spasmolytic effect of Aloysia citriodora, Palau (South American cedrón) is partially due to its vitexin but not isovitexin on rat duodenums

The spasmolytic effects of an acqueous extract of cedrón (AEC) were studied on rat isolated duodenums. This plant (Aloysia citriodora Palau, Verbenaceae) is widely used for gastrointestinal disorders and as eupeptic in South America. AEC non-competitively inhibited the dose-response curve (DRC) of Ach (IC50 of 1.34 +/- 0.49 mg lyophilized/mL) and the DRC of Ca(2+) in high-[K(2-)](o) (IC50 of 2.64 +/- 0.23 mg/mL). AEC potentiated the non-competitive inhibition of either 30 micromol/L W-7 (a calmodulin blocker) and 5-15 micromol/L papaverine on the Ca(2+)-DRC. Also, AEC relaxed the contracture produced by high-[K(+)](o) (IC50 of 2.6 +/- 0.2 mg/mL) until 81.0 +/- 3.2% of the maximal effect of papaverine and 78.1+/- 5.0% of the quercetin, the most selective inhibitor of PDE. The AEC relaxation was non-competitively inhibited by 10-30 micromol/L methylene blue and competitively antagonized by 40 mmol/L TEA. The relaxation of 1mg/mL AEC was inhibited by hypoxia, but not that of 2mg/mL. Two flavonoids were identified by HPLC in the AEC: vitexin and isovitexin. Vitexin non-competitively inhibited the Ach-DRC (pD(2') of 5.7 +/- 0.4) but significantly run leftward the DRC of Ca(2+). Isovitexin did not significantly inhibit the DRC of Ach nor Ca(2+). The results suggest that the spasmolytic effect of AEC could be mostly associated to the increase in cGMP (target shared with the PDE inhibitors) and the activation of K(+)-channels. At low concentrations, AEC also inhibits the aerobic metabolism. The flavonoid vitexin is partially responsible for the effect, since it non-competitively inhibits Ach but not the Ca(2+) influx. Isovitexin was devoid of activity on duodenums.

Flavonoids from seabuckthorn protect endothelial cells (EA.hy926) from oxidized low-density lipoprotein induced injuries via regulation of LOX-1 and eNOS expression

The present investigation was undertaken to determine the protective effects of flavonoids from seabuckthorn (FSBT), a traditional Chinese medicine, on endothelial cell line EA.hy926 injury induced by oxidized low-density lipoprotein (ox-LDL). Possible mechanisms were then explored. The effects of quercetin and isorhamnetin, 2 major components of FSBT, were examined as well. Indices such as cell viability, lactate dehydrogenase, nitric oxide (NO), superoxide dismutase, and superoxide were measured. Reverse transcription polymerase chain reaction, Western blot, and immunocytochemistry were employed to determine the endothelial constitutive NO synthase (eNOS) and lectinlike low-density lipoprotein receptor-1 (LOX-1) expression. Cell viability decreased significantly after 24 hours treatment with ox-LDL, accompanied with apparent secretion disorders such as NO reduction and lactate dehydrogenase increase. FSBT pretreatment could remarkably prevent both cell death and secretion disorders in a concentration-dependent manner. Besides, it was observed that ox-LDL triggered superoxide production and suppressed the superoxide dismutase activity, both of which could be prevented by FSBT pretreatment. Moreover, ox-LDL inhibited eNOS expression and increased LOX-1 expression, whereas FSBT pretreatment partly abolished these effects. Similar effects were obtained with quercetin and isorhamnetin, implying that they may contribute, at least in part, to the protective effects of FSBT. The data indicate that the protective effects of FSBT against ox-LDL induced endothelial cell injuries might derive from its antioxidant activity and its capability in modulating the expression of eNOS and LOX-1. And quercetin and isorhamnetin may contribute to these effects of FSBT.

