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ELLAGIC
ACID - scientific studies III
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Low
concentrations of quercetin and ellagic acid synergistically influence
proliferation, cytotoxicity and apoptosis in MOLT-4 human leukemia
cells
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Mertens-Talcott SU, Talcott ST, Percival SS.
Food Science and Human Nutrition Department, University of Florida,
Gainesville, FL 32611, USA.
PJ Nutr. 2003 Aug;133(8):2669-74.
Little information is available regarding possible synergistic or
antagonistic biochemical interactions among polyphenols contained
in fruits and vegetables. Identifying potential interactions among
these compounds may help to define the efficiency of polyphenol-containing
foods in cancer prevention as related to structure-function activity
of the compounds. The objective of this study was to
investigate interactions between quercetin and ellagic acid, two
polyphenolics that are present predominantly in small fruits, on
cell death and proliferation-related variables in the MOLT-4 human
leukemia cell line. Assays were performed to determine cell cycle
kinetics, proliferation, apoptotic DNA-fragmentation and caspase-3-activity
after 12, 24 and 48 h. Ellagic acid significantly potentiated the
effects of quercetin (at 5 and 10 micro mol/L each) in the reduction
of proliferation and viability and the induction of apoptosis. Significant
alterations in cell cycle kinetics were also observed. The synergy
was confirmed by an isobolographic analysis of the cell
proliferation data. The interaction of ellagic acid and quercetin
demonstrated an enhanced anticarcinogenic potential of polyphenol
combinations, which was not based solely on the additive effect
of individual compounds, but rather on synergistic biochemical interactions.
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Intestinal epithelial cell accumulation of the cancer preventive polyphenol
ellagic acid-extensive binding to protein and DNA |
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Whitley AC, Stoner GD, Darby MV, Walle T.
Department of Cellular and Molecular Pharmacology and Experimental
Therapeutics, Medical University of South Carolina, 173 Ashley Avenue,
PO Box 250505, 29425, Charleston, SC, USA
Biochem Pharmacol. 2003 Sep 15;66(6):907-915.
Ellagic acid (EA), a polyphenol present in many berries, has been
demonstrated to be preventive of esophageal cancer in animals both
at the initiation and promotion stages. To be able to extrapolate
these findings to humans we have studied the transcellular absorption
and epithelial cell accumulation of [14C]EA in the human intestinal
Caco-2 cells. The apical (mucosal) to basolateral
(serosal) transcellular transport of 10microM [14C]EA was minimal
with a P(app) of only 0.13x10(-6)cm/s, which is less than for the
paracellular transport marker mannitol. In spite of observations
of basolateral to apical efflux, Caco-2 cell uptake studies showed
high accumulation of EA in the cells (1054+/-136pmol/mg protein),
indicating facile absorptive transport across the apical
membrane. Surprisingly, as much as 93% of the cellular EA was irreversibly
bound to macromolecules (982+/-151pmol/mg protein). To confirm the
irreversible nature of the binding to protein, Caco-2 cells treated
with 10microM [14C]EA were subjected to SDS-PAGE analysis. This
resulted in radiolabeled protein bands trapped in the stacking gel,
consistent with [14C]EA-crosslinked proteins. Treatment of Caco-2
cells with 10microM [14C]EA also revealed irreversible binding of
EA to cellular DNA as much as five times higher than for protein
(5020+/-773pmol/mg DNA). Whereas the irreversible binding to protein
required oxidation of EA by reactive oxygen species, this did not
seem to be the case with the DNA binding. The avid irreversible
binding to cellular DNA and protein may be the reason for its highly
limited transcellular absorption. Thus, EA appears to accumulate
selectively in the epithelial cells of the aerodigestive tract,
where its cancer preventive actions may be displayed.
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IGF-II down regulation associated cell cycle arrest in colon cancer
cells exposed to phenolic antioxidant ellagic acid |
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Narayanan BA, Re GG.
American Health Foundation, 1, Dana Road Valhalla, NY 10595,
USA.
Anticancer Res. 2001 Jan-Feb;21(1A):359-64.
Altered cell and tissue differentiation is characteristic of premalignant
lesions long before they become invasive and metastatic. One approach
to controlling preneoplastic lesions is to block their expansion
with non-toxic agents that suppress cell proliferation and induce
apoptosis. Here, we show that ellagic acid, a natural, dietary phenolic
antioxidant when given at 10(-5) M for 48 hours to colon cancer
cells (SW 480), induced down regulation of insulin like growth factor
IGF-II, activated p21(waf1/Cip1), mediated a cumulative effect on
G1/S transition phase and caused apoptotic cell death. SW480 colon
cancer cells expressed significant mRNA levels for the mitogenic
insulin like growth factor (IGF-II). Collectively, these observations
suggest that growth inhibition by ellagic acid is
mediated by signaling pathways that mediate DNA damage, triggers
p53, which in turn activates p21 and at the same time alters the
growth factor expression, resulting in the down regulation of IGF-II.
