Study on the mutagenic activity of 13 bioflavonoids with the Salmonella Ara test

Myricetin: a Multifunctional Flavonol in Biomedicine

PURPOSE OF REVEIW

The root cause of many diseases like CVD, cancer, and aging is free radicals which exert their effect by interfering with different metabolic pathways. The sources of free radicals can be exogenous, like UV rays from sunlight, and endogenous due to different metabolic by-products.In our body, there are defense mechanisms present, such as antioxidant enzymes and antioxidant molecules to combat these free radicals, but if there is an overload of these free radicals in our body, the defense system may not be sufficient to neutralize these free radicals. In such situations, we are exposed to a chronic low dose of oxidants creating oxidative stress, which is responsible for eliciting different diseases.

RECENT FINDINGS

Pubmed and Google Scholar are the search engines used to sort out relevant papers on myricetin and its role in combating many diseases. Myricetin is present in many fruits and vegetables and is a known antioxidant. It can elevate the antioxidant enzyme levels; reduces the lipid peroxidation; and is known to protect against cancer. In the case of myocardial dysfunction, myricetin has been shown to suppress the inflammatory cytokines and reduced the mortality rate. Myricetin has also been found to reduce platelet aggregation and control the viral infections by interfering in the DNA replication pathways.

SUMMARY

In this paper, we have briefly reviewed about the different type and site of free radicals and the role of myricetin in addressing the ROS and different diseases.

Evaluation of the safety of ethanolic extract from Piper amalago L. (Piperaceae) leaves in vivo: Subacute toxicity and genotoxicity studies

Piper amalago L. (Piperaceae) is traditionally used due to its anti-inflammatory, analgesic, diuretic, and antiparasitic properties. However, few studies have focused on its adverse effects, compromising its safe use. This study evaluated the toxicological safety of ethanolic extract from Piper amalago leaves (EEPA), through subacute toxicity and genotoxicity assays in rodents. In subacute toxicity, 100, 200 or 300 mg/kg of EEPA were tested in female Wistar rats, by gavage, for 28 days. For genotoxicity test, female Swiss mice were orally treated with 17.5, 175 or 1750 mg/kg of EEPA and the comet, micronucleus, and splenic phagocytic assays were evaluated. In subacute toxicity, the extract induced an increase in the food and water intakes, as well as in the liver absolute weight, and in the heart and kidney relative weights. EEPA also provoked alterations in histopathological analysis of liver and in hemato-biochemical parameters, evidenced by a decrease in hematocrit levels and albumin levels, and an increase in the number of platelets and in alkaline phosphatase and cholesterol levels. However, EEPA did not presented genotoxic nor mutagenic properties. EEPA showed hemato-biochemical toxicity profile in rats and should be used with caution, especially when for prolonged period.

Polyphenols with Anti-Amyloid β Aggregation Show Potential Risk of Toxicity Via Pro-Oxidant Properties

Alzheimer's disease (AD) is the most common form of dementia among older people. Amyloid β (Aβ) aggregation has been the focus for a therapeutic target for the treatment of AD. Naturally occurring polyphenols have an inhibitory effect on Aβ aggregation and have attracted a lot of attention for the development of treatment strategies which could mitigate the symptoms of AD. However, considerable evidence has shown that the pro-oxidant mechanisms of polyphenols could have a deleterious effect. Our group has established an assay system to evaluate the pro-oxidant characteristics of chemical compounds, based on their reactivity with DNA. In this review, we have summarized the anti-Aβ aggregation and pro-oxidant properties of polyphenols. These findings could contribute to understanding the mechanism underlying the potential risk of polyphenols. We would like to emphasize the importance of assessing the pro-oxidant properties of polyphenols from a safety point of view.