Comparative study of the vasorelaxant activity, superoxide-scavenging ability and cyclic nucleotide phosphodiesterase-inhibitory effects of hesperetin and hesperidin

This study investigated the vasorelaxant activity, superoxide radicals (O2(*-))-scavenging capacity and cyclic nucleotide phosphodiesterase (PDE)-inhibitory effects of hesperidin and hesperetin, two flavonoids mainly isolated from citrus fruits. Hesperetin concentration-dependently relaxed the isometric contractions induced by noradrenaline (NA, 1 microM) or by a high extracellular KCl concentration (60 mM) in intact rat isolated thoracic aorta rings. However, hesperetin (10 microM-0.3 mM) did not affect the contractile response induced by okadaic acid (OA, 1 microM). Mechanical removal of endothelium and/or pretreatment of aorta rings with glibenclamide (GB, 10 microM), tetraethylammonium (TEA, 2 mM) or nifedipine (0.1 microM) did not significantly modify the vasorelaxant effects of this flavonoid. Hesperetin (10 microM-0.1 mM) did not affect the basal uptake of (45)Ca(2+) but decreased the influx of (45)Ca(2+) induced by NA and KCl in endothelium-containing and endothelium-denuded rat aorta. Hesperetin (10 microM-0.1 mM) did not scavenge O2(*-) generated by the phenazine methosulfate (PMS)-reduced beta-nicotinamide adenine dinucleotide (NADH) system. Hesperetin (0.1 mM) significantly reversed the inhibitory effects of NA (1 microM) and high KCl (60 mM) on cyclic nucleotide (cAMP and cGMP) production in cultured rat aortic myocytes. Hesperetin preferentially inhibited calmodulin (CaM)-activated PDE1 and PDE4 isolated from bovine aorta with IC(50) values of about 74 microM and 70 microM respectively. In contrast, the 7-rhamnoglucoside of hesperetin, hesperidin (10 microM-0.1 mM), was inactive in practically all experiments, although it inhibited basal and cGMP-activated PDE2 isolated from platelets (IC(50) values of 32+/-4 microM and 137+/-34 microM respectively). These results suggest that the vasorelaxant effects of hesperetin are basically due to the inhibition of PDE1 and PDE4 activities.

Vasorelaxant effects of grape polyphenols in rat isolated aorta. Possible involvement of a purinergic pathway

The purpose of this study was to investigate the mechanism of the vascular relaxation produced by polyphenolic substances from red wine, with a particular focus on the possible involvement of purinoceptors. With this aim, relaxing responses induced by procyanidin from grape seeds (GSP), anthocyanins, catechin and epicatechin were assessed in rat isolated aortic rings left intact (+E) or endothelium-denuded (-E). In preparations precontracted with noradrenaline, incubation with NG-nitro-L-arginine methyl ester (100 microM, 30 min) fully inhibited the GSP-induced relaxations. Concentration-effect curves to these substances (from 10(-7) to 10(-1) g/L) were determined in depolarized (60 mM KCl) preparations in control condition, after incubation with reactive blue 2 (an antagonist of P2Y purinoceptors, 30 microM), with apyrase (an enzyme which hydrolyses ATP and ADP, 0.8 U/mL) or with alpha,beta-methylene ATP (an inhibitor of ecto ATPases, 10 microM). In (+E) rings, relaxations (expressed as percentage of initial contraction) were 41 +/- 2 and 37 +/- 3 for GSP and anthocyanins, respectively. Only modest relaxations (ca. 10%) were observed in (-E) rings, as it was the case for catechin and epicatechin in (+/- E) rings. Reactive blue 2 or apyrase inhibited the GSP- and anthocyanin-induced relaxations in (+E) rings, while alpha,beta-methylene ATP shifted to the left the relaxation curves obtained with GSP. These data confirm that modest relaxations observed with catechin and epicatechin are not endothelium-dependent but that GSP and anthocyanins induce a relaxing effect, which is related to the integrity of the endothelium and the synthesis and release of nitric oxide (NO). Furthermore, the inhibition by apyrase and the increase by ecto-ATPase inhibition of the GSP- and anthocyanin-induced relaxation suggest that these substances could act via an initial release of nucleotides, which in turn could activate P2Y1 and/or P2Y2 purinoceptors of endothelial cells, trigger the synthesis and release of NO and then lead to relaxation.

