Flavonoids: a review of probable mechanisms of action and potential applications

Three-year comparison of the content of antioxidant microconstituents and several quality characteristics in organic and conventionally managed tomatoes and bell peppers

Understanding how the environment and production and cultivation practices influence the composition and quality of food crops is fundamental to the production of high-quality nutritious foods. In this 3-year study, total phenolics, percent soluble solids, ascorbic acid, and the flavonoid aglycones quercetin, kaempferol, and luteolin were measured in two varieties of tomato (Lycopersicon esculentum L. cv. Ropreco and Burbank) and two varieties of bell peppers (Capsicum annuum L. cv. California Wonder and Excalibur) grown by certified organic and conventional practices in a model system. Significantly higher levels of percent soluble solids (17%), quercetin (30%), kaempferol (17%), and ascorbic acid (26%) were found in Burbank tomatoes (fresh weight basis; FWB), whereas only levels of percent soluble solids (10%) and kaempferol (20%) were significantly higher in organic Ropreco tomatoes (FWB). Year-to-year variability was significant, and high values from 2003 influenced the 3-year average value of quercetin reported for organic Burbank tomatoes. Burbank tomatoes generally had higher levels of quercetin, kaempferol, total phenolics, and ascorbic acid as compared to Ropreco tomatoes. Bell peppers were influenced less by environment and did not display cropping system differences.

Metabolism of ATP-binding cassette drug transporter inhibitors: complicating factor for multidrug resistance

Membrane transport proteins belonging to the ATP-binding cassette (ABC) family of transport proteins play a central role in the defence of organisms against toxic compounds, including anticancer drugs. However, for compounds that are designed to display a toxic effect, this defence system diminishes their effectiveness. This is typically the case in the development of cellular resistance to anticancer drugs. Inhibitors of these transporters are thus potentially useful tools to reverse this transporter-mediated cellular resistance to anticancer drugs and, eventually, to enhance the effectiveness of the treatment of patients with drug-resistant cancer. This review highlights the various types of inhibitors of several multidrug resistance-related ABC proteins, and demonstrates that the metabolism of inhibitors, as illustrated by recent data obtained for various natural compound inhibitors, may have considerable implications for their effect on drug transport and their potential for treatment of drug resistance.

Resveratrol—A boon for treating Alzheimer's disease?

Resveratrol, a red wine polyphenol, is known to protect against cardiovascular diseases and cancers, as well as to promote antiaging effects in numerous organisms. It also modulates pathomechanisms of debilitating neurological disorders, such as strokes, ischemia, and Huntington's disease. The role of resveratrol in Alzheimer's disease is still unclear, although some recent studies on red wine bioactive compounds suggest that resveratrol modulates multiple mechanisms of Alzheimer's disease pathology. Emerging literature indicates that mechanisms of aging and Alzheimer's disease are intricately linked and that these mechanisms can be modulated by both calorie restriction regimens and calorie restriction mimetics, the prime mediator of which is the SIRT1 protein, a human homologue of yeast silent information regulator (Sir)-2, and a member of NAD+-dependent histone deacetylases. Calorie restriction regimens and calorie restriction-mimetics trigger sirtuins in a wide variety of organisms, ranging from bacteria to mouse. In a mouse model of Huntington's disease, resveratrol-induced SIRT1 was found to protect neurons against ployQ toxicity and in Wallerian degeneration slow mice, resveratrol was found to protect the degeneration of neurons from axotomy, suggesting that resveratrol may possess therapeutic value to neuronal degeneration. This paper mainly focuses on the role of resveratrol in modulating AD pathomechanisms.

Acute effect of tea, wine, beer, and polyphenols on ecto-alkaline phosphatase activity in human vascular smooth muscle cells

Alkaline phosphatase (ALP) is an ecto-enzyme widely distributed across species. It modulates a series of transmembranar transport systems, has an important role in bone mineralization, and can also be involved in vascular calcification. Polyphenol-rich diets seem to have protective effects on human health, namely, in the prevention of cardiovascular diseases. We aimed to investigate the effects of polyphenols and polyphenol-rich beverages upon membranar alkaline phosphatase (ecto-ALP) activity in intact human vascular smooth muscle cells (AALTR). The ecto-ALP activity was determined at pH 7.8, with p-nitrophenyl phosphate as the substrate, by absorbance spectrophotometry at 410 nm. Cell viability was assessed by the lactate dehydrogenase (LDH) method, and the polyphenol content of beverages was assessed using the Folin-Ciocalteu reagent. All polyphenols tested inhibited ecto-ALP activity, in a concentration-dependent way. Teas, wines, and beers also inhibited ecto-ALP activity, largely according to their polyphenol content. All tested compounds and beverages improved or did not change AALTR cell viability. Stout beer was an exception to the described behavior. Although more studies must be done, the inhibition of AALTR ecto-ALP activity by polyphenolic compounds and polyphenol-containing beverages may contribute to their cardiovascular protective effects.

Effect of quercetin on altered vascular reactivity in aortas isolated from streptozotocin-induced diabetic rats

The present work examined ex vivo the acute effect of quercetin on diabetic rat aortic ring reactivity in response to endothelium-dependent (acetylcholine, ACh) and endothelium-independent (sodium nitroprusside, SNP) relaxants, and to the alpha(1)-adrenergic agonist phenylephrine (PE). Responses were compared to those of aortic rings from age- and sex-matched euglycemic rats. Compared to euglycemic rat aortic rings, diabetic rings showed less relaxation in response to ACh and SNP, and greater contraction in response to PE. Pretreatment with quercetin (10microM, 20min) increased ACh-induced relaxation and decreased PE-induced contraction in diabetic, but did not affect euglycemic rat aortic ring responses. Following pretreatment with the nitric oxide synthase inhibitor Nomega-nitro-l-arginine methyl ester (l-NAME, 10microM), quercetin reduced PE-induced contractions in both aortic ring types, although l-NAME attenuated the reduction in the diabetic rings. Quercetin did not alter SNP vasodilatory effects in either ring type compared to their respective controls. These findings indicate that quercetin acutely improved vascular responsiveness in blood vessels from diabetic rats, and that these effects were mediated, at least in part, by enhanced endothelial nitric oxide bioavailability. These effects of quercetin suggest the possible beneficial effects of quercetin in vivo in experimental diabetes and possibly in other cardiovascular diseases.

Polyphenolic apple juice extracts and their major constituents reduce oxidative damage in human colon cell lines

Apple juice containing high amounts of antioxidative polyphenols might protect the intestine against oxidative cell damage. We investigated the preventive effectiveness of polyphenolic juice extracts of different origins (cider and table apples) in comparison to their major constituents in human colon cell lines (Caco-2, HT29). Parameters studied were (oxidative) DNA damage (Comet assay), glutathione level (photometric kinetic assay), cellular redox status (dichlorofluorescein assay) and antioxidant capacity. The extracts (50-250 microg/mL) modulated DNA damage and redox status in a concentration-dependent manner at 24-h incubation. The pomace extraction technology, applied for juice preparation, and the preferential selection of cider apple varieties influenced the polyphenolic pattern and increased the biological effectiveness of the extracts. The preventive potential of major juice constituents (1-100 microM, 24 h) strongly differed: rutin, epicatechin and caffeic acid clearly reduced (oxidative) DNA damage (Caco-2), chlorogenic acid efficiently decreased cellular reactive oxygen species level (HT29, Caco-2). The aglyca quercetin and phloretin exhibited the highest preventive/antioxidant capacity in all assays. The stability of the compounds inversely correlated with their preventive effectiveness and might contribute to the observed cell specific sensitivities. In conclusion, apple juice extracts distinctly reduce oxidative cell damage in human colon cell lines, an effect, which in part can be accounted for by their major constituents.

