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At least 19 recordsLinked to original sources
PubMed2004

Magnesium and branched chain amino acids in rats intoxicated with Pb2+ or Cd2+ and receiving certain bioflavonoids or bioflavonoids with glutamine.

Experiment was carried on Wistar male rats. Eleven groups, each of 6 rats, were given: group I: plumbum nitrate (500 mg Pb/dm3), group II: plumbum ions--500 mg Pb/dm3 and quercetin--200 mg/dm3, group III the same what group II and glutamine 4 g/dm3, group IV: Pb(NO3)2--500 mg Pb/dm3 and catechin (200 mg/dm3), and group V the same as group IV, Pb ions, catechin, and additionally glutamine--4 g/dm3. The IA - VA groups obtained the same that groups I-V but they received instead of lead cadmium chloride in amount of 500 mg Cd/dm3. Group IX was a control group, and that animals received redistilled water to drink. After six weeks of experiment blood, liver and kidneys were collected, and magnesium and branched amino acids concentrations were determined. The aim of these studies was to determine the influence of administered quercetin and catechin individually or with free glutamine on magnesium and BCAAs concentrations in blood serum, liver and kidneys of rats.

Amino Acids, Branched-Chain↗
PubMed2003

Bioflavonoids attenuate renal proximal tubular cell injury during cold preservation in Euro-Collins and University of Wisconsin solutions.

BACKGROUND: Cold ischemia and reperfusion during kidney transplantation are associated with release of free oxygen radicals and damage of renal tubular cells. Bioflavonoids may diminish cold storage-induced injury due to antioxidant and iron chelating activities. This study was designed to delineate the renoprotective mechanisms of bioflavonoids and to define the structural features conferring cytoprotection from cold injury. METHODS: LLC-PK1 cells were preincubated for three hours with bioflavonoids and cold stored in University of Wisconsin (UW)- or Euro-Collins (EC)-solution for 20 hours. After rewarming, cell viability was assessed by the lactate dehydrogenase (LDH) release, MTT-test, and amino acid transport activity. Lipid peroxidation was assessed from the generation of thiobarbituric acid-reactive substances. RESULTS: Twenty-hours of cold storage of LLC-PK1 cells resulted in a substantial loss of cell integrity that was more pronounced in the EC (LDH release, 93.6 +/- 1.6%) than the UW solution (67.2 +/- 6.9%; P < 0.0001). Pretreatment with quercetin significantly enhanced cell survival (LDH release, 5.4 +/- 2.7% for UW and 8.4 +/- 4.2% for EC) in a concentration dependent manner. Structure-activity studies revealed similar renoprotection for kaempferol, luteolin and fisetin, unlike myricetin, morin, apigenin, naringenin, catechin, silibinin and rutin. Lipid peroxidation was reduced (UW alone, 2.7 +/- 1.2 vs. UW+quercetin 0.5 +/- 0.2 nmol/mg protein, P < 0.01), and l-threonine uptake completely sustained by pretreatment with quercetin, kaempferol, luteolin, and fisetin. However, renoprotection by fisetin was rapidly lost during rewarming. Protective properties of bioflavonoids were governed by the number and arrangement of hydroxyl substitutes, electron-delocalization, sterical planarity, and lipophilicity of the basic diphenylpyran skeleton. CONCLUSION: Cold storage-induced renal tubular cell injury is ameliorated by bioflavonoids. Renoprotective effects of bioflavonoids are defined by structure, suggesting that flavonoids are incorporated into membrane lipid bilayers and interfere with membrane lipid peroxidation.

Adenosine↗
PubMed2004

Influence of bioflavonoids from the radix extract of Scutellaria baicalensis on the level of serum lipids, and the development of laboratory rats fed with fresh and oxidized fats.

