Flavonoids: Dietary occurrence and biochemical activity

In vitro antimalarial activity of flavonoid derivatives dehydrosilybin and 8-(1;1)-DMA-kaempferide

Multidrug-resistant Plasmodium falciparum strains are an increasing problem in endemic areas and are partly responsible for the worsening malaria situation around the world. New cheap and effective compounds active in combination with available drug in the field are urgently needed. The aim of this work was to explore the potential antiplasmodial effect of flavonoid derivatives on parasites growth in vitro. In vitro antiplasmodial activity of dehydrosilybin and 8-(1;1)-DMA-kaempferide has been evaluated by real time PCR for five P. falciparum strains. Both revealed significative antimalarial activity against the different strains. Since this drug family has been largely used and well-tolerated in humans, flavonoid derivatives could be in the near future associated with already available drugs in order to delay the spread of P. falciparum resistance.

Characterization of anthocyanin-rich waste from purple corncobs (Zea mays L.) and its application to color milk

Pigment production from anthocyanin-rich purple corncobs generates a deeply colored waste precipitate. Our objectives were to characterize this anthocyanin-rich waste (ARW) and to find a suitable application in a food matrix. Composition and solubility characteristics of ARW were evaluated. Color (CIELAB) and pigment (monomeric anthocyanin and HPLC profiles) stability of ARW in milk (35 mg/100 mL) were evaluated using an accelerated test at 70 degrees C and phosphate buffer as a control. ARW provided milk an attractive purple hue (324-347 degrees ). Monomeric anthocyanin degradation followed zero-order kinetics in skim and whole milk and second-order kinetics in the control, with half-lives of 173, 223, and 44 min at 70 degrees C, respectively. ARW shows potential as a natural colorant for a pH range unusual for anthocyanin applications. A protective effect of matrix constituents on the stability of anthocyanins was evident. Anthocyanins may interact with different compounds in biological systems when the pH values are close to neutral.

Determination of phenolic compounds in Perilla frutescens L. by capillary electrophoresis with electrochemical detection

A method based on capillary electrophoresis with electrochemical detection has been developed to analyze flavonoids and phenolic acids in Perilla frutescens L. for the first time. Catechin, ferulic acid, apigenin, luteolin, rosmarinic acid, and caffeic acid are major important active ingredients in the plant. Operated in a wall-jet configuration, a 300 microm diameter carbon-disk electrode was used as the working electrode, which exhibits a good response at 0.90 V (versus saturated calomel electrode) for the analytes. Under the optimum conditions, the analytes were baseline separated within 20 min in a 100 mmol/L borax buffer (pH 8.7). Notably, excellent linearity was obtained over 3 orders of magnitude with detection limits (S/N = 3) ranging from 2 x 10(-7) to 1 x 10(-6) g/mL for all analytes. This proposed method has been successfully applied to monitor the flavonoids and phenolic acids contents in the leaves and seeds of P. frutescens L. at different growth stages with relatively simple extraction procedures, and the assay results were satisfactory.

Genotoxicity of phytoestrogens

Plant extracts containing phytohormones are very popular as 'alternative' medicine for many kinds of diseases. They are especially favored by women who enter menopause and are concerned about the side effects of hormone replacement therapy. However, adverse health effects of phytoestrogens have often been ignored. This review examines the literature on genotoxicity and apoptotic effects of phytohormones. Genistein, coumestrol, quercetin, zearalenone, and resveratrol exerted genotoxic effects in in vitro test systems. Other phytoestrogens such as lignans, the isoflavones daidzein and glycetein, anthocyanidins, and the flavonol fisetin exhibited only weak or no effects in vitro. However, some metabolites of daidzein showed a genotoxic activity in vitro. Practically all of the phytoestrogens exhibit pro-apoptotic effects in some cell systems. Further investigations regarding dose-response-relationships and other aspects relevant for extrapolation to human exposure seem necessary. Until then, care may be advised in taking concentrated phytohormones. Nevertheless, the intake of substantial amounts of plant-food in a normal diet constitutes an important, individual contribution to cancer prevention.

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 and Breast Cancer Risk in Italy

Few epidemiologic studies have investigated the potential relation between flavonoids and breast cancer risk. We have applied recently published data on the composition of foods and beverages in terms of six principal classes of flavonoids (i.e., flavanones, flavan-3-ols, flavonols, flavones, anthocyanidines, and isoflavones) on dietary information collected in a large-case control study of breast cancer conducted in Italy between 1991 and 1994. The study included 2,569 women with incident, histologically confirmed breast cancer, and 2,588 hospital controls. Odds ratios (OR) and 95% confidence intervals were estimated by multiple logistic regression models. After allowance for major confounding factors and energy intake, a reduced risk of breast cancer was found for increasing intake of flavones (OR, 0.81, for the highest versus the lowest quintile; P-trend, 0.02), and flavonols (OR, 0.80; P-trend, 0.06). No significant association was found for other flavonoids, including flavanones (OR, 0.95), flavan-3-ols (OR, 0.86), anthocyanidins (OR, 1.09), as well as for isoflavones (OR, 1.05). The findings of this large study of an inverse association between flavones and breast cancer risk confirm the results of a Greek study.