Direct effects of quercetin on impaired reactivity of spontaneously hypertensive rat aortae: comparative study with ascorbic acid

1. There is a growing interest in the anti-oxidant characteristics and use of flavonoids in the management of cardiovascular diseases. The cardiovascular mechanism of action of these plant derivatives remains controversial. This study compared the effects of the flavonoid quercetin with those of the anti-oxidant vitamin ascorbic acid (vitamin C) on the reactivity of aortic rings from spontaneously hypertensive rats (SHR). 2. The phenylephrine (PE)-induced contractile and the endothelium-dependent and independent relaxant responses of aortic rings from 21 to 22 week old SHR and age-matched normotensive Wistar (WKY) rats were observed in the presence of quercetin or ascorbic acid. All the experiments were performed in the presence of the cyclooxygenase inhibitor, indomethacin (10 micromol/L). 3. The endothelium-dependent and independent relaxations to acetylcholine (ACh) and sodium nitroprusside (SNP), respectively, were significantly lesser in the SHR compared to the WKY tissues whereas the contractile responses to PE were similar in both tissues. Pretreatment of WKY rings with quercetin or ascorbic acid had no effect on the responses to ACh or PE. In the SHR tissues, however, quercetin or ascorbic acid significantly improved the relaxation responses to ACh and reduced the contractions to PE with greater potency for quercetin. Both compounds lacked any effects on the responses to SNP in either aortic ring types. N(omega)-nitro-L-arginine methyl ester (l-NAME, 10 micromol/L) significantly attenuated the vasodepressor effects of quercetin and ascorbic acid, raising the responses to PE to a level similar to that observed in the control SHR tissues. In l-NAME pretreated aortic rings, quercetin and ascorbic acid inhibited the contractile responses to PE with the same magnitude in WKY and SHR tissues. 4. The present results suggest that acute exposure to quercetin improves endothelium-dependent relaxation and reduces the contractile responses of hypertensive aortae with a greater potency than ascorbic acid. This suggests a better vascular protection with this flavonoid than ascorbic acid in the SHR model of hypertension and possibly in human cardiovascular diseases.

Therapeutic effects of Semecarpus anacardium Linn. nut milk extract on the changes associated with collagen and glycosaminoglycan metabolism in adjuvant arthritic Wistar rats

The effect of milk extract of Semecarpus anacardium Linn. nut milk extract (SA) was studied to gain some insight into this intriguing disease with reference to collagen metabolism. Arthritis was induced in rats by injecting Freund's complete adjuvant containing 10mg of heat killed mycobacterium tuberculosis in 1 ml paraffin oil (0.1 ml) into the left hind paw of the rat intradermally. After 14 days of induction, SA (150 mg/kg body weight/day) was administered orally by gastric intubations for 14 days. Decreased levels of collagen and glycosaminoglycans (GAGS) components (chondroitin sulphate, heparan sulphate, hyaluronic acid) and increase in the levels of connective tissue degrading lysosomal glycohydrolases such as acid phosphatase, beta-glucuronidase, beta-N-acetyl glucosaminidase and cathepsin-D observed in arthritic animals were reverted back to near normal levels upon treatment with SA. The drug effectively regulated the uriniray markers of collagen metabolism namely hexosamine, hexuronic acid, hydroxyproline and total GAGS. Electron microscopic studies also revealed the protective effect of SA. Hence, it can be suggested that SA very effectively regulate the collagen metabolism that derange during arthritic condition.

SIRT1 stimulation by polyphenols is affected by their stability and metabolism

Silent information regulator two ortholog 1 (SIRT1) is the human ortholog of the yeast sir2 protein; one of the most important regulators of lifespan extension by caloric restriction in several organisms. Dietary polyphenols, abundant in vegetables, fruits, cereals, wine and tea, were reported to stimulate the deacetylase activity of recombinant SIRT1 protein and could therefore be potential regulators of aging associated processes. However, inconsistent data between effects of polyphenols on the recombinant SIRT1 and on in vivo SIRT1, led us to investigate the influence of (1) stability of polyphenols under experimental conditions and (2) metabolism of polyphenols in human HT29 cells, on stimulation of SIRT1. With an improved SIRT1 deacetylation assay we found three new polyphenolic stimulators. Epigallocatechin galate (EGCg, 1.76-fold), epicatechin galate (ECg, 1.85-fold) and myricetin (3.19-fold) stimulated SIRT1 under stabilizing conditions, whereas without stabilization, these polyphenols strongly inhibited SIRT1, probably due to H2O2 formation. Using metabolically active HT29 cells we were able to show that quercetin (a stimulator of recombinant SIRT1) could not stimulate intracellular SIRT1. The major quercetin metabolite in humans, quercetin 3-O-glucuronide, slightly inhibited the recombinant SIRT1 activity which explains the lack of stimulatory action of quercetin in HT29 cells. This study shows that the stimulation of SIRT1 is strongly affected by polyphenol stability and metabolism, therefore extrapolation of in vitro SIRT1 stimulation results to physiological effects should be done with caution.

Protective effects of Asian green vegetables against oxidant induced cytotoxicity

AIM

To evaluate the antioxidant and phase II detoxification enzyme inducing ability of green leaf vegetables consumed in Asia.

METHODS

The antioxidant properties of six commonly consumed Asian vegetables were determined using the ABTS, DPPH, deoxyribose, PR bleaching and iron- ascorbate induced lipid peroxidation assay. Induce of phase II detoxification enzymes was also determined for each respective vegetable extract. Protection against authentic ONOO- and HOCl mediated cytotoxicity in human colon HCT116 cells was determined using the MTT 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrasodium bromide) viability assay.

RESULTS

All of the extracts derived from green leaf vegetables exhibited antioxidant properties, while also having cytoprotective effects against ONOO- and HOCl mediated cytotoxicity. In addition, evaluation of the phase II enzyme inducing ability of each extract, as assessed by quinone reductase and glutathione-S-transferase activities, showed significant variation between the vegetables analyzed.

CONCLUSION

Green leaf vegetables are potential sources of antioxidants and phase II detoxification enzyme inducers in the Asian diet. It is likely that consumption of such vegetables is a major source of beneficial phytochemical constituents that may protect against colonic damage.

Effect of naringin pretreatment on bioavailability of verapamil in rabbits

The aim of present study is to investigate the effect of naringin on the pharmacokinetics of verapamil and its major metabolite, norverapamil in rabbits. The pharmacokinetic parameters of verapamil and norverapamil were determined after administering verapamil (9 mg/kg) orally to rabbits in the pretreated with naringin (1.5, 7.5, and 15 mg/kg). Naringin pretreatment significantly altered the pharmacokinetic parameters of verapamil. Compared with the control group (given verapamil alone), the Ka, Cmax and AUC of verapamil were significantly (p<0.05 or p<0.01) increased in the pretreatment of naringin, However there were no significant change in Tmax and t1/2 of verapamil. Consequently, pretreatment of naringin significantly (p<0.05, p<0.01) increased the AB% of verapamil significantly in a dose dependent manner (p<0.05 or p<0.01), and elevated the RB% of verapamil by 1.26- to 1.69-fold. the MR of verapamil were significantly (p<0.05) increased in the pretreatment of naringin, implying that pretreatment of naringin may effectively inhibit the CYP3A4-mediated metabolism of verapamil. In conclusion, pretreatment of naringin enhanced the oral bioavailability of verapamil. Based on these results, the verapamil dosage should be adjusted when given with naringin or a naringin-containing dietary supplement.

Curative effect of Semecarpus anacardium Linn. nut milk extract against adjuvant arthritis—With special reference to bone metabolism

Localised bone loss in the form of bone erosions and peri-articular osteopenia constitutes an important criteria for the diagnosis of rheumatoid arthritis. In the present study, the effect of Semecarpus anacardium Linn. nut milk extract (SA) on the metabolism of bone turn over has been studied by analyzing various markers of bone turnover and by histological and radiological analysis of the joints in adjuvant arthritis in rats. Arthritis was induced in rats by injecting Freund's complete adjuvant containing 10mg of heat killed mycobacterium tuberculosis in 1 ml paraffin oil (0.1 ml) into the left hind paw of the rat intradermally. After 14 days of induction, SA (150 mg/kg body weight/day) was administered orally by gastric intubations for 14 days. SA significantly reverted the alterations in the bone turnover observed in arthritic animals by modulating the levels of calcium, phosphorus and the activities of the enzymes names tartrate resistant acid phosphatase, acid phosphatase and alkaline phosphatase. The drug increased the bone weights that were found to be decreased during arthritis. Protective effect of SA was also observed by the decrease in the levels and expression of tumour necrosis factor alpha (TNF-alpha) as well as the histopathological and radiological observations. From all these observations it can be concluded that SA possesses strong anti-arthritic property by regulating bone turnover.