Liquid chromatography/high resolution tandem mass spectrometry - Tool for the study of polyphenol profile changes during micro-scale biogas digestion of grape marcs

A microscale discontinuous fermenter was used for anaerobic digestion of wine waste - a hardly gasifiable feedstock material. Efficiency of biogas production, i.e. changes in content of nitrogen, oxygen, carbon dioxide and methane in gas phase, was monitored by gas chromatography/mass spectrometry. Liquid chromatography/high resolution tandem mass spectrometry in combination with principal component analysis and orthogonal projection to latent structures was used to reveal main chemical differences of gasified wine waste mixture from commonly used ones in agricultural biogas plants. Compounds with particular polyphenolic structures appeared among the most distinctive markers. Analysis of samples collected during acidogenic phase and unstabilized methanogenesis indicates formation of certain dihydro-flavonoids in early stages of the process and their consequent degradation. Due to formerly described higher toxicity of some dihydroflavonoids (e.g. taxifolin) compared to their more common counterparts (e.g. quercetin, malvidin etc.), unstabilized digestate would represent a potential environmental risk when used as a fertilizer deserving a proper control.

In vitro Evaluation of the Anti-Picornavirus Activities of New Synthetic Flavonoids

Substituted oxazolinylflavons and oxazolinylflavanones were synthesized in order to compare their anti-picornavirus activities with those of related natural and synthetic compounds. The antiviral potencies of the new compounds were evaluated against rhino-virus type 1B and poliovirus type 2 by a plaque reduction assay in HeLa cell cultures. Among the substituted flavanones only 6-chloro-4′-oxazolinylflavanone showed activity against both viruses. A comparison of the effects of 3-substituted flavones indicated that the presence of a 3-methoxy group enhances the activity against rhinovirus, while the presence of a 3-hydroxy group enhances the activity against poliovirus.

Mutagenic Activity of Indigofera truxillensis and I. suffruticosa Aerial Parts

Indigofera truxillensis and I. suffruticosa, are used as a source of indigo dye and to treat several diseases. The mutagenic activity of the methanolic extracts from aerial parts, glycerolipid, flavonoid and alkaloid fractions of the extract were evaluated by means of Salmonella/microsome assays using TA100, TA98, TA102 and TA97a strains. The methanolic extract of I. truxillensis showed mutagenic activity in the TA98 strain without S9 while glycerolipid fraction was devoid of activity. The flavonoid and alkaloid fractions of both plants showed mutagenicity. Chemical analysis of flavonoid fractions of I. truxillensis and I. suffruticosa resulted in the identification of kaempferol, quercetin and their derivatives. The alkaloid fraction of both the species contained indigo and indirubin and indigo was found mainly responsible for the mutagenic activity.

Toxicity study of ethanolic extract of Chrysanthemum morifolium in rats

Chrysanthemum morifolium extract (CME) has many pharmacological effects, and the effective components of CME are luteolin and apigenin which have been reported with cytotoxicity in vitro. The purpose of this study was to evaluate the safety of CME in Sprague-Dawley (S-D) rats. In the acute toxicity study, a single oral dose of 15 g/kg body weight (bw) CME was administered to rats, then the rats were observed for 14 d. No treatment-related death was observed, and the maximal tolerance dose estimated was greater than 15 g/kg bw in rats. In the long-term toxicity study, the rats were administered daily by gavage at dose levels of 320, 640, and 1280 mg/kg bw/d for consecutive 26 wk followed by 4 wk recovery period. The results showed that no toxicological changes in body weight, food, and water consumption, hematologic examination, blood biochemical examination, organ weight, and microscopic histopathologic examination were found in any treatment group. Therefore, CME is considered to be safe in general in rats at the limited dose level.

Preclinical colorectal cancer chemopreventive efficacy and p53-modulating activity of 3',4',5'-trimethoxyflavonol, a quercetin analogue