Oxygenolysis of Flavonoid Compounds: DFT Description of the Mechanism for Quercetin

Flavonoids are naturally occurring phenol derivatives present in substantial amounts in a large variety of plants, fruits and vegetables daily eaten by humans. Most of these compounds exhibit several interesting biological activities, such as antiradical and antioxidant actions. Indeed, by complexation with specific enzymes, flavonoids are notably liable to metabolize molecular dioxygen. On the basis of experimental results describing oxygenolysis of the flavonoid quercetin, activated by the enzyme quercetin 2,3-dioxygenase (2,3-QD),ur attention has focused on the role of metal center in the activation of the substrate quercetin. Thus, in the present study, by means of DFT calculations at the B3LYP/ 6-31(+)G* level on model molecular systems, we describe different mechanisms for dioxygen metabolization by quercetin. Stationary points are described, and energetic and structural analyses along the reaction paths are reported. Our calculations show that the copper cation must act as an oxidant towards the substrate and that the reaction proceeds through a 1,3-cycloaddition.

Supplementation with cactus pear (Opuntia ficus-indica) fruit decreases oxidative stress in healthy humans: a comparative study with vitamin C

BACKGROUND

Cactus pear (Opuntia ficus-indica) fruit contains vitamin C and characteristic betalain pigments, the radical-scavenging properties and antioxidant activities of which have been shown in vitro.

OBJECTIVE

We investigated the effects of short-term supplementation with cactus pear fruit compared with vitamin C alone on total-body oxidative status in healthy humans.

DESIGN

In a randomized, crossover, double-treatment study, 18 healthy volunteers received either 250 g fresh fruit pulp or 75 mg vitamin C twice daily for 2 wk, with a 6-wk washout period between the treatments. Before (baseline) and after each treatment, 8-epi-prostaglandin F(2alpha) (8-epi-PGF(2alpha)) and malondialdehyde in plasma, the ratio of reduced to oxidized glutathione (GSH:GSSG) in erythrocytes, and lipid hydroperoxides in LDL were measured as biomarkers of oxidative stress; plasma Trolox-equivalent antioxidant activity (TEAC) and vitamins A, E, and C were evaluated as indexes of antioxidant status.

RESULTS

Both treatments caused comparable increases compared with baseline in plasma concentrations of vitamin E and vitamin C (P < 0.05); vitamin A and TEAC did not change significantly. After supplementation with cactus pear fruit, 8-epi-PGF(2)alpha and malondialdehyde decreased by approximately 30% and 75%, respectively; GSH:GSSG shifted toward a higher value (P < 0.05); and LDL hydroperoxides were reduced by almost one-half. Supplementation with vitamin C did not significantly affect any marker of oxidative stress.

CONCLUSIONS

Consumption of cactus pear fruit positively affects the body's redox balance, decreases oxidative damage to lipids, and improves antioxidant status in healthy humans. Supplementation with vitamin C at a comparable dosage enhances overall antioxidant defense but does not significantly affect body oxidative stress. Components of cactus pear fruit other than antioxidant vitamins may play a role in the observed effects.

Dietary fiber and reduced cough with phlegm: a cohort study in Singapore

Smoking is the major risk factor for chronic respiratory symptoms, but dietary factors may also play a role. Most studies of diet and lung disease have been cross-sectional and conducted in populations with a Western-style diet. We analyzed the relation between dietary intake at baseline and new onset of cough with phlegm in a population-based cohort of 63,257 middle-aged Chinese men and women initiated in Singapore between 1993 and 1998. Beginning in 1999, we ascertained respiratory symptoms by telephone interview and have identified 571 incident cases of cough with phlegm among the 49,140 cohort members with completed follow-up. Nonstarch polysaccharides, a major component of dietary fiber, total fruit, and soy isoflavones had the strongest associations. Odds ratios comparing highest and lowest quartiles after adjustment for age, sex, dialect group, total energy intake, and smoking were 0.61 (95% confidence interval [CI]: 0.47, 0.78; p for trend < 0.001) for nonstarch polysaccharides, 0.67 (95% CI: 0.52, 0.87; p for trend = 0.006) for fruit, and 0.67 (95% CI: 0.53, 0.86; p for trend = 0.001) for soy isoflavones. These data suggest that a diet high in fiber from fruit and, possibly, soyfoods may reduce the incidence of chronic respiratory symptoms. Associated nutrients, such as flavonoids, may contribute to this association.

Intake of specific flavonoid classes and coronary heart disease—a case–control study in Greece

OBJECTIVE

Dietary intake of flavonoids has been reported to protect against coronary heart disease (CHD) risk, but associations of specific classes of flavonoids with CHD have not been adequately studied.

DESIGN

Hospital-based case-control study relying on interviewer administered questionnaires.

SETTING

Cardiology Department of the University of Athens Medical School in the Hippokrateion General Hospital (1990-1991).

SUBJECTS

Cases were 329 patients with electrocardiographically confirmed first coronary infarct or a first positive coronary arteriogram, or both (participation fraction 93%). Controls were 570 patients admitted to the same hospital for minor conditions unrelated to nutrition (participation fraction 95%). All cases and controls were interviewed in the hospital wards by experienced interviewers, and a 110-item food frequency questionnaire was administered.

RESULTS

There was statistically significant evidence (P approximately 0.03) for an inverse association between intake of flavan-3-ols and CHD risk, an increase of about 21 mg per day corresponding to a 24% decrease in CHD risk. The inverse association between flavan-3-ols and CHD risk was largely accounted for by the intake of wine and to a lesser extent tea. For none of the other flavonoid classes was there statistically significant evidence of an association.

CONCLUSION

Flavan-3-ols, which are largely found in wine and tea, are inversely associated with, and may be protective against, coronary heart disease.