Chemical structure of flavonols in relation to modulation of angiogenesis and immune-endothelial cell adhesion

The antioxidant activity of flavonoids has been suggested to contribute to several health benefits associated with the consumption of fruits and vegetables. Four flavonols - myricetin (M), quercetin (Q), kaempferol (K) and galangin (G), all with different numbers of hydroxyl moieties (-OH) - were examined for their antioxidant activity and cytotoxicity on human umbilical vein endothelial cells (HUVECs) and for their potential antiangiogenic and cell adhesion effects. The relative antioxidant capacity of these flavonols in cell culture medium (cell-free system) and their intracellular antioxidant activity were M = Q > K = G, which correlated respectively with the presence of 3, 2, 1 and 0 moieties of -OH on their B-ring. The higher the numbers of -OH moieties on the B-ring the less toxic the flavonol was to HUVEC, and the LD50 was determined as: M (100 microM) > Q (50 microM) > K (20 microM) > G (10 microM). These flavonols at approximately 0.5 LD50 doses suppressed the vascular endothelial growth factor (VEGF)-stimulated HUVEC tubular structure formation by: M (47%) > Q (37%) > K (15%) > G (14%), which was not linearly associated with their numbers of -OH moieties. However, the magnitude of flavonols' suppression of activated U937 monocytic cells adhesion to HUVEC was associated with the number of -OH moieties on the B-ring. This was prominent when U937 cells were pretreated with these flavonols. In contrast, the numbers of -OH moiety had no apparent influence on the adhesion or expression of adhesion molecules when activated HUVECs were pretreated with these flavonols. The presence of different numbers of -OH moieties on the B-ring of the flavonols may contribute to their antioxidant activity as well as their toxicity and may play an important role in their potency for biological action such as angiogenesis and immune-endothelial cell adhesion, which, respectively, are important processes in the development of cancer and atherosclerosis.

Oxidative stress and protective effects of polyphenols: comparative studies in human and rodent kidney. A review

Reactive oxygen species (ROS) play a key role in the pathophysiological processes of a wide range of renal diseases. Thus, antioxidants are expected to decrease the vulnerability of the kidney to oxidative challenges. Polyphenols, particularly abundant in red wine, could act as ROS scavengers, iron chelators and enzyme modulators. In addition, chronic exposure to moderate amounts of ethanol results in increased activity of the renal antioxidant enzymes, further supporting a renoprotective effect of red wine based on its antioxidant properties. An enhancement of plasma antioxidant capacity following red wine consumption has been reported both in man and rodents, thereby providing a contributory factor to its renoprotective effect because the kidney is a highly perfused organ. Although phenol concentration of red wine does not influence the activity of antioxidant enzymes of the kidney, the concentration of these compounds is negatively correlated with tissue lipid peroxidation, assessed by thiobarbituric acid reactive substances, and positively correlated with the antioxidant capacity of plasma. Moreover, amelioration of myoglobinuric renal damage was found in rats following chronic exposure to flavonol-rich red wine. Also, pretreatment with resveratrol, or other red wine polyphenols, decreased kidney damage caused by ischaemia-reperfusion. The aim of the present review is to examine the pathophysiological basis of the renoprotective effect of red wine in man and rodents, based on functional, biochemical and ultrastructural evidence.

Clustering of haemostatic variables and the effect of high cashew and walnut diets on these variables in metabolic syndrome patients

We investigated the effect of a high walnut and cashew diet on haemostatic variables in people with the metabolic syndrome. Factor analysis was used to determine how the haemostatic variables cluster with other components of the metabolic syndrome and multiple regression to determine possible predictors. This randomized, control, parallel, controlled-feeding trial included 68 subjects who complied with the Third National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol criteria. After a 3-week run-in following the control diet, subjects were divided into three groups receiving either walnuts or cashews (20 energy%) or a control diet for 8 weeks. The nut intervention had no significant effect on von Willebrand factor antigen, fibrinogen, factor VII coagulant activity, plasminogen activator inhibitor 1 activity, tissue plasminogen activator activity or thrombin activatable fibrinolysis inhibitor. Statistically, fibrinogen clustered with the body-mass-correlates and acute phase response factors, and factor VII coagulant activity clustered with high-density lipoprotein cholesterol (HDL-C). Tissue plasminogen activator activity, plasminogen activator inhibitor 1 activity and von Willebrand factor antigen clustered into a separate endothelial function factor. HDL-C and markers of obesity were the strongest predictors of the haemostatic variables. We conclude that high walnut and cashew diets did not influence haemostatic factors in this group of metabolic syndrome subjects. The HDL-C increase and weight loss may be the main focus of dietary intervention for the metabolic syndrome. Furthermore, diet composition may have only limited effects if weight loss is not achieved.

Structural characterization of flavonol 3,7-di-O-glycosides and determination of the glycosylation position by using negative ion electrospray ionization tandem mass spectrometry

Flavonol 3,7-di-O-glycosides were investigated by negative ion electrospray ionization tandem mass spectrometry using a quadrupole linear ion trap (LIT) mass spectrometer. The results indicate that the fragmentation behavior of flavonol 3,7-di-O-glycosides is substantially different from that of their isomeric mono-O-diglycosides. In order to characterize a flavonoid as a flavonol 3,7-di-O-glycoside, both [Y3(0) - H]-* and [Y(0) - 2H]- ions should be present in [M - H]- product ion spectrum. The MS(3) product ion spectra of Y3(0)-, [Y3(0) - H]-* and Y7(0)- ions generated from the [M - H]- ion provide sufficient structural information for the determination of glycosylation position. Furthermore, the glycosylation positions are determined by comparing the relative abundances of Y3(0)- and Y7(0)- ions and their specific fragmentation patterns with those of flavonol mono-O-glycosides. In addition, a [Y3(0) - H]-* ion formed by the homolytic cleavage of 3-O glycosidic bond with high abundance points to 3-O glycosylation, while a [Y(0) - 2H]- ion formed by the elimination of the two sugar residues is consistent with glycosylation at both the 3-O and 7-O positions. Investigation of negative ion ESI-MS(2) and MS(3) spectra of flavonol O-glycosides allows their rapid characterization as flavonol 3,7-di-O-glycoside and their differentiation from isomeric mono-O-diglycosides, and also enables their direct analysis in crude plant extracts.

Evaluation of P53 and BAX gene expression and induction of apoptosis and necrosis by the cis-Pt(II) complex of 3-aminoflavone in comparison with cis-diamminedichloroplatinum(II) (cis-DDP) in human lymphocytes

Currently cis-diamminedichloroplatinum(II) (cis-DDP) is one of the most commonly applied compounds in chemotherapy of many types of cancer. However, a drawback is that its effectiveness presents with many side effects. Therefore, human normal lymphocytes were chosen as a model system to study cis-bis(3-aminoflavone)dichloroplatinum(II) (the cis-Pt(II) complex of 3-aminoflavone) in comparison with cis-DDP. We examined the effect of both tested compounds on cell viability and induction of apoptosis and necrosis. Trypan blue and acridine orange/ethidium bromide staining were carried out, as well as quantitative analysis of the apoptotic signal of P53 and BAX induction caused by the cis-Pt(II) complex of 3-aminoflavone in comparison with cis-DDP. cis-DDP induced a decrease of cell viability and led to a higher increase in necrosis and apoptosis than did the cis-Pt(II) complex of 3-aminoflavone. Moreover, at the molecular level cis-DDP increased P53 and BAX expression in comparison with the other tested compound. The cis-Pt(II) complex of 3-aminoflavone showed a weaker genotoxic effect in normal lymphocytes in comparison with cis-DDP, which was a stronger inducer of apoptosis and necrosis.