The aim of this study was to assess the influence of bioflavonoids from the radix of Scurellaria baicalensis on the level of lipids, via the determination of the concentrations of triglycerides, total cholesterol and high-density lipoprotein (HDL) cholesterol in the plasma of laboratory rats fed high-fat and high-cholesterol diets, and via the calculation of their atherogenic index. We also studied the influence of bioflavonoids on their physical development by measuring the increase in their body mass and liver mass. The rats were fed a diet with a 15% content of fresh or oxidized lard or sunflower oil, along with 0.5% added cholesterol. 0.05% S. baicalensis radix extract was added to the diet of half of the rats as the source of bioflavonoids. In the group of rats fed a diet containing oxidized oil we observed a significantly lower increase in body mass (15.5 +/- 7.6 g/4 weeks/rat) than that observed for the control rats (77.0 +/- 15.7 g/4 weeks/rat). The addition of S. baicalensis radix extract to the diet raised the increase in body mass in the groups receiving oil as the source of fat; those receiving fresh oil had a 40% increase, and those receiving oxidized oil showed a 300% increase relative to the appropriate controls. In all the groups of rats fed a diet with bioflavonoids added, a beneficial decrease in the plasma triglyceride content was observed relative to the appropriate controls. In the plasma of rats on a diet containing the extract and fresh or oxidized oil or fresh lard, we observed a beneficial reduction in the total cholesterol level relative to the appropriate controls. The atherogenic index was higher for the group of animals fed with fresh lard than for those fed with fresh oil, and higher for those fed with oxidized oil than for those fed with oxidized lard. The addition of bioflavonoids to the diet beneficially reduced the atherogenic index value in the group fed with fresh oil, and increased its value in the group fed with oxidized lard.

Animals↗
PubMed1988

Bioflavonoid interaction with rat uterine type II binding sites and cell growth inhibition.

Competition analysis with a number of known bioflavonoids demonstrated that these compounds (luteolin, quercetin, pelargonin) compete for [3H]estradiol binding to cytosol and nuclear type II sites in rat uterine preparations. The inhibition of [3H]estradiol binding to type II sites was specific and these bioflavonoids did not interact with the rat uterine estrogen receptor. Since estradiol stimulation of nuclear type II sites in the rat uterus is highly correlated with cellular hypertrophy and hyperplasia, we assessed the effects of these compounds on the growth of MCF-7 human breast cancer cells in culture and on estradiol stimulation of uterine growth in the immature rat. The data demonstrated that addition of quercetin (5-10 micrograms/ml) to MCF-7 cell cultures resulted in a dose-dependent inhibition of cell growth (DNA/flask). This effect was reversible by removal of quercetin from the culture medium, or by the addition of 10 nM estradiol-17 beta to these cell cultures containing this bioflavonoid. Since estradiol-17 beta (10 nM) stimulated nuclear type II sites and proliferation of MCF-7 cells, we believe bioflavonoid inhibition of MCF-7 cell growth may be mediated through an interaction with nuclear type II sites. This hypothesis was confirmed by in vivo studies which demonstrated that injection of luteolin or quercetin blocked estradiol stimulation of nuclear type II sites in the immature rat uterus and this correlated with an inhibition of uterine growth (wet and dry weight). These studies suggest bioflavonoids, through an interaction with type II sites, may be involved in cell growth regulation.

Animals↗
PubMed1978

The use of water-soluble bioflavonoid-ascorbic acid complex in the treatment of recurrent herpes labialis.

The efficacy of a water-soluble bioflavonoid-ascorbic acid complex was evaluated in the treatment of fifty episodes of recurrent herpes labialis. Twenty episodes were treated with a complex of 600 mg. of water-soluble bioflavonoids and 600 mg. of ascorbic acid, administered in equal increments three times daily. Twenty episodes were treated with a complex of 1,000 mg. of water-soluble bioflavonoids and 1,000 mg. of ascorbic acid, administered in equal increments five times daily. Ten episodes were treated with a lactose placebo. The therapeutic regimen was maintained for 3 days after the recognition of the initial symptoms associated with recurrent herpes labialis. The water-soluble bioflavonoid-ascorbic acid complex was observed to reduce vesiculation and to prevent the disruption of the vesicular membrane. The therapeutic measure was found to be most effective when initiated during the prodomal stage of the disease process. Optimum remission of symptoms was observed in 4.2 +/- 1.7 days with the 600 mg. dosage of the water-soluble bioflavonoid-ascorbic acid complex. No adverse reactions were reported by any of the patients who participated in this investigation.