Recovery of phenolic antioxidants from wine industry by-products

The recovery process of the phenolic compounds contained in the wine industry by-products and their antioxidant activity were examined in this work. To this purpose, a combined process of liquid and supercritical solvent extraction was employed. At first the effect of various process parameters of the liquid solvent extraction--the type of solvent and the pretreatment of the raw material (composition (skins, seeds, stems) and crushing)--on the antioxidant activity of the extract was examined. It was shown that an extract of a higher antioxidant activity was obtained by using ethyl acetate as solvent and raw material free of stems. These extracts were further treated with supercritical carbon dioxide (SC CO(2)) at various extraction pressures, which resulted in their significant enrichment in phenolic compounds and the improvement of their antioxidant and organoleptic properties, especially at pressures higher than 100 bar. The antioxidant activity of the products was determined by using the Rancimat method, as well as a simple and not time-consuming free radical method. It was proved that both the ethyl acetate extracts and those treated with SC CO(2) had antioxidant activity comparable to that of antioxidants commonly used in industry, that is butylhydroxytoluene (BHT), a synthetic antioxidant, and Rosemary extract, a widely known natural one.

Flavonoids in food and their health benefits

There has been increasing interest in the research of flavonoids from dietary sources, due to growing evidence of the versatile health benefits of flavonoids through epidemiological studies. As occurrence of flavonoids is directly associated with human daily dietary intake of antioxidants, it is important to evaluate flavonoid sources in food. Fruits and vegetables are the main dietary sources of flavonoids for humans, along with tea and wine. However, there is still difficulty in accurately measuring the daily intake of flavonoids because of the complexity of existence of flavonoids from various food sources, the diversity of dietary culture, and the occurrence of a large amount of flavonoids itself in nature. Nevertheless, research on the health aspects of flavonoids for humans is expanding rapidly. Many flavonoids are shown to have antioxidative activity, free-radical scavenging capacity, coronary heart disease prevention, and anticancer activity, while some flavonoids exhibit potential for anti-human immunodeficiency virus functions. As such research progresses. further achievements will undoubtedly lead to a new era of flavonoids in either foods or pharmaceutical supplements. Accordingly, an appropriate model for a precise assessment of intake of flavonoids needs to be developed. Most recent research has focused on the health aspects of flavonoids from food sources for humans. This paper reviews the current advances in flavonoids in food, with emphasis on health aspects on the basis of the published literature, which may provide some guidance for researchers in further investigations and for industries in developing practical health agents.

The chemopreventive bioflavonoid apigenin modulates signal transduction pathways in keratinocyte and colon carcinoma cell lines

Apigenin is a nonmutagenic chemopreventive agent found in fruits and green vegetables. In this study, we used two different epithelial cell lines (308 mouse keratinocytes and HCT116 colon carcinoma cells) to determine the effect of apigenin on the mitogen-activated protein kinase (MAPK) cascade. Apigenin induced a dose-dependent phosphorylation of both extracellular signal-regulated protein kinase (ERK) and p38 kinase but had little effect on the phosphorylation of c-jun amino terminal kinase (JNK). We used immunoprecipitation-coupled kinase assays to show that apigenin increased the kinase activity of ERK and p38 but not JNK. Consistent with these results, we found that apigenin induced a 7.4-fold induction in the phosphorylation of Elk, the downstream phosphorylation target of ERK kinase. Similarly, apigenin induced a 3.2-fold induction in the phosphorylation of activating transcription factor-2, the downstream phosphorylation target of p38 kinase. Little change was observed in the phosphorylation of c-jun, the phosphorylation target of JNK. These data suggest that part of the chemopreventive activity of apigenin may be mediated by its ability to modulate the MAPK cascade.

A quantum chemical and statistical study of flavonoid compounds (flavones) with anti-HIV activity

The molecular orbital semi-empirical method AM1 was employed to calculate a set of molecular properties (variables) of 22 flavonoid compounds (flavones) with anti-HIV-1 activity and nine new compounds were proposed for anti-HIV-1 activity prediction. Pattern recognition techniques, principal component analysis (PCA), hierarchical cluster analysis (HCA), stepwise discriminant analysis (SDA) and K-nearest neighbor (KNN), were employed in order to reduce dimensionality and investigate which subset of variables could be more effective for classifying the flavones according to their degree of anti-HIV-1 activity. The PCA, HCA, SDA and KNN studies showed that the variables log P (partition coefficient), molecular volume (VOL) and electron affinity (EA) are responsible for the separation between anti-HIV-1 active and inactive compounds. The prediction study was done with a new set of nine analog compounds by using the PCA, HCA, SDA and KNN methods and only one of them was predicted as active against HIV-1.

Flavonoid intake and breast cancer risk: a case--control study in Greece

Flavonoids have been investigated for possible inverse associations with various chronic degenerative diseases, but there are no epidemiologic data concerning a possible association between several of the main flavonoid categories and breast cancer risk. We have applied recently published data on the flavonoid content of several foods and beverages on dietary information collected in the context of a large case-control study of 820 women with breast cancer and 1548 control women, conducted in Greece. We found a strong, statistically significant inverse association of flavone intake with breast cancer. The odds ratio for an increment equal to one standard deviation of daily flavone intake (i.e. 0.5 mg day(-1)) was 0.87, with 95% confidence interval 0.77-0.97. The association persisted after controlling for fruit and vegetable consumption, or for other flavonoid intake. This inverse association is compatible with and may explain the reported inverse association of breast cancer with consumption of vegetables, particularly leafy vegetables. After controlling for dietary confounding, there was no association of breast cancer risk with flavanones, flavan-3-ols, flavonols, anthocyanidins or isoflavones.

