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Flavonoids represent a diverse group of low molecular weight natural polyphenolic componds. In plants, flavonoids occur in different forms, such as free aglycones, glycosides, and biflavonoids.
Flavonoids are benzo-?-pyrone derivatives consisting of phenolic and pyran rings and are classified according to substitutions. Coumaroyl-CoA, an intermediate formed by the phenylpropanoid pathway is a substrate for the enzyme chalcone synthase (CHS) and stilbene synthase (STS). Further, the reduction of keto group in the C-ring is reduced by the action of dihydroflavonol reductase (DFR), and then anthocyanidin synthase (ANS) introduces two double bonds in the C-ring forming anthocyanidin. Robinson’s Synthesis: Flavones can be obtained from o-hydroxyacetophenone which is treated with benzoic acid anhydride and sodium benzoate and then subsequently heated [8].
Kostanecki synthesis: Von-Konstanecki method for the synthesis of flavonols utilizes Claisen condensation between benzaldehyde and o-hydroy acetophenone.
Flavonoids, including anthocyanins enable the plants to adapt to the increasing amounts of UV-B radiation [9]. They are not only present in plants as constitutive agents but are also formed in plant tissues in response to microbial attack. Owing to the widespread ability of ?avonoids to inhibit spore germination of plant pathogens, they have been proposed for use against fungal pathogens of man [9].
Certain plants species containing flavonoids have been used for thousands of years in traditional Eastern medicine.
This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. When checked, Shutterstock's safe search screens restricted content and excludes it from your search results. Het flavonoid quercetin-7-glucoside, dat aanwezig is in extracten van de banaba - wetenschappelijke naam: Lagerstroemia speciosa - beschermt waarschijnlijk tegen besmetting met virussen. Producenten zetten banabasupplementen en banabathee in China, Vietname en de Filipijnen vooral op de markt als producten die tegen diabetes type-2 moeten beschermen, maar lokale genezers gebruiken extracten van de banaba ook wel eens tegen infectieziekten.
De onderzoekers vergeleken de anti-viruswerking van quercetin-7-glucoside met die van het virusremmende medicijn ribavirin.
De onderzoekers vermoeden dan ook dat quercetin-7-glycoside niet interacteert met het virus, maar in de eerste uren na het contact voorkomt dat het virus zich in de cellen vermenigvuldigt.
Het onderzoek is niet betaald door industrie, maar door de universiteit van onderzoeksleider en immunoloog Hwa Jung Choi.
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The Effect of Flavonoids in Soybean Products in Lymphocytes from IBD and Colon Cancer Patients After Treatment with Food Mutagens and Hydrogen PeroxideMojgan Najafzadeh1, Malgorzata Kurzawa-Zegota1, Adolf Baumgartner1, 3, P.
Quercetin-Bromelain supplies the flavonoid quercetin extracted from seed pods of the Dimorphandra mollis plant.
Suggested Use: As a dietary supplement, take 2 capsules three times daily, preferably 30 to 60 minutes before meals. Flavonoids function throughout the plant kingdom as UV protectants, attract insects for pollination, and antimicrobial compounds.
Flavonoids can be useful in the prevention of cancer and heart diseases as they influence cell signaling pathways and gene expression. The polyphenolic structure allows a large number of further substitutions, including phenolic hydroxy groups, methoxy groups, O-sugars, C-sugars, and sulfates, thus producing an extremely diverse range of derivatives.
The basic pathways to the core flavonoid skeletons have been established both enzymatically and genetically.7,8 The flavonoid biosynthesis, starts with general phenylpropanoid pathway. The substituted o-hydroxy acetophenones on benzoylation with benzoyl chloride is converted to esters.
Flavanone is obtained on acidification of condensation product, which on reaction with isoamyl nitrite and subsequent hydrolysis gives flavonols. Almost all green plants contain flavonoid pigments, which act as UV filters by absorbing the radiation of 280-315 nm region. The flavone baicalein is reported to be largely responsible for the plant’s antimicrobial effects.
Karanjin a furano favonol obtained from the seeds of karanja tree (Pongamia glabara Vent.) showed promising antifungal activity. Researchers are investigating inhibitory activity of some flavonoids against human immunodeficiency virus (HIV).