Some naturally occurring flavonols, exemplified by quercetin, seem to possess experimental cancer chemopreventive efficacy. Modulation of p53 is a mechanism thought to contribute to their activity. The hypothesis was tested that a synthetic flavonol, 3',4',5'-trimethoxyflavonol (TMFol), can interfere with tumor development and p53 expression in two models of colorectal carcinogenesis, Apc(Min) mice and human-derived HCT116 adenocarcinoma-bearing nude mice. Mice received TMFol with their diet (0.2%) from weaning to week 16 in the case of Apc(Min) or from either day 7 before ("TMFol early") or day 7 after ("TMFol late") tumor inoculation in HCT116 mice. The ability of TMFol to affect tumor proliferation or apoptosis, as reflected by staining for Ki-67 or cleaved caspase-3, respectively, was studied in HCT116 tumors. TMFol tumor levels were measured by high-performance liquid chromatography. Consumption of TMFol reduced small intestinal adenoma burden in Apc(Min) mice by 47%, compared with control mice (P < 0.002). The TMFol early regimen approximately halved HCT116 tumor size (P < 0.05), decreased tumor proliferation, and increased apoptosis, whereas the TMFol late regimen had no significant effect when compared with controls. In tumor tissues from mice, in which TMFol reduced tumor development, p53 expression was increased 3-fold in Apc(Min) and 1.5-fold in HCT116 tumor-bearing mice (P = 0.02). TMFol increased p53 also in cells derived from these tumors. TMFol was detected in HCT116 tumors, but levels did not correlate with tumor burden. TMFol was not mutagenic in the Ames test. The results suggest that chemical modification of the flavonol structure may generate safe and efficacious cancer chemopreventive agents.

Health effects of quercetin: from antioxidant to nutraceutical

Quercetin, a member of the flavonoids family, is one of the most prominent dietary antioxidants. It is ubiquitously present in foods including vegetables, fruit, tea and wine as well as countless food supplements and is claimed to exert beneficial health effects. This includes protection against various diseases such as osteoporosis, certain forms of cancer, pulmonary and cardiovascular diseases but also against aging. Especially the ability of quercetin to scavenge highly reactive species such as peroxynitrite and the hydroxyl radical is suggested to be involved in these possible beneficial health effects. Consequently, numerous studies have been performed to gather scientific evidence for these beneficial health claims as well as data regarding the exact mechanism of action and possible toxicological aspects of this flavonoid. The purpose of this review is to evaluate these studies in order to elucidate the possible health-beneficial effects of the antioxidant quercetin. Firstly, the definitions as well as the most important aspects regarding free radicals, antioxidants and oxidative stress will be discussed as background information. Subsequently, the mechanism by which quercetin may operate as an antioxidant (tested in vitro) as well as the potential use of this antioxidant as a nutraceutical (tested both ex vivo and in vivo) will be discussed.

Base excision repair pathway is involved in the repair of lesions generated by flavonoid-enriched fractions of pepper tree (Schinus terebinthifolius, Raddi) stem bark

Cell-free and bacterial assays indicate that flavonoid-enriched fractions and the flavonoids of pepper tree stem bark from Schinus terebinthifolius Raddi have genotoxic rather than antigenotoxic properties. In the present report, we have examined the ability of flavonoid-enriched fractions to damage plasmid DNA and the repair pathways involved in the recognition of these DNA lesions. High concentrations of two flavonoid-enriched fractions were able to break phosphodiester bonds in DNA. In addition, studies using bacterial strains deficient in nucleotide excision repair and base excision repair (BER) enzymes indicated that the flavonoid-enriched fractions generated lesions that were substrates for enzymes belonging to the BER pathway. In addition, in vitro studies indicated that the DNA damage produced by the flavonoid-enriched fractions was also a substrate for exonuclease III and that the phosphodiester breakage was amplified by copper ions. These results indicate that flavonoids from the pepper tree (Schinus terebinthifolius, Raddi) generate lesions on DNA that are potential targets of FPG and MutY glycosylase from the BER pathway. Chromatographic and spectral analyses helped to support the hypothesis that the flavonoids of the Brazilian pepper tree bark are the main factors involved in the fraction's damage potential. The isolated flavonoids from Fraction II were also tested in vitro and support the oxidative damage potential of these flavonoids.

