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

Effects of epigallocatechin gallate on the oral bioavailability and pharmacokinetics of tamoxifen and its main metabolite, 4-hydroxytamoxifen, in rats

The effects of epigallocatechin gallate (EGCG) on the oral bioavailability and pharmacokinetics of tamoxifen and its metabolite, 4-hydroxytamoxifen, were investigated in rats. A single dose of tamoxifen was administered intravenously (2 mg/kg) and orally (10 mg/kg) with or without epigallocatechin (0.5, 3 and 10 mg/kg) to rats. The presence of EGCG significantly altered the pharmacokinetics of orally administered tamoxifen. Compared with the oral control group (given tamoxifen alone), the area under the plasma concentration-time curve and the peak plasma concentration of tamoxifen significantly (P<0.05 for 3 mg/kg of EGCG, P<0.01 for 10 mg/kg of EGCG) increased 48.4-77.0 and 57.1-89.7%, respectively. Consequently, the absolute bioavailability of tamoxifen in the presence of EGCG (3 and 10 mg/kg) was 48.9-78.1%, which was significantly enhanced (P<0.05 for 3 mg/kg of EGCG, P<0.01 for 10 mg/kg of EGCG) compared with the oral control group (23.7%). Moreover, the relative bioavailability of tamoxifen was 1.48-1.77-fold greater than that of the control group. EGCG at a dose of 10 mg/kg significantly increased the area under the plasma concentration-time curve (P<0.05, 40.3%) of 4-hydroxytamoxifen, but the metabolite-parent ratio of 4-hydroxytamoxifen was also significantly altered (P<0.05 for 10 mg/kg of EGCG), implying that the formation of 4-hydroxytamoxifen was considerably affected by EGCG. The increase in bioavailability of tamoxifen is likely to be due to the decrease in first-pass metabolism in the intestine and liver by inhibition of P-glycoprotein and CYP3A by EGCG. The increase in oral bioavailability of tamoxifen in the presence of EGCG should be taken into consideration of potential drug interactions between tamoxifen and EGCG.

Antioxidant activity of some plant extracts towards xanthine oxidase, lipoxygenase and tyrosinase

Natural products have the potential to be developed into new drugs for the treatment of various diseases. The aim of the present study was to screen the antioxidant activities of some common edible fruits, garden plants and medicinal plants indigenous to Taiwan. This was performed by assessing the activities of lipoxygenase, xanthine oxidase and tyrosinase following incubation with extracts from these plants. A further aim was to use HPLC-DAD and tyrosinase to chromatographically identify the antioxidative constituents obtained from an extract exhibiting strong antioxidative properties. The acetone extracts of 27 cultivated plant species from Taiwan were tested for antioxidant activities towards xanthine oxidase, tyrosinase and lipoxygenase using spectrophotometric assays. Koelreuteria henryi, Prunus campanulata, and Rhodiola rosea showed the highest xanthine oxidase inhibitory activities. Camellia sinensis, Rhodiola rosea, and Koelreuteria henryi exhibited good tyrosinase inhibitory activities and potent anti-lipoxygenase activities. As Koelreuteria henryi had notable significant inhibitory activities towards xanthine oxidase, tyrosinase, and lipoxygenase, it was further tested with tyrosinase and HPLC-DAD. The results from this part of the study revealed that the more powerful the antioxidant capability of the extracted component, the greater the decrease in peak height obtained after reacting with tyrosinase. Additional studies are warranted to further characterize the compounds responsible for the antioxidant properties of the examined extracts.

Enhancement of vascular relaxation in rat aorta by phytoestrogens from Curcuma comosa Roxb

The present study aims to examine the effects and mechanisms of Curcuma comosa Roxb., an indigenous medicinal plant containing phytoestrogens, on vascular relaxation. Using an organ bath system, acute exposure of intact or endothelium-denuded aortic rings to the hexane extract of C. comosa or an isolated diarylheptanoid compound, D3, did not induce relaxation. However, pre-incubation of aortic rings for 20 min with hexane extract of C. comosa (10 microg/ml) or the isolated diarylheptanoid compound, D3, (0.1, 1 and 10 microg/ml) markedly enhanced endothelial-dependent relaxation in response to ACh. The hexane extract did not modulate the relaxation of denuded aortic rings in response to SNP, which suggested a predominant effect on endothelial cells rather than on vascular smooth muscle cells. Co-incubation with ICI 182,780 (estrogen receptor antagonist), L-NAME (nitric oxide synthase inhibitor) or ODQ (guanylase cyclase inhibitor) inhibited the enhancing effects of C. comosa on ACh-induced relaxation. These findings suggest that the actions of C. comosa are mediated through estrogen receptor (ER) and NO-cGMP-dependent mechanisms. In addition, C. comosa also increased the phosphorylation of serine 1177 eNOS and serine 473 Akt proteins, and these effects were abolished by ICI 182,780. The results suggest that C. comosa acutely increases endothelium-dependent relaxation of aortic rings through the ER-Akt-eNOS pathway. This is the first evidence indicating non-genomic action of a novel phytoestrogen from C. comosa, on vascular relaxation.