Inhibition of angiotensin converting enzyme activity by flavanol-rich foods

Angiotensin converting enzyme (ACE) activity was evaluated in the presence of flavanol-rich foods, i.e., wines, chocolates, and teas, and of purified flavonoids. All foods assayed inhibited ACE activity, red wines being more effective than white wine, and green tea more effective than black tea. The inhibition of ACE activity was associated with both phenolic and flavanol content in the foods. When isolated polyphenols were assayed, procyanidins (dimer and hexamer) and epigallocatechin significantly inhibited enzyme activity; similar concentrations of (+)-catechin, (-)-epicatechin, gallic acid, chlorogenic acid, caffeic acid, quercetin, kaempferol, and resveratrol were ineffective. When ACE activity was assayed in rat kidney membranes in the presence of chocolate extracts or purified procyanidins, it was observed that the inhibition depended on the chocolate content of flavanols and the number of flavanol units constituting the procyanidin. These experiments demonstrate that flavanols either isolated or present in foods could inhibit ACE activity. The occurrence of such inhibition in vivo needs to be determined, although is supported by the association between the consumption of flavanol-rich foods and reductions in blood pressure observed in several experimental models.

Flavothionato metal complexes: implications for the use of hydroxyflavothiones as green pesticides

Transition-metal complexes of 3-hydroxyflavothiones have been prepared and structurally characterized; the photochemical properties of these complexes have been examined and are discussed in the context of the use of these compounds as photodegradable pesticides.

In vitro basal and metabolism-mediated cytotoxicity of flavonoids

The purpose of this study was to compare the basal cytotoxicity and metabolism-mediated cytotoxicity of kaempferol, quercetin and rutin. McCoy cells were exposed to various concentrations of the flavonols with and without the S9 system. The neutral red uptake assay was used to determine viability after 24 h at 35-37 degrees C. Dose-response curves were established for each flavonol in the presence and absence of external metabolizing systems. Kaempferol and quercetin were cytotoxic and provoked a dose-dependent decrease in cell viability, without the S9 system. The hepatic S9 microsomal fraction metabolized these compounds to less cytotoxic metabolites. In contrast, rutin at 500 microg/ml failed to produce any overt signs of toxicity in either assay.

Single and repeated moderate consumption of native or dealcoholized red wine show different effects on antioxidant parameters in blood and DNA strand breaks in peripheral leukocytes in healthy volunteers: a randomized controlled trial (ISRCTN68505294)

BACKGROUND

Red wine (RW) is rich in antioxidant polyphenols that might protect from oxidative stress related diseases, such as cardiovascular disease and cancer. Antioxidant effects after single ingestion of RW or dealcoholized RW (DRW) have been observed in several studies, but results after regular consumption are contradictory. Thus, we examined if single or repeated consumption of moderate amounts of RW or DRW exert antioxidant activity in vivo.

METHODS

Total phenolic content and concentration of other antioxidants in plasma/serum, total antioxidant capacity (TEAC) in plasma as well as DNA strand breaks in peripheral leukocytes were measured in healthy non-smokers A) before, 90 and 360 min after ingestion of one glass of RW, DRW or water; B) before and after consumption of one glass of RW or DRW daily for 6 weeks. DNA strand breaks (SB) were determined by single cell gel electrophoresis (Comet Assay) in untreated cells and after induction of oxidative stress ex vivo with H2O2 (300 microM, 20 min).

RESULTS

Both RW and DRW transiently increased total phenolic content in plasma after single consumption, but only RW lead to a sustained increase if consumed regularly. Plasma antioxidant capacity was not affected by single or regular consumption of RW or DRW. Effects of RW and DRW on DNA SB were conflicting. DNA strand breaks in untreated cells increased after a single dose of RW and DRW, whereas H2O2 induced SB were reduced after DRW. In contrast, regular RW consumption reduced SB in untreated cells but did not affect H2O2 induced SB.

CONCLUSION

The results suggest that consumption of both RW and DRW leads to an accumulation of phenolic compounds in plasma without increasing plasma antioxidant capacity. Red wine and DRW seem to affect the occurrence of DNA strand breaks, but this cannot be referred to antioxidant effects.

Novel mechanisms of natural antioxidant compounds in biological systems: involvement of glutathione and glutathione-related enzymes

Polyphenols are wide variety of compounds that occur in fruits and vegetables, wine, tea, extra virgin olive oil, chocolate and other cocoa products. Several polyphenols have been demonstrated to have clear antioxidant properties in vitro, and many of their biological actions have been attributed to their intrinsic reducing capabilities. However, this concept appears now to be a simplistic way to conceive their activity. Evidence is indeed accumulating that polyphenols might exert several other specific biological effects that are as yet poorly understood. In this article we review the most recent data on the subject and describe the additional functions that polyphenols can have in biological systems, focusing on their effects on glutathione and its related enzymes. Experimental data indicate that polyhenols may offer an indirect protection by activating endogenous defense systems. Several lines of evidence suggest a tight connection between exogenous and endogenous antioxidants that appear to act in a coordinated fashion. It is reasonable to hypothesize that this is achieved, at least in part, through antioxidant responsive elements (AREs) present in the promoter regions of many of the genes inducible by oxidative and chemical stress. The latest studies strongly suggest that dietary polyphenols can stimulate antioxidant transcription and detoxification defense systems through ARE.

Grapefruit-seed extract attenuates ethanol-and stress-induced gastric lesions via activation of prostaglandin, nitric oxide and sensory nerve pathways

AIM: Grapefruit-seed extract (GSE) containing flavonoids, possesses antibacterial and antioxidative properties but whether it influences the gastric defense mechanism and gastroprotection against ethanol- and stress-induced gastric lesions remains unknown.

METHODS: We compared the effects of GSE on gastric mucosal lesions induced in rats by topical application of 100% ethanol or 3.5 h of water immersion and restraint stress (WRS) with or without (A) inhibition of cyclooxygenase (COX)-1 activity by indomethacin and rofecoxib, the selective COX-2 inhibitor, (B) suppression of NO-synthase with L-NNA (20 mg/kg ip), and (C) inactivation by capsaicin (125 mg/kg sc) of sensory nerves with or without intragastric (ig) pretreatment with GSE applied 30 min prior to ethanol or WRS. One hour after ethanol and 3.5 h after the end of WRS, the number and area of gastric lesions were measured by planimetry, the gastric blood flow (GBF) was assessed by H₂-gas clearance technique and plasma gastrin levels and the gastric mucosal generation of PGE2, superoxide dismutase (SOD) activity and malonyldialdehyde (MDA) concentration, as an index of lipid peroxidation were determined.

RESULTS: Ethanol and WRS caused gastric lesions accompanied by the significant fall in the GBF and SOD activity and the rise in the mucosal MDA content. Pretreatment with GSE (8-64 mg/kg i g) dose-dependently attenuated gastric lesions induced by 100% ethanol and WRS; the dose reducing these lesions by 50% (ID₅₀) was 25 and 36 mg/kg, respectively, and this protective effect was similar to that obtained with methyl PGE2 analog (5 μg/kg i g). GSE significantly raised the GBF, mucosal generation of PGE₂, SOD activity and plasma gastrin levels while attenuating MDA content. Inhibition of PGE₂ generation with indomethacin or rofecoxib and suppression of NO synthase by L-NNA or capsaicin denervation reversed the GSE-induced protection and the accompanying hyperemia. Co-treatment of exogenous calcitonine gene-related peptide (CGRP) with GSE restored the protection and accompanying hyperemic effects of GSE in rats with capsaicin denervation.

CONCLUSION: GSE exerts a potent gastroprotective activity against ethanol and WRS-induced gastric lesions via an increase in endogenous PG generation, suppression of lipid peroxidation and hyperemia possibly mediated by NO and CGRP released from sensory nerves.

Can herbs provide a new generation of drugs for treating Alzheimer's disease?