Ascorbic Acid↗
PubMed2000

Dietary bioflavonoids induce cleavage in the MLL gene and may contribute to infant leukemia.

Chromosomal translocations involving the MLL gene occur in about 80% of infant leukemia. In the search for possible agents inducing infant leukemia, we identified bioflavonoids, natural substances in food as well as in dietary supplements, that cause site-specific DNA cleavage in the MLL breakpoint cluster region (BCR) in vivo. The MLL BCR DNA cleavage was shown in primary progenitor hematopoietic cells from healthy newborns and adults as well as in cell lines; it colocalized with the MLL BCR cleavage site induced by chemotherapeutic agents, such as etoposide (VP16) and doxorubicin (Dox). Both in vivo and additional in vitro experiments demonstrated topoisomerase II (topo II) as the target of bioflavonoids similar to VP16 and Dox. Based on 20 bioflavonoids tested, we identified a common structure essential for topo II-induced DNA cleavage. Reversibility experiments demonstrated a religation of the bioflavonoid as well as the VP16-induced MLL cleavage site. Our observations support a two-stage model of cellular processing of topo II inhibitors: The first and reversible stage of topo II-induced DNA cleavage results in DNA repair, but also rarely in chromosome translocations; whereas the second, nonreversible stage leads to cell death because of an accumulation of DNA damage. These results suggest that maternal ingestion of bioflavonoids may induce MLL breaks and potentially translocations in utero leading to infant and early childhood leukemia.

Adult↗
PubMed2005

Bioflavonoids effectively inhibit smooth muscle cell-mediated contraction of collagen matrix induced by angiotensin II.

Plant-derived bioflavonoids have been recognized to support arterial wall structural integrity and interfere with a variety of proatherosclerotic stimuli. In this study we tested the effects of bioflavonoids on the contractile activity of cultured human aortic smooth muscle cells (SMC) embedded in a 3-dimensional type I collagen matrix. Collagen I solution mixed with human aortic SMC in 24-well plates were allowed to form gels. Tested compounds were added to the wells, and the gels were set afloat by gentle tapping. Digital photographs of the gels were taken after 24 hours of incubation at 37 degrees C. The area of contracted gel was measured and expressed as a percentage of the control gel area from 3 or more replicates. Expression of matrix metalloproteinase (MMP-2) in conditioned media was assessed by gel zymography. Different classes of bioflavanoids showed variable efficiency in inhibiting angiotensin II (ATII)-dependent collagen gel contraction by SMCs. An increase in the number of gallate groups per catechin molecule was associated with increased inhibition of angiotensin II-dependent collagen gel contraction by SMC. Antioxidants (N-acetyl cysteine and ascorbic acid) did not inhibit collagen gel contraction. Bioflavonoid inhibition of collagen gel contraction by SMC correlated with inhibition of matrix metalloproteinase-2 expression. Bioflavonoids participate in the regulation of SMC-mediated contraction and have a strong potential in counteracting pathophysiological effects of ATII. Bioflavonoid activity depends on structural characteristics and can be related to extracellular matrix integrity.

Angiotensin II↗
PubMed2000

Effect of bioflavonoids extracted from the bark of Pinus maritima on proinflammatory cytokine interleukin-1 production in lipopolysaccharide-stimulated RAW 264.7.

