Mutagenicity of hydrolysates of tea infusions

Myricetin enhances on apoptosis induced by serum deprivation in PC12 cells mediated by mitochondrial signaling pathway

Polyphenols have many beneficial effects and an effective disease therapeutic auxiliary drug. Previously, myricetin, a polyphenol, had been reported to possess various biological effects on human physiology. However, mechanism of myricetin on apoptosis induced in PC12 cells is still unclear. PC12 cells were treated with myricetin in two concentration levels comprising 0.1 and 1 μM under serum-free condition. As a result, morphological changes were observed using trypan blue assay. DNA fragmentation was determined by DNA ladder assay to evaluate DNA damage levels. Western blotting results showed that cytosolic cytochrome c which was released from mitochondria. Subsequently, tumor suppressor gene p53, pro-apoptotic and anti-apoptotic Bcl-2 family proteins Bax and Bcl-2 were expressed. The caspase cascade reaction was induced through caspase 3 and 9 expression. From these results, it is suggested that myricetin significantly enhanced the apoptosis induced by serum deprivation in a dose-dependent manner in PC12 cells.

Genotoxicity evaluation of the flavonoid, myricitrin, and its aglycone, myricetin

Myricitrin, a flavonoid extracted from the fruit, leaves, and bark of Chinese bayberry (Myrica rubra SIEBOLD), is currently used as a flavor modifier in snack foods, dairy products, and beverages in Japan. Myricitrin is converted to myricetin by intestinal microflora; myricetin also occurs ubiquitously in plants and is consumed in fruits, vegetables, and beverages. The genotoxic potential of myricitrin and myricetin was evaluated in anticipation of worldwide marketing of food products containing myricitrin. In a bacterial reverse mutation assay, myricetin tested positive for frameshift mutations under metabolic activation conditions whereas myricitrin tested negative for mutagenic potential. Both myricitrin and myricetin induced micronuclei formation in human TK6 lymphoblastoid cells under conditions lacking metabolic activation; however, the negative response observed in the presence of metabolic activation suggests that rat liver S9 homogenate may detoxify reactive metabolites of these chemicals in mammalian cells. In 3-day combined micronucleus/Comet assays using male and female B6C3F1 mice, no induction of micronuclei was observed in peripheral blood, or conclusive evidence of damage detected in the liver, glandular stomach, or duodenum following exposure to myricitrin or myricetin. Our studies did not reveal evidence of genotoxic potential of myricitrin in vivo, supporting its safe use in food and beverages.

Structural characteristics for superoxide anion radical scavenging and productive activities of green tea polyphenols including proanthocyanidin dimers

The purpose of this paper is to report structural characteristics for superoxide anion radical (O(2(-))) scavenging and productive activities of green tea polyphenols. (-)-Epicatechin 3-O-gallate (5), (-)-epigallocatechin (6), (-)-epigallocatechin 3-O-gallate (7), (+)-gallocatechin-(4alpha-->8')-epigallocatechin (8), and (-)-epigallocatechin-(2beta-->O-->7', 4beta-->8')-epicatechin 3'-O-gallate (9) were isolated from the tea plant Camellia sinensis L. (+)-Epigallocatechin-(2beta-->O-->7, 4beta-->8')-epicatechin (10) was prepared by hydrolyzing 9. The polyphenols, as well as commercially available pyrogallol (1), methyl gallate (2), (+)-catechin (3), (-)-epicatechin (4), and the flavonol myricetin (11), produced O(2(-)) in descending order 1, 6 asymptotically equal to11 asymptotically equal to8, 7, 10, 2 asymptotically equal to9, 5 asymptotically equal to4. In the polyphenols with the pyrogallol-type B-ring and/or galloyl group, electron-withdrawing substituents (carbonyl and ketal carbons) and/or intramolecular hydrogen bonding constituted structural characteristics against the autoxidation reaction. The O(2(-))-productive activity partially counteracted O(2(-))-scavenging activity. However, such structural characteristics appeared to enhance the scavenging activity, accordingly the polyphenols in effect served as O(2(-))-scavengers in descending order 9 asymptotically equal to7, 2, 11, 8, 10, 3 asymptotically equal to4. On the other hand, 6, having no such structural characteristic, acted as a O(2(-))-generator, as well as 1. Further assessments covering tannins (e.g., A-type proanthocyanidin dimer 9) are needed to identify which green tea polyphenols are the most desirable chemopreventive agents.