The overall aim of this review is to discuss cellular mechanisms at work in the progression of AD and current therapeutic strategies for treating AD, with a focus on the potential efficacy of herbal treatments. Recent advances in molecular, cellular, and animal model studies have revealed that formation of the 4-kDa amyloid beta peptide is a key factor in the development and progression of AD. Several cellular changes have been identified that are related to amyloid beta plaques and neurofibrillary tangles found in the autopsied brains of AD patients and in AD animal models. Several therapeutic strategies have been developed to treat AD, including anti-inflammatory, anti-oxidant, and anti-amyloid approaches. Recently, herbal treatments have been tested in animal and cellular models of AD and in clinical trials with AD subjects. In AD animal models and cell models, herbal extracts appear to have fewer adverse effects than beneficial effects on A beta and cognitive functions. These extracts have multi-functional properties (pro-cholinergic, anti-oxidant, anti-amyloid, and anti-inflammatory), and their use in the treatment of AD patients looks promising. The chemical compositions of herbs and their potential for alleviating or reducing symptoms of AD or for affecting the disease mechanism need to be further studied.

Epoxide formation on the aromatic B ring of flavanone by biphenyl dioxygenase of Pseudomonas pseudoalcaligenes KF707

Prokaryotic dioxygenase is known to catalyze aromatic compounds into their corresponding cis-dihydrodiols without the formation of an epoxide intermediate. Biphenyl dioxygenase from Pseudomonas pseudoalcaligenes KF707 showed novel monooxygenase activity by converting 2(R)- and 2(S)-flavanone to their corresponding epoxides (2-(7-oxabicyclo[4.1.0]hepta-2,4-dien-2-yl)-2, 3-dihydro-4H-chromen-4-one), whereby the epoxide bond was formed between C2' and C3' on the B ring of the flavanone. The enzyme also converted 6-hydroxyflavanone and 7-hydroxyflavanone, which do not contain a hydroxyl group on the B-ring, to their corresponding epoxides. In a previous report (S.-Y. Kim, J. Jung, Y. Lim, J.-H. Ahn, S.-I. Kim, and H.-G. Hur, Antonie Leeuwenhoek 84:261-268, 2003), however, we found that the same enzyme showed dioxygenase activity toward flavone, resulting in the production of flavone cis-2',3'-dihydrodiol. Extensive structural identification of the metabolites of flavanone by using high-pressure liquid chromatography, liquid chromatography/mass spectrometry, and nuclear magnetic resonance confirmed the presence of an epoxide functional group on the metabolites. Epoxide formation as the initial activation step of aromatic compounds by oxygenases has been reported to occur only by eukaryotic monooxygenases. To the best of our knowledge, biphenyl dioxygenase from P. pseudoalcaligenes KF707 is the first prokaryotic enzyme detected that can produce an epoxide derivative on the aromatic ring structure of flavanone.

Photoprotection by topical application of Achyrocline satureioides ('Marcela')

It has been demonstrated that the use of topical antioxidants can contribute to controling the free radicals excess produced by ultraviolet (UV) irradiation of the skin, being beneficial for processes such as photo aging and eventually cancer. Some plant extracts, particularly because of their polyphenolic constituents, can be beneficial for skin photo damage. Plant extracts of Achyrocline satureioides (AS) and Epilobium parviflorum (EP), potent antioxidant medicinal plants, were mixed with a cosmetic base and applied to the back skin of rabbits. Afterwards the skin was exposed to 1 h of UV irradiation from a known source. The production of the hydroxyl (OH.) radical was assessed in the skin after UV by measuring 2,3-dyhydroxybenzoic acid (2,3-DHBA), produced by the hydroxylation of sodium salicylate, previously injected intracutaneously (i.c.) in the irradiated areas. The UV provoked a marked increase in 2,3-DHBA that was significantly decreased by the AS cosmetic preparation. The EP extract did not show any effect on 2,3-DHBA production. It is concluded that the cosmetic preparation containing the AS extract is able to scavenge OH. production likely to be due to the presence of high concentrations of flavonoid aglycones such as quercetin, luteolin and 3-O-methylquercetin.

Neuronal protection by sirtuins in Alzheimer's disease

Silent information regulator 2, a member of NAD+-dependent histone deacetylase in yeast, and its homologs in mice and humans, participate in numerous important cell functions, including cell protection and cell cycle regulation. The sirtuin family members are highly conserved evolutionarily, and are predicted to have a role in cell survival. The science of sirtuins is an emerging field and is expected to contribute significantly to the role of sirtuins in healthy aging in humans. The role of sirtuins in neuronal protection has been studied in lower organisms, such as yeast, worms, flies and rodents. Both yeast Sir2 and mammalian sirtuin proteins are up-regulated under calorie-restricted and resveratrol treatments. Increased sirtuin expression protects cells from various insults. Caloric restriction and antioxidant treatments have shown useful effects in mouse models of aging and Alzheimer's disease (AD) and in limited human AD clinical trials. The role sirtuins may play in modifying and protecting neurons in patients with neurodegenerative diseases is still unknown. However, a recent report of Huntington's disease revealed that Sirtuin protects neurons in a Huntington's disease mouse model, suggesting that sirtuins may protect neurons in patients with neurodegenerative diseases, such as AD. In this review, we discuss the possible mechanisms of sirtuins involved in neuronal protection and the potential therapeutic value of sirtuins in healthy aging and AD.

Differential modulation of ochratoxin A absorption across Caco-2 cells by dietary polyphenols, used at realistic intestinal concentrations

The effect of polyphenols (PPs) on the absorption of ochratoxin A (OTA), a food-borne mycotoxin, was investigated in an in vitro model of the human intestinal barrier based on Caco-2 cells cultivated in a bicameral system. Two intraluminal concentrations of OTA approaching physiological levels were chosen (0.75 nM and 7.5 nM) through calculations based on estimated daily intakes. The transport of OTA from the apical to the basolateral side of Caco-2 cells, i.e. absorption, was directly proportional to its initial apical concentration. Very significant increase in both OTA absorption and cellular accumulation was observed upon co-incubation with certain PPs, i.e. chrysin, quercetin, genistein, biochanin A, resveratrol, at concentrations that should be encountered in the gastrointestinal tract, as well as with MK571, a specific inhibitor of MRPs efflux pumps. As these PPs have been reported to be metabolized in Caco-2 cells into substrates of MRP-2, we hypothesize that PPs and/or metabolites could impair the OTA efflux, previously proposed to be mediated by the MRP-2, through competitive inhibition for the pump. These data imply that interactions between OTA and PPs may lead to a greater bioavailability of the mycotoxin in the bloodstream with possible adverse effects for human health.

Enhanced diltiazem bioavailability after oral administration of diltiazem with quercetin to rabbits

The aim of this study was to investigate the effect of quercetin on the bioavailability of diltiazem after administering diltiazem (15 mg/kg) orally to rabbits either co-administered or pretreated with quercetin (2, 10, 20 mg/kg). The plasma concentrations of diltiazem in the rabbits pretreated with quercetin were increased significantly (p<0.05, at 2 mg/kg; p<0.01, at 10 and 20 mg/kg) compared with the control, but the plasma concentrations of diltiazem co-administered with quercetin were not significant. The areas under the plasma concentration-time curve (AUC) and the peak concentrations (Cmax) of the diltiazem in the rabbits pretreated with quercetin were significantly higher (p<0.05, at 2 mg/kg; p<0.01, at 10 and 20 mg/kg) than the control. The absolute bioavailability (AB%) of diltiazem in the rabbits pretreated with quercetin was significantly (p<0.05 at 2 mg/kg, p<0.01 at 10 and 20 mg/kg) higher (9.10-12.81%) than the control (4.64%). AUC, AB% and Cmax of diltiazem co-administered with quercetin were higher than the control, but these were not significant. The bioavailibility of diltiazem in the rabbits pretreated with quercetin is increased significantly compared with the control, but not in the rabbits co-administered with quercetin. The increased bioavailability of diltiazem in the rabbits pretreated with quercetin might have been resulted result from the quercetin, which inhibits the efflux pump P-glycoprotein and the first-pass metabolizing enzyme CYP 3A4.