Soy-based formulas and phyto-oestrogens: a safety profile

Phyto-oestrogens are non-steroidal plant-derived compounds that possess oestrogenic activity and act as selective oestrogen receptor modulators (SERMs). Among the dietary oestrogens, the isoflavone class enjoy a wide-spread distribution in most of the members of the Leguminosae family, including such prominent high-content representatives as soybean. Phyto-oestrogen research has grown rapidly in recent years owing to epidemiological studies suggesting that diets rich in soy may be associated with potential health benefits. There is a paucity of data on endocrine effects of soy phytochemicals during infancy, the most sensitive period of life for the induction of toxicity. The safety of isoflavones in infant formulas has been questioned recently owing to reports of possible hormonal effects. Infants fed soy formula receive high levels of phyto-oestrogens in the form of isoflavones (genistein, daidzein and their glycosides). To date, no adverse effects of short- or long-term use of soy proteins have been observed in humans and exposure to soy-based infant formulas does not appear to lead to different reproductive outcomes than exposure to cow milk formulas. Soy formula seems to be a safe feeding option for most infants. Nevertheless, much closer studies in experimental animals and human populations exposed to phyto-oestrogen-containing products, and particularly soy-based infant formulas, are necessary.

Action of quercetin on glycogen catabolism in the rat liver

1. The influence of quercetin on glycogen catabolism and related parameters was investigated in the isolated perfused rat liver and subcellular systems. 2. Quercetin stimulated glycogenolysis (glucose release). This effect was already evident at a concentration of 50 microM maximal at 300 microM and declined at higher concentrations. Quercetin also stimulated oxygen consumption, with a similar concentration dependence. 3. Lactate production from endogenous glycogen (glycolysis) was diminished by quercetin without significant changes in pyruvate production. 4. Quercetin did not inhibit glucose transport into cells but decreased intracellular sequestration of [5-(3)H]glucose under conditions of net glucose release. 5. In isolated mitochondria, quercetin diminished the energy transduction efficiency. It also inhibited several enzymatic activities, e.g. the K(+)-ATPase/Na(+)-ATPase of plasma membrane vesicles and the glucose 6-phosphatase of isolated microsomes. 6. No significant changes of the cellular contents of AMP, ADP and ATP were found. The cellular content of glucose 6-phosphate, however, was increased (3.12-fold). 7. Some of the effects of quercetin (glycogenolysis stimulation) can be attributed to its action on mitochondrial energy metabolism, as, for example, uncoupling of oxidative phosphorylation. However, the multiplicity of the effects on several enzymatic systems certainly produces an intricate interplay that also generates complex and apparently contradictory effects.

Evaluation of the estrogenic effects of legume extracts containing phytoestrogens

Seven legume extracts containing phytoestrogens were analyzed for estrogenic activity. Methanol extracts were prepared from soybean (Glycine max L.), green bean (Phaseolus vulgaris L.), alfalfa sprout (Medicago sativa L.), mung bean sprout (Vigna radiata L.), kudzu root (Pueraria lobata L.), and red clover blossom and red clover sprout (Trifolium pratense L.). Extracts of kudzu root and red clover blossom showed significant competitive binding to estrogen receptor beta (ERbeta). Estrogenic activity was determined using an estrogen-dependent MCF-7 breast cancer cell proliferation assay. Kudzu root, red clover blossom and sprout, mung bean sprout, and alfalfa sprout extracts displayed increased cell proliferation above levels observed with estradiol. The pure estrogen antagonist, ICI 182,780, suppressed cell proliferation induced by the extracts, suggesting an ER-related signaling pathway was involved. The ER subtype-selective activities of legume extracts were examined using transiently transfected human embryonic kidney (HEK 293) cells. All seven of the extracts exhibited preferential agonist activity toward ERbeta. Using HPLC to collect fractions and MCF-7 cell proliferation, the active components in kudzu root extract were determined to be the isoflavones puerarin, daidzin, genistin, daidzein, and genistein. These results show that several legumes are a source of phytoestrogens with high levels of estrogenic activity.

Protective effects of flavonoids on the cytotoxicity of linoleic acid hydroperoxide toward rat pheochromocytoma PC12 cells

The protective effects of nine flavonoids, including apigenin, eriodictyol, 3-hydroxyflavone, kaempherol, luteolin, quercetin, rutin, and taxifolin (Table 1), on the cytotoxicity of linoleic acid hydroperoxide (LOOH) toward rat pheochromocytoma PC12 cells were examined. The cytotoxicity was assessed by the trypan blue exclusion test and so-called MTT assay. When cells were preincubated with each flavonoid prior to LOOH exposure, quercetin, 3-hydroxyflavone, or luteolin decreased LOOH cytotoxicity toward undifferentiated cells, while only luteolin decreased efficiently LOOH cytotoxicity toward differentiated cells. On the other hand, when cells were coincubated with each flavonoid and LOOH, kaempherol, eriodictyol, quercetin, 3-hydroxyflavone, luteolin, or taxifolin decreased LOOH cytotoxicity toward undifferentiated and differentiated cells. On both preincubation prior to LOOH exposure and coincubation with LOOH, luteolin acted as the most efficiently protective agent against LOOH cytotoxicity. Further, these flavonoids showed protective effects on coincubation rather than preincubation. Flow cytometry using the fluorescence probe 2',7'-dichlorofluorescin diacetate revealed that LOOH increases the intracellular level of reactive oxygen species in undifferentiated cells in a dose-dependent manner, and that desferrioxamine mesylate suppresses the LOOH-induced increase in the level. These flavonoids suppress the LOOH-induced increase. Further, the protective effect of flavonoids on LOOH cytotoxicity correlates with the suppression of the LOOH-induced increase. These results suggest that such flavonoids are beneficial for neuronal cells under oxidative stress.