Assessment of DNA damage by extracts and fractions of Strychnos pseudoquina, a Brazilian medicinal plant with antiulcerogenic activity

Strychnos pseudoquina St. Hil. is a native plant of the Brazilian Savannah, used in popular medicine to treat a number of conditions. Since it contains large quantities of alkaloids with proven antiulcer activity, we tested the genotoxic potential of crude extracts and fractions containing alkaloids and flavonoids from the leaves of this plant, on Salmonella typhimurium and performed the micronucleus test on peripheral blood cells of mice treated in vivo. The results showed that the methanol extract of the leaves of S. pseudoquina is mutagenic to the TA98 (-S9) and TA100 (+S9, -S9) strains of Salmonella. The dichloromethane extract was not mutagenic to any of the tested strains. Fractions enriched with alkaloids or flavonoids were not mutagenic. In vivo tests were done on the crude methanol extract in albino Swiss mice, which were treated, by gavage, with three different doses of the extract. The highest dose tested (1800 mg/kgb.w.) induced micronuclei after acute treatment, confirming the mutagenic potential of the methanol extract of the leaves of S. pseudoquina. In high doses, constituents of S. pseudoquina compounds act on DNA, causing breaks and giving rise to micronuclei in the blood cells of treated animals.

Antioxidant status and mineral contents in tissues of rutin and baicalin fed rats

The versatile benefit effects of flavonoids lead some nutritionists to believe that they are micronutrients. However, excess intake of flavonoids may cause side effects. In this paper, the effects produced by a higher intake of rutin and baicalin on antioxidant status as well as trace minerals such as iron, copper and zinc in rat tissues were studied. When rats were fed a rutin or baicalin containing diet (1%) for 20 days, the body weight gain was lower than that of the control group. Both rutin and baicalin caused significant a decrease of catalase activity and a moderate increase of total superoxide dismutase activity in the liver. The total antioxidant status of flavonoid fed rats was increased in the liver but decreased in the serum. In comparison to the control group, the lipid peroxidation level in the liver of the rutin fed group was significantly decreased; however, there was no statistical significance in the liver of the baicalin fed group and the brain of both flavonoids groups. The liver homogenates of both flavonoid fed rats significantly inhibited alkyl radical-induced lipid peroxidation. The iron contents in the liver of flavonoid fed rats were significantly decreased; rutin also caused zinc and copper decrease in the liver. These results indicated that high flavonoid intake can improve rat antioxidant systems in the liver; while it can also cause a trace mineral decrease and, in turn, reduce the activities of some metal-containing enzymes and may cause harmful effects on health.

The role of quinone reductase (NQO1) and quinone chemistry in quercetin cytotoxicity

The effects of quercetin on viability and proliferation of Chinese Hamster Ovary (CHO) cells and CHO cells overexpressing human quinone reductase (CHO+NQO1) were studied to investigate the involvement of the pro-oxidant quinone chemistry of quercetin. The toxicity of menadione was significantly reduced in CHO+NQO1 cells compared to wild-type CHO cells, validating the NQO1-overexpression in the CHO+NQO1 transfectant. Quercetin inhibited the proliferation of wild-type CHO and CHO+NQO1 cells to a similar extent without affecting cell viability, indicating that NQO1 enrichment of CHO cells did not provide increased protection. On the other hand, inhibition of NQO1 in both types of cells by dicoumarol significantly potentiated the inhibitory effect of quercetin on cell proliferation, revealing the role of NQO1 in cellular protection against quercetin. Altogether, these results can be explained by the hypothesis that both wild-type CHO and CHO+NQO1 cells contain sufficient NQO1 activity for optimal protection against the pro-oxidant effect of quercetin on cell proliferation. The results also point at a cellular NQO1 threshold for optimal protection against quercetin. This NQO1 threshold seems to be in the range of NQO1 activities already present in various tissues.