Antioxidant flavonoids are naturally present in fruits, vegetables, tea and wine and have been found in vitro to inhibit oxidation of low-density protein (LDL).
Flavonoids and their derivatives from both natural and synthetic sources have been investigated for various activities. Many drugs available today are either from plant source or modified from the plant derived compounds. Dat suggereert een in vitro-studie die Koreaanse onderzoekers publiceerden in de Journal Of Medicinal Food. De figuur hieronder vertelt hoeveel procent van de cellen 2 dagen later niet was besmet toen de onderzoekers de cellen een uur voor de blootstelling Time = - 1, of op Time = 0, Time = 1, Time = 2, Time = 3, Time = 4, Time = 5, Time = 6 of Time = 12 in contact brachten met ribavirin of quercetin-7-glucoside.
Their presence in plant is responsible for various colours and combination of colours exhibited by roots, bark, heartwood, leaves, flowers, fruits and seeds of plants [1]. Flavonoids and isoflavonoids may be of ecotoxicological importance because they are present in the heartwood of tree species used for wood pulp.
Moreover, they can induce mechanisms that can inhibit tumor invasion and kill cancer cells. Some of the activities attributed to flavonoids include: anti-allergic, antioxidant, anti-inflammatory and anti-viral.
Dietary flavonoids differ in the arrangements of hydroxyl, methoxy, and glycosidic side groups, and in the conjugation between the A- and B- rings. The synthesis of phenylpropanoids starts with the removal of the amino group of phenylalanine by phenyl ammonium lyase (PAL) to produce trans-cinnamic acid. Esters undergo rearrangement in the presence of a base to the diketones, which then undergo cyclisation to flavones [7].
The contribution of flavonoids in warding off microbial infection and protecting plants from herbivory is well known.
The phenolic groups in the flavonoids provide antimicrobial activity and this activity is further enhanced by additional phenolic groups. Research groups have also isolated and identified the structure of various flavonoids possessing antibacterial activity. The antioxidant activity of flavonoids arise from their ability to inhibit lipid peroxidation, chelate redox-active metals, and attenuate other processes involving reactive oxygen species [4].
Flavonoids are among the most ubiquitous polyphenolic compounds found in nature that show wide range of biological activity viz.
De onderzoekers brachten die cellen in contact met het human rhinovirus 2, en keken of blootstelling aan quercetin-7-glucoside, een flavonoid uit de banaba, kon voorkomen dat het virus de cellen infecteerde. De onderzoekers gebruikten de virusbeschermende stoffen in een concentratie van 10 microgram per milliliter.
Confounding factors for healthy individuals and colon cancer patients and their influence on the baseline DNA damage using the Comet assay. Davies2 and Diana Anderson1[1] School of Life Sciences, Genetic and Reproductive Toxicology Group, Division of Biomedical Sciences, University of Bradford, Bradford, UK[2] Bradford Royal Infirmary, Bradford, BD9 6RJ, UK and St Luke’s Hospital, Bradford, UK[3] Department of Paediatric Cardiology, Cardiac Centre, University Of Leipzig, Germany1.
They are characterized by the flavan nucleus, consisting of two aromatic rings (A and B) interconnected by a three carbon atom heterocyclic ring C as shown below [2]. Structurally, they consist of two main groups, the 2-phenylchromans (the flavonoids, including flavanones, flavones, flavonols, flavan-3-ols, and anthocyanidins) and the 3-phenylchromans (the isoflavonoids, including isoflavones, isoflavans, and pterocarpans [3, 4].
The aromatic ring of trans-cinnamic acid is then hydroxylated to produce p-coumaric acid by the enzyme cinnamate 4-hydroxylate (C4H). However, different plant species may vary in their ability to resist the harmful effects of UV-B radiation. The biological properties of flavonoids are considered in an evaluation of the medicinal and nutritional values of these compounds. Flavonoids can inhibit reverse transcriptases of different origin and can act as antiretroviral agents. Other flavonoids whose mechanisms of action have been investigated include apigenin, rutin, robinetin, myricetin and galangin. The ? symbols followed by a number indicate individual outliers with the respective patient number.Table 1.