Epicatechin-copper 9II) complexes: Damage of small intestinal epithelium

Four epicatechins [(−)-epicatechin (EC), (−)-epicatechin gallate (ECg), (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCg)] and their corresponding copper complexes were compared with regard to their effect on the viability of Caco-2 colon cancer cells in vitro, measured by 3-(4,5-dimethylthyazol-2-yl) 2,5-diphenyltetrazolium bromide (MTT) assay. The viability of Caco-2 cells exposed to EC (1 mM), ECg (1 mM) or EGC (1mM) respectively, for 30 min, was comparable to that of the saline control group, while EGCg (1 mM) apparently enhanced cellular activity. in contrast, the cells treated with epicatechin-copper complexes were killed. Bivalent copper 91 mM), in similar conditions, did not affect the cells. No cell leakage or other histological differences were observed, implying a rapid cell death. The suggested mechanism of killing is by OH radical attack, produced in the presence of epicatechin-copper complexes, but not in the presence of either of the epicatechins or copper alone. The reaction sites are discussed.

Effects of gamma-irradiation on the free radical and antioxidant contents in nine aromatic herbs and spices

Nine spice and aromatic herb samples (i.e., basil, bird pepper, black pepper, cinnamon, nutmeg, oregano, parsley, rosemary, and sage) were gamma-irradiated at a dose of 10 kGy according to commercial practices. The effects of the disinfection treatment on the content of organic radicals and some nutrients (namely, vitamin C and carotenoids) in the samples were investigated by chromatographic and spectroscopic techniques. Irradiation resulted in a general increase of quinone radical content in all of the investigated samples, as revealed by electron paramagnetic resonance spectroscopy. The fate of these radicals after storage for 3 months was also investigated. The cellulose radical was clearly observed in a few samples. Significant losses of total ascorbate were found for black pepper, cinnamon, nutmeg, oregano, and sage, whereas a significant decrease of carotenoids content was observed for cinnamon, oregano, parsley, rosemary, bird pepper, and sage.

Bioactive compounds in foods: their role in the prevention of cardiovascular disease and cancer

"Bioactive compounds" are extranutritional constituents that typically occur in small quantities in foods. They are being intensively studied to evaluate their effects on health. The impetus sparking this scientific inquiry was the result of many epidemiologic studies that have shown protective effects of plant-based diets on cardiovascular disease (CVD) and cancer. Many bioactive compounds have been discovered. These compounds vary widely in chemical structure and function and are grouped accordingly. Phenolic compounds, including their subcategory, flavonoids, are present in all plants and have been studied extensively in cereals, legumes, nuts, olive oil, vegetables, fruits, tea, and red wine. Many phenolic compounds have antioxidant properties, and some studies have demonstrated favorable effects on thrombosis and tumorogenesis and promotion. Although some epidemiologic studies have reported protective associations between flavonoids or other phenolics and CVD and cancer, other studies have not found these associations. Various phytoestrogens are present in soy, but also in flaxseed oil, whole grains, fruits, and vegetables. They have antioxidant properties, and some studies demonstrated favorable effects on other CVD risk factors, and in animal and cell culture models of cancer. However, because phytoestrogens act both as partial estrogen agonists and antagonists, their effects on cancer are likely complex. Hydroxytyrosol, one of many phenolics in olives and olive oil, is a potent antioxidant. Resveratrol, found in nuts and red wine, has antioxidant, antithrombotic, and anti-inflammatory properties, and inhibits carcinogenesis. Lycopene, a potent antioxidant carotenoid in tomatoes and other fruits, is thought to protect against prostate and other cancers, and inhibits tumor cell growth in animals. Organosulfur compounds in garlic and onions, isothiocyanates in cruciferous vegetables, and monoterpenes in citrus fruits, cherries, and herbs have anticarcinogenic actions in experimental models, as well as cardioprotective effects. In summary, numerous bioactive compounds appear to have beneficial health effects. Much scientific research needs to be conducted before we can begin to make science-based dietary recommendations. Despite this, there is sufficient evidence to recommend consuming food sources rich in bioactive compounds. From a practical perspective, this translates to recommending a diet rich in a variety of fruits, vegetables, whole grains, legumes, oils, and nuts.

Absorption of anthocyanins from blueberries and serum antioxidant status in human subjects

In recent years, numerous studies have shown that the polyphenolics present in fruit and vegetable products exhibit a wide range of biological effects. However, there is little reliable information on the absorption of glycosylated and acylated anthocyanins in humans. In the present study, the absorption of anthocyanins in humans was investigated after the consumption of a high-fat meal with a freeze-dried blueberry powder containing 25 individual anthocyanins including 6 acylated structures. Nineteen of the 25 anthocyanins present in the blueberries were detected in human blood serum. Furthermore, the appearance of total anthocyanins in the serum was directly correlated with an increase in serum antioxidant capacity (ORAC(acetone), P < 0.01). These results show that anthocyanins can be absorbed in their intact glycosylated and possibly acylated forms in human subjects and that consumption of blueberries, a food source with high in vitro antioxidant properties, is associated with a diet-induced increase in ex vivo serum antioxidant status.

Hormonal and genotoxic activity of resveratrol

Resveratrol (RES) is a natural polyphenol present in red wines and various human food items. The estrogenic activity of RES was demonstrated in two in vitro assay systems, i.e. binding to human estrogen receptor alpha and stimulation of MCF-7 cell proliferation. To investigate the inhibition of cell proliferation observed at high concentrations of RES, we analyzed the compound for genotoxic potential. RES induced cellular toxicity, micronuclei, and metaphase chromosome displacement in L5178Y mouse lymphoma cells. Likewise, the induction of micronuclei was observed in Chinese hamster V79 cells. Determination of kinetochore signals in micronuclei and cell cycle analysis suggested that RES did not cause a direct disturbance of mitosis. In support of this notion, cell-free tubulin polymerization studies indicated no direct effect of RES on microtubule assembly. According to an estimation of daily intake and bioavailability, concentrations that were found genotoxic in vitro might be reached in human exposure. On the other side, the estrogenic acitivity might be beneficial. Therefore, further investigations of mechanisms, possibly including animal models, would be desirable to clarifiy a potential risk for humans.