Modulation of lipid metabolism by Centella asiatica in oxidative stress rats

A study was carried out to investigate the effects of Centella asiatica leaf on lipid metabolism of oxidative stress rats. The rats were fed 0.1% hydrogen peroxide (H(2)O(2)) with either 0.3% (w/w) C. asiatica extract, 5%C. asiatica powder (w/w), or 0.3% (w/w) alpha-tocopherol for 25 wk. Results of the study showed that C. asiatica powder significantly (P < 0.05) lowered serum low-density lipoprotein compared to that of control rats (rats fed H(2)O(2) only). At the end of the study C. asiatica-fed rats were also found to have significantly (P < 0.05) higher high-density lipoprotein and lower triglyceride level compared to rats fed only normal diet. However, cholesterol level of rats fed both C. asiatica extract and powder was found to be significantly (P < 0.05) higher compared to that of control rats. It was interesting to note that consumption of C. asiatica significantly decreased body and liver weights of the rats. Histological examinations revealed no obvious changes in all rats studied. Quantitative analysis of C. asiatica leaf revealed high concentration of total phenolic compounds, in particular, catechin, quercetin, and rutin.

Lysophosphatidylcholine induces endothelial cell injury by nitric oxide production through oxidative stress

OBJECTIVE

To determine whether lysophosphatidylcholine (LPC) induces endothelial cell injury by altering the production of nitric oxide (NO) and thereby increasing reactive oxygen species (ROS).

METHODS

Human umbilical vein endothelial cells (HUVECs) were cultured and exposed to LPC, LPC with N(G)-nitro-l-arginine methyl ester (L-NAME), LPC with antioxidants. LPC-induced cell injury and viability were determined using LDH and Resazurin assays. The Mann-Whitney U test was used for statistical analysis.

RESULTS

LPC induced HUVEC injury in a concentration-dependent manner. LPC induced the overproduction of NO and ROS in HUVECs and LPC-induced HUVEC injury is significantly inhibited by the eNOS inhibitor (L-NAME) and the antioxidants (p < 0.05).

CONCLUSIONS

These findings suggest that LPC induces the overproduction of NO, which may increase the oxidative stress on endothelial cells and lead to endothelial cell injury.

Red wine protects against ethanol-induced oxidative stress in rat liver

Ethanol consumption may be deleterious to the liver. However, alcoholic beverages contain, besides ethanol (EtOH), complex chemical mixtures that can modify EtOH's adverse effects. Red wine (RW) is rich in polyphenolic antioxidants, often reported as hepatoprotective agents. This study aimed to investigate the effects of 6 months of RW ingestion on hepatic oxidative stress and inflammation. Six-month-old Wistar rats were treated with RW or EtOH; controls were pair-fed. EtOH increased 8-hydroxy-2'-deoxyguanosine and decreased reduced and oxidized glutathione. These animals also displayed stimulated superoxide dismutase, catalase, and glutathione reductase activities. RW treatment decreased malondialdehyde and reduced glutathione levels. Glutathione-S-transferase and selenium-dependent glutathione peroxidase activities were stimulated and glutathione reductase activity was inhibited by RW intake. No modifications were detected in nuclear factor-kappa B or alkaline phosphatase activities. EtOH consumption induced fibrosis in portal spaces and hepatocyte lipid accumulation that were absent with RW treatment. This paper highlights the importance of RW nonalcoholic components and the relevance of biological matrix in the study of EtOH oxidative effects.

Systematic evaluation of the antioxidant potential of different parts of Foeniculumvulgare Mill. from Portugal

Fennel (Foeniculum vulgare Mill.) is a widespread perennial umbeliferous (Apiaceae) herb, traditionally used for medicinal purposes and human consumption. It is highly recommended for diabetes, bronchitis and chronic coughs, and for the treatment of kidney stones; some of those chronic diseases are related to the production of radical species involved in the oxidative stress. Therefore, the antioxidant potential of this herb might explain some of their empirical uses in folk medicine. This is the first time that a systematic study on different parts of fennel is performed, in order to understand differences in the antioxidant potential of shoots, leaves, steams, and inflorescences, particularly related to their composition in antioxidant compounds such as vitamins (ascorbic acid and tocopherols) and phenolics. The shoots seems to have the highest radical-scavenging activity and lipid peroxidation inhibition capacity (EC(50) values<1.4 mg/ml), which is in agreement with the highest content in phenolics (65.85+/-0.74 mg/g) and ascorbic acid (570.89+/-0.01 microg/g) found in this part. The shoots also revealed high concentration of tocopherols (34.54+/-1.28 microg/g) and were the only part with flavonoids.

Simulation of Phenolic Compounds Transformations and Interactions in an In Vitro Model of the Human Alimentary Tract

Phenolic compounds play an important role in the defense system of the human organism against reactive oxygen species. They are present mainly in fruit and vegetables, but their bioavailability is the key factor determining their concentration in blood and tissues. The aim of this article was to study the transformations that apple polyphenols undergo during digestion. An in vitro model with dialysate membranes simulating the human alimentary tract was used for evaluating the composition and antioxidant properties of fresh apples and products of their digestion in dialysates. Epicatechin, chlorogenic acid, and procyanidins were the main antioxidant compounds in the whole fruits and flesh of the two varieties of apples analyzed. In the apple peel additionally quercetin glycosides were present. As a result of in vitro digestion both polyphenolic compounds concentration and the antioxidant activity of the dialysates increased as compared to the raw materials (from 35% to 95% and from 50% to 236%, respectively). In the simulated alimentary tract, it was proved that procyanidins disintegrate to (+)catechin, which is well absorbed from the small intestine, while chlorogenic acid and quercetin glycosides were characterized by a low bioavailability.