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Ellagic [correction of ellagica] acid inhibits arylamine N-acetyltransferase
activity and DNA adduct formation in human bladder tumor cell lines
(T24 and TSGH 8301) |
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Lin SS, Hung CF, Tyan YS, Yang CC, Hsia TC, Yang
MD, Chung JG.
Department of Radiological Technology, Chungtai Institute of
Health Sciences and Technology, Taichung, Taiwan, Republic of China.
Urol Res. 2001 Dec;29(6):371-6. Urol Res. 2001 Dec;29(6):371-6.
The fact that vitamin C (ascorbic acid) exhibits a protective effect
in certain types of cancer is well documented. Our previous studies
demonstrated that human bladder tumor cell line (T24) has N-acetyltransferase
(NAT) activity in cytosols and intact cells. The present studies
examined the inhibition of arylamine NAT activity and carcinogen
(2-aminofluorene)-DNA adduct formation by ellagic acid (EA) in human
bladder tumor cell lines (T24 and TSGH 8301). Two assay systems
were performed, one with cellular cytosols (9,000 g supernatant),
the other with intact bladder tumor cell suspensions. NAT activity
and 2-aminofluorene-DNA adduct formation in T24 and TSGH 8301 cells
was inhibited by EA in a dose-dependent manner in both systems,
i.e.. the greater the concentration of EA in the reaction the greater
the inhibition of NAT activity (dose- and time-course dependent
effects). The data also indicated that EA decreased the apparent
Km and Vmax of NAT enzymes from T24 and TSGH 8301 cells in cytosols.
NAT activity and 2-aminofluorene-DNA adducts in T24 is higher than
in TSGH 8301. This report is the first to demonstrate that EA affects
human bladder tumor cell NAT activity.
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Effect of chemopreventive agents on DNA adduction induced by the potent
mammary carcinogen dibenzo[a,l]pyrene in the human breast cells MCF-7 |
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Smith WA, Freeman JW, Gupta RC. Graduate Center
for Toxicology, 354 Health
Sciences Research Building, University of Kentucky Medical Center,
Lexington, KY 40536-0305, USA.
Mutat. Res. 2001 Sep 1; 480-481: 97-108.
Over 1500 structurally diverse chemicals have been identified which
have potential cancer chemopreventive properties. The efficacy and
mechanisms of this growing list of chemoprotective agents may be
studied using short-term bioassays that employ relevant
end-points of the carcinogenic process. In this study, we have examined
the effects of eight potential chemopreventive agents, N-acetylcysteine
(NAC), benzylisocyanate (BIC), chlorophyllin, curcumin, 1,2-dithiole-3-thione
(D3T), ellagic acid, genistein, and
oltipraz, on DNA adduction of the potent mammary carcinogen dibenzo[a,l]pyrene
(DBP) using the human breast cell line MCF-7. Bioactivation of DBP
by MCF-7 cells resulted in the formation of one predominant (55%)
dA-derived and several other dA- or
dG-derived DNA adducts. Three test agents, oltipraz, D3T, and chlorophyllin
substantially (>65%) inhibited DBP-DNA adduction at the highest
dose tested (30 microM). These agents also significantly inhibited
DBP adduct levels at a lower dose of 15 microM, while oltipraz was
effective even at the lowest dose of 5 microM. Two other agents,
genistein and ellagic acid were moderate (45%) DBP-DNA adduct inhibitors
at the highest dose tested, while NAC, curcumin, and BIC were ineffective.
These studies indicate that the MCF-7 cell line is an applicable
model to study the efficacy of cancer chemopreventive agents in
a human setting. Moreover, this
model may also provide information regarding the effect of the test
agents on carcinogen bioactivation and detoxification enzymes.
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p53/p21(WAF1/CIP1)
expression and its possible role in G1 arrest and apoptosis in ellagic
acid treated cancer cells |
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Narayanan B.A.; Geoffroy O.; Willingham M.C.; Re
G.G.; Nixon D.W.
B.A. Narayanan, Hollings Cancer Center, Medical University South
Carolina, 171 Ashley Ave., Charleston, SC 29425 United States
Cancer Letters ( CANCER LETT. ) (Ireland) 1999, 136/2 (215-221)
Ellagic acid is a phenolic compound present in fruits and nuts including
raspberries, strawberries and walnuts. It is known to inhibit certain
carcinogen-induced cancers and may have other chemopreventive properties.
The effects of ellagic acid on cell cycle events and apoptosis were
studied in cervical carcinoma (CaSki) cells. We found that ellagic
acid at a concentration of 10sup -sup 5 M induced G1 arrest within
48 h, inhibited overall cell growth and induced apoptosis in CaSki
cells after 72 h of treatment. Activation of the cdk inhibitory protein
p21 by ellagic acid suggests a role for ellagic acid in cell cycle
regulation of cancer cells. |
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Inhibitory
effects of ellagic acid on the direct-acting mutagenicity of aflatoxin
B1 in the Salmonella microsuspension assay. |
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Loarca-Pina G, Kuzmicky PA, de Mejia EG, Kado NY
Departamento de Investigacion y Posgrado, Facultad de Quimica,
Universidad Autonoma de Queretaro, Qro., Mexico.