High-temperature beverages and foods and esophageal cancer risk--a systematic review

Coffee, tea and maté may cause esophageal cancer (EC) by causing thermal injury to the esophageal mucosa. If so, the risk of EC attributable to thermal injury could be large in populations in which these beverages are commonly consumed. In addition, these drinks may cause or prevent EC via their chemical constituents. Therefore, a large number of epidemiologic studies have investigated the association of an indicator of amount or temperature of use of these drinks or other hot foods and beverages with risk of EC. We conducted a systematic review of these studies and report the results for amount and temperature of use separately. By searching PubMed and the ISI, we found 59 eligible studies. For coffee and tea, there was little evidence for an association between amount of use and EC risk; however, the majority of studies showed an increased risk of EC associated with higher drinking temperature which was statistically significant in most of them. For maté drinking, the number of studies was limited, but they consistently showed that EC risk increased with both amount consumed and temperature, and these 2 were independent risk factors. For other hot foods and drinks, over half of the studies showed statistically significant increased risks of EC associated with higher temperature of intake. Overall, the available results strongly suggest that high-temperature beverage drinking increases the risk of EC. Future studies will require standardized strategies that allow for combining data and results should be reported by histological subtypes of EC.

Identification and characterization of inhibitors of human apurinic/apyrimidinic endonuclease APE1

APE1 is the major nuclease for excising abasic (AP) sites and particular 3′-obstructive termini from DNA, and is an integral participant in the base excision repair (BER) pathway. BER capacity plays a prominent role in dictating responsiveness to agents that generate oxidative or alkylation DNA damage, as well as certain chain-terminating nucleoside analogs and 5-fluorouracil. We describe within the development of a robust, 1536-well automated screening assay that employs a deoxyoligonucleotide substrate operating in the red-shifted fluorescence spectral region to identify APE1 endonuclease inhibitors. This AP site incision assay was used in a titration-based high-throughput screen of the Library of Pharmacologically Active Compounds (LOPAC¹²⁸⁰), a collection of well-characterized, drug-like molecules representing all major target classes. Prioritized hits were authenticated and characterized via two high-throughput screening assays – a Thiazole Orange fluorophore-DNA displacement test and an E. coli endonuclease IV counterscreen – and a conventional, gel-based radiotracer incision assay. The top, validated compounds, i.e. 6-hydroxy-DL-DOPA, Reactive Blue 2 and myricetin, were shown to inhibit AP site cleavage activity of whole cell protein extracts from HEK 293T and HeLa cell lines, and to enhance the cytotoxic and genotoxic potency of the alkylating agent methylmethane sulfonate. The studies herein report on the identification of novel, small molecule APE1-targeted bioactive inhibitor probes, which represent initial chemotypes towards the development of potential pharmaceuticals.

Tea consumption: fluid intake and bladder cancer risk in Southern Taiwan

OBJECTIVES

To determine whether tea consumption and intake of other beverages increases bladder cancer risk.

METHODS

A case-control study was conducted in Kaohsiung, Taiwan between August 1996 and June 1997. Index patients studied were consecutive patients with histologically confirmed, newly diagnosed bladder cancer in two major hospitals. For each patient, 4 controls were selected from patients with non-neoplastic and nonurologic diseases undergoing surgical operations in the same hospital and individually matched by sex, age, and date of admission. Using a structured questionnaire, a trained interviewer interviewed 40 patients and 160 controls. Conditional logistic regression analysis adjusting for ethnicity, family history, and smoking status and matching variables were used to estimate the odds ratio (OR) and 95% confidence interval (CI).

RESULTS

Tea consumption overall was associated with increased bladder cancer risk (OR 3.29, 95% CI 1.34 to 8.05). Compared with non-tea drinkers, the odds ratios of bladder cancer for oolong tea drinkers was 3.00 (95% CI 1.20 to 7.47); for non-oolong tea drinkers (black and/or other green tea), it was 14.86 (95% CI 2.13 to 103.83). The risk was greater among those who began to drink tea before age 40 (OR 9.50, 95% CI 2.39 to 37.75) and those who had been drinking tea for more than 30 years (OR 17.75, 95% CI 3.00 to 105.17). Coffee, tap water, and alcohol consumption were associated with a slightly increased risk, and both soy juice and rice juice consumption were associated with reduced risk; none of these odds ratio estimates were statistically significant, however.