Quercetin protects C6 glial cells from oxidative stress induced by tertiary-butylhydroperoxide

The anti-oxidant and cyto-protective activity of quercetin against tertiary-butylhydroperoxide (t-BOOH) induced oxidative stress on C6 glial cells is reported. Exposure of the cells to t-BOOH resulted in a significant increase in cytotoxicity, reactive oxygen species (ROS) generation and lipid peroxidation. There was a significant increase in DNA strand breaks and fall in reduced GSH levels in cells exposed to t-BOOH. A significant increase in calcium ion influx was noticed in cells exposed to t-BOOH. Pre-treatment of cells with quercetin, vitamin C (vit C), Trolox, and deferoxamine (DFO) significantly inhibited t-BOOH induced cytotoxicity and ROS generation. Pretreatment of cells with quercetin, Trolox and DFO inhibited the DNA damage, maintained higher GSH levels and prevented calcium influx significantly. Although vit C protected the cells from cytotoxicity induced by t-BOOH, the intracellular Ca(2+) levels were significantly higher than the control cells. However, anti-oxidants like butylated hydroxy toluene (BHT), vitamin E (vit E), N-acetyl cysteine (NAC) did not have significant cytoprotection against t-BOOH induced oxidative injury in C6 glial cells.

An investigation of the antioxidant properties and colour of glasshouse grown tomatoes

The colour and the antioxidant content of five different cultivars of tomatoes (Lycopersicon esculentum L.), grown in glasshouses using commercial hydroponic techniques, were measured in freshly harvested tomatoes and after 2 and 5 days of storage in the dark at 15 degrees C. The two cocktail cultivars of tomatoes, Aranca and Flavourine, were the smallest tomatoes but they contained higher dry matter contents compared with the three standard salad cultivars, Excell, Celero and Dutch Chaser. There were significant differences (P < 0.001) in lycopene (the major carotenoid), ascorbic acid and total antioxidant activity in the whole fruit of the five different cultivars evaluated at harvest, while the total phenolic contents were very similar. The lycopene levels of all the cultivars increased significantly (P < 0.001) after storage for 2 and 5 days at 15 degrees C. Overall, the total phenolic content of all the cultivars did not change appreciably after storage at 15 degrees C while the levels of ascorbic acid fell by 12.6% when stored for 5 days in the dark. There was a significant difference (P < 0.001) in the total antioxidant activity between the five different cultivars when freshly harvested; the highest levels of total antioxidant activity were observed in the two cocktail cultivars, Aranca and Flavourine. Antioxidant activity showed different patterns of change depending on cultivar. An increase in the total antioxidant values could be seen in cultivars Dutch chaser and Excell, after storage for 5 days at 15 degrees C. The total antioxidant activity values of Flavourine and Celero fell on storage while the values for stored Aranca were very similar to the values when freshly harvested. The skin colour, as shown by Commission Internationale l'Eclairage (CIE) L*a*b* values of each cultivar were markedly different at harvest even though each cultivar was harvested at the same maturity. The a* value of each cultivar increased significantly (P < 0.001) when they were stored in the dark, for either 2 or 5 days, at 15 degrees C. Regression analysis showed that overall there was no significant relationship (R(2) = 0.14) between the lycopene content and the a* value of all the tomatoes; however, when examined individually, the two cocktail tomatoes Aranca and Flavourine showed strong correlation-R(2) = 0.96 and R(2) = 0.97, respectively. Overall, the (a*/b*)(2) was the most reliable indicator of lycopene concentration (R(2) = 0.96) in the tomatoes examined in this study.

Oral co-administration of α-lipoic acid, quercetin and captopril prevents gallium arsenide toxicity in rats

Gallium arsenide (GaAs), an inter-metallic semiconductor, known to exhibit superior optical and electronic properties compared to silicon, promotes its use in semiconductor industries. Extensive use of GaAs will inevitably lead to an increase in the exposure of workers manufacturing these products. Antioxidants are exogenous or endogenous compounds acting in several ways, including scavenging reactive oxygen species (ROS) or their precursors, inhibiting ROS formation, and binding metal ions needed for the catalysis of ROS generation. In the present study we investigated the protective efficacy of α-lipoic acid, quercetin and captopril individually against gallium arsenide exposure. Co-administration of α-lipoic acid with GaAs was most effective in reducing GaAs induced inhibition of blood δ-aminolevulinic acid dehydratase (ALAD) activity, liver, kidney and brain reduced glutathione (GSH) level and elevation of oxidized glutathione (GSSG). Captopril, on the other hand was effective in reducing thiobarbituric acid reactive substance (TBARS) levels, while quercetin reduced ROS in liver and kidney. The results suggest comparatively better preventive efficacy of concomitant α-lipoic acid administration during Gallium arsenide exposure compared to quercetin and captopril in preventing GaAs induced oxidative stress.

Study of genotoxic, antigenotoxic and antioxidant activities of the digallic acid isolated from Pistacia lentiscus fruits

The digallic acid obtained from the fruit Pistacia lentiscus exhibits an inhibitory activity against nitrofurantoine and B[a]P induced genotoxicity when tested by the SOS chromotest bacterial assay system in the presence of Escherichia coli PQ37 strain. The antioxidant activity of the tested compound was determined by its ability to scavenge the free radical ABTS(+), to inhibit the xanthine oxidase, involved in the generation of free radicals, and to inhibit the lipid peroxidation induced by H(2)O(2) in the K562 cell line. Our results revealed that digallic acid shows an important free radical scavenging activity towards the ABTS(+) radical (99%) and protection against lipid peroxidation (68%).