In vitro metabolism of genistein and tangeretin by human and murine cytochrome P450s

Recombinant cytochrome P450 (CYP) 1A2, 3A4, 2C9 or 2D6 enzymes obtained from Escherichia coli and human liver microsomes samples were used to investigate the ability of human CYP enzymes to metabolize the two dietary flavonoids, genistein and tangeretin. Analysis of the metabolic profile from incubations with genistein and human liver microsomes revealed the production of five different metabolites, of which three were obtained in sufficient amounts to allow a more detailed elucidation of the structure. One of these metabolites was identified as orobol, the 3'-hydroxylated metabolite of genistein. The remaining two metabolites were also hydroxylated metabolites as evidenced by LC/MS. Orobol was the only metabolite formed after incubation with CYP1A2. The two major product peaks after incubation of tangeretin with human microsomes were identical with 4'-hydroxy-5,6,7,8-tetramethoxyflavone and 5,6-dihydroxy-4',7,8-trimethoxyflavone, previously identified in rat urine in our laboratory. By comparison with UV spectra and LC/MS fragmentation patterns of previously obtained standards, the remaining metabolites eluting after 14, 17 and 20 min. were found to be demethylated at the 4',7-, 4',6-positions or hydroxylated at the 3'- and demethylated at the 4'-positions, respectively. Metabolism of tangeretin by recombinant CYP1A2, 3A4, 2D6 and 2C9 resulted in metabolic profiles that qualitatively were identical to those observed in the human microsomes. Inclusion of the CYP1A2 inhibitor fluvoxamine in the incubation mixture with human liver microsomes resulted in potent inhibition of tangeretin and genistein metabolism. Other isozymes-selective CYP inhibitors had only minor effects on tangeretin or genistein metabolism. Overall the presented observations suggest major involvement of CYP1A2 in the hepatic metabolism of these two flavonoids.

In vitro investigation of cytochrome P450-mediated metabolism of dietary flavonoids

Human and mouse liver microsomes and membranes isolated from Escherichia coli, which expressed cytochrome P450 (CYP) 1A2, 3A4, 2C9 or 2D6, were used to investigate CYP-mediated metabolism of five selected dietary flavonoids. In human and mouse liver microsomes kaempferol, apigenin and naringenin were hydroxylated at the 3'-position to yield their corresponding analogs quercetin, luteolin and eriodictyol, whereas hesperetin and tamarixetin were demethylated at the 4'-position to yield eriodictyol and quercetin, respectively. Microsomal flavonoid metabolism was potently inhibited by the CYP1A2 inhibitors, fluvoxamine and -naphthoflavone. Recombinant CYP1A2 was capable of metabolizing all five investigated flavonoids. CYP3A4 recombinant protein did not catalyze hesperetin demethylation, but showed similar metabolic profiles for the remaining compounds, as did human microsomes and recombinant CYP1A2, although the reaction rates in general were lower as compared to CYP1A2. CYP2C9 catalyzed the 4'-demethylation of tamarixetin, whereas CYP2D6 did not seem to play any role in the metabolism of the selected flavonoids. The major involvement in flavonoid metabolism of human CYP1A2, which mediates the formation of metabolites with different biochemical properties as compared to the parent compound and furthermore is known to be expressed very differently among individuals, raises the important question of whether individual differences in the CYP enzyme activity might affect the beneficial outcome of dietary flavonoids, rendering some individuals more or less refractory to the health-promoting potential of dietary flavonoids.

Potential health impacts of excessive flavonoid intake

Plant flavonoids are common dietary components that have many potent biological properties. Early studies of these compounds investigated their mutagenic and genotoxic activity in a number of in vitro assays. Recently, a renewed interest in flavonoids has been fueled by the antioxidant and estrogenic effects ascribed to them. This has led to their proposed use as anticarcinogens and cardioprotective agents, prompting a dramatic increase in their consumption as dietary supplements. Unfortunately, the potentially toxic effects of excessive flavonoid intake are largely ignored. At higher doses, flavonoids may act as mutagens, pro-oxidants that generate free radicals, and as inhibitors of key enzymes involved in hormone metabolism. Thus, in high doses, the adverse effects of flavonoids may outweigh their beneficial ones, and caution should be exercised in ingesting them at levels above that which would be obtained from a typical vegetarian diet. The unborn fetus may be especially at risk, since flavonoids readily cross the placenta. More research on the toxicological properties of flavonoids is warranted given their increasing levels of consumption.