CONCLUSIONS

Our results suggest that tea consumption is associated with an increased risk of bladder cancer.

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.

Risk factors for renal cell carcinoma in Denmark. I. Role of socioeconomic status, tobacco use, beverages, and family history

Risk factors for renal cell carcinoma were examined in a population based case-control study in Denmark. A total of 368 cases and 396 age- and gender-matched controls were interviewed in their homes. Increased risk was associated with low socioeconomic status. For men, an increasing risk with decreasing socioeconomic status was seen (odds ratio [OR] = 2.2, 95 percent confidence interval [CI] = 1.0-4.6 for men in the lowest socioeconomic stratum cf the highest). For women, the risk was lower in the highest socioeconomic stratum compared with the rest (OR = 2.4, CI = 0.9-5.9 for the lowest strata cf the highest). Cigarette smoking was a risk factor in men with an OR = 2.3 (CI = 1.1-5.1) for cigarette smokers with a total consumption of more than 40 pack-years compared with nonsmokers. Family history of kidney cancer was associated with an increased risk in both genders (for men, OR = 4.1, CI = 1.1-14.9; for women, OR = 4.8, CI = 1.0-23). Observations were inconsistent regarding coffee and alcohol consumption, and we found no association with tea drinking. The association with socioeconomic status remained after adjustment for other factors.

Teas and tea components as inhibitors of carcinogen formation in model systems and man

BACKGROUND

Epidemiological evidence points to a cancer protective role of green-yellow-orange vegetables and fruits. The involvement of teas as a protective factor in carcinogenesis has not received the attention it seems to merit. To gain relevant information, attempts were made to stimulate in vitro those conditions to which human groups are actually exposed.

METHODS

The inhibitory effects of infusions of Chinese, Japanese, and Ceylonese teas were examined by adding them to a nitrosation mixture consisting of 0.8 mg sodium nitrite and 340 mg equivalent of a widely consumed salt-preserved fish (Pak Wik) and estimating the frequency of mutants in TA 1535 strain of Salmonella typhimurium.

RESULTS

The tea samples exhibited a strong inhibitory effect at concentrations that are actually ingested by man. A comparable inhibition was obtained by several tea phenolics. A second series of experiments dealt with the formation of nitrosoproline (NPRO) which can be strongly inhibited in vitro by the tea infusions and tea phenolics. The effects of the tea infusions and caffeic acid on the endogeneous formation of NPRO in man were examined by having volunteers ingest 300 mg sodium nitrate and 30 min later 300 mg proline, collecting urine samples over a 24-hr period, and estimating the excreted NPRO. The tested teas, at doses regularly consumed, again exerted a strong inhibitory effect on endogeneous NPRO formation in humans. Comparable inhibitory effects were obtained by ingesting caffeic acid, chlorogenic acid, or ferulic acid with the nitrosation mixture.

CONCLUSIONS

These results indicate that the simultaneous intake of teas with food products that are being nitrosated within the stomach of human subjects should exert a protective, beneficial effect.

Implication of active oxygen species in the direct-acting mutagenicity of tea

The present study shows that the L-arabinose resistance test with Salmonella typhimurium detects that freshly infused tea is highly mutagenic in the absence of mammalian microsomal activation. Both the mutagenesis protocol (preincubation test) and the additional genetic characteristics of the bacterial tester strain (excision repair deficiency, normal lipopolysaccharide barrier and the presence of plasmid pKM101) were critical factors in the optimal induction by tea of forward mutations to L-arabinose resistance. The TA104 strain--a histidine auxotroph specific to oxidative mutagens--was the most sensitive tester strain of the Ames test to the direct-acting mutagenicity of tea. In comparison with strain TA104, the sensitivity of the Ara forward mutation test was 18 times higher, one cup of tea (200 ml) inducing 3 X 10(6) AraR mutants. More than 90% of the mutagenicity of 150 microliter of a fresh tea infusion, or that of the equivalent amount (1.32 mg) of the corresponding lyophilized residue, was suppressed by 10 units of catalase. In contrast to catalase, superoxide dismutase was rather ineffective. These results indicate that hydrogen peroxide is produced in tea solutions, playing an essential role in its mutagenicity. In comparison, the role of superoxide anion seems negligible. Like catalase, the chelating agent DETAPAC showed a protective effect with respect to the mutagenicity of tea, suggesting the additional implication of hydroxyl radicals.