Mutat Res 1998 Feb 26;398(1-2):183-7
Ellagic acid (EA) is a phenolic compound that exhibits both antimutagenic
and anticarcinogenic activity in a wide range of assays in vitro and
in vivo. It occurs naturally in some foods such as strawberries, raspberries,
and grapes. In the previous work, we used the Salmonella microsuspension
assay to examine the antimutagenicity of EA against the potent mutagen
aflatoxin B1 (AFB1) using tester strains TA98 and TA100. Briefly,
the microsuspension assay was
approximately 10 times more sensitive than the standard Salmonella/microsome
(Ames) test in detecting AFB1 mutagenicity, and EA significantly inhibited
mutagenicity of all AFB1 doses in both tester strains with the addition
of S9. The greatest inhibitory effect of EA on AFB1 mutagenicity occurred
when EA and AFB1 were incubated together (with metabolic enzymes).
Lower inhibition was apparent when the cells were first incubated
with EA followed by a second incubation with AFB1, or when the cells
were first incubated with AFB1 followed by a second incubation with
EA alone, all with metabolic enzymes. The result of these sequential
incubation studies indicates that one mechanism of inhibition could
involve the formation of an AFB1-EA chemical complex. In the present
study, we further examine the effect of EA on AFB1 mutagenicity, but
without the addition of exogenous metabolic enzymes. We report the
mutagenicity of AFB1 in the microsuspension assay using TA98 and TA100
without the addition of S9.
Neither the concentrations of AFB1 (0.6, 1.2, and 2.4 microg/tube)
nor the concentrations of EA (0.3, 1.5, 3, 10, and 20 microg/tube)
were toxic to the bacteria. The results indicate that AFB1 is a direct-acting
mutagen, and that EA
inhibits AFB1 direct-acting mutagenicity. |
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Structure-function
relationships of the dietary anticarcinogen ellagic acid |
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Barch D.H.; Rundhaugen L.M.; Stoner G.D.; Pillay
N.S.; Rosche W.A.
Department of Medicine, Lakeside Veterans Affairs Med Center, Northwestern
University Med School,Chicago, IL 60611 United States
Carcinogenesis ( CARCINOGENESIS ) (United Kingdom) 1996, 17/2 (265-269)
Ellagic acid is a complex planar molecule which demonstrates a variety
of anticarcinogenic activities. Ellagic acid has been shown to inhibit
the CYP1A1-dependent activation of benzo(a)pyrene; to bind to and
detoxify the diol-epoxide of benzo(a)pyrene; to bind to DNA and reduce
the formation of 0sup 6-methylguanine by methylating carcinogens;
and to induce the phase II detoxification enzymes glutathione S-transferase
Ya and NAD(P)H:quinone reductase. Chemical analogs of ellagic acid
were synthesized to examine the relationship between the hydroxyl
and lactone groups of the ellagic acid molecule and its different
anticarcinogenic activities. These studies demonstrated that both
the 3-hydroxyl and the 4-hydroxyl groups were required for ellagic
acid to directly detoxify the diol-epoxide of benzo(a)pyrene, while
only the 4-hydroxyl groups were necessary for ellagic acid to inhibit
CYP1A1-dependent benzo(a)pyrene hydroxylase activity. Induction of
glutathione S-transferase Ya and NAD(P):quinone reductase required
the lactone groups of ellagic acid, but the hydroxyl groups were not
required for the induction of these phase II enzymes. In addition,
the
lactone groups, but not the hydroxyl groups, were required for the
analogs to reduce the carcinogen-induced formation of 0sup 6-methylguanine.
Thus, different portions of the ellagic acid molecule are responsible
for its different putative anticarcinogenic activities. |
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The
dietary anticancer agent ellagic acid is a potent inhibitor of DNA
topoisomerases in vitro |
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Constantinou A.; Stoner G.D.; Mehta R.; Rao K.;
Runyan C.; Moon R.
Surgical Oncology, University of Illinois, College of Medicine,
840 South Wood St.,Chicago, IL 60612 United States
Nutrition and Cancer (United States) 1995, 23/2 (121-130)
Ellagic acid and 12 related agents have been tested for their ability
to inhibit the activities of human DNA topoisomerase (topo) I and
II. Using specific in vitro assays, we found ellagic acid and flavellagic
acid to be potent inhibitors of the catalytic activities of the two
topoisomerases. The minimum concentration required to inhibit >=
50% of catalytic activity (IC$D5inf 0) of ellagic acid was etermined
at 0.6 and 0.7 mug/ml for topo I and topo II, respectively. Flavellagic
acid's IC50 was determined at 3.0 and 3.6 mug/ml for topo I and topo
II, respectively. Unlike topoisomerase poisons, these two plant phenols
did not trap the enzyme-DNA reaction intermediate, known as the cleavable
complex. In contrast, ellagic acid prevented other topo I and topo
II poisons from stabilizing the cleavable complex, suggesting that
the mode of its action is that of an antagonist. Structure-activity
studies identified the 3,3'-hydroxyl groups and the lactone groups
as the most essential elements for the topoisomerase inhibitory actions
of plant phenols. On the basis of these findings and other properties
of ellagic acid, a mechanistic model for the documented anticarcinogenic
effects of the agent is proposed. |
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Antimutagenic
effects of polyphenolic compounds |
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Teel R.W.; Castonguay A.