Silibinin prevents amyloid beta peptide-induced memory impairment and oxidative stress in mice

BACKGROUND AND PURPOSE

Accumulated evidence suggests that oxidative stress is involved in amyloid beta (Abeta)-induced cognitive dysfunction. Silibinin (silybin), a flavonoid derived from the herb milk thistle (Silybum marianum), has been shown to have antioxidative properties; however, it remains unclear whether silibinin improves Abeta-induced neurotoxicity. In the present study, we examined the effect of silibinin on the memory impairment and accumulation of oxidative stress induced by Abeta(25-35) in mice.

EXPERIMENTAL APPROACH

Aggregated Abeta(25-35) (3 nmol) was intracerebroventricularly administered to mice. Treatment with silibinin (2, 20 and 200 mg.kg(-1), once a day, p.o.) was started immediately after the injection of Abeta(25-35). Locomotor activity was evaluated 6 days after the Abeta(25-35) treatment, and cognitive function was evaluated in a Y-maze and novel object recognition tests 6-11 days after the Abeta(25-35) treatment. The levels of lipid peroxidation (malondialdehyde) and antioxidant (glutathione) in the hippocampus were measured 7 days after the Abeta(25-35) injection.

KEY RESULTS

Silibinin prevented the memory impairment induced by Abeta(25-35) in the Y-maze and novel object recognition tests. Repeated treatment with silibinin attenuated the Abeta(25-35)-induced accumulation of malondialdehyde and depletion of glutathione in the hippocampus.

CONCLUSIONS AND IMPLICATIONS

Silibinin prevents memory impairment and oxidative damage induced by Abeta(25-35) and may be a potential therapeutic agent for Alzheimer's disease.

Antioxidant and anti-inflammatory properties of tomato fruits synthesizing different amounts of stilbenes

Resveratrol, a plant phenolic compound, is found in grapes and red wine, but is not widely distributed in other common food sources. The pathway for resveratrol biosynthesis is well characterized. Metabolic engineering of this compound has been achieved in tomato plants (Lycopersicon esculentum Mill.) in order to improve their nutritional value. Tomato plants synthesizing resveratrol were obtained via the heterologous expression of a grape (Vitis vinifera L.) cDNA encoding for the enzyme stilbene synthase (StSy), under the control of the fruit-specific promoter TomLoxB. The resulting LoxS transgenic plants accumulated trans-resveratrol and trans-piceid, in particular in the skin of the mature fruits. Quantitative analyses carried out on LoxS fruits were compared with those of a tomato line constitutively expressing the stsy gene (35SS). The LoxS fruits contained levels of trans-resveratrol that were 20-fold lower than those previously reported for the 35SS line. The total antioxidant capability and ascorbate content in transformed fruits were also evaluated, and a significant increase in both was found in the LoxS and 35SS lines. These results could explain the higher capability of transgenic fruits to counteract the pro-inflammatory effects of phorbol ester in monocyte-macrophages via the inhibition of induced cyclo-oxygenase-2 enzyme.

Heterocyclic aromatic amine intake increases colorectal adenoma risk: findings from a prospective European cohort study

BACKGROUND

Heterocyclic aromatic amines (HCAs), which arise from cooking meat and fish at high temperatures, may increase the risk of colorectal adenomas. Conversely, flavonoids might counteract the negative effects of HCAs.

OBJECTIVE

The association between dietary HCA intake and colorectal adenoma incidence was investigated in a prospective cohort study.

DESIGN

At recruitment (1994-1998), detailed information on diet, anthropometric measures, lifestyle, and medication use was assessed in 25,540 participants of the European Prospective Investigation into Cancer and Nutrition-Heidelberg cohort study. Dietary HCA intake was estimated by using information from food-frequency questionnaires on meat consumption, applied cooking methods, and preferred degree of browning. Until June 2007, 516 verified incident colorectal adenomas were identified. Participants with negative colonoscopy (n = 3966) were also included in the analytic cohort. Multivariate Cox proportional hazards regression was used to examine the association between colorectal adenoma risk and intake of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), and 2-amino-3,4,8-dimethylimidazo[4,5-f]quinoxaline (DiMeIQx).

RESULTS

In multivariate analyses, the intake of PhIP as the most abundant dietary HCA was associated with an increased risk of colorectal adenoma (relative risk: 1.47; 95% CI: 1.13, 1.93; quartile 4 compared with quartile 1; P for trend = 0.002), but no statistically significant associations were observed for MeIQx and DiMeIQx intakes. In addition, adenoma risk also increased with the consumption of strongly or extremely browned meat (P for trend = 0.04). The association of PhIP intake with adenoma risk was most pronounced for small adenomas (P for trend = 0.01) and adenomas localized in the distal colon (P for trend = 0.002).

CONCLUSION

The results of this first European cohort study support data from case-control studies of a positive association between HCA intake and colorectal adenoma risk.