Naringenin inhibits phosphoinositide 3-kinase activity and glucose uptake in 3T3-L1 adipocytes

Previous studies have shown that flavonoids inhibit glucose uptake in cultured cells. In this report, we show that the grapefruit flavanone naringenin inhibited insulin-stimulated glucose uptake in 3T3-L1 adipocytes in a dose-dependent manner. Naringenin acts by inhibiting the activity of phosphoinositide 3-kinase (PI3K), a key regulator of insulin-induced GLUT4 translocation. Although naringenin did not alter the phosphotyrosine status of the insulin receptor, insulin receptor substrate proteins, or PI3K, it did inhibit the phosphorylation of the downstream signaling molecule Akt. In an in vitro kinase assay, naringenin inhibited PI3K activity. A physiologically attainable dose of 6 microM naringenin reduced insulin-stimulated glucose uptake by approximately 20%. This inhibitory effect remained 24h after the removal of naringenin from the culture medium. Collectively, our findings suggest that the regular consumption of naringenin in grapefruit may exacerbate insulin resistance in susceptible individuals via impaired glucose uptake in adipose tissue.

The biochemistry and medical significance of the flavonoids

Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.

Effect of quercetine on survival and morphological properties of cultured embryonic rat spinal motoneurones

Quercetine a flavonoid compound present in many plants and in the extract of Ginkgo biloba was shown to enhance the survival of purified rat spinal embryonic motoneurones, sampled at day embryonic 15 and maintained in culture for several days. Survival of embryonic spinal motoneurones is dose dependent and concentrations of quercetine ranging from 1 to 10 microM increase by 25% the number of living motoneurones in the culture. Excepted a slight significant decrease in the number of branches at day 3 and a small reduction of total neuritic length, no drastic changes in the motoneurones morphologies were observed in presence of quercetine. Results are discussed in term of neuronal protective effect of quercetine.

Effect of procyanidolic oligomers on the permeability of the blood-brain barrier

Blood-brain barrier (BBB) is the site of regulatory mechanisms which control the exchange of substances between the brain and the blood through the wall of 'true' brain capillaries with tight junctions between endothelial cells. In some pathological situations the permeability of the BBB is increased because of a partial proteolytic degradation of some constituents of the capillary basement lamina. In such cases it is important to restore normal permeability. The effect of procyanidolic oligomers (PCO) on the BBB was investigated in vivo with quantitative morphologic procedures. We also investigated the action of this drug on collagen and basement lamina constituents (Matrigel) in vitro. Collagenase injected in lateral brain ventricles was shown to increase BBB permeability. Per os administration of PCO to rats greatly increased the resistance of brain capillaries to bacterial collagenase, as shown by the inhibition of the diffusion of fluorescein-isothiocyanate-marked dextran particles from the blood-stream into the brain tissues. Calf skin collagen pretreated in vitro with PCO became more resistant to the hydrolytic action of collagenase. Similar, even more intense protective effect was seen when basal lamina constituents containing type IV collagen was incubated with PCO before exposure to pronase. These in vitro effects may partly explain the in vivo protective effect of PCO against the alteration of brain capillaries by i.v. injected bacterial collagenase.

Differential effects of flavonoids on 3T3-L1 adipogenesis and lipolysis

Flavonoids, polyphenolic compounds that exist widely in plants, inhibit cell proliferation and increase cell differentiation in many cancerous and noncancerous cell lines. Because terminal differentiation of preadipocytes to adipocytes depends on proliferation of both pre- and postconfluent preadipocytes, we predicted that flavonoids would inhibit adipogenesis in the 3T3-L1 preadipocyte cell line. The flavonoids genistein and naringenin inhibited proliferation of preconfluent preadipocytes in a time- and dose-dependent manner. When added to 2-day postconfluent preadipocytes at the induction of differentiation, genistein inhibited mitotic clonal expansion, triglyceride accumulation, and peroxisome proliferator-activated receptor-gamma expression, but naringenin had no effect. The antiadipogenic effect of genistein was not due to inhibition of insulin receptor subtrate-1 tyrosine phosphorylation. When added 3 days after induction of differentiation, neither flavonoid inhibited differentiation. In fully differentiated adipocytes, genistein increased basal and epinephrine-induced lipolysis, but naringenin had no significant effects. These data demonstrate that genistein and naringenin, despite structural similarity, have differential effects on adipogenesis and adipocyte lipid metabolism.