IntroductionThe generation of DNA damage by environmental, medical or life style factors is considered to be an important initial event in carcinogenesis. Coumaric acid can then be ligated to coenzyme A by a ligase [ 4-coumaroyl-CoA ligase (4CL) ]. They are considered for treating human diseases and especially for controlling the HIV virus (the causative agent of AIDS).


The study of these compounds may help the development of a pharmacologically acceptable antimicrobial agent or class of agents. A double bond and carbonyl function in the heterocycle or polymerization of the nuclear structure increases activity by affording a more stable flavonoid radical through conjugation and electron delocalization. At the cellular level, a balance between the production of oxidative radicals and the compensational action of antioxidants, which might become pro-oxidant at high concentrations (Anderson et al., 1994) is crucial for our health.
Studies also revealed that common flavonols and an aurone were strongly active and inhibited the tomato ringspot virus [12].
Antioxidant properties depends on the number of hydroxyl groups which help in free radical scavenging. Pasinetti, Flavonoids and Isoflavonoids: From Plant Biology to Agriculture and Neuroscience, Plant Physiology, 2010, 154, 453–457.
Markham, FLAVONOIDS Chemistry, Biochemistry and Applications, CRC Press Taylor & Francis Group, 2006, 143 – 201. DNA damage induced in vitro in lymphocytes from healthy individuals and colon cancer patients by the food mutagens IQ and PhIP and its reduction by flavonoid supplementation with various concentrations of quercetin (Q) and rutin (R).
Imbalance on either side, especially towards an increase in oxidative stress, might result in various detrimental effects including cell death and cancer. Quercetin and other flavonoids appear to interfere with an early event in the virus life cycle.
Meyer, The antimicrobial activity of 3,5,7-trihydroxy?avone isolated from the shoots of Helichrysum aureonitens. Details of patient and control groups relating to confounding factors and their significant differences.
Despite various cellular mechanisms to counteract these adverse events the sheer number of potentially carcinogenic compounds leading to oxidative stress can negatively affect the DNA integrity of cells. Quercetin at a concentration of 5 µg ml-1 resulted in 70% inhibition of local lesion development of the virus on the test plant Chenopodium quinoa [13].
Bobilya, Flavonoid antioxidants: chemistry, metabolism and structure-activity relationships.
Dietary flavonoids acting as antioxidants (Rice-Evans, 2001) have been identified to be capable of counteracting these adverse oxidative effects (Ross and Kasum, 2002). They are classified as low-molecular-weight polyphenolic compounds that are ubiquitously present in fruit and vegetables and categorised according to their chemical structure into flavonols, flavones, flavanones, isoflavones, catechins, anthocyanidins and chalcones. Flavonoids such as quercetin and rutin present in soybean products have potent antioxidant properties and mimic oestrogens, hence are being used to ease menopausal symptoms. Soy flavonoids are also believed to lower the blood level of triglicerydes and cholesterol preventing coronary heart disease as well as osteoporosis (Valachovicova et al., 2004). The antioxidant potency of several widespread dietary flavonoids showed a dose-dependent reduction of induced oxidative DNA damage in vitro, highlighting an even higher protective effect than vitamin C (Noroozi et al., 1998). It has also been shown that flavonoid intake can lower the mortality rate caused by coronary heart disease (Kaur et al., 2007). Typical flavonoids are kaempferol, quercetin and rutin (the common glycoside of quercetin), belonging to the class of flavonols.
HCA are formed by cooking proteinaceous food, mainly seen as heat-induced non-enzymatic browning that involves creatinine, free amino acids and monosaccharides (Schut and Snyderwine, 1999). Heterocyclic amines like IQ are able to generate free radicals in the presence of NADPH and cytochrome b5 reductase (Maeda et al., 1999). Colorectal tissue is constantly exposed to different chemicals and free oxygen radicals formed during metabolic activation. High intracolonic levels of free radicals may form active carcinogens or mitogenic tumour promoters through the oxidation of procarcinogens, either by hydroxyl radicals in faecal water or by secondary peroxyl radicals (Babbs, 1990).