Currently, bioflavonoids have been known to have strong antioxidant capacities, and a variety of efforts have been made to identify the utilities of bioflavonoids in treating various diseases based on their antioxidant capacities. The effects of bioflavonoids extracted from the bark of Pinus maritima Pycnogenol (PYC) on free radical formation, activation of redox sensitive transcription factors, as well as interleukin-1 beta (IL-1 beta) production were investigated in murine macrophage cell lines. PYC exerted strong scavenging activities against reactive oxygen species generated either by H(2)O(2) or PMA in RAW 264.7 and IC-21 cells, respectively. In situ ELISA, immunoblot analysis, and competitive RT-PCR demonstrated that PYC pretreatment of LPS-stimulated RAW 264.7 cells dose-dependently reduced both the production of IL-1 beta and its mRNA levels. Furthermore, in the same cells, PYC blocked the activation of nuclear factor kappa B (NF-kappa B) and activator protein-1 (AP-1), two major transcription factors centrally involved in IL-1 beta gene expression. When RAW 264.7 cells were stimulated with LPS, the inhibitor protein I kappa B largely disappeared from cytosolic fractions. However, pretreatment of the cells with PYC abolished the LPS-induced I kappa B degradation. These results suggest that PYC can inhibit the expression of the proinflammatory cytokine IL-1 by regulating redox-sensitive transcription factors. This study may support the possibility that bioflavonoids including PYC can be used as antiinflammatory and immunosuppressive drugs based on their radical scavenging activities.

Animals↗
PubMed2000

Bioflavonoids as antiradicals, antioxidants and DNA cleavage protectors.

Flavonoids have recently aroused considerable interest because of their broad pharmacological activity. In fact, flavonoids have been reported to have antiviral, antiallergic, antiplatelet, anti-inflammatory and antitumoral activities. The pharmacological properties of bioflavonoids have been ascribed both to the concomitant inhibition of enzymes involved in the production of free radicals and to their free-radical scavenging and iron chelating capacity. However the antioxidant capacity of bioflavonoids due to free-radical scavenging and/or to iron chelating is still controversial. In this study, we have investigated the free-radical scavenging capacity of bioflavonoids (rutin, catechin, and naringin). In addition, the effects of these polyphenols on xanthine oxidase activity, spontaneous lipid peroxidation, and DNA cleavage were investigated. The bioflavonoids under examination showed a dose-dependent free-radical scavenging effect, a significant inhibition of xanthine oxidase activity, and an antilipoperoxidative capacity. In addition, they showed a protective effect on DNA cleavage.

Animals↗
PubMed2005

Beneficial effects of the bioflavonoids curcumin and quercetin on early function in cadaveric renal transplantation: a randomized placebo controlled trial.

BACKGROUND: The bioflavonoids quercetin and curcumin are renoprotective natural antioxidants. We wished to examine their effects on early graft function (EF). METHODS: Between September 2002 and August 2004, 43 dialysis dependent cadaveric kidney recipients were enrolled into a study using Oxy-Q which contains 480 mg of curcumin and 20 mg of quercetin, started after surgery and taken for 1 month. They were randomized into three groups: control (placebo), low dose (one capsule, one placebo) and high dose (two capsules). Delayed graft function (DGF) was defined as first week dialysis need and slow function (SGF) as Cr >2.5 mg/dl by day 10. Category variables were compared by chi squared and continuous variables by Kruskal-Wallis. RESULTS: There were four withdrawals: one by patient choice and three for urine leak. The control group had 2/14 patients with DGF vs. none in either treatment group. Incidence of EF was control 43%, low dose 71% and high dose 93% (P=0.013). Serum creatinine was significantly lower at 2 days (control 7.6+/-2.1, low 5.4+/-0.6, high 3.96+/-.35 P=0.0001) and 30 days (control 1.82+/-.16, low 1.65+/-.09, high 1.33 +/-.1, P=0.03). Acute rejection incidence within 6 months was control 14.3%, low dose 14.3% and high dose 0%. Tremor was detected in 13% of high dose patients vs. 46% of others. Urinary HO-1 was higher in bioflavonoid groups. CONCLUSION: Bioflavonoid therapy improved early graft function. Acute rejection and neurotoxicity were lowest in the high dose group. These bioflavonoids improve early outcomes in cadaveric renal transplantation, possibly through HO-1 induction.

Adult↗
PubMed2004

Strong inhibitory effects of common tea catechins and bioflavonoids on the O-methylation of catechol estrogens catalyzed by human liver cytosolic catechol-O-methyltransferase.