Characterization and quantification of flavonoids and hydroxycinnamic acids in curly kale (Brassica oleracea L. Convar. acephala Var. sabellica) by HPLC-DAD-ESI-MSn

Kale is a leafy green vegetable belonging to the Brassicaceae family, a group of vegetables including cabbage, broccoli, cauliflower, and Brussels sprouts, with a high content of health-promoting phytochemicals. The flavonoids and hydroxycinammic acids of curly kale ( Brassica oleracea L. ssp. oleracea convar. acephala (DC.) Alef. var. sabellica L.), a variety of kale, were characterized and identified primarily through HPLC-DAD-ESI-MS(n) analysis. Thirty-two phenolic compounds including glycosides of quercetin and kaempferol and derivatives of p-coumaric, ferulic, sinapic, and caffeic acid were tentatively identified, providing a more complete identification of phenolic compounds in curly kale than previously reported. Moreover, three hydroxycinnamic acids and one flavonoid with an unusual high grade of glycosylation, quercetin-3-disinapoyl-triglucoside-7-diglucoside, have been tentatively identified for the first time. The influence of different extraction conditions (extraction method, solvent type, solvent/solid ratio, and duration of extraction) was investigated. The total flavonol and hydroxycinnamic acid contents in curly kale determined as rutin equivalents (RE) were 646 and 204 mg of RE/100 g of fresh weight (fw), respectively. The contents of individual flavonoids ranged from 2 to 159 mg of RE/100 g of fw, with main compounds kaempferol-3-sinapoyl-diglucoside-7-diglucoside (18.7%) and quercetin-3-sinapoyl-diglucoside-7-diglucoside (16.5%). After acidic hydrolysis, two flavonol aglycones were identified in curly kale, quercetin and kaempferol, with total contents of 44 and 58 mg/100 g of fw, respectively.

Inhibition studies of bovine xanthine oxidase by luteolin, silibinin, quercetin, and curcumin

Xanthine oxidoreductase (XOR) is a molybdenum-containing enzyme that under physiological conditions catalyzes the final two steps in purine catabolism, ultimately generating uric acid for excretion. Here we have investigated four naturally occurring compounds that have been reported to be inhibitors of XOR in order to examine the nature of their inhibition utilizing in vitro steady-state kinetic studies. We find that luteolin and quercetin are competitive inhibitors and that silibinin is a mixed-type inhibitor of the enzyme in vitro, and, unlike allopurinol, the inhibition is not time-dependent. These three natural products also decrease the production of superoxide by the enzyme. In contrast, and contrary to previous reports in the literature based on in vivo and other nonmechanistic studies, we find that curcumin did not inhibit the activity of purified XO nor its superoxide production in vitro.

Antihypertensive and vasorelaxant effects of tilianin isolated from Agastache mexicana are mediated by NO/cGMP pathway and potassium channel opening

Current investigation was undertaken to elucidate the mode of action of tilianin, isolated from Agastache mexicana, as a vasorelaxant agent on in vitro functional rat thoracic aorta test and to investigate the in vivo antihypertensive effect on spontaneously hypertensive rats (SHR). Tilianin (0.002-933 microM) induced significant relaxation in a concentration- and endothelium-dependent and -independent manners in aortic rings pre-contracted with noradrenaline (NA, 0.1 microM), and serotonin (5-HT, 100 microM). Effect was more significant (p < 0.05) in endothelium-intact (+E) aorta rings than when endothelium was removed(E). Pre-treatment with N-nitro-L-arginine methyl ester (L-NAME; 10 microM) or 1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one (ODQ, 1 microM) produced a significant change of the relaxant response and activity was markedly inhibited, but not by indomethacin (10 microM) or atropine (1 microM). Furthermore, tilianin (130 microM) provoked a significant displacement to the left in the relaxation curve induced by sodium nitroprusside (SNP; 0.32 nM to 0.1 microM). Moreover, tilianin induced significant in vitro NO overproduction (1.49 +/- 0.86 microM of nitrites/g of tissue) in rat aorta compared with vehicle (p < 0.05). In addition, pre-treatment with tetraethylammonium (TEA, 5 mM) and 2-aminopyridine (2-AP, 0.1 microM) shifted to the right the relaxant curve induced by tilianin (p < 0.05). Finally, a single oral administration of tilianin (50 mg/kg) exhibited a significant decrease in systolic and diastolic blood pressures (p < 0.05) in SHR model. Results indicate that tilianin mediates relaxation mainly by an endothelium-dependent manner,probably due to NO release, and also through an endothelium-independent pathway by opening K+ channels, both causing the antihypertensive effect.

Influence of polyphenols on Escherichia coli resistance to oxidative stress

Among all polyphenols tested (tannic acid and flavonoids belonging to different subclasses) only tannin and quercetin significantly enhanced resistance of Escherichia coli to peroxide stress. Pretreatment of the cells with quercetin and tannin resulted in a decrease in the growth arrest duration under moderate H(2)O(2) concentration (2 mM) and an increase in survival under high (10 mM) doses. The shorter growth recovery period in pretreated cells was connected with more rapid H(2)O(2) elimination because of induced activity of scavenging enzymes. This effect was absent in the Delta oxyR mutant, which was unable to induce genes responding to peroxide stress. The data obtained suggest that the observed protection was a result of two overlapping effects: induction of OxyR regulon by low concentrations of H(2)O(2), accumulated during extracellular autoxidation of quercetin and tannin, and protection of synthesis of OxyR-regulated antioxidant enzymes during H(2)O(2) stress because of intracellular binding of iron by quercetin and tannin and suppressing Fenton chemistry.