Epigallocatechin gallate increase the prostacyclin production of bovine aortic endothelial cells

We describe the effect of (-) epigallocatechin gallate (EGCg), one of catechins known in tea, on the prostacyclin (PGI) production by bovine aortic endothelial cells. The amounts of 6-keto-PGF(1alpha) and Delta(17)-6-keto-PGF(1alpha), stable metabolites of PGI(2) and PGI(3), released in culture medium were measured using gas chromatography/selected ion monitoring (GC/SIM). The prostacyclin production of endothelial cells was increased by EGCg in a dose- and time-dependent manner. The effect by EGCg was stronger than any other catechins (catechin, epicatechin, epigallocatechin, and epicatechin gallate). When endothelial cells incubated with EGCg and arachidonic acid (AA) or eicosapentaenoic acid (EPA), PGI(2), and PGI(3) production were increased greater than those incubated with AA or EPA alone. Furthermore, gallic acid, that also has a pyrogallol structure, increased PGI(2) production. These observations indicate that catechins increase the prostacyclin production and that the pyrogallol structure is significant to this function.

Reactivities of flavonoids with different hydroxyl substituents for the cleavage of DNA in the presence of Cu(II)

DNA strand scission reactions of flavonoids in the presence of Cu(II) have been extended by using flavonoids with a variety of patterns of hydroxyl substitution. In particular we have examined for the first time a flavonoid (7,8-dihydroxyflavone) that lacks the possibility of forming a complex involving the oxygen at position 4. By comparing the reactivities of several flavonoids, including data from the literature, we draw generalizations for the correlation of structure and activity and present evidence for at least three different modes of action of flavonoids as genotoxic agents.

Tyrosine kinase-independent inhibition of cyclic-AMP phosphodiesterase by genistein and tyrphostin 51

The phosphodiesterase activity in the HT4.7 neural cell line was pharmacologically characterized, and phosphodiesterase isozyme 4 (PDE4) was found to be the predominant isozyme. The Km for cAMP was 1-2 microM, indicative of a "low Km" phosphodiesterase, and the activity was inhibited by PDE4-selective inhibitors rolipram and Ro20-1724, but not PDE3- or PDE2-selective inhibitors. Calcium, calmodulin, and cGMP, regulators of PDE1, PDE2, and PDE3, had no effect on cAMP hydrolysis. The protein tyrosine kinase inhibitor, genistein, inhibited HT4.7 cAMP phosphodiesterase activity by 85-95% with an IC50 of 4 microM; whereas daidzein, an inactive structural analog of genistein, had little effect on phosphodiesterase activity. This is a common pharmacological criterion used to implicate the regulation by a tyrosine kinase. However, genistein still inhibited phosphodiesterase activity with a mixed pattern of inhibition even when ion-exchange chromatography was used to partially purify phosphodiesterase away from the tyrosine kinase activity. Moreover, tyrphostin 51, another tyrosine kinase inhibitor, was found to also inhibit partially purified phosphodiesterase activity noncompetitively. These data suggest that HT4.7 phosphodiesterase activity is dominated by PDE4 and can be regulated by genistein and tyrphostin 51 by a tyrosine kinase-independent mechanism.

Effect of isoorientin isolated from Arum palaestinum on uterine smooth muscle of rats and guinea pigs

The phytochemical investigation of Arum palaestinum resulted in the isolation of two flavone C-glucosides, namely isoorientin (luteolin 6-C-glucoside) and vitexin (apigenin 8-C glucoside). The effects of isoorientin on rat isolated aorta, ileum, trachea and uterus and on guinea-pig uterus were studied. Isoorientin (10(-7)M-6 x 10(-4)M) caused concentration-dependent inhibition of the amplitude and the frequency of the phasic contractions of the rat and guinea-pig uterus but did not affect the isolated aorta, ileum or trachea. The results were discussed in relation to the effects of its aglycone luteolin reported in the literature.