In the present investigation, we studied the inhibitory effects of three tea catechins [catechin, epicatechin, and (-)-epigallocatechin-3-O-gallate] and two bioflavonoids (quercetin and fisetin) on the O-methylation of 2- and 4-hydroxyestradiol (2-OH-E(2) and 4-OH-E(2), respectively) by human liver cytosolic catechol-O-methyltransferase (COMT). We found that catechin and epicatechin each inhibited the O-methylation of 2-OH-E(2) and 4-OH-E(2) in a concentration-dependent manner. The IC(50) values for inhibition of 2-OH-E(2) methylation by catechin and epicatechin were 14 to 17 microM and 44 to 65 microM, respectively, and their IC(50) values for inhibition of 4-OH-E(2) methylation were 5 to 7 microM and 10 to 18 microM, respectively. Our data showed that these two catechins had 2- to 6-fold higher inhibition potency for the O-methylation of 4-OH-E(2) than for the O-methylation of 2-OH-E(2). (-)-Epigallocatechin-3-O-gallate was found to have a distinctly high inhibition potency for the O-methylation of 2- and 4-OH-E(2) (IC(50) values of 0.04-0.07 microM and 0.2-0.5 microM, respectively). The crude extracts from green tea and black tea also showed very strong activity in inhibiting human liver COMT-mediated O-methylation of catechol estrogens. We also determined, for comparison, two common bioflavonoids (quercetin and fisetin) for their inhibitory effects on human liver COMT-mediated O-methylation of catechol estrogens. The IC(50) values for quercetin and fisetin were 0.9 to 1.5 microM and 3.3 to 4.5 microM, respectively, for inhibiting the O-methylation of 2-OH-E(2), and 0.5 to 1.2 microM and 2.6 to 4.2 microM, respectively, for inhibiting the O-methylation of 4-OH-E(2). Enzyme kinetic analyses showed that both tea catechins and bioflavonoids inhibited human liver COMT-mediated O-methylation of 4-OH-E(2) (a representative substrate) with a mixed mechanism of inhibition (competitive plus noncompetitive). In summary, the catechol-containing tea catechins and bioflavonoids are strong inhibitors of human liver COMT-mediated O-methylation of catechol estrogens. More studies are warranted to determine the extent of such inhibition in human subjects and the potential biological consequences.

Catalysis↗
PubMed2000

The bioflavonoid galangin blocks aryl hydrocarbon receptor activation and polycyclic aromatic hydrocarbon-induced pre-B cell apoptosis.

Bioflavonoids are plant compounds touted for their potential to treat or prevent several diseases including cancers induced by common environmental chemicals. Much of the biologic activity of one such class of pollutants, polycyclic aromatic hydrocarbons (PAH), is mediated by the aryl hydrocarbon receptor/transcription factor (AhR). For example, the AhR regulates PAH immunotoxicity that manifests as pre-B cell apoptosis in models of B cell development. Because bioflavonoids block PAH-induced cell transformation and are structurally similar to AhR ligands, it was postulated that some of them would suppress PAH-induced, AhR-dependent immunotoxicity, possibly through a direct AhR blockade. This hypothesis was tested using a model of B cell development in which pre-B cells are cultured with and are dependent on bone marrow stromal or hepatic parenchymal cell monolayers. Of seven bioflavonoids screened, galangin (3,5,7-trihydroxyflavone) blocked PAH-induced but not C(2)-ceramide- or H(2)O(2)-induced pre-B cell apoptosis. Because galangin blocked AhR-dependent reporter gene expression, AhR complex-DNA binding, and AhR nuclear translocation, inhibition of a relatively early step in AhR signaling was implicated. This hypothesis was supported by the ability of galangin to bind the AhR and stabilize AhR-90-kDa heat shock protein complexes in the presence of AhR agonists. These studies demonstrate the utility of pre-B cell culture systems in identifying compounds capable of blocking PAH immunotoxicity, define at least one mechanism of galangin activity (i.e., repression of AhR activation), and motivate the use of this and similar dietary bioflavonoids as relatively nontoxic inhibitors of AhR agonist activity and as pharmacologic agents with which to dissect AhR signaling pathways.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

In vitro antioxidant and in vivo photoprotective effects of an association of bioflavonoids with liposoluble vitamins.