Dept of Physiology and Pharmacology, School of Medicine, Loma Linda
University,Loma Linda, CA 92350 United States
Cancer Letters ( CANCER LETT. ) (Ireland) 1992, 66/2 (107-113)
Smokers expose themselves to potent carcinogens daily. One of them
is the nicotine-derived nitrosamine 4-(methylnitrosamino)1-(3-pyridyl)-1-butanone
(NNK). Since estimates are that humans consume 1 g of phenolic compounds/day,
we investigated the inhibitory effects of five structurally related
polyphenolic compounds on the mutagenicity of NNK in Salmonella typhimurium
TA1535. NNK at a concentration of 80 mM was activated by hamster liver
microsomes. The antimutagenic effilcacies were dose-related between
the non-toxic concentrations of 0.1 and 0.5 mmol/dish in the following
order: esculetin > ellagic acid > (+)-catechin > propyl gallate
> (-)esculin. At the highest non-toxic dose tested (0.5 mmol/dish),
these polyphenolics inhibited mutagenesis in TA1535 by 77%, 67%, 62%,
59% and 53%, respectively. The results of this study demonstrated
that polyphenolic compounds may inhibit the activation of NNK. |
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Protective
effects of antioxidants on experimental liver injuries |
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Suzuki M.; Kumazawa N.; Ohta S.; Kamogawa A.; Shinoda
M.
Faculty of Pharmaceutical Science, Hoshi University, 2-4-41 Ebara,
Shinagawa-ku, Tokyo 142 Japan
Yakugaku Zasshi ( YAKUGAKU ZASSHI ) (Japan) 1990, 110/9 (697-701)
Protective effects of 14 kinds of antioxidant on liver injury induced
by carbon tetrachloride (CCl4) were investigated in terms of serum
enzyme activities and bilirubin concentration. Consequently, the significant
protective effects were found in sesamol, ellagic acid, cysteamine
and cysteine. These antioxidants clearly decreased the lipid peroxide
in the liver tissue. The protective effects on CCl4-induced liver
injury in vivo were independent of the inhibitory activities on lipid
peroxidation in hepatic mitochondria fraction in vitro. |
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Chemoprevention
of esophageal tumorigenesis by dietary administration of lyophilized
black raspberries
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Kresty LA, Morse MA, Morgan C, Carlton PS, Lu J,
Gupta A, Blackwood M, Stoner GD.
Division of Environmental Health Sciences, School of Public Health,
Comprehensive Cancer Center, The Ohio State University, Columbus,
Ohio 43210, USA.
Cancer Res. 2001 Aug 15;61(16):6112-9.
Fruit and vegetable consumption has consistently been associated with
decreased risk of a number of aerodigestive tract cancers, including
esophageal cancer. We have taken a "food-based" chemopreventive
approach to evaluate the inhibitory potential of
lyophilized black raspberries (LBRs) against N-nitrosomethylbenzylamine
(NMBA)-induced esophageal tumorigenesis in the F344
rat, during initiation and postinitiation phases of carcinogenesis.
Anti-initiation studies included a 30-week tumorigenicity bioassay,
quantification of DNA adducts, and NMBA metabolism study. Feeding
5 and 10% LBRs, for 2 weeks prior to NMBA treatment (0.25 mg/kg, weekly
for 15 weeks) and throughout a 30-week bioassay, significantly reduced
tumor multiplicity (39 and 49%, respectively). In a short-term bioassay,
5 and 10% LBRs inhibited formation of the promutagenic adduct O(6)-methylguanine
(O(6)-meGua) by 73 and 80%, respectively, after a single dose of NMBA
at 0.25 mg/kg. Feeding 5% LBRs also significantly inhibited adduct
formation (64%) after NMBA administration at 0.50 mg/kg. The postinitiation
inhibitory potential of berries was evaluated in a second bioassay
with sacrifices at 15, 25, and 35 weeks. Administration of LBRs began
after NMBA treatment (0.25 mg/kg, three times per week for 5 weeks).