The role of non-nutritive dietary constituents in carcinogenesis

Very low levels of a large variety of non-nutritive chemicals occur in the diet. Among those that occur naturally are metabolites of molds (for example, mycotoxins) and bacteria (for example, nitrosamines) and natural constituents of plants (for example, pyrrolizidine alkaloids). Many of these are occasional contaminants, whereas others are normal components of relatively common foods. Some compounds (for example, aflatoxin, nitrosamines, and hydrazones) have been found to be carcinogenic in laboratory animals and mutagenic in bacterial and other systems, thereby posing a potential risk to humans. However, there have been very few definitive epidemiologic studies. Therefore, further investigations are necessary to determine the significance of these experimental findings for humans. It is apparent that many foods naturally contain substances with mutagenic properties and that some substances found in foods can enhance or inhibit the mutagenic activity of other compounds. Furthermore, mutagens can be formed during the cooking or processing of foods. However, caution is needed in the interpretation of these findings. Although mutagens by definition are "suspect" carcinogens, many mutagens detected in foods have not been adequately tested for carcinogenicity, and therefore their significance for human health cannot be fully assessed. With the exception of studies on non-nutritive sweeteners like saccharin and cyclamate, or those on nitrate and nitrite, very few epidemiologic studies have been conducted to examine the effect of food additives on cancer risk. Of the few direct food additives that have been tested and found to be carcinogenic in animals, all except saccharin have been banned from use in the food supply. Minute residues of a few indirect additives that are known either to produce cancer in animals (for example, vinyl chloride and acrylonitrile) or to be carcinogenic in humans (for example, vinyl chloride) are occasionally detected in foods. Thus far, the increasing use of food additives does not seem to have contributed significantly to the overall cancer risk for humans. However, the relatively short duration of use of many of these substances and the inadequacy of the data base preclude definitive conclusions. Very low levels of a large and chemically diverse group of substances--environmental contaminants (for example, residues of pesticides, polycyclic aromatic hydrocarbons, and traces of toxic metals)--may be present in foods.(ABSTRACT TRUNCATED AT 400 WORDS)

Genotoxicity of cocoa in a series of short-term assays

Cocoa powder was evaluated for genotoxic activity and found to be inactive in the Ames assay, the mouse lymphoma assay, cytogenetic assays measuring chromosome breakage and SCE, and a cell transformation assay using Balb/c-3T3 cells. Although pure theobromine has been shown to be active in some of these test procedures, the levels of this methylxanthine present in cocoa powder were insufficient to elicit responses in this battery of tests.

Absence of overt toxicity from feeding the flavonol, quercetin, to rainbow trout (Salmo gairdneri)

The toxicity of the plant flavonol, quercetin, to rainbow trout (Salmo gairdneri) was investigated. Quercetin, which had been confirmed to be mutagenic in the Ames Salmonella/mammalian microsome test, was fed to trout at levels of 1 or 5% in the diet for 8 months. Survival, growth and feed conversion efficiency, selected haematological parameters and the relative weights of heart, liver and spleen were unaffected by the ingestion of quercetin, and there were no histopathological changes in any of the tissues examined.

Mutagen content of wines contaminated with common yeasts

Wines exhibiting a microbial haze were collected and their microbial contents identified. Contaminant yeast species were cultured in grape musts under controlled conditions and extracts of the resultant wines were assayed for mutagen content using four strains of Salmonella in the Ames Salmonella/microsome/faecalase system. The wine extracts exhibited some toxicity to Salmonella but no mutagen content. It would appear that mutagen content is more a function of the grape species and must preparation than of microbial metabolism during fermentation.