A new tendency in cosmetic formulations is the association of botanical extracts and vitamins to improve skin conditions by synergic effects. The objective of this study was to determine the antioxidant activity of associated bioflavonoids, retinyl palmitate (RP), tocopheryl acetate (TA) and ascorbyl tetraisopalmitate (ATIP), as well as their photoprotective effects in preventing increased erythema, transepidermal water loss (TEWL) and sunburn cell formation in hairless mouse skin. The antioxidant activity of solutions containing the association or each substance separately was evaluated in vitro by a chemiluminescence assay. The photoprotective effect was evaluated by means of in vivo tests. Dorsal skin of hairless mice was treated daily by topical applications for 5 days with formulations containing or not containing (vehicle) the flavonoid-vitamins association (5%). The skin was irradiated (UVA/B) 15 minutes after the last application. The results showed that bioflavonoids had in vitro antioxidant properties and also that when they were associated with vitamins their antioxidant activity was more pronounced. On the other hand, erythema and UV damage to the permeability barrier function (TEWL) was not significantly reduced by previous treatment with the flavonoid-vitamin-association formulations, when compared to the irradiated vehicle-treated area. However, the treatment protected the skin from UV damage because it reduced the number of sunburn cells, when compared to the vehicle-treated area. Finally, the association of vitamins and bioflavonoids added to a dermocosmetic formulation showed a relevant biological activity in terms of photoprotection, because the association of bioflavonoids and vitamins acted by different mechanisms, such as antioxidation and absorption of UV radiation, which suggests its use in antiaging and photoprotective products.

Animals↗
PubMed2000

Effect of a bioflavonoid dietary supplement on acetaminophen-induced oxidative injury to feline erythrocytes.

OBJECTIVE: To determine the effect of a commercial bioflavonoid antioxidant on acetaminophen-induced oxidative injury to feline erythrocytes. DESIGN: Randomized controlled study. ANIMALS: 45 healthy age-matched cats. PROCEDURE: Cats were assigned to 3 experimental groups. Groups 1 and 3 received a bioflavonoid antioxidant (10 mg/d) orally for 2 weeks. Groups 2 and 3 received an oxidative challenge with acetaminophen (90 mg/kg [41 mg/lb] of body weight, PO) on day 7. Packed cell volume, percentage of erythrocytes with Heinz bodies, blood methemoglobin concentration, and blood reduced and oxidized glutathione concentrations were determined at various times during the 2-week study period. RESULTS: Adverse effects were not associated with bioflavonoid antioxidant administration alone. Acetaminophen administration resulted in a significant increase in methemoglobin concentration in groups 2 and 3; differences were not detected between these groups. Heinz body concentrations in groups 2 and 3 increased after acetaminophen administration; however, the increase in cats that received the antioxidant was significantly less than in group-2 cats. Total blood glutathione concentrations did not change significantly in groups 2 and 3 after acetaminophen administration; however, ratio of reduced to oxidized glutathione concentration increased significantly after administration in group-2 cats, compared with group-3 cats. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of bioflavonoid antioxidants to cats at risk for oxidative stress may have a beneficial effect on their ability to resist oxidative injury to erythrocytes.

Acetaminophen↗
PubMed2005

Dietary bioflavonoids induce apoptosis in human leukemia cells.

Dietary bioflavonoids are secondary metabolites of plants that are known to have a variety of bio-effects, including anti-cancer activity. In this study, we examined the effects of flavonoids on the growth of human leukemia cells and found that certain flavonoids induce apoptosis in a variety of human leukemia cells. The apoptosis induced by bioflavonoids was dose-dependent and was accompanied by a disruption of the mitochondrial transmembrane potential and the activation of caspase. Our data suggests that dietary bioflavonoids may be useful chemotherapeutic reagents for leukemia patients.

Annexin A5↗
PubMed2000

Effect of bioflavonoids on vincristine transport across blood-brain barrier.