Ulcerative Colitis and Crohn's disease are inflammatory disorders of the gastrointestinal tract, associated with increased risk for colorectal cancer (Soderlund et al., 2010), which are unevenly distributed within the populations throughout the world. Although the exact cause of inflammatory bowel disease (IBD) remains unknown, the epidemiology of IBD has provided an insight into the pathogenesis of the disease by examining geographic, ethnic and other IBD risk factors (genetic, environmental, etc.) as well as their natural history (Danese and Fiocchi, 2006).
Oxidative stress has been linked to cancer, aging, atherosclerosis, ischemic injury, inflammation and neurodegenerative diseases (Davies, 1995).
Oxidative stress arising from the pathophysiology of cancer, may even serve as a biomarker (Hopkins et al., 2010), when there is an imbalance between production of ROS and their removal by intrinsic antioxidants (catalase) and antioxidant micronutrients. In the present study, we used the Comet assay, which evaluates direct DNA breaks and is a fast and reliable method to assess DNA integrity in virtually any cell type without the requirement for cell culture (Moller, 2006). Three groups of individuals served as blood donors: healthy volunteers, IBD patients as well as patients with histopathologically confirmed, untreated colon cancer.
Separated lymphocytes from IBD patients and healthy individuals were treated with H2O2 co-treated with quercetin and IQ with epicatechin. Also lymphocytes from colon cancer patients and healthy individuals were treated with IQ and PhIP with and without the supplementation of the antioxidant flavonoids, quercetin and rutin to show that these three flavonoids are able to reliably protect cells against the damaging effects of reactive oxygen species, even in the context of diseases like IBD or colorectal cancer where levels of ROS are already highly increased. Non-physiological doses were used in vitro to study the genotoxicological responses where higher, yet non cytotoxic doses are used as a routine procedure.2. ChemicalsThe chemicals for the Comet assay were purchased from the following suppliers: RPMI-1640 medium, agarose and low melting point agarose from Invitrogen, Ltd. The food mutagens, IQ (2-amino-3-methyl-3h-imidazo[4,5-f]quinoline) and PhIP (2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine), were obtained from Toronto Research Chemicals, Inc.
Collection of samplesAfter informed consent, approximately 10 ml heparinised blood were taken by venepuncture from the IBD and colon cancer patients at the Department of Gastroenterology, Bradford Royal Infirmary (BRI) and St.
Healthy volunteers were recruited within the Division of Biomedical Sciences at the University of Bradford (West Yorkshire, UK). Over a period of three years, a set of samples from healthy controls, IBD patients and colon cancer patients was obtained. Questionnaire for patients and controlsA questionnaire was administered to each donor immediately after taking the blood sample. The completed questionnaire for the patient and control groups provided essential information about lifestyle, endogenous (gender, age) and exogenous factors (intake of medicines and alcohol, smoking habits and diet). There were two different studies performed: study I involving IBD patients and study II – colorectal cancer patients. The buffy coat layer of lymphocytes (above the Lymphoprep layer) was then transferred to another tube pre-filled with 10 ml of saline and centrifuged (15 minutes at 500 g). The supernatant was removed without disturbing the pellet which was then resuspended in PBS or RPMI-1640 medium and used for the in vitro experiments. Cell viability Cell viability at the concentrations chosen for each experiment was checked after treatment and before performing the Comet assay. Viability was determined by Trypan blue dye exclusion indicating intact cell membranes (Phillips, 1973).
As lymphocytes showed little or no difference in response with metabolic activation, the Comet assay was performed in the absence of metabolic activation to avoid any confounding factors (Anderson, 1997, 1998). Alkaline comet assayThe slide preparation for the Comet assay and the assay itself was carried out as previously described (Tice et al., 2000).
An aliquot of 100 µl of lymphocyte suspension was mixed with 100 µl of 1% low melting point agarose (in PBS, <40 °C warm) and 100 µl of this suspension were spread onto each of the two microscope glass slides pre-coated with 1% normal melting point agarose (in water, dried overnight). Once the agarose set, the cover-slips were removed and a final third layer of 0.5% low melting point agarose (in PBS) was added and allowed to solidify as well on ice for 5 min. After electrophoresis, the slides were removed from the tank and soaked three times for 5 minutes each with neutralizing Tris buffer (400 mM, pH 7.4).