Regulation of polyphenols accumulation by combined overexpression/silencing key enzymes of phenylpropanoid pathway

There is a growing interest in the metabolic engineering of plant with increased desirable polyphenols such as chlorogenic acid (CGA) and rutin. In this study, the effects of overexpression of both phenylalanine ammonia lyase (AtPAL2), the first enzyme of the phenylpropanoid pathway, and hydroxycinnamoyl-CoA quinate:hydroxycinnamoyl transferase (NtHQT), the last enzyme of CGA biosynthesis, and the overexpression of AtPAL2 together with silencing of NtHQT were investigated in tobacco. Transgenic tobacco plants overexpressing AtPAL2 showed two and five times increases of CGA and rutin levels than the wild-type (WT) plants, respectively. Overexpression of NtHQT further increases the accumulation of CGA in the AtPAL2 plants to about three times than that of the WT level, while silencing of NtHQT in AtPAL2 plants results in about 12 times increase in rutin level than that of the WT plants. Simultaneous overexpression of phenylalanine ammonia lyase (PAL) and overexpression/silencing HQT could be used for the production of functional food with increased polyphenols.

Measurement of xanthine oxidase inhibition activity of phenolics and flavonoids with a modified cupric reducing antioxidant capacity (CUPRAC) method

Various dietary polyphenolics have been found to show an inhibitory effect on xanthine oxidase (XO) which mediates oxidative stress-originated diseases because of its ability to generate reactive oxygen species (ROS), including superoxide anion radical (O(2)(-)) and hydrogen peroxide. XO activity has usually been determined by following the rate of uric acid formation from xanthine-xanthine oxidase (X-XO) system using the classical XO activity assay (UV-method) at 295nm. Since some polyphenolics have strong absorption from the UV to visible region, XO-inhibitory activity of polyphenolics was alternatively determined without interference by directly measuring the formation of uric acid and hydrogen peroxide using the modified CUPRAC (cupric reducing antioxidant capacity) spectrophotometric method at 450nm. The CUPRAC absorbance of the incubation solution due to the reduction of Cu(II)-neocuproine reagent by the products of the X-XO system decreased in the presence of polyphenolics, the difference being proportional to the XO inhibition ability of the tested compound. The structure-activity relationship revealed that the flavones and flavonols with a 7-hydroxyl group such as apigenin, luteolin, kaempferol, quercetin, and myricetin inhibited XO-inhibitory activity at low concentrations (IC(50) values from 1.46 to 1.90microM), while the flavan-3-ols and naringin were less inhibitory. The findings of the developed method for quercetin and catechin in the presence of catalase were statistically alike with those of HPLC. In addition to polyphenolics, five kinds of herbs were evaluated for their XO-inhibitory activity using the developed method. The proposed spectrophotometric method was practical, low-cost, rapid, and could reliably assay uric acid and hydrogen peroxide in the presence of polyphenols (flavonoids, simple phenolic acids and hydroxycinnamic acids), and less open to interferences by UV-absorbing substances.

Response of rice advance line PB-95 to potassium application in saline-sodic soil

A field experiment was conducted to evaluate the response of rice crop to potassium fertilization in saline-sodic soil during 2005. Soil samples were collected before transplanting of rice crop and analysed for physical and chemical properties of the soil. In this experiment five rates of K2O (0, 25, 50, 75 and 100 kg ha(-1)) were applied in the presence of basal doses of N and P2O5 i.e., 110 and 90 kg ha(-1), respectively. Whole of P, K and 1/2 of N were applied at the time of rice transplanting. Twelve and halfkg ha(-1) ZnSO4 was also applied 15 days after rice transplanting. The remaining half of N was applied 30 days after rice transplanting. The system of layout was Randomized Complete Block Design with four replications. The net plot size was 6x4 m. Fertilizer sources of NPK were urea, TSP and SOP, respectively. Rice salt tolerant line PB-95 was used as test crops. The data of growth parameters and yield was recorded and samples of paddy and straw were collected treatment-wise and analysed for N, P and K contents. Soil samples after harvesting the crop were also collected, processed and analysed for the changes in the extractable soil K. The results showed that increasing rates of potassium fertilizer increased the number of tillers m(-2), plant height (cm), 1000-paddy weight and paddy as well as straw yield significantly. Maximum paddy (3.24 t ha(-1)) and straw (3.92 t ha(-1)) yields were obtained in T5 (100 kg K2O ha(-1)) which was at par with T4 (75 kg K2O ha(-1)). With increasing rates of potassium fertilizer, concentration of potassium in paddy and straw increased significantly. After harvesting the crop, the extractable potassium contents of soil increased from that of the original soil. It was concluded from the results that there was an increase of 30.65% in paddy over control by applying potassium (100 kg K2O ha(-1)) in saline-sodic soil.

Bioactivity and structure of biophenols as mediators of chronic diseases

Biophenols and their associated activity have generated intense interest. Current topics of debate are their bioavailability and bioactivity. It is generally assumed that their plasma concentrations are insufficient to produce the health benefits previously attributed to their consumption. However, data on localized in vivo concentrations are not available and many questions remain unanswered. Potential mechanisms by which they may exert significant bioactivity are discussed together with structure activity relationships. Biophenols are highly reactive species and they can react with a range of other compounds. Products of their reaction when functioning as antioxidants are examined.

Iron behaving badly: inappropriate iron chelation as a major contributor to the aetiology of vascular and other progressive inflammatory and degenerative diseases

BACKGROUND

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular 'reactive oxygen species' (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation.