LBRs inhibited tumor progression as evidenced by significant reductions
in the formation of preneoplastic esophageal lesions, decreased tumor
incidence and multiplicity, and reduced cellular proliferation. At
25 weeks, both 5 and 10% LBRs significantly reduced tumor incidence
(54 and 46%, respectively), tumor multiplicity (62 and 43%, respectively),
proliferation rates, and
preneoplastic lesion development. Yet, at 35 weeks, only 5% LBRs significantly
reduced tumor incidence and multiplicity, proliferation indices and
preneoplastic lesion formation. In conclusion, dietary administration
of LBRs inhibited events associated with both the initiation and promotion/progression
stages of carcinogenesis, which is promising considering the limited
number of chemopreventives with this potential. |
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Strong
antioxidant activity of ellagic acid in mammalian cells in vitro revealed
by the comet assay |
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Festa F, Aglitti T, Duranti G, Ricordy R, Perticone
P, Cozzi R.
Dipartimento di Biologia, Universita degli Studi Roma TRE, Italy.
Oxidative stress due to oxygen and various radical
species is associated with the induction of DNA single- and double-strand
breaks and is considered to be a first step in several human degenerative
diseases, cancer and ageing. Naturally occurring antioxidants are
being extensively analysed for their ability to protect DNA against
such injury. We studied three naturally occuring compounds,
Ascorbic Acid, Melatonin and Ellagic acid, for their ability to
modulate DNA damage produced by two strong radical oxygen inducers
(H2O2 and Bleomycin) in cultured CHO cells. The alkaline Comet assay
was used to measure DNA damage and a cytofluorimetric analysis was
performed to reveal the intracellular oxidative species. The data
showed a marked reduction of H2O2- and Bleomycin-induced DNA damage
exerted by Ellagic Acid. On the contrary Ascorbic acid and Melatonin
appeared to induce a slight increase in DNA damage per se. In combined
treatments, they caused a slight reduction of H2O2-induced damage,
but they did not efficiently modulate the Bleomycin-induced one.
The Dichlorofluorescein diacetate (DCFH-DA) cytofluorimetric test
confirmed the strong scavenging action exerted by Ellagic Acid.
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Effects
of ellagic acid by oral administration on N-acetylation and metabolism
of 2-aminofluorene in rat brain tissues |
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Lin SS, Hung CF, Ho CC, Liu YH, Ho HC, Chung JG.
Department of Radiological Technology, Chungtai Institute of Health
Sciences and Technology, Taichung, Taiwan, Republic of China.
Neurochem Res. 2000 Nov;25(11):1503-8.
Numerous studies have demonstrated that the Acetyl Coenzyme A-dependent
arylamine NAT enzyme exist in many tissues of experimental animals
including humans, and that NAT has been shown to be exist in mouse
brain tissue. Increased NAT activity levels are associated with increased
sensitivity to the mutagenic effects of arylamine carcinogens. Attenuation
of liver NAT activity is related to breast and bladder cancer processes.
Therefore, the effects of ellagic acid (EA) on the in vitro and in
vivo N-acetylation of 2-aminofluorene (AF) were investigated in cerebrum,
cerebellum and pineal gland tissues from male Sprague-Dawley rats.
For in vitro examination, cytosols with or without EA (0.5-500 microM)
co-treatment decreased 7-72%, 15-63% and 10-78% of AF acetylation
for cerebrum, cerebellum and pineal gland tissues, respectively. For
in vivo examination, EA and AF at the same time treated groups with
all 3 examined tissues did show significant differences (the changes
of total amounts of AF and AF metabolites based on the Anova analysis)
when compared to the ones without EA cotreatment rats. The pretreatment
of male rats with EA (10 mg/kg) 24
hr prior to the administration of AF (50 mg/kg) (one day of EA administration
suffice to induce large changes in phase II enzyme activity) resulted
in a 76% decrease in total AF and metabolites in pineal gland but
did not show significant differences in cerebrum and cerebellum tissues.
This is the first demonstration to show that EA decreases the N-acetylation
of carcinogens in rat brain tissues. |
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Prevention
of N-nitrosodiethylamine-induced lung tumorigenesis by ellagic acid
and quercetin in mice |
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Khanduja KL, Gandhi RK, Pathania V, Syal N.
Department of Biophysics, Postgraduate Institute of Medical Education
& Research, Chandigarh, India.
Food Chem Toxicol. 1999 Apr;37(4):313-8.