Free radical chemistry of flavan-3-ols: determination of thermodynamic parameters and of kinetic reactivity from short (ns) to long (ms) time scale

The physical chemistry and the free radical chemistry of the most abundant polyphenolic flavan-3-ols in food, catechin, its methylated metabolites, and several methylated analogues, have been investigated by laser flash photolysis and cyclic voltammetry studies. Two independent phenoxyl radicals formed upon oxidation of flavan-3-ols have been characterized and identified unambiguously: a short-lived resorcinol-like radical characterized by an absorption band at lambda = 495 nm and a long-lived catechol-like transient absorbing at lambda = 380 nm. The determination of all the thermodynamic constants of each phenolic function of flavan-3-ols, namely, redox potential (E degrees (3') = 0.13(5) V/SCE, E degrees (4') = 0.11(0) V/SCE, E degrees (5) = 0.28(5) V/SCE) and microscopic dissociation constants (pK(a3') = 9.02, pK(a4') = 9.12, pK(a5) = 9.43, pK(a7) = 9.58) were performed. These values are discussed and compared to the prediction of the density functional theory calculations made on the different species catechin, catechin phenoxyl, and catechin phenolate for each phenolic site.

Analysis of antioxidants from orange juice obtained by countercurrent supercritical fluid extraction, using micellar electrokinetic chromatography and reverse-phase liquid chromatography

Antioxidants from orange juice were determined by the combined use of countercurrent supercritical fluid extraction (CC-SFE) prior to reverse-phase liquic chromatography (RP-LC) or micellar electrokinetic chromatography (MEKC). The separation of antioxidants found in the SFE fractions was achieved by using a new MEKC method and a published LC procedure, both using diode array detection. The characterization of the different antioxidants was further done by LC-mass spectrometry. Advantages and drawbacks of LC and MEKC for analyzing the antioxidants found in the different orange extracts are discussed. Although LC yields higher peak area and slightly better reproducibility than MEKC, the latter technique provides information about the CC-SFE extracts in analysis times 7 times faster than by LC. This analysis advantage can be used for the quick adjustment of CC-SFE conditions, thus providing a fast way to obtain orange fractions of specific composition.

Antimutagenic effect of various honeys and sugars against Trp-p-1

Honey has been used since ancient times as a flavorful sweetener and for its therapeutic and medicinal effects. Consumers' demand for natural, healthy products has driven renewed interest in honey's health benefits. The commonly encountered food mutagen, Trp-p-1, has been demonstrated to be mutagenic in bacteria and carcinogenic in animals. Chemically, honey is quite complex. Honey is comprised primarily of sugars; however, it contains many other potentially biologically active components, such as antioxidants. Sugars have been reported to display both mutagenic and antimutagenic effects in different systems; antioxidants often display antimutagenic activity. Little information exists about potential antimutagenic effects of honey. Antimutagenicity of honeys from seven different floral sources against Trp-p-1 was tested via the Ames assay and compared to that of a sugar analogue and to individually tested simple sugars. All honeys exhibited significant inhibition of Trp-p-1 mutagenicity; most demonstrated a linear correlation between percentage inhibition and log transformed honey concentration from 10 microg/mL to 20 mg/mL. Each displayed significant degrees of inhibition of mutagenicity above concentrations of 1 mg/mL, with individual variations in degree of effectiveness. Buckwheat honey displayed the greatest inhibition at 1 mg/mL, with slightly less effectiveness at higher concentrations. A sugar analogue demonstrated a pattern of inhibition similar to that of the honeys, with enhanced antimutagenicity at concentrations greater than 1 mg/mL. Glucose and fructose were also similar to honeys and were more antimutagenic than maltose and sucrose.

Flavonoids suppress the cytotoxicity of linoleic acid hydroperoxide toward PC12 cells

The suppressive effect of flavonoids on the cytotoxicity of linoleic acid hydroperoxide (LOOH) toward rat phenochromocytoma PC12 cells was examined. The extent of cytotoxicity was shown on the basis of % survival determined by the trypan blue exclusion test. On preincubation of cells with either 3-hydroxyflavone, quercetin, or luteolin prior to LOOH exposure, the cytotoxicity was considerably suppressed. In contrast, on coincubation of cells with either eriodictyol, quercetin, kaempherol, luteolin, or 3-hydroxyflavone and LOOH, it was markedly suppressed. Regardless of incubation conditions, quercetin, 3-hydroxyflavone, and luteolin were thus more effective as protective agents against the cytotoxicity than the other flavonoids. These flavonoids further showed a suppressive effect on coincubation rather than on preincubation. These results suggest that such flavonoids are beneficial for cells under oxidative stress.