REVIEW

We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation).The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible.This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, since in some circumstances (especially the presence of poorly liganded iron) molecules that are nominally antioxidants can actually act as pro-oxidants. The reduction of redox stress thus requires suitable levels of both antioxidants and effective iron chelators. Some polyphenolic antioxidants may serve both roles.Understanding the exact speciation and liganding of iron in all its states is thus crucial to separating its various pro- and anti-inflammatory activities. Redox stress, innate immunity and pro- (and some anti-)inflammatory cytokines are linked in particular via signalling pathways involving NF-kappaB and p38, with the oxidative roles of iron here seemingly involved upstream of the IkappaB kinase (IKK) reaction. In a number of cases it is possible to identify mechanisms by which ROSs and poorly liganded iron act synergistically and autocatalytically, leading to 'runaway' reactions that are hard to control unless one tackles multiple sites of action simultaneously. Some molecules such as statins and erythropoietin, not traditionally associated with anti-inflammatory activity, do indeed have 'pleiotropic' anti-inflammatory effects that may be of benefit here.

CONCLUSION

Overall we argue, by synthesising a widely dispersed literature, that the role of poorly liganded iron has been rather underappreciated in the past, and that in combination with peroxide and superoxide its activity underpins the behaviour of a great many physiological processes that degrade over time. Understanding these requires an integrative, systems-level approach that may lead to novel therapeutic targets.

Cocoa: antioxidant and immunomodulator

Cocoa, a product consumed since 600 BC, is now a subject of increasing interest because of its antioxidant properties, which are mainly attributed to the content of flavonoids such as ( - )-epicatechin, catechin and procyanidins. Moreover, recent findings suggest a regulatory effect of cocoa on the immune cells implicated in innate and acquired immunity. Cocoa exerts regulatory activity on the secretion of inflammatory mediators from macrophages and other leucocytes in vitro. In addition, emerging data from in vivo studies support an immunomodulating effect. Long-term cocoa intake in rats affects both intestinal and systemic immune function. Studies in this line suggest that high-dose cocoa intake in young rats favours the T helper 1 (Th1) response and increases intestinal gammadelta T lymphocyte count, whereas the antibody-secreting response decreases. The mechanisms involved in this activity are uncertain; nonetheless, because redox-sensitive pathways control immune cell function, the action of cocoa flavonoids on modulating cell signalling and gene expression deserves investigation.

The flavonoid kaempferol sensitizes human glioma cells to TRAIL-mediated apoptosis by proteasomal degradation of survivin

Resistance to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) limits its potential as a drug for cancer therapy. Here, we report that kaempferol, a bioactive plant flavonoid, sensitizes U251 and U87 glioma cells to TRAIL-mediated apoptosis. In contrast, U373 cells are not affected by kaempferol treatment. Treatment of kaempferol alone for 24 h did not induce apoptosis in the cell lines. We provide evidence that TRAIL-induced apoptosis is partially driven by kaempferol-mediated reduction of survivin protein levels. On kaempferol treatment, proteasomal degradation of survivin was observed. Inhibition of proteasomal degradation with MG132 in kaempferol-treated cells restored survivin protein levels in both glial cell lines. Consequently, overexpression of survivin attenuated TRAIL-kaempferol-induced apoptosis. In addition, we show that kaempferol mediates down-regulation of phosphorylated Akt, thereby further reducing survivin protein level. Furthermore, the blockage of the serine/threonine kinase Akt activity by kaempferol is important for inhibition of survivin because active phosphorylated Akt enhances the stability of survivin. However, we also show that the combined treatment of TRAIL and kaempferol induces cleavage (activation) of caspase-8, thereby exerting a proapoptotic effect independent of survivin known not to inhibit caspase-8 activation. Other effects induced by kaempferol were suppression of X-linked inhibitor of apoptosis proteins as the antiapoptotic members of the Bcl-2 family, Bcl-2, Bcl-xL, and Mcl-1 in a concentration-dependent manner. In summary, we showed that suppression of survivin is an essential mechanism in TRAIL-kaempferol-mediated apoptosis.

Enhanced tamoxifen bioavailability after oral administration of tamoxifen in rats pretreated with naringin

The aim of this study was to investigate the effect of naringin on the bioavailability and pharmacokinetics of tamoxifen and of its metabolite, 4-hydroxytamoxifen in rats. The pharmacokinetic parameters of tamoxifen and 4-hydroxytamoxifen were determined by HPLC after pretreating with naringin (1.5, 7.5, and 15 mg/kg) 30 min before orally administering tamoxifen (10 mg/kg). Compared with the control group (treated with tamoxifen alone), naringin pretreated animals showed significantly (p<0.01) increased areas under the plasma concentration-time curves (AUC) and peak tamoxifen concentrations (Cmax). The absolute bioavailabilities (AB%) of tamoxifen in naringin pretreated animals were enhanced versus control (from 32.8% to 47.1%), and the relative bioavailabilities (RB%) of tamoxifen in the naringin pretreated groups were 2.02-2.88 times higher than that in the control. No significant changes in the terminal half-life (t(1/2)) or Tmax of tamoxifen were observed in the naringin pretreated groups. The AUCs of 4-hydroxytamoxifen after pretreating naringin were also significantly elevated (p<0.05) versus the control. But metabolite ratios (MR; AUC of 4-hydroxytamoxifen to tamoxifen) were significantly lower. These results suggest that the enhanced bioavailability of tamoxifen in the presence of naringin might be due to the inhibition of CYP3A4 by naringin. If the results of this study are further confirmed by clinical trials, tamoxifen dosages should be adjusted to avoid potential drug interaction when tamoxifen is used clinically in combination with naringin-containing dietary supplements.