Natural dietary polyphenolic compounds cause endothelium-dependent vasorelaxation in rat thoracic aorta

This study investigated the possible active principles which support the endothelial nitric oxide-dependent relaxation produced by red wine and other plant polyphenolic compounds in thoracic aorta from male Wistar rats (12-14 wk old). Relaxation experiments were recorded isometrically on vessels precontracted with norepinephrine. Ten different chromatographic fractions (3-18 mg) isolated from red wine polyphenolic compounds (RWPC) and some available defined polyphenols (10-15 mg) were tested. Fractions enriched into either anthocyanins or oligomeric condensed tannins exhibited endothelium-dependent vasorelaxant activity (maximal relaxation in the range of 59-77%) comparable to the original RWPC. However, polymeric condensed tannins elicited a weaker vasorelaxant activity than the original RWPC (maximal relaxation ranged between 20-47%, P < 0.01). Moreover, the representative of either phenolic acid derivatives (benzoic acid, vanillic acid, gallic acid), hydroxycinnamic acid (p-coumaric acid, caffeic acid) or the flavanol [(+)-epicatechin] classes failed to induce this type of response. Among the anthocyanins, delphinidin (maximal relaxation being 89%), but not malvidin or cyanidin, showed endothelium-dependent vasorelaxation. These results show that anthocyanins and oligomeric-condensed tannins exhibited a pharmacological profile comparable to the original RWPC. These compounds may be involved in the reduction of cardiovascular mortality related to the presence of wine, fruits and vegetables in the diet.

Role of tyrosine phosphorylation in excitation-contraction coupling in vascular smooth muscle

Increasingly it is recognized that tyrosine phosphorylation plays an important part in the regulation of function in differentiated contractile vascular smooth muscle. Tyrosine kinases and phosphatases are present in large amounts in vascular smooth muscle and have been reported to influence a number of processes crucial to contraction, including ion channel gating, calcium homeostasis and sensitization of the contractile process to [Ca2+]i. This review summarizes current understanding regarding the role of tyrosine phosphorylation in excitation-contraction coupling in blood vessels.

Dietary flavonol quercetin induces chloride secretion in rat colon

The aim of this study was to investigate the possible effects of the flavonol quercetin, the most abundant dietary flavonoid, on the intestinal mucosa. In vitro experiments were performed with various segments of the rat intestine, using the Ussing chamber technique. Quercetin increased the short-circuit current (Isc) in the jejunum, ileum, and proximal and distal colon. Additional experiments were performed using preparations of the proximal colon. The maximum effective dose of quercetin was found to be approximately 100 microM. The quercetin-induced increase in Isc was inhibited by the Cl- channel blocker 5-nitro-2-(3-phenylpropylamino)-benzoic acid. Adding blockers of the Na+-K+-2Cl- cotransporter to the serosal compartment diminished the increase of Isc due to quercetin. Ion substitution and flux measurements indicated that the effect of quercetin was due to electrogenic Cl- and HCO-3 secretion. In contrast to the aglycone, the quercetin glycoside rutin had no effect. The effect of quercetin on Isc was additive to the Isc increase induced by forskolin, but the flavonoid diminished the Isc evoked by carbachol. The phosphodiesterase inhibitor theophylline blocked the effect of quercetin. Genistein, a related isoflavone, did not alter the Isc evoked by quercetin. These findings demonstrate that the dietary flavonol quercetin induces Cl- secretion and most likely HCO-3 secretion in rat small and large intestine. The effects are restricted to the flavonol aglycone.