Effects of anthocyanins and other phenolic compounds on the production of tumor necrosis factor alpha in LPS/IFN-gamma-activated RAW 264.7 macrophages

Flavonoids have been reported to demonstrate their benefits in lowering oxidative stress and beneficial effects on cardiovascular and chronic inflammatory diseases. Common phenolic compounds, including phenolic acids, flavonols, isoflavones, and anthocyanins, present in fruits, vegetables, and grains were investigated for their effects on the production of tumor necrosis factor alpha (TNF-alpha) in LPS/IFN-gamma-activated RAW 264.7 macrophages. Gallic acid and (+)-catechin showed small but significant effects, whereas chlorogenic acid had no effect on TNF-alpha production. The flavonol quercetin inhibited TNF-alpha production, but kaempferol and myricetin induced the secretion of TNF-alpha. The isoflavone genistein was an inhibitor of TNF-alpha, whereas daidzein induced TNF-alpha production. Glycosylation of genistein changed its inhibitory effects to TNF-alpha induction, and glycosylation of daidzein had no effect on its activity. Anthocyanidins/anthocyanins and anthocyanin-rich extracts induced TNF-alpha production and acted as modulators of the immune response in activated macrophages. This is the first study to report the effects of anthocyanins and berry extracts on TNF-alpha production.

Flavonoid phytochemicals regulate activator protein-1 signal transduction pathways in endometrial and kidney stable cell lines

Phytochemicals bind to and regulate the human estrogen receptors (ERalpha and ERbeta), mimicking actions of the endogenous estrogen, 17beta-estradiol, and known antiestrogens such as ICI 182,780. Recently, however, some of these estrogenic phytochemicals have been shown to affect other signal transduction pathways, such as receptor tyrosine kinases and mitogen-activated protein kinases (MAPK). Previously, we found that certain phytochemicals, such as flavone, apigenin, kaempferide and chalcone, have potent antiestrogenic activity. However, the antiestrogenicity of these compounds does not correlate with their ER binding capacity, suggesting alternative signaling as a mechanism for their antagonistic effects. In this study, we examined the effects of these compounds on the transcription factor activator protein-1 (AP-1). Using AP-1-luciferase stable human endometrial adenocarcinoma Ishikawa and human embryonic kidney (HEK) 293 cells, chalcone, flavone and apigenin all stimulated AP-1 activity. Additionally, we determined the effects of the phytochemicals on transcription factors that are downstream targets of various MAPK pathways. To test this, we used HEK 293 cells stably cointegrated with GAL4 transcriptional activation systems of Elk-1, c-Jun or C/EBP homologous protein (CHOP). Chalcone was the only phytochemical that activated all three transcription factors [Elk-1, 2.7-fold (P < 0.001); c-Jun, 2.7-fold (P = 0.025); CHOP, 3.0-fold (P = 0.002)], whereas apigenin stimulated CHOP (3.9-fold; P < 0.001), but inhibited phorbol myristoyl acetate-induced c-Jun activity (71%;P = 0.006). This work suggests that phytochemicals affect multiple signaling pathways that converge at the level of transcriptional regulation. The ability of flavonoids to regulate MAPK-responsive pathways in a selective manner indicates a mechanism by which phytochemicals may influence human health and disease.

Supplementation of naringenin and its synthetic derivative alters antioxidant enzyme activities of erythrocyte and liver in high cholesterol-fed rats

The antioxidative effects of naringenin (1) and its synthetic derivative, naringenin 7-O-cetyl ether (2), were tested. Male rats were fed a 1 g/100 g high-cholesterol diet for 6 weeks with supplements of either 1 or 2 (0.073 mmol/100 g diet) to study the effects on the antioxidant enzyme activities in the erythrocyte and liver. The erythrocyte catalase (CAT) and superoxide dismutase (SOD) activities were significantly higher in the compounds 1 or 2 supplemented groups than in the control group, whereas the hepatic SOD and CAT activities were significantly lower in the compound 2 supplemented group. The compounds 1 and 2 supplements to a high cholesterol diet lowered or tended to lower the plasma TBARS levels, that is, lipid peroxide products, while enhancing the plasma paraoxonase activity. These results indicate that the supplementation of 1 and 2 was effective in improving the antioxidant capacity of the erythrocyte and liver, plus the synthetic functional compound 2 appeared to be as potent as 1 in enhancing the antioxidant defense system.

Fast- and slow-release tablets for oral administration of flavonoids: rutin and quercetin

Many derivatives of rutin (Rt) and its metabolite quercetin (Q) are employed in clinics for cardiovascular chronic pathology, and are also known for their antiulcer behavior in vivo and antiproliferative and antimutagenic activity in vitro. Unfortunately, the absorption of quercetin and rutin from the gastrointestinal tract is slow and irregular, probably due to their very slight solubility in water and slow dissolution rate. In this work the dissolution rate of the drugs from oral formulations has been improved using some enhancers such as cross-linked sodium carboxy, methylcellulose (CMC-XL), sodium carboxymethylstarch (E), and cross-linked polyvinylpyrrolidone (P). The drugs were loaded on the hydrophilic carriers by different techniques such as mixing or co-milling. The in vitro dissolution profiles of the mixed or co-milled drug/polymer systems, obtained in various media with different pH, were compared. The results show that the drug dissolution rate from the co-milled drug/carrier systems is faster than that from mixed systems, and CMC-XL and sodium carboxymethylstarch systems are able to enhance the dissolution rate. For this reason, these co-milled drug/carrier systems were used for the production of both fast- and slow-release tablets. The co-milled drug/CMC-XL system was used for the preparation of fast-release tablets containing rutin, while three different fast-release tablets were formulated and tested using respectively Q/CMC-XL, Q/E, and Q/P co-milled systems. The effect of the presence of sodium lauryl sulfate in the aqueous medium on the dissolution profile of flavonoids alone was also studied. The prolonged-release formulations have been developed using hydroxypropylmethylcellulose (HPMC) of different viscosity grades as retarding polymer. An extended release of the drugs for times ranging from 6 to 14 hr could be obtained, depending on the type and viscosity of the HPMC used.