Phenolic compounds from blueberries can inhibit colon cancer cell proliferation and induce apoptosis

Research has shown that diets rich in phenolic compounds may be associated with lower risks of several chronic diseases including cancer. This study systematically evaluated the bioactivities of phenolic compounds in rabbiteye blueberries and assessed their potential antiproliferation and apoptosis induction effects using two colon cancer cell lines, HT-29 and Caco-2. Polyphenols in three blueberry cultivars, Briteblue, Tifblue, and Powderblue, were extracted and freeze-dried. The extracts were further separated into phenolic acids, tannins, flavonols, and anthocyanins using an HLB cartridge and LH20 column. Some individual phenolic acids and flavonoids were identified by HPLC with >90% purity in anthocyanin fractions. The dried extracts and fractions were added to the cell culture medium to test for antiproliferation activities and induction of apoptosis. Flavonol and tannin fractions resulted in 50% inhibition of cell proliferation at concentrations of 70-100 and 50-100 microg/mL in HT-29 and Caco-2 cells, respectively. The phenolic acid fraction showed relatively lower bioactivities with 50% inhibition at approximately 1000 microg/mL. The greatest antiproliferation effect among all four fractions was from the anthocyanin fractions. Both HT-29 and Caco-2 cell growth was significantly inhibited by >50% by the anthocyanin fractions at concentrations of 15-50 microg/mL. Anthocyanin fractions also resulted in 2-7 times increases in DNA fragmentation, indicating the induction of apoptosis. The effective dosage levels are close to the reported range of anthocyanin concentrations in rat plasma. These findings suggest that blueberry intake may reduce colon cancer risk.

Vasorelaxant and Antioxidant Activity of Flavonols and Flavones: Structure-Activity Relationships

We investigated the structure-activity relationships regarding vascular and antioxidant activity of a range of synthetic flavonols and flavones with 3 or fewer hydroxyl (OH) or methoxyl substitutions. The relaxant responses and ability of the flavones/flavonols to inhibit phenylephrine (PE)- and Ca-induced contraction was determined in rat isolated thoracic aorta. The ability of these compounds to reduce the level of superoxide and preserve endothelium-dependent relaxation in the presence of oxidative stress was also examined. Four compounds impaired contraction to PE or Ca, in the potency order 3'-hydroxyflavonol>3',4'-dihydroxyflavonol>7,4'-dihydroxyflavonol>3',4'-dihydroxyflavone. Flavonol, 3',4'-dimethoxyflavonol, and flavone were significantly less active. The flavonoids caused concentration-dependent reductions in superoxide produced by rat aorta in the presence of NADPH. The most active compounds, 3',4'-dihydroxyflavonol and 7,4'-dihydroxyflavonol, preserved endothelium-dependent relaxation in the presence of oxidative stress caused by pyrogallol or xanthine/xanthine oxidase. The results indicate that the catechol group is not critical for vascular relaxant or antioxidant activity, but rather, the important determinants for higher vascular and antioxidant activity of these compounds are the presence of a C3 OH group and the total number of OH substituents, respectively. These results have allowed the identification of the structural characteristics that promote vascular and antioxidant activity of flavonols, which may lead to the development of agents useful in treatment of cardiovascular disease.

Metabolic and pharmacological properties of rutin, a dietary quercetin glycoside, for treatment of inflammatory bowel disease

PURPOSE

Orally administered rutin reportedly ameliorates 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced colitis of rats. We investigated the metabolic and pharmacological properties of rutin underlying the rutin-mediated amelioration of the rat colitis.

METHODS

Apparent partition coefficients of rutin and its aglycone quercetin were compared. The biochemical/chemical stability of rutin was examined in the contents of various segments of gastrointestinal tracts of rats. Inflammatory indices were determined in the colitis rats after oral administration of rutin or rectal administration of quercetin. In human colon epithelial cells, the effect of quercetin on tumor necrosis factor-alpha (TNF-alpha)-induced nuclear factor kappa B (NFkappaB) activation was examined.

RESULTS

The sugar residue in rutin greatly lowered the apparent partition coefficient and was rapidly deglycosylated to liberate quercetin in the cecal contents, whereas it was stable in the contents of the upper intestine. Not only oral administration of rutin but also rectal administration of quercetin remarkably ameliorated TNBS-induced colitis rats, indicating that quercetin liberated from rutin is therapeutically active. Furthermore, quercetin dose-dependently inhibited an inflammatory signal TNF-alpha-dependent NFkappaB activation.

CONCLUSIONS

Our data suggest that rutin acted as a quercetin deliverer to the large intestine and its anti-inflammatory action in TNBS-induced colitis rats may be through quercetin-mediated inhibition of TNF-alpha-induced NFkappaB activation.

Xanthine oxidase activity in vitro: effects of food extracts and components

There is significant interest in the direct antioxidant activities of dietary polyphenols, due to associations between consumption of polyphenol-rich foods, such as fruits and vegetables, and decreased incidence of oxidative-stress related disease. However, indirect antioxidant action, such as the inhibition of ROS-producing enzymes, may be equally relevant to health benefits through a general reduction in oxidative stress in vivo. To this end, the effects of food extracts and individual compounds on the in vitro activity of xanthine oxidase (XO) were assessed, many for the first time. Several compounds were shown to be potent inhibitors in vitro, including hesperetin and theaflavin-3,3'-digallate with IC50 values of 39 and 49 microM, respectively. Of the extracts, cranberry juice, purple grape juice, and black tea were the most potent, with IC50 values of 2.4, 3.5, and 5.8% of extracts, respectively. Some samples were shown to promote XO activity over the concentration ranges tested, including orange juice and pink grapefruit juice. Certain "inhibitors", such as purple grape juice and black tea, promoted XO activity at low concentration. The possible role of dietary inhibitors of XO in reducing oxidative stress in vivo is discussed.

Inhibitory effects of apigenin on the growth of gastric carcinoma SGC-7901 cells

AIM

To explore the growth inhibition and apoptosis-inducing effect of apigenin on human gastric carcinoma SGC-7901 cells.

METHODS

The effects of apigenin on the growth, clone formation and proliferation of human gastric carcinoma SGC-7901 cells were observed by MTT, clone-forming assay, and morphological observation. Fluorescent staining and flow cytometry analysis were used to detect apoptosis of cells.

RESULTS

Apigenin obviously inhibited the growth, clone formation and proliferation of SGC-7901 cells in a dose-dependent manner. Inhibition of growth was observed on d 1 at the concentration of 80 micromol/L, while after 4 d, the inhibition rate (IR) was 90%. The growth IRs at the concentration of 20, 40, and 80 micromol/L were 38%, 71%, and 99% respectively on the 7th d. After the cells were treated with apigenin for 48 h, the number of clone-forming in control, 20, 40, and 80 micromol/L groups was 217+/-16.9, 170+/-11.1 (P < 0.05), 98+/-11.1 (P < 0.05), and 25+/-3.5 (P < 0.05) respectively. Typical morphological changes of apoptosis was found by fluorescent staining. The cell nuclei had lost its smooth boundaries, chromatin was condensed, and cell nuclei were broken. Flow cytometry detected typical apoptosis peak. After the cells were treated with apigenin for 48 h, the apoptosis rates were 5.76%, 19.17%, and 29.30% respectively in 20, 40, and 80 micromol/L groups.

CONCLUSION

Apigenin shows obvious inhibition on the growth and clone formation of SGC-7901 cells by inducing apoptosis.

Semecarpus anacardium Linn. nut milk extract, an indigenous drug preparation, modulates reactive oxygen/nitrogen species levels and antioxidative system in adjuvant arthritic rats

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are highly reactive transient chemical species, which play an important role in the etiology of tissue injury in rheumatoid arthritis (RA). The effects of milk extract of Semecarpus anacardium Linn. nut (SA) was studied on adjuvant arthritis in rats. Arthritis was induced by injecting 0.1 ml of heat killed mycobacterium tuberculosis (10 mg/ml of paraffin oil) intradermally into the left hind paw. A significant increase in the levels of lipid peroxides (LPO), ROS (superoxide radical, hydroxyl radical, H(2)O(2) and myeloperoxidase) and RNS (nitrate+nitrite) observed in adjuvant arthritic animals were found to be significantly decreased on administration of the drug at 150 mg/kg body weight/day. The antioxidant defense system studied in arthritic animals were altered significantly as evidenced by the decrease in antioxidants. Treatment with SA recouped the altered antioxidant defense components to near normal levels. These evidences suggest that the free radical mediated damage during arthritis could have been controlled by SA by its free radical quenching and antioxidative potential.