Involvement of the Bcl-2 family members in Pinus massoniana bark extract induced apoptosis in HeLa cells

Pinus massoniana bark extract (PMBE) contains a variety of flavonoids whose antioxidant properties have been confirmed in vitro. This study was undertaken to evaluate the cytotoxic effects and the mechanism of cell death on the PMBE-treated human cervical cancer cell line, HeLa. PMBE treatment led to cell growth inhibition in a dose- and time-dependent manner, and PMBE-induced apoptosis was confirmed by DAPI staining, TUNEL assays and sub-G1 phase accumulation. Cell cycle was also arrested in G2/M phase. Immunoblotting analysis showed that cytochrome c was released, the protein expression of Bax was increased, the protein expression of Bcl-2 was down-regulated and caspase-9 and -3 were activated in PMBE-treated HeLa cells. Taken together, PMBE inhibited proliferation, induces apoptosis and causes cell cycle arrest in HeLa cells, indicating that PMBE may be a potential therapeutic agent for cancer.

Anti-inflammatory and hypolipemic effects in vitro of simvastatin comparing to epicatechin in patients with type-2 hypercholesterolemia

OBJECTIVE

The study involved 25 patients with type-2 hypercholesterolemia (mean age 49.3+/-11.3). The control group consisted of 28 healthy individuals (mean age 50.7+/-7.2).

METHODS

The cholesterol concentrations in plasma membranes of erythrocytes were measured by means of Liebermann-Burchard reagent. The membrane lipid peroxidation in whole erythrocytes was determined. The membrane fluidity was estimated by spin labelled method.

RESULTS

The in vitro study shows that the cholesterol concentration in membranes incubated with simvastatin and epicatechin decreases; in healthy donors there are no changes. Simvastatin does not lead to changes in the lipid peroxidation in the in vitro data. Epicatechin decreases the level of membrane lipid peroxidation in patients with hypercholesterolemia and in healthy donors. Simvastatin and epicatechin cause an increase in the fluidity of plasma membranes of erythrocytes.

CONCLUSIONS

Simvastatin causes the decrease in cholesterol concentration in erythrocytes membranes not only in the in vivo but also the in vitro experiments. Flavonoids have antioxidant properties in vitro. Simvastatin influences the lipid peroxidation only in vivo, not in vitro systems. This observation is an additional contribution to the statins' pleiotropic effect.

Neuroprotective effect of cocoa flavonoids on in vitro oxidative stress

BACKGROUND

Cocoa is a rich source of flavonoids that, among other functions, can act as antioxidants. In living systems, the production of reactive oxygen species (ROS) activate an array of intracellular cascades, including mitogen-activated protein kinases (MAPK), that are closely associated with cell death or survival pathways.

AIM OF THE STUDY

To ascertain the role of a cocoa extract and its main flavonoid, (-)-epicatechin, in an in vitro model of oxidative stress induced in a neuronal cell line.

METHODS

We analyzed ROS production by fluorometry (dichlorofluorescein assay), and activation of MAPK pathways including extracellular signal-regulated kinases 1/2 (ERK 1/2), c-Jun N-terminal kinase (JNK), and p-38, by Western blot analysis.

RESULTS

Cells incubated with cocoa extract or (-)-epicatechin, reduced ROS production in a dose-dependent manner, reaching 35% inhibition. pJNK and p38, involved in apoptosis, were down-modulated by cocoa extract and (-)-epicatechin with p38 inhibition reaching up to 70%.

CONCLUSIONS

Our results show that cocoa extract and (-)-epicatechin may exert a neuroprotective action by reducing ROS production and modulating MAPK activation.

Atheroprotective and plaque-stabilizing effects of enzymatically modified isoquercitrin in atherogenic apoE-deficient mice

OBJECTIVE

Enzymatically modified isoquercitrin (EMIQ), isoquercitrin with malto-oligosaccharides, has been recognized as "generally recognized as safe" by the Flavor and Extracts Manufacturers Association in the United States since 2003. The long-term antiatherogenic effect of EMIQ was examined using apolipoprotein E (apoE)-deficient atherogenic mice.

METHODS

Male apoE-deficient mice (6 wk old) were fed with a high-fat diet alone or a diet containing EMIQ for 14 wk. At 20 wk old, atherosclerotic lesions in the aorta and aortic sinus were measured by morphometry and histomorphometry.

RESULTS

In apoE-deficient mice, EMIQ did not significantly affect body weight, plasma total cholesterol, triacylglycerol, and high-density lipoprotein cholesterol throughout the experiment. EMIQ significantly suppressed the aortic atherosclerotic lesion area (control 8.8 +/- 3.5% versus EMIQ 4.4 +/- 1.5%, mean +/- SD, P = 0.022). Similarly, atherosclerotic plaque lesions in the aortic sinus were significantly reduced by EMIQ (control 37.7 +/- 3.6% versus EMIQ 30.2 +/- 2.0%, P = 0.010). Of note, the immunostained area for macrophage or 4-hydroxy-2-nonenal, a well-recognized marker of oxidative stress, at the plaque in the aortic sinus was markedly suppressed, whereas the area for collagen or smooth muscle cell were increased by EMIQ, suggesting a plaque-stabilizing effect of EMIQ.

CONCLUSION

EMIQ has atheroprotective and plaque-stabilizing effects.