Slides were examined using a fluorescence microscope equipped with a charge couple device (CCD) monochrome camera and a computerised image analysis system, Komet 4.0 (Kinetic Imaging, Liverpool, UK) to measure the comet parameters. All slides were coded by an independent person ensuring that scoring took place completely randomized and in a “blind” manner (Faust et al., 2004).
Normal distributions were checked through the Kolmogorov-Smirnoff and Shapiro-Wilk’s Test to assess whether parametric statistics could be used.
Study I: Gaussian normality was violated for many of the scale variables as endorsed by the Kolmogorov-Smirnov test. Therefore, non-parametric test procedures were adopted wherever necessary, such as the Kruskal-Wallis (K-W) and the Mann-Whitney (M-W) tests for independent samples.
When testing intra-subject differences in DNA damage, the Wilcoxon Signed Rank (WSR) test was applied. Throughout the analyses, a significance level of 5% was used and unilateral alternative hypotheses preferred to bidirectional tests (wherever appropriate). Study II: differences in measured parameters between healthy and colon cancer subjects were assessed by the parametric One Way ANOVA Test, since data were normally distributed. The relationship between DNA damage and various parameters characterising colon cancer status and unexposed control was analyzed using Post-hoc analysis (Dunnett test). Differences between two experimental groups were tested by the unpaired Student t-test when comparing confounding factors due to gender, diet, smoking and drinking habits. The SPSS package version 16 was used to compare patient and control groups at different doses of H2O2, food mutagens and flavonoids.Statistical analyses were performed on mean values for each cluster group (healthy individuals, IBD and colon cancer patients) for each possible combination of chemicals. The Comet data parameters used to measure DNA damage were Olive tail moment (OTM; arbitrary unit, the fraction of DNA in the tail multiplied by the tail length) and % tail DNA (the percentage of DNA in the tail) recommended to be the most reliable comet measurements with OTM being the most statistically significant (Kumaravel and Jha, 2006).


Of these two parameters, OTM is one of the most commonly reported measures of DNA damage but is recommended to be provided together with % tail DNA (Tice et al., 2000).
Supplementing the treatment with various concentrations of the flavonoids, quercetin, epicatechin and rutin, the reduction of the genotoxic impact of chemicals was also evaluated.
As expected, the two different control groups showed similar baseline DNA damage (M-W, p = 0.174). Also there was less induced DNA damage in the study group treated with H2O2 and quercetin compared with the study group treated with IQ and epicatechin although the patients were selected randomly. Ethnicity, age, gender, smoking and drinking habitsThere were small differences of median levels of DNA damage in Caucasians (n = 13) and Asians (n = 7) after treatment with H2O2 and quercetin as well as in males and females. Previous medication in the IBD group as a confounding factorPatients had been treated with a range of drugs for IBD, namely, azathioprine, mesalazine and pentasa, asacol, prednisolone, mercaptopurine alone or in combination prior to taking part in the study. Within the treatment groups, there appeared to be differences but they were not significant. Patient versus control groups Treating lymphocytes from healthy individuals and cancer patients with food mutagens IQ and PhIP in vitro resulted in a dose-dependent statistically significant induction of DNA damage for both parameters measured, Olive tail moment (OTM) and % tail DNA (Table 3). For the 25?M IQ treatment of lymphocytes from colon cancer patients, the induced DNA damage measured in % tail DNA reached significance while the evaluated OTM did not.
For lymphocytes from healthy individuals, only the lowest quercetin dose together with IQ and the lowest dose for rutin together with IQ and PhIP measured in OTM, as well as the lowest dose of rutin together with PhIP when evaluating % tail DNA did not reach significant levels. Confounding factorsConfounding factors such as age, gender, diet, smoking habits and alcohol intake were also investigated (Table 4).
Table 4.Confounding factors for healthy individuals and colon cancer patients and their influence on the baseline DNA damage using the Comet assay. DiscussionCrohn’s disease (CD) and Ulcerative Colitis (UC), known as inflammatory bowel disease (IBD), are fairly common chronic inflammatory conditions of the gastrointestinal tract. Although the exact aetiology of IBD remains uncertain, dysfunctional immunoregulation of the gut is believed to be the main cause. An imbalance between antioxidants and ROS results in oxidative stress, leading to cellular damage (Rezaie et al., 2007) and subsequently cell death or cancer.