Several grapefruit juice bioflavonoids, including quercetin, are reported to stimulate P-glycoprotein-mediated drug efflux from cultured tumor cells. To see whether these bioflavonoids alter the permeation of vincristine across the blood-brain barrier, we conducted experiments with cultured mouse brain capillary endothelial cells (MBEC4 cells) in vitro and ddY mice in vivo. The steady-state uptake of [3H]vincristine by MBEC4 cells was decreased by 10 microM quercetin, but increased by 50 microM quercetin. Similarly, the in vivo brain-to-plasma concentration ratio of [3H]vincristine in ddY mice was decreased by coadministration of 0.1 mg/kg quercetin, but increased by 1.0 mg/kg quercetin. Kaempferol had a similar biphasic effect on the in vitro uptake of [3H]vincristine. Other aglycones tested (chrysin, flavon, hesperetin, naringenin) increased [3H]vincristine uptake in the 10-50 microM range, and glycosides (hesperidin, naringin, rutin) were without effect. We then addressed the mechanism of the concentration-dependent biphasic action of quercetin. Verapamil, a P-glycoprotein inhibitor, inhibited the efflux of [3H]vincristine from MBEC4 cells, while 10 microM quercetin significantly stimulated it. The uptake of [3H]vincristine by MBEC4 cells was increased by inhibitors of protein kinase C, but decreased by phorbol 12-myristate-13-acetate (PMA), as well as by 10 microM quercetin. The phosphorylation level of P-glycoprotein was increased in the presence of 5 microM quercetin or 100 nM PMA, but decreased by the protein kinase C inhibitor H7 (1-(5-isoquinolinesulfonyl)-2-methylpiperazine, 30 microM). We conclude that low concentrations of quercetin indirectly activate the transport of [3H]vincristine by enhancing the phosphorylation (and hence activity) of P-glycoprotein, whereas high concentrations of quercetin inhibit P-glycoprotein. Our results indicate that patients taking drugs which are P-glycoprotein substrates may need to restrict their intake of bioflavonoid-containing foods and beverages, such as grapefruit juice.

3-O-Methylglucose↗
PubMed1999

Treatment of progressive pigmented purpura with oral bioflavonoids and ascorbic acid: an open pilot study in 3 patients.

BACKGROUND: Bioflavonoids and ascorbic acid have been shown to increase capillary resistance and to mediate potent antioxidative radical scavenging activities. OBJECTIVE: We evaluated the clinical effect of oral bioflavonoids and ascorbic acid in patients with chronic progressive pigmented purpura (PPP). METHODS: In an open pilot study, oral rutoside (50 mg twice a day) and ascorbic acid (500 mg twice a day) were administered to 3 patients with chronic PPP. RESULTS: At the end of the 4-week treatment period, complete clearance of the skin lesions was achieved in all 3 patients. No adverse reactions were noted. All patients remained free of lesions at the end of 3 months after treatment. CONCLUSION: Our results suggest a beneficial effect of bioflavonoids in combination with ascorbic acid on PPP. Because the disease is mostly resistant to other treatment modalities, placebo-controlled studies are necessary to determine the usefulness of this therapy in PPP.

Administration, Oral↗
PubMed2001

Bioflavonoid rescue of ascorbate at a membrane interface.

In aqueous solution, ascorbate potently prevents bleaching of cytochrome c on exposure to excess H2O2 or t-butyl hydroperoxide. Ascorbate failed to protect cytochrome c in the presence of liposomes of mitochondrial membranelike composition. Like the redox mediator N,N,N,'N'-tetramethyl-p-phenylenediamine (TMPD), however, the bioflavonoids epicatechin and quercetin restored the protection afforded by ascorbate in the presence of liposomes and gave further protection. The quercetin glycoside, rutin, was much less effective, as was the vitamin E analog Trolox. In the presence of liposomes, quercetin alone was relatively ineffective, but cooperated with ascorbate to extend protection synergistically. The results bear specific implications in antioxidant protection of cytochrome c and in moderation of its hydroperoxidase activities in biological membranes. The data also reveal a situation where ascorbate is without effect except in the presence of a bioflavonoid, and substantiate a possibly vital role for certain bioflavonoids in mediating electron transfer from ascorbate into a hydrophobic environment.

Animals↗