Effects of red and white wine on endothelium-dependent vasorelaxation of rat aorta and human coronary arteries

Beneficial effects of wine on myocardial infarction mortality may be because of its vasodilatory properties. This study investigated whether the vasodilatory activity involves the endothelium and is specific for certain wines. Effects of different red and white wines and phenolic grape ingredients on vascular tension and cGMP content were studied in human coronary arteries and rat aortic rings in vitro. Only French and Italian red wines produced "en barrique" (Bordeaux, Châteauneuf du Pape, Barolo) (1:1,000, vol/vol), quercetin (1-100 microM), and tannic acid (1-100 microgram/ml) decreased tension of precontracted vascular rings and increased vascular cGMP content (both P < 0.001). The effects were abolished after endothelial denudation and reversible by nitric oxide synthase inhibition. Red wines not produced en barrique (Valpolicella, Ahr Spätburgunder), white wines (en barrique-produced Rioja, Chardonnay, Mosel-Riesling), and ethanol did not affect vascular tension or cGMP content. Thus endothelium-dependent vasodilatory effects appear to be specific for red barrique wines, possibly because of their high content of phenolic substances. Divergent effects of wines indicate that a general view on the effects of wine and alcoholic beverages is not warranted.

A review of the plants of the genus Phyllanthus: their chemistry, pharmacology, and therapeutic potential

The plants of the genus Phyllanthus (Euphorbiaceae) are widely distributed in most tropical and subtropical countries, and have long been used in folk medicine to treat kidney and urinary bladder disturbances, intestinal infections, diabetes, and hepatitis B. In recent years, the interest in the plants has increased considerably. Substantial progress on their chemistal and pharmacological properties, as well as a few clinical studies of some Phyllanthus species have been made. This review discusses the current knowledge of their chemistry, the in vitro and in vivo pharmacological, biochemical, and clinical studies carried out on the extracts, and the main active constituents isolated from different species of plants of the genus Phyllanthus. These studies carried out with the extracts and purified compounds from these plants support most of their reported uses in folk medicine as an antiviral, in the treatment of genitourinary disorders, and as antinociceptive agents. However, well-controlled, double-binding clinical trials are lacking. Several compounds including alkaloids, flavonoids, lignans, phenols, and terpenes were isolated from these plants and some of them interact with most key enzymes. Together this data strongly supports the view that the plants belonging to the genus Phyllanthus have potential beneficial therapeutic actions in the management of hepatitis B, nefrolitiase, and in painful disorders.

Pharmacological effects of selected flavonoids on rat isolated ileum: structure-activity relationship

1. Eleven selected flavonoids were studied to evaluate their effects on the rat isolated ileum and to determine their structure-activity relationships. 2. The flavonoids rutin and 3',5,7-trihydroxy-4' methoxyflavone-7-rutinoside, which have a sugar moiety (O-rha-glu), had no significant effect on the ileum, indicating that the presence of sugar substitution reduces the biological activity of the flavonoids. 3. Nine other flavonoids caused inhibition of tonic and phasic contractions of the ileum with the following order of potency from highest to lowest: galangin, quercetin, chrysin, xanthomicrol, flavone, naringenin, fisetin, morin, and flavanone. 4. Flavones were more potent than flavanones, indicating that the double bond at carbon 2-3 increases the potency of the flavonoid. 5. Galangin, quercetin, chrysin, and xanthomicrol, which have hydroxyl substituents on carbon 3 and/or 5, showed higher potency than flavone, indicating that such hydroxyl groups are essential for the activity. 6. Galangin was more potent than quercetin, morin, and fisetin, suggesting that the hydroxyl substituents on ring B attenuate the potency. 7. Quercetin caused more potent relaxation of the ileum than morin, suggesting that the presence of a hydroxyl group at C-2' of ring B attenuates the myolytic activity.

Vasorelaxing activity of resveratrol and quercetin in isolated rat aorta

1. Both resveratrol and quercetin dose-dependently inhibited the contractile response to noradrenaline (NA) in isolated endothelium-intact rat aorta. This inhibitory effect on vascular contraction was blocked by pretreatment of the blood vessel with the nitric oxide (NO) synthase inhibitor, L-NNA (1 microM). 2. Quercetin at a concentration > 1 x 10(-5) M, and resveratrol at > 3 x 10(-5) M, caused relaxation of the phenylephrine (PE) precontracted endothelium-intact aorta, and L-NNA, at 1 x 10(-6) M, reversed the relaxation. 3. At higher concentrations, > 6 x 10(-5) M, resveratrol and quercetin also relaxed the endothelium-denuded aortic rings. However, this effect could not be reversed by the NO inhibitor. 4. It is concluded that resveratrol and quercetin exert both indirect and direct vasodilator effects on the blood vessel by nitric oxide-mediated and non-NO-mediated mechanisms, respectively.