Colorectal cancer is a heterogeneous neoplasm consisting of cancer cells with various proliferation rates and the potential to metastasise (Ozdemirler Erata et al., 2005). Genetic alterations caused by cellular overproduction of ROS are required for neoplastic progression (Soderlund et al., 2010).
As the onset of cancer is a prolonged multi-stage process where successive mutations are accumulated, continuous erosion of the genome and defects in repair contribute to this process (Hoeijmakers, 2001; Jiricny and Marra, 2003). HCA have been widely investigated and all of them have so far been described as mutagenic and carcinogenic (Gooderham et al., 2007). Food mutagens may cause different types of DNA damage from chromosomal aberrations to subtle nucleotide alterations.
Most food mutagens like HCA are able to form reactive DNA adducts by covalently binding to nucleotides. However the effect of food mutagens in carcinogenesis can be modified by heritable traits, namely, low-penetrant genes that affect exposure of the mutagen to DNA through metabolic activation and detoxification or other cellular responses to DNA damage.
Able to activate and detoxify heterocyclic amines may be enzymes like CYP1A2, N-acetyltransferase, sulfotransferase, prolyl tRNA synthetase, phosphorylase and COX isomers (Wolz et al., 2000). In a recent case-control study, no associations were found between colorectal cancer (CRC) risk and polymorphisms within the genes of those enzymes (Sachse et al., 2002). This comprehensive analysis, however, failed to consider commensal bacteria and their potential impact on HCA activation, an effect independent of the host genotype. The pro-carcinogen IQ is predominantly produced through the pyrolysis of creatinine with sugars and becomes significantly mutagenic in the presence of hepatic microsomes (Sugimura and Sato, 1983).
Anaerobic colonic bacteria can convert IQ to 2-amino-3-methyl-3H-imidazo[4,5-f]quinoline-7-one (HOIQ), a direct-acting mutagen (Bashir et al., 1987). These commensal bacteria can strongly influence IQ-induced DNA damage in colonic cells and also in hepatocytes as measured by the alkaline comet assay (Knasmuller et al., 2001). Flavonoids are known to have antioxidative properties in vivo (Rice-Evans, 2001) and modulate effects of food mutagens in vitro in human lymphocytes and sperm (Anderson et al., 1998).
Green tea and, to a lesser extent, black tea are a rich source of still another group of flavonoids called catechins. The activity of quercetin is believed to be due to its antioxidative properties, however, it has been suggested that quercetin may also have pro-oxidative activities, which might then directly affect genotoxicity (Lee et al., 2003). There was a significant increase of DNA damage after treating lymphocytes from healthy controls, IBD and colon cancer patients with H2O2, PhIP and IQ, while a significant protective effect was found in the presence of the flavonoids quercetin, rutin and epicatechin (Figures 1, 2 and 3, Table 1 and 3).In the study I, the protective in vitro effect of quercetin and epicatechin against oxidative stress in lymphocytes from IBD patients and healthy individuals (Figure 1) was observed.
We were able to show that untreated lymphocytes from IBD patients had significantly increased DNA damage when compared to healthy individuals as shown previously with other IBD patients (Najafzadeh et al., 2007).
In vitro treatment with H2O2 and IQ significantly induced DNA damage by oxidative stress in both groups. Flavonoids reduced the baseline DNA damage in lymphocytes from IBD patients treated with H2O2 and IQ.
When co-treated with flavonoids, a significant protective effect was shown against free radical damage to the DNA generated by H2O2 or IQ (Figure 1). There was a very high level of damage in the patient group without any treatment because of their background inflammation and IBD therapeutic drugs which they had taken, but both patients and controls showed a parallel and gradual reduction in DNA damage after treating with flavonoids (Figure 1 and Table 1).
It becomes obvious that an excessive production of ROS and radical nitrogen metabolites occur during the inflammation of the intestine in IBD patients (Kruidenier et al., 2003).