Luteolin, a flavone, does not suppress postprandial glucose absorption through an inhibition of alpha-glucosidase action

In order to clarify the postprandial glucose suppression via alpha-glucosidase (AGH) inhibitory action by natural compounds, flavonoids were examined in this study. Among the flavonoids (luteolin, kaempferol, chrysin, and galangin), luteolin showed the potent maltase inhibitory activity with the IC50 of 2.3 mM, while less inhibitions were observed against sucrase. In addition, the effects of maltase inhibition by flavonoids were observed in the descending order of potency of luteolin > kaempferol > chrysin > galangin. Apparently, the AGH inhibition power greatly increased with the replacement of hydroxyl groups at 3' and 4'-position of the B-ring. However, the inhibitory power of luteolin was poorer than a therapeutic drug (acarbose: IC50; 430 nM). As a result of a single oral administration of maltose or sucrose (2 g/kg) in SD rats, no significant change in blood glucose level with the doses of 100 and 200 mg/kg of luteolin was observed. These findings strongly suggested that luteolin given at less than 200 mg/kg did not possess the ability to suppress the glucose production from carbohydrates through the inhibition of AGH action in the gut.

Inhibitory effects of anthocyanins and other phenolic compounds on nitric oxide production in LPS/IFN-gamma-activated RAW 264.7 macrophages

Flavonoids have been reported to lower oxidative stress and possess beneficial effects on cardiovascular diseases and chronic inflammatory diseases associated with nitric oxide (NO). Common phenolic compounds, including phenolic acids, flavonols, isoflavones, and anthocyanins, present in fruits were investigated for their effects on NO production in LPS/IFN-gamma-activated RAW 264.7 macrophages. Phenolic compounds at the range of 16-500 microM that inhibited NO production by > 50% without showing cytotoxicity were the flavonols quercetin and myricetin, the isoflavone daidzein, and the anthocyanins/anthocyanidins pelargonidin, cyanidin, delphinidin, peonidin, malvidin, malvidin 3-glucoside, and malvidin 3,5-diglucosides. Anthocyanins had strong inhibitory effects on NO production. Anthocyanin-rich crude extracts and concentrates of selected berries were also assayed, and their inhibitory effects on NO production were significantly correlated with total phenolic and anthocyanin contents. This is the first study to report the inhibitory effects of anthocyanins and berry phenolic compounds on NO production.

Flavonoids: structural requirements for antiproliferative activity on breast cancer cells

Several classes of flavonoids (flavones, flavanones, 2'-hydroxychalcones and flavan-4-ols) having a variety of substituents on A ring were investigated for their antiproliferative activity against MCF-7 human breast cancer cells. Structure-activity relationships of these compounds were discussed. 2'-hydroxychalcones and methoxylated flavanones were found to be potent inhibitors of MCF-7 cells growth whereas flavones and flavan-4-ols appeared to be weak inhibitory agents except 7,8-dihydroxyflavone.

Isolation of antioxidant compounds from orange juice by using countercurrent supercritical fluid extraction (CC-SFE)

Antioxidants from orange juice are isolated by the use of countercurrent supercritical fluid extraction (CC-SFE) and characterized by reversed-phase liquid chromatography (RPLC) coupled to mass spectrometry (MS) and diode-array detection (DAD). A pilot-scale SFE plant equipped with a packed column has been employed for countercurrent extraction and fractionation of raw orange juice with carbon dioxide. Several experiments have been performed in order to study the effect of the countercurrent conditions on the content of antioxidative compounds. In this study, the main variable that has been considered is the solvent-to-feed ratio (S/F) because it plays an essential role in the extraction efficiency. The values tested covered a wide range of sample and solvent (CO(2)) flow rates. In each experimental run, two different extracted fractions and the residual nonextracted juice were obtained and characterized. Different flavonoids have been identified in the fractions obtained after CC-SFE. The possibility of using this process for antioxidant compounds enrichment is discussed.

Antioxidant effect of flavonoids after ascorbate/Fe2+-induced oxidative stress in cultured retinal cells11Abbreviations: BME, basal medium of Eagle; DCFH2, 2′,7′-dichlorodihydrofluorescein; LDH, lactate dehydrogenase; PC, partition coefficient; Rf, retardation factor; ROS, reactive oxygen species; TBA, thiobarbituric acid; and TBARS, thiobarbituric acid-reactive substances

In this study, we investigated the structure-activity relationship of four flavonoids, i.e. eriodictyol, luteolin, quercetin, and taxifolin, in cultured retinal cells after ascorbate/Fe(2+)-induced oxidative stress. The relative order of antioxidant efficacy, determined by the thiobarbituric acid method, was the following: eriodictyol > quercetin > luteolin > taxifolin. Upon preincubation, the flavonoids were also effective in reducing the extent of lipid peroxidation. Oxidative stress, determined by the changes in fluorescence of 2',7'-dichlorodihydrofluorescein, was also decreased in the presence of the flavonoids, showing the following order of antioxidant efficacy: eriodictyol > taxifolin approximately quercetin > luteolin. Ascorbate/Fe(2+)-induced oxidative stress or incubation in the presence of the flavonoids did not significantly affect the viability of retinal cells. We also evaluated the degree of membrane partition of the flavonoids. In this system, the results strongly suggest that the higher antioxidant activity of the flavonoids is not correlated with the presence of a double bond at C(2)-C(3) and/or a hydroxyl group at C(3) on the C ring, but rather may depend on the capacity to inhibit the production of reactive oxygen species to interact hydrophobically with membranes. Eriodictyol was shown to be the most efficient antioxidant in protecting against oxidative stress induced by ascorbate/Fe(2+) in the retinal cells.