Oxidant induced injury of erythrocyte—Role of green tea leaf and ascorbic acid

Oxidant and free radical-generating system were used to promote oxidative damage in erythrocytes. Among the oxidants used, phenylhydrazine represents one of the most investigated intracellular free radical-generating probes, which in the presence of haemoglobin auto-oxidises and give rise to hydroxyl radical, a marker for cellular damage. Erythrocyte, as a single cell, is a good model to be used for studying the haemolytic mechanism of anaemia. Our present investigations reveal increased lipid peroxidation of erythrocyte using phenylhydrazine as well as other oxygen-generating systems (hydrogen peroxide, iron with hydrogen peroxide). It has further been observed that not only lipid peroxidation, phenylhydrazine causes significant elevation in methemoglobin formation, catalase activity and turbidity, in the above system, which are the typical characteristics of haemolytic anaemia. However, exogenous administration of green tea leaf extract and ascorbic acid as natural antioxidants and free radical scavengers were shown to protect separately increased lipid peroxidation caused by phenylhydrazine, though the degree of protection is more in case of green tea leaf extract than ascorbic acid. Results suggest that oxidative damage in vivo due to haemolytic disease may be checked to some extent by using natural antioxidants.

Enhanced P53 and BAX gene expression and apoptosis in A549 cells by cis-Pt(II) complex of 3-aminoflavone in comparison with cis-DDP

Lung cancer remains one of the most common causes of cancer-related death worldwide. Approximately 80% is histologically non-small cell lung carcinoma (NSCLC) and in about 70% of patients it is an unresectable type. Clinical studies indicated that application of platinum derivatives caused good results and combinations of platinum with other agents could improve median survivals. In view of the central problem of sufficient efficiency of drugs in chemotherapy, efforts have focused on the development of alternative platinum-based analogues that can be more effective in cancer treatment. cis-bis(3-aminoflavone)dichloroplatinum(II) (cis-Pt(II) complex of 3-aminoflavone) represents a novel class of platinum-based potential antitumour agents. In order to evaluate the degree of apoptosis, acridine orange/ethidium bromide and Hoechst 33258/propidum iodide double staining as well as RT-PCR (P53 and BAX expression evaluation) were used in lung cancer cell line A549 after treatment with this compound in comparison with cis-diamminedichloroplatinum(II) (cis-DDP). Apoptotic cells at early and late stages and also necrotic ones were observed after usage of cis-Pt(II) complex of 3-aminoflavone and the percentage of these cells outnumbered the values obtained after cis-DDP application. The former compound induced a higher percentage of P53 and BAX expression in A549 cells in comparison with the latter one. Results indicate the beneficial properties of cis-Pt(II) complex of 3-aminoflavone as a potential antitumor drug.

The isolation and antioxidative effects of vitexin from Acer palmatum

Free radicals and reactive oxygen species (ROS) caused by UV exposure or other environmental factors are critical players in cellular damage and aging. In order to develop a new anti-photoaging agent, this work focused on the antioxidant effects of the extract of tinged autumnal leaves of Acer palmatum. One compound was isolated from an ethyl acetate soluble fraction of the A. palmatum extract using silica gel column chromatography. The chemical structure was identified as apigenin-8-C-beta-D-glucopyranoside, more commonly known as vitexin, by spectral analysis including LC-MS, FT-IR, UV, 1H-, and 13C-NMR. The biological activities of vitexin were investigated for the potential application of its anti-aging effects in the cosmetic field. Vitexin inhibited superoxide radicals by about 70% at a concentration of 100 microg/mL and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals by about 60% at a concentration of 100 microg/mL. Intracellular ROS scavenging activity was indicated by increases in dichlorofluorescein (DCF) fluorescence upon exposure to UVB 20 mJ/cm2 in cultured human dermal fibroblasts (HDFs) after the treatment of vitexin. The results show that oxidation of 5-(6-)chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (CM-H2DCFDA) is inhibited by vitexin effectively and that vitexin has a potent free radical scavenging activity in UVB-irradiated HDFs. In ROS imaging using a confocal microscope we visualized DCF fluorescence in HDFs directly. In conclusion, our findings suggest that vitexin can be effectively used for the prevention of UV-induced adverse skin reactions such as free radical production and skin cell damage.

Tissue distribution of quercetin in rats and pigs

Quercetin is a dietary polyphenolic compound with potentially beneficial effects on health. Claims that quercetin has biological effects are based mainly on in vitro studies with quercetin aglycone. However, quercetin is rapidly metabolized, and we have little knowledge of its availability to tissues. To assess the long-term tissue distribution of quercetin, 2 groups of rats were given a 0.1 or 1% quercetin diet [approximately 50 or 500 mg/kg body weight (wt)] for 11 wk. In addition, a 3-d study was done with pigs fed a diet containing 500 mg quercetin/kg body wt. Tissue concentrations of quercetin and quercetin metabolites were analyzed with an optimized extraction method. Quercetin and quercetin metabolites were widely distributed in rat tissues, with the highest concentrations in lungs (3.98 and 15.3 nmol/g tissue for the 0.1 and 1% quercetin diet, respectively) and the lowest in brain, white fat, and spleen. In the short-term pig study, liver (5.87 nmol/g tissue) and kidney (2.51 nmol/g tissue) contained high concentrations of quercetin and quercetin metabolites, whereas brain, heart, and spleen had low concentrations. These studies have for the first time identified target tissues of quercetin, which may help to understand its mechanisms of action in vivo.

Electrochemical genosensing of the interaction between the potential chemotherapeutic agent, cis-bis(3-aminoflavone)dichloroplatinum(II) and DNA in comparison with cis-DDP

The interaction of cis-diamminedichloroplatinum(II) (cis-DDP) and the potential novel chemotherapeutic agent, cis-bis(3-aminoflavone)dichloroplatinum(II) (cis-BAFDP) was studied electrochemically with calf thymus double-stranded DNA (dsDNA) by using differential pulse voltammetry (DPV) with disposable pencil graphite electrode (PGE) at the surface. These studies were prompted by beneficial biological properties of cis-BAFDP in comparison with cis-DDP, which were proven in vitro both in human normal and cancer cells and in vivo. The changes in the experimental parameters such as the concentration of cis-DDP and cis-BAFDP were studied by using DPV; in addition, the reproducibility of this genosensor and the detection limit for each compound were determined. After the interaction of cis-DDP with dsDNA, the DPV signal of guanine and adenine was found to be decreasing. In comparison with cis-DDP, a dramatic decrease at adenine signal was also obtained after the interaction of cis-BAFDP and dsDNA. Similar results were also found in solution phase after the latter compound interacts with poly[A]. The features of the proposed electrochemical method for the detection of cis-BAFDP with DNA in comparison with cis-DDP are discussed and compared with those methods previously reported for the other type of DNA-targeted agents in the literature.

Antioxidant activity of the flavonoid hesperidin in chemical and biological systems

The antioxidant hesperidin, a major flavonoid in sweet orange and lemon, was evaluated using chemical and biological systems. The chemical assay evaluates the hesperidin capacity to sequester 1,1-diphenyl-2-picrylhydrazyl (DPPH*). Biological studies were done using the eukaryotic cells of superoxide-dismutase proficient and deficient strains of Saccharomyces cerevisiae treated with hesperidin and the stressing agents hydrogen peroxide or paraquat (methylviologen; 1,1'-dimethyl-4,4'-bipyridinium dichloride). Hesperidin was able to reduce significantly the level of the free radical DPPH* with similar efficacy of trolox (positive control). When the yeast cells were exposed to the flavonoid hesperidin before the stressing agents, there was a significant increase in the survival of all strains. Paraquat induced higher catalase and superoxide dismutase than did hydrogen peroxide, which only increased catalase activity. Previous addition of hesperidin to these treatments was able to reduce significantly both enzymatic levels. These observations clearly demonstrate that hesperidin provides strong cellular antioxidant protection against the damaging effects induced by paraquat and peroxide hydrogen.