It seems that a misbalanced production of pro-inflammatory and anti-inflammatory cytokines is characteristic of IBD and severely affects the immune homeostasis in peripheral blood cells, even more in CD than in UC patients (Sventoraityte et al., 2008). However, all subgroups react in the same way towards exogenous oxidative stressors as well as towards the inhibition of oxidative stress by flavonoids.
The detrimental effects of two common food mutagens, IQ and PhIP, on the DNA were investigated in study II by treating in vitro lymphocytes from healthy individuals and from patients diagnosed with colon cancer.
Both HCA caused in a dose-dependent manner similar levels of DNA damage in lymphocytes of both groups for the Comet assay parameters OTM and % tail DNA (Table 3), supporting the classification for IQ as “probably carcinogenic to humans” and for PhIP as “possibly carcinogenic to humans” (IARC, 1993).
IQ on the other hand can form DNA adducts like N-(deoxyguanosin-8-yl)-IQ in the presence of nitric oxide constituting a possible cancer risk for individuals with colon inflammation (Lakshmi et al., 2008). In our study the DNA damage induced in lymphocytes of both donor groups by food mutagens IQ and PhIP was effectively and dose-dependently reduced by supplementation with the flavonoids quercetin and rutin (Table 3). The level of DNA damage from the highest HCA dose reduced by the highest dose (500 µM) of flavonoids was comparable to that of a six times (for IQ) and 7.5 times (for PhIP) lower non-supplemented dose of food mutagen.
In human lymphocytes quercetin and rutin already showed a dose-dependently protective effect against DNA damage caused by the mutagenic anticancer drug mitomycin C (Undeger et al., 2004). However, neither myricetin, quercetin nor rutin increased the rate of DNA strand break repair in various cell types such as Caco-2, Hep G2 and V79 (Aherne and O'Brien, 2000).
Our results indicate that the baseline DNA damage was higher for all experiments in lymphocytes from colon cancer patients when compared to healthy individuals (Table 3 and Figure 3). Disease states which involve an overproduction of ROS may therefore inflict significantly higher DNA damage in peripheral lymphocytes from patients when compared to the baseline level of damage in healthy individuals. Even the modulating effect of flavonoids in a co-treatment with a high dose of food mutagen (Table 3) seem to be affected by the higher baseline damage as the induced DNA damage in lymphocytes from colon cancer patients was not reduced to the levels of healthy individuals.
A possible reason for this finding could be a reduced repair capacity which was found for breast cancer patients after in-vitro treatment of lymphocytes with N-methyl-N-nitro-N-nitrosoguanidine or ionising radiation (Smith et al., 2003).
When examining the confounding effect aspects the numbers of participants were reduced yet we still found statistically significant effects for age (>50.
We are aware our groups are not best matched for age however these were the only individuals available at the time. DNA damage in male lymphocytes, however, was significantly higher than in lymphocytes from females for the Comet assay parameter % tail DNA but not for OTM.
After in vitro treatment with IQ and PhIP an increase in DNA damage in lymphocytes was observed in our study but confounding factors such as diet, smoking and drinking habits did not seem to influence this response, even though numerous environmental and lifestyle compounds can have an impact on the exposure, metabolism and cell proliferation response of HCA (Felton et al., 2004). It has been estimated that up to 90% of the cases of colorectal cancer could be prevented with life style modifications such as balanced diet, avoidance of smoking and alcohol and physical activity (Boursi and Arber, 2007). Lymphocytes from IBD, cancer patients and controls had increased DNA damage possibly due to an overproduction of ROS and there was a significant difference in response between all donor groups to treatment with HCA alone and together with flavonoids in both studies. It is believed that flavonoids operate through their antioxidant properties and responses of H2O2 and HCA to quercetin, epicatechin and rutin observed throughout the study, support the hypothesis that food mutagens target DNA by generating ROS.
Although the possible health benefits of consuming flavonoids seem to be obvious, there are so many biological activities attributed to them, that further study may be justified.The flavonoids significantly reduce DNA damage in vitro in lymphocytes of IBD and colorectal cancer patients as well as healthy individuals.
Thus, a diet containing flavonoids could be very effective in reducing baseline and exogenously induced oxidative DNA damage of IBD and colorectal cancer patients. AcknowledgementsThe authors want to thank the clinical staff of Bradford Royal Infirmary Hospital and St.



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