Evaluation of the mutagenicity and antimutagenicity of forty-two 3-substituted flavones in the Ames test

The mutagenic and antimutagenic activities of forty-two synthetic flavones were assessed by the Ames test. The tested flavones included twenty-three 3-nitroflavones, eighteen 3-aminoflavones and the 3-chloroflavone. The mutagenicity was evaluated with Salmonella typhimurium TA100 and YG1042 (an overproducing nitroreductase and O-acetyltransferase TA100 strain) with and without metabolic activation (S9 mix). The antimutagenicity of the non mutagenic derivatives was evaluated against 11 known reference mutagens. A total of 39 synthetic flavones were mutagenic. The mutagenic activities ranged from 0.1 rev/nmole (4'-chloro-6-methoxy-3-nitroflavone) to 6240 rev/nmole (4'-methoxy-3, 3'-diaminoflavone). Two differences were found between the 3-amino and the 3-nitroflavones: (i) the mutagenicity of the 3-aminoflavones required the presence of the metabolic activation; (ii) the 3-amino derivatives were more mutagenic than their 3-nitro counterparts. Increased mutagenicity, as assessed with strain YG1042, was limited to 17/39 derivatives. The mutagenic activity was induced by the presence of the double bond at the 2,3-position for conjugation of the lone-pair electron with the carbonyl group on the 'C' ring. This mutagenicity was modulated by substituents at the 2'-position. Additional mutagenicity was brought by the aminoaromatic and nitroaromatic group reduction by bacterial nitroreductases and by the S9 mix; it was modulated by different substituents on the aromatic rings of the flavones. Three flavones: 3-chloroflavone (1C), 4'-hydroxy-3-nitroflavone (23N) and 2',3-diaminoflavone (2A) showed antimutagenic properties. Compound 1C was efficient against benzo(a)pyrene (BaP), 2-aminofluorene (2AF), 2-aminoanthracene (2AA), 4-nitroquinoline-1-oxide (4NQO) and 1-methyl-3'-nitro-1-nitrosoguanidine (MNNG). Compound 23N inhibited the mutagenicity of BaP and MNNG. The antimutagenic activity of 2A was limited to MNNG.

Biological effects of myricetin

1. Myricetin is a natural bioflavonoid whose occurrence in nature is widespread among plants. 2. It has been demonstrated to possess both antioxidative properties and prooxidative properties. 3. It is a potent anticarcinogen and antimutagen, although it has been shown to promote mutagenesis with the use of the Ames Test. 4. Its therapeutic potential and benefits in cardiovascular diseases and diabetes mellitus also are reviewed.

Genotoxicity testing of different types of beverages in the Drosophila wing Somatic Mutation And Recombination Test

Five wines and one brandy of Spanish origin as well as three herbal teas and ordinary black tea were tested for genotoxicity in the wing Somatic Mutation And Recombination Test (SMART) which makes use of the two recessive wing cell markers multiple wing hairs (mwh) and flare (flr3) on the left arm of chromosome 3 of Drosophila melanogaster. 3-day-old larvae trans-heterozygous for these two markers were fed the beverages at different concentrations and for different feeding periods using Drosophila instant medium. Somatic mutations or mitotic recombinations induced in the cells of the wing imaginal discs give rise to mutant single or twin spots on the wing blade of the emerging adult flies showing either the mwh phenotype or/and the flr phenotype. One of the red wines showed a clear genotoxic activity that was not due to its ethanol content. Two herbal teas (Urtica dioica, Achillea millefolium) and black tea (Camellia sinensis) proved to be weakly genotoxic as well. Furthermore, it was shown that quercetin and rutin, two flavonols present in beverages of plant origin, also exhibited weak genotoxic activity in the somatic cells of Drosophila. These results demonstrate that Drosophila in vivo somatic assays can detect the genotoxicity of complex mixtures such as beverages. In particular, it is possible to administer these test materials in the same form as that in which they are normally consumed.