The polyphenolic antioxidants, consumed as an integral part of vegetables,
fruits and beverages, are suggested as possessing anticarcinogenic
properties. In the present study we have looked into the anticarcinogenic
potential of plant polyphenols ellagic acid (EA) and quercetin against
N-nitrosodiethylamine-induced lung tumorigenesis in mice. Ellagic
acid was able to significantly reduce tumour incidence to 20% from
the control value of 72.2%. Similarly, tumour burden was also decreased,
although not significantly, from 3.15 to 2.5. Quercetin (QR) caused
the tumour incidence to decrease from 76.4% to 44.4% when fed until
the third dose of carcinogen. Both of the polyphenols suppressed the
tumour incidence mainly by acting at the initiation phase of the carcinogenesis,
since continuing the feeding of polyphenols until the termination
of the experiment did not cause any apparent change in tumour
incidence or tumour burden. Besides this, ellagic acid was found to
be a better chemopreventor than quercetin. In order to search for
their mechanism of action, the effect of feeding of these compounds
on reduced glutathione (GSH), an important endogenous antioxidant,
and on lipid peroxidation was investigated. Both ellagic acid and
QR caused a significant increase in GSH and decrease in
NADPH- and ascorbate-dependent lipid peroxidation. Ellagic acid was
found to be more effective in decreasing the lipid peroxidation and
increasing the GSH. This may be one of the reasons for its observed
better anticarcinogenic property as compared to quercetin. |
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Anti-tumor
promoting activity of polyphenols from Cowania mexicana and Coleogyne
ramosissima |
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Ito H.; Miyake M.; Nishitani E.; Mori K.; Hatano
T.; Okuda T.; Konoshima T.; Takasaki M.; Kozuka M.; Mukainaka T.;
Tokuda H.; Nishino H.; Yoshida T. T. Yoshida,
Faculty of Pharmaceutical Sciences, Okayama University, Tsushima,
Okayama 700-8530 Japan
yoshida@pheasant.pharm.okayama-u.ac.jp
Cancer Letters (Ireland) 1999, 143/1 (5-13)
Chemical investigation on polyphenol-rich fractions of Cowania mexicana
and Coleogyne ramosissima (Rosaceae) which showed significant inhibitory
effects on Epstein-Barr virus early antigen (EBV-EA) activation induced
by 12-O-tetradecanoylphorbol-13-acetate (TPA), has led to the characterization
of 10 compounds including C-glucosidic ellagitannin monomers and dimers
from the former plant, and 17 polyphenols including flavonoid glycosides
from the latter. The effects of individual components and their analogues
with related structures on the TPA-induced EBV-EA activation were
then evaluated. Among the compounds isolated from C. mexicana, two
C-glucosidic ellagitannins, alienanin B and stenophyllanin A and a
nitrile glucoside (lithospermoside), and among the constituents from
C. ramosissima, two flavonoid glycosides, isorhamnetin 3-O-beta-D-glucoside
and narcissin were revealed to possess strong inhibitory effects on
EVB-EA activation, the potencies of which were either comparable to
or stronger than that of a green tea polyphenol, (-)-epigallocatechin
gallate. These polyphenols except for nitrile glucoside, which was
not tested owing to an insufficient amount, were also found to exhibit
anti-tumor promoting activity in two-stage mouse skin carcinogenesis
using 7,12-dimethylbenz[a]anthracene
(DMBA) and TPA. |
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Determining
efficacy of cancer chemopreventive agents using a cell-free system
concomitant with DNA adduction |
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Smith WA, Gupta RC.
Graduate Center for Toxicology, Room 354, Health Sciences Research
Building, University of Kentucky Medical Center, Lexington, KY 40536-0305,
USA.
Mutat Res. 1999 Mar 10;425(1):143-52.
The large (>2000) and expanding number of natural and synthetic
agents with potential cancer chemopreventive properties renders it
economically and physically impossible to test each of these agents
for their efficacy in the widely accepted 2-year animal bioassay and
clinical trials. Therefore, there is a growing need for relevant short-term
screening tests to study these compounds such that only the most efficacious
ones undergo extensive long-term studies. We have previously reported
in a pilot study that the use of a microsome-mediated test system
concomitant with DNA adduction is a pertinent and relevant model for
rapidly studying the efficacy and mechanisms of cancer chemopreventive
agents. We have extended this study to investigate 26 additional agents
for their potential chemopreventive abilities by studying their effects
on microsome-mediated benzo[a]pyrene (BP)-DNA adduction. These agents
had differential effects on the two major adducts of BP-DNA, i.e.,
BP-7,8-diol-9,10-epoxide (BPDE)-deoxyguanosine (dG) and 9-OH-BP-dG-derived
adducts. These agents were therefore categorized into five classes.
Three test agents (ellagic acid, genistein and oltipraz) were strong
inhibitors of both adducts. These agents diminished BP-DNA adduction
by 65-95% and were categorized as Class I agents. Six other agents
(benzyl isocyanate, R(+)-1-phenylethyl isocyanate, linoleic acid ethyl
ester, (+)-biotin, indole-3-carboxylic acid and beta-carotene) moderately
inhibited both BP-DNA adducts (25-64%); these compounds were identified
as Class II agents. Six additional test agents inhibited only one
adduct selectively and nine others were ineffective; these agents
were ategorized as Class III and Class IV, respectively. Interestingly,
seven test agents enhanced BPDE-dG or 9-OH-BP-dG or both adducts and
were
categorized as Class V agents. Four of these Class V agents concomitantly
inhibited BPDE-dG while enhancing 9-OH-BP-dG. This emphasizes the
importance of studying individual DNA adducts in contrast to total
DNA binding. In conclusion, Class I and Class II agents may be good
candidates for further chemoprevention studies. Copyright 1999 Elsevier
Science B.V. |
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Isothiocyanates
and freeze-dried strawberries as inhibitors of esophageal cancer |
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Stoner GD, Kresty LA, Carlton PS, Siglin JC, Morse MA.