Time-course of mutagenicity due to flavonols in a pickled vegetable

The mutagenicity of the leafy vegetable, Takana (Brassica juncia var. integrifolia), pickled with salt for various durations was examined. The mutagenicity increased with increasing duration of pickling time, and analysis by HPLC showed that is was caused by mutagenic flavonols. The flavonols contained in the fresh Takana as glycosides were found to be freed by pickling. This was confirmed by acid hydrolysis.

Mutagenic activities of gentisin and isogentisin from Gentianae radix (Gentianaceae)

The mutagenic activities of 2 hydroxyxanthones, gentisin and isogentisin, obtained from the methanol extract of Gentianae radix (Gentianaceae) were investigated. The methanol extract of Gentianae radix, which showed mutagenicity in the Ames test in Salmonella typhimurium strain TA100 with S9 mix, was fractionated by column chromatography on Sephadex LH-20, and the fractions were purified by preparative TLC and column chromatography on polyamide. 2 mutagenic materials thus obtained, S1 and S2, each gave a single band on TLC. Identification of S1 and S2 was accomplished by comparing the analytical (mps, elementary analyses) and spectral (UV, IR, mass, NMR) results for S1 and S2 with literature data for gentisin and isogentisin. At doses below 10 micrograms, S1 (gentisin) and S2 (isogentisin) had similar specific mutagenic activities. At doses of over 10 to 50 micrograms, the mutagenic activities of S2 and S1 were 19.1 and 6.94 revertants per microgram respectively. This much lower activity of S1 than S2 may be a result of its poor solubility owing to the presence of the OMe group at C-3. The combined yield of S1 and S2 was about 76 mg (40 mg as S1 and 36 mg as S2), which accounted for 76% of the content of mutagenic compounds (100 mg) estimated roughly from the total mutagenic activity in the extract of the starting materials (100 g).

Activation of rutin by human oral bacterial isolates to the carcinogen-mutagen quercetin

Oral streptococci, isolated from the mouths of 2 healthy subjects, hydrolysed innocuous rutin, a flavonoid glycoside, to its genotoxic aglycon quercetin, in vitro. The isolates were identified as Streptococcus milleri. The glycosidase, rutinase, was studied in cell-free extracts derived from one of the isolates, grown anaerobically in batch cultures by the use of a bioassay, the Ames test, in which S-9 was replaced by the cell-free extracts. This streptococcal rutinase was: constitutive, partly inducible, cytosolic, most active for rutin and most active at pH 6.5. Type-culture collection strains of other oral streptococci (Streptococcus salivarius ATCC 25975 and Streptococcus mutans strain 6715-10) showed no capacity for rutin degradation. A hypothesis for a novel role of the oral microflora in a disease process other than caries and periodontal disease, namely intra-oral cancer, is presented. The possibility of a bacterial liberation of the genotoxic quercetin in situ could be but one example of its involvement in the local carcinogenic process.

Inhibitory effects of phenolics, teas and saliva on the formation of mutagenic nitrosation products of salted fish

The objectives of this study were to simulate in vitro some of the conditions that may prevail in man during the ingestion of a meal and to quantitate the inhibitory effect of phenolics and phenolic-containing beverages on the formation of mutagenic nitrosation products. The test system consisted of nitrosating (pH 2, 1 h, 37 degrees C) an aqueous fraction of a salt-preserved Chinese fish (Pak Wik) with or without the inhibitors to be tested and estimating the frequency of his+ revertants per survivor of Salmonella typhimurium (strain TA1535). The phenolics and teas were added to the nitrosation mixture. Catechin, chlorogenic acid, gallic acid, pyrogallol and tannic acid suppressed the formation of mutagenic nitrosation products. The inhibitory efficiency was comparable to that of ascorbic acid. A Japanese, a Chinese and a Ceylonese tea also prevented the formation of mutagenic nitrosated fish products at doses which are usually consumed by man. Moreover, saliva exerted an inhibitory effect. The inhibitory effect was not additive when the phenolics or saliva were added concurrently to the nitrosation mixture. The possibility that phenolics are involved in the apparent chemopreventive effect of fruits and vegetables is discussed.