Effects of ipriflavone and its metabolites on human articular chondrocytes cultivated in clusters

Ipriflavone (IP) is an isoflavone derivative that was suggested to have bone-sparing effects in post-menopausal and senile osteoporosis. A moderate stimulatory effect of IP and its metabolites on proliferation of osteoblastic cells was reported in rat osteoblastic osteosarcoma cell line. We investigated the effects of different concentrations (0, 1, 10 and 100 micrograms/ml) of IP and its metabolites (MET I, II, III and V) on the incorporation of [3H] thymidine and production of proteoglycans (PG) and type II collagen (COL II) by human articular chondrocytes during a 12-day period, in a three-dimensional chondrocyte culture model. [3H]thymidine uptake was measured in chondrocyte clusters, and specific PG and COL II radioimmunoassays were performed every 4 days on the culture medium and cell clusters. Incubation with IP or its metabolites did not affect [3H]thymidine uptake regardless of the dose. PG released into the culture medium and PG cluster content rose significantly (P < 0.025) in presence of IP (1, 10 and 100 micrograms/ml). MET I increased PG release in culture medium (10 and 100 micrograms/ml) and PG cluster content (100 micrograms/ml). MET II has no effect on PG production. MET III increased PG in culture medium (100 microgram/ml) but did not influence PG cluster content while MET V (100 micrograms/ml) increased both PG release in culture medium and PG cluster content. COL II release in culture medium and COL II cluster content were significantly (P < 0.025) increased in presence of IP (10 and 100 micrograms/ml), MET III (1, 10 and 100 micrograms/ml) or MET V (100 micrograms/ml). MET I and II did not significantly affect COL II production.

Flavonoids extracted from fonio millet (Digitaria exilis) reveal potent antithyroid properties

Digitaria exilis (fonio) is a tiny variety of millet commonly eaten by inhabitants of semiarid regions. A sample of fonio collected right in the middle of a severely iodine-depleted goitrous endemic was submitted to phytochemical investigations in order to assess the potential contributory roles played by vegetable molecules to the goitrogenic processes. The total content of flavonoids amounts to 500 mg/kg of the edible whole cereal grains. Their extraction and identification fail to detect the C-glycosylflavones described in other millet varieties but point out the presence of apigenin (A = 150 mg/kg) and of luteolin (L1 = 350 mg/kg). Ten percent of A and 80% of L1 are present in free form, whereas the remaining 90% of A and 20% of L1 are bound as O-glycosylflavones. Both A and L1 aglycones manifest strong anti-thyroid peroxidase (TPO) activities, resulting in a significant reduction of the hormonogenic capacity of this enzyme. In addition, L1 significantly depresses the cyclic AMP phosphodiesterase, implying a concomitant overproduction of the thyrotropin-dependent nucleotide. These last unreported data are regarded as counteracting to some extent the TPO-mediated goitrogenic properties of L1. Since fonio is devoid of other molecules likely to interfere with the thyroid function, our results are directly and casually attributed to A and L1 found in the customary diet.

Inhibition of constitutive endothelial NO-synthase activity by tannin and quercetin

The effect of natural polyphenols on three isoforms of NO-synthase was investigated. Among the compounds tested, tannin was the most potent, inhibiting endothelial constitutive NO synthase (eNOS) with an IC50 of 2.2 microM. Other NOS isoforms (i.e. neuronal constitutive NOS and smooth muscle inducible NOS) were also inhibited but at much higher concentrations (selectivity ratio of approx. 20-30). Quercetin was also an effective but less potent inhibitor of eNOS (IC50 = 220 microM). The kinetics of tannin inhibition were investigated to gather information on the mechanism of action. Tannin did not interfere with the interaction of the enzyme with the co-substrates L-arginine and NADPH nor with the cofactor tetrahydrobiopterin. The inhibition level was also independent of free Ca2+ concentration as well as of the presence of high exogenous calmodulin concentrations.