Division of Environmental Health Sciences, The Ohio State University
School of Public Health, and The Ohio State University Comprehensive
Cancer Center, The Ohio State University, Columbus 43210, USA.
Toxicol Sci. 1999 Dec;52(2 Suppl):95-100.
A group of arylalkyl isothiocyanates were tested for their abilities
to inhibit tumorigenicity and DNA methylation induced by the esophageal-specific
carcinogen, N-nitrosomethylbenzylamine (NMBA) in the F344 rat esophagus.
Phenylpropyl isothiocyanate (PPITC) was more potent than either phenylethyl
isothiocyanate (PEITC) or benzyl isothiocyanate (BITC). Phenylbutyl
isothiocyanate (PBITC), however, had a lesser inhibitory effect on
esophageal tumorigenesis, and phenylhexyl isothiocyanate (PHITC) actually
enhanced esophageal tumorigenesis. Thus, the two- and three-carbon
isothiocyanates were more effective inhibitors of NMBA-esophageal
carcinogenesis than the longer chain isothiocyanates. The effects
of the isothiocyanates on tumorigenesis were well correlated as to
their effects on DNA adduct formation. The most likely mechanism of
inhibition of tumorigenesis by these isothiocyanates is via inhibition
of the cytochrome P450 enzymes responsible for the metabolic activation
of NMBA in rat esophagus. A freeze-dried strawberry preparation was
also evaluated for its ability to inhibit NMBA-esophageal tumorigenesis.
It proved to be an effective inhibitor, although not as potent as
either PEITC or PPITC. The inhibitory effect of the berries could
not be attributed solely to the content of the chemopreventive agent,
ellagic acid, in the berries. |
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Protective
effect of curcumin, ellagic acid and bixin on radiation induced genotoxicity |
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Dr. R. Kuttan, Amala Cancer Research Centre, Amala
Nagar, Trichur - 680 553 Kerala State India
Journal of Experimental and Clinical Cancer Research ( J. EXP.
CLIN. CANCER RES. ) (Italy) 1998, 17/4 (431-434)
Thresiamma K.C.; George J.; Kuttan R.
Induction of micronuclei and chromosomal aberrations produced by whole
body exposure of r-radiation (1.5-3.0 Gy) in mice was found to be
significantly inhibited by oral administration of natural antioxidants,
curcumin (400 mu moles), ellagic acid (200 mu moles) and bixin (200
mu moles) per kilogram body weight. These antioxidants induced inhibition
of micronucleated polychromatic and normochromatic erythrocytes, was
comparable with alpha-tocopherol (200 mu moles)
administration. Curcumin and ellagic acid were also found to significantly
reduce the number of bone marrow cells with chromosomal aberrations
and chromosomal fragments as
effectively as alpha- tocopherol. Moreover, administration of antioxidants
inhibited the DNA strand breaks produced in rat lymphocytes upon radiation
as seen from the DNA unwinding studies. These results indicated that
antioxidant curcumin, ellagic acid and bixin provide protection against
chromosome damage produced by radiation. |
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Protective
effect of food additives on aflatoxin-induced mutagenicity and hepatocarcinogenicity |
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Soni K.B.; Lahiri M.; Chackradeo P.; Bhide S.V.;
Kuttan R.
R. Kuttan, Amala Cancer Research Centre, Amala Naga, Trichur 680
553, Kerala India
Cancer Letters ( CANCER LETT. ) (Ireland) 1997, 115/2 (129-133)
Food additives such as turmeric (Curcuma longa), and active ingredient
curcumin (diferuloyl methane), asafoetida (flavouring agent), butylated
hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and ellagic acid
were found to inhibit the mutagenesis induced by aflatoxin Binf 1
(AFBinf 1) (0.5 mug/plate) in Salmonella tester strains TA 98 and
TA 100. Turmeric and curcumin, which were the most active, inhibited
mutation frequency by more than 80% at concentrations of 2 mug/plate.
Other food additives were also significantly effective. Dietary administration
of turmeric (0.05%), garlic (0.25%), curcumin and ellagic acid (0.005%
each) to rats significantly
reduced the number of gammaglutamyl transpeptidase-positive foci induced
by AFBinf 1 which is considered as the precursor of hepatocellular
neoplasm. These results indicate the usefulness of antioxidant food
additives in ameliorating aflatoxin-induced mutagenicity and carcinogenicity.
|
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Inhibition
of liver fibrosis by ellagic acid |
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Thresiamma K.C.; Kuttan R.
Amala Cancer Research Centre, Amala Nagar,Trichur 680 553 India
Indian Journal of Physiology and Pharmacology ( INDIAN J. PHYSIOL.