Vascular protection by dietary polyphenols

Consumption of polyphenol-rich foods, such as fruits and vegetables, and beverages derived from plants, such as cocoa, red wine and tea, may represent a beneficial diet in terms of cardiovascular protection. Indeed, epidemiological studies demonstrate a significant inverse correlation between polyphenol consumption and cardiovascular risk. Among the numerous plausible mechanisms by which polyphenols may confer cardiovascular protection, improvement of the endothelial function and inhibition of angiogenesis and cell migration and proliferation in blood vessels have been the focus of recent studies. These studies have indicated that, in addition to and independently from their antioxidant effects, plant polyphenols (1) enhance the production of vasodilating factors [nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and prostacyclin] and inhibit the synthesis of vasoconstrictor endothelin-1 in endothelial cells; and (2) inhibit the expression of two major pro-angiogenic factors, vascular endothelial growth factor (VEGF) and matrix metalloproteinase-2 (MMP-2) in smooth muscle cells. The mechanisms of these effects involve: (1) in endothelial cells, increased Ca(2+) level and redox-sensitive activation of the phosphoinositide 3 (PI3)-kinase/Akt pathway (leading to rapid and sustained activation of nitric oxide synthase and formation of EDHF) and enhanced expression of nitric oxide synthase; and (2) in smooth muscle cells, both redox-sensitive inhibition of the p38 mitogen-activated protein kinase (p38 MAPK) pathway activation (leading to inhibition of platelet-derived growth factor (PDGF)-induced VEGF gene expression) and redox-insensitive mechanisms (leading to inhibition of thrombin-induced MMP-2 formation). The current evidence suggests that all these mechanisms are triggered by polyphenols with specific structures, although the structural requirements may be different from one effect to the other, and that they all contribute to the vasoprotective, anti-angiogenic, anti-atherogenic, vasorelaxant and anti-hypertensive effects of acute or chronic administration of plant polyphenols found in vivo in animals and in patients.

Cytotoxicity of flavonoids toward cultured normal human cells

The cytotoxicity of flavonoids, including apigenin, eriodictyol, 3-hydroxyflavone, kaempherol, luteolin, naringenin, quercetin, rutin, and taxifolin, toward cultured human normal cells, i.e., human lung embryonic fibroblasts (TIG-1) and human umbilical vein endothelial (HUVE) cells, was examined. When these normal human cells were incubated with each flavonoid in culture medium for 24 h, some of the flavonoids showed considerable cytotoxicity at relatively high concentrations and in a dose-dependent manner. 3-Hydroxyflavone, luteolin, and apigenin were more toxic toward TIG-1 cells than the other flavonoids, and luteolin, 3-hydroxyflavone, and quercetin were more toxic toward HUVE cells. HUVE cells were more vulnerable to flavonoid cytotoxicity than TIG-1 cells. Using 2',7'-dichlorofluorescin diacetate (DCF-DA), the intracellular reactive oxygen species (ROS) level of flavonoid-treated TIG-1 cells was examined. The ROS level increased significantly in the presence of the flavone apigenin or luteolin or the flavonol 3-hydroxyflavone, quercetin, or kaempherol. These results suggest that these flavones and flavonols exert cytotoxicity through increasing intracellular ROS levels. Further, the incorporation of apigenin, 3-hydroxyflavone, luteolin, and quercetin, which are more toxic, into TIG-1 cells during 24-h incubation was examined. These flavonoids were incorporated into them and the order of their incorporation efficiency was similar to that of their cytotoxicity. In conclusion, some flavonoids are cytotoxic at higher concentrations toward human normal cells. Further, it is suggested that they are incorporated into cells, increase intracellular ROS levels, and then exert cytotoxicity.

Flavonoids from almond skins are bioavailable and act synergistically with vitamins C and E to enhance hamster and human LDL resistance to oxidation

Consumption of tree nuts such as almonds has been associated with a reduced risk of coronary heart disease. Flavonoids, found predominantly in the skin of almonds, may contribute to their putative health benefit, but their bioactivity and bioavailability have not previously been studied. Almond skin flavonoids (ASF) were extracted with HCl:H2O:methanol (1:19:80) and their content of catechins and flavonols identified by HPLC with electrochemical detection. ASF bioactivity was assessed in vitro by their capacity to increase the resistance of human LDL to oxidation induced by 10 micromol/L Cu2+. ASF from 0.18 to 1.44 mumol gallic acid equivalent (GAE)/L increased the lag time to LDL oxidation in a dose-dependent manner (P < or = 0.0001). Combining ASF with vitamin E or ascorbic acid extended the lag time >200% of the expected additive value (P < or = 0.05). The bioavailability and in vivo antioxidant activity of 40 micromol ASF were examined in BioF1B hamsters. Peak plasma concentrations of catechin, epicatechin, and flavonols (quercetin, kaempferol, and isorhamnetin) occurred at 60, 120, and 180 min, respectively. The concentration of isorhamnetin was significantly elevated in liver at 180 min. Absorbed ASF enhanced the ex vivo resistance of hamster LDL collected at 60 min to oxidation by 18.0% (P = 0.028), and the in vitro addition of 5.5 micromol/L vitamin E synergistically extended the lag time of the 60-min sample by 52.5% (P < or = 0.05). Thus, ASF possess antioxidant capacity in vitro; they are bioavailable and act in synergy with vitamins C and E to protect LDL against oxidation in hamsters.

Comparative analysis of topoisomerase IB inhibition and DNA intercalation by flavonoids and similar compounds: structural determinates of activity

Flavonoids and other polyphenolic compounds have been shown to inhibit human topoisomerase IB (topo I) through both inhibition of relaxation activity and through stabilization of the cleavable complex (poisoning). Some flavonoids have also been shown to intercalate DNA, and an association of topoisomerase inhibition with intercalation has been noted. We surveyed 34 polyphenolic compounds, primarily flavonoid glycones and aglycones, for their ability to inhibit topo I and to intercalate DNA using an in vitro gel electrophoresis method. We show that the most potent topo I poisons are the flavones and flavonols, and that these generally, but not always, are found to be DNA intercalators. There was no clear correlation, however, of topo-I-poisoning activity with the degree of DNA unwinding. Surprisingly, both DNA intercalation and topo I poisoning were shown to occur with some flavone glycones, including the C-glycosylflavone orientin. Inhibition of relaxation activity by flavonoids was found to be difficult to quantify and was most likely to be due to non-specific inhibition through flavonoid aggregation. As part of a structure-activity analysis, we also investigated the acid-base chemistry of flavonoids and determined that many flavonoids show acid-base activity with a pK(a) in the physiological pH region. For this reason, subtle pH changes can have significant effects on solution activity of flavonoids and their concomitant biological activity. In addition, these effects may be complicated by pH-dependent aggregation and oxidative degradation. Finally, we develop a simple model for the intercalation of flavonoids into DNA and discuss possible consequences of intercalation and topoisomerase inhibition on a number of cellular processes.

Discovery of a novel superfamily of type III polyketide synthases in Aspergillus oryzae

Identification of genes encoding type III polyketide synthase (PKS) superfamily members in the industrially useful filamentous fungus, Aspergillus oryzae, revealed that their distribution is not specific to plants or bacteria. Among other Aspergilli (Aspergillus nidulans and Aspergillus fumigatus), A. oryzae was unique in possessing four chalcone synthase (CHS)-like genes (csyA, csyB, csyC, and csyD). Expression of csyA, csyB, and csyD genes was confirmed by RT-PCR. Comparative genome analyses revealed single putative type III PKS in Neurospora crassa and Fusarium graminearum, two each in Magnaporthe grisea and Podospora anserina, and three in Phenarocheate chrysosporium, with a phylogenic distinction from bacteria and plants. Conservation of catalytic residues in the CHSs across species implicated enzymatically active nature of these newly discovered homologs.