Inhibition of mutagenicity of a model nitrosation reaction by naturally occurring phenolics, coffee and tea

Several plant phenolics, one instant coffee, one instant decaffeinated coffee, one roasted coffee, one Japanese tea, one black Indian tea, and one Chinese tea were examined for their inhibitory properties on mutagenicity resulting from the nitrosation of methylurea. Mutagenicity was estimated as the number of his+ revertants per survivor of Salmonella typhimurium TA1535 which was exposed in suspension to the nitrosation mixtures and the modulating agents for 20 min. Tannic acid, gallic acid and chlorogenic acid suppressed the mutagenicity of the model nitrosation system at concentrations similar to or even lower than ascorbic acid. The three tested coffees and three tested teas exerted an inhibitory effect on the mutagenicity of the test system at doses at which they are consumed.

Mutagenicity of hydrolysates of citrus fruit juices

Hydrolysates of citrus fruit juice were mutagenic according to the Ames test. The citrus fruit juices were hydrolysed with 1 M HCl, hesperidinase, naringinase and human intestinal bacteria. The hydrolysates were successively extracted with n-hexane, chloroform, diethyl ether and ethyl acetate. The mutagenicities of extracts were assayed by the Ames test, and the mutagens were analysed by gas chromatography and mass spectrometry (GC-MS). Mutagenicities of hydrolysates of citrus fruit juice were found in both the chloroform extracts and the ether extracts. The chloroform extracts were mutagenic to TA98 and TA100 with S9 mix, and the ether extracts were mutagenic to TA98 and TA100 with or without S9 mix. Some known flavonols such as kaempferol and quercetin were detected in the extracts of the hydrolysates by GC-MS. It is suggested that the mutagenicity of the extracts originated from those flavonols in the citrus fruit juice.

Nonmutagenicity in vivo of the food flavonol quercetin

Mice given quercetin per os at concentrations that were about 10(3) times greater than the estimated average human intake of total flavonols were tested for mutagenicity with 2 complementary in vivo mutagenicity/carcinogenicity screening tests--the micronucleus test and the host-mediated assay employing the Ames Salmonella tester strain TA 98 as indicator organism. No mutagenic effect was detected with either test.

Mutagenicity screening of foods I. Results with beverages

Following a number of recent reports on the presence of mutagens in certain foods, a general survey of the mutagenic potential of a wide variety of food products has been initiated. Here, results for samples of 28 widely consumed beverages from 13 general categories are reported. Each sample was concentrated and fractionated by polarity and solubility to give up to seven fractions, each of which was assayed for mutagenic potential with Salmonella typhimurium TA98 and TA100 +/- fortified liver homogenate. Fractions showing evidence of either mutagenicity or toxicity were retested at the same and lower concentrations. The utility of the fractionation procedure and the sensitivity of the screening strategy were established by assaying six beverages spiked with known mutagens prior to fractionation. Statistical analysis of the data resulted in positive findings for seven beverages, although confirmation of these results through analysis of a second sample was obtained only for red wine, grape juice, and instant coffee. The remaining 21 beverages showed no strong evidence of mutagenic activity. For those foods for which the variation among replicate plates was largest, the false-positive rate for the two-stage screening procedure employed was estimated to be less than 1% while the false-negative rate for a beverage inducing a threefold increase in the background mutation rate was conservatively estimated to be limited to 14%.

A comparative genotoxicity study of chlorogenic acid (3-0-caffeoylquinic acid)

Chlorogenic acid, a compound which occurs naturally in many food items, was assayed for genotoxic activity in 3 different test systems: reverse mutations in the preincubation test with Salmonella typhimurium, gene conversion with Saccharomyces cerevisiae strain D7, and chromosome aberrations in Chinese hamster ovary (CHO) cells. Chlorogenic acid was directly convertogenic and clastogenic, but lacked a mutagenic capacity in the Salmonella bioassay. The transition metal Mn2+ enhanced the clastogenic and convertogenic activity of chlorogenic acid. In the presence of Mn2+ (10(-4)M), chlorogenic acid increased the frequency of his+ revertants in TA98 and TA100 strains of S. typhimurium. Caffeic acid and, to a lesser degree, quinic acid, which are components of chlorogenic acid, also showed genotoxic activity. The results show the importance of using several assays in combination with transition metals when testing for genotoxicity.