PHARMACOL. ) (India) 1996, 40/4 (363-366)
Chronic administration of carbon tetrachloride in liquid paraffin
(1:7) ip; 0.15 ml, (20 doses) has been found to produce severe hepatotoxicity,
as seen from the elevated levels of serum and liver glutamate-pyruvate
transaminase, alkaline phosphatase and lipid peroxides. The chronic
administration of carbon tetrachloride was also found to produce liver
fibrosis as seen from pathological analysis as well as elevated liver-hydroxy
proline. Oral administration of ellagic acid was found to significantly
reduce the elevated levels of enzymes, lipid peroxide and liver hydroxy
proline in these animals and rectified liver pathology. These results
indicate that ellagic acid administration orally can circumvent the
carbon tetrachloride toxicity and subsequent
fibrosis. |
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Antitumorigenic
and antipromoting activities of ellagic acid, ellagitannins and oligomeric
anthocyanin and procyanidin |
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Castonguay A.; Gali H.; Perchellet E.M.; Gao X.M.;
Boukharta M.; Jalbert G.; Okuda T.; Yoshida T.; Hatano T.; Perchellet
J.-P.
Dr. A. Castonguay, Lab. Cancer Etiology/Chemoprevention, School
of Pharmacy, Laval University, Quebec City, Que. G1K 7P4 Canada
International Journal of Oncology ( INT. J. ONCOL. ) (Greece) 1997,
10/2 (367-373)
We previously showed that ellagic acid (EA) was inhibiting lung tumorigenesis
induced by the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-
1-butanone (NNK) in A/J mice. In the present study, we observed that
the inhibition of lung tumorigenesis was independent of the solvent
used to purified EA. Pomegranate peels extract containing punicalagin
(alpha and beta anomers) (10 g/kg diet) and oligomeric anthocyanins
(6 g/kg diet) did not inhibit lung tumorigenesis. Raspberry extract
(2 x 15 mg) containing sanguiin H6 and lambertianin D as well as oligomeric
procyanidins (2 x 15 mg) inhibit 12-O-tetradecanoylphorbol-13-acetate
(TPA)-induced ornithine decarboxylase (ODC) activity by about 30%.
The same treatments inhibit TPA-stimulated hydroperoxide (HPx) production
by about 30 and 70%. Raspberry ellagitannins and oligomeric procyanidins
respectively inhibit TPA stimulated DNA synthesis by 42 and 26%. Our
results suggest that hydrolyzable and condensed tannins from various
sources, which can inhibit the ODC, HPx, and DNA responses to TPA,
might also inhibit the tumor-promoting activity of this agent. The
results of this study show that EA and ellagitannins have different
antitumorigenic and antipromoting activities. |
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Isothiocyanates
and plant polyphenols as inhibitors of lung and esophageal cancer |
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Stoner G.D.; Morse M.A.
G.D. Stoner, Div. Environmental Health Sciences, The Ohio State
University, School of Public Health, 300 West Tenth Avenue, Columbus,
OH 43210 United States
Cancer Letters ( CANCER LETT. ) (Ireland) 1997, 114/1-2 (113-119)
A group of arylalkyl isothiocyanates were tested for their abilities
to inhibit tumorigenicity and DNA methylation induced by both the
tobacco-specific nitrosamine, NNK, in A/J mouse lung and the esophageal-specific
carcinogen, NMBA, in F344 rat esophagus. In addition, ellagic acid
was tested for its ability to inhibit NMBA-induced esophageal tumorigenesis.
In the strain A lung tumor model, PEITC effectively inhibited NNK-induced
lung tumors at a dose of 5 mumol, but was not inhibitory
at lower doses. PPITC, PBITC, PPeITC, and PHITC were all considerably
more potent inhibitors of NNK lung tumorigenesis than PEITC, and PHITC
was the most potent inhibitor of all. Thus, in the strain A lung tumor
model, there was a trend of increased inhibitory efficacy among arylalkyl
isothiocyanates with increased alkyl chain length. In the F344 rat
esophageal tumor model, PPITC was clearly more potent-than PEITC,
BITC and PBITC had little inhibitory effect on esophageal tumorigenesis,
and in a separate experiment, PHITC actually enhanced esophageal tumorigenesis.
Thus, the structure-activity relationships for inhibition of tumorigenesis
by arylalkyl isothiocyanates were considerably different in the two
animal models. However, the effects of the isothiocyanates on tumorigenesis
were well-correlated to their effects on DNA adduct formation in either
model. The most likely mechanism of inhibition of tumorigenesis by
these isothiocyanates is via inhibition of the cytochrome p450 enzymes
responsible for activation of NNK in mouse lung or NMBA in rat esophagus.
Ellagic acid was an effective inhibitor of esophageal tumorigenesis,
although not as potent as PEITC or PPITC. Like the isothiocyanates,
ellagic acid inhibits cytochrome p450-mediated activation of NMBA.
|
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The
effects of dietary ellagic acid on rat hepatic and esophageal mucosal
cytochromes P450 and phase II enzymes |
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Ahn D.; Putt D.; Kresty L.; Stoner G.D.; Fromm D.;
Hollenberg P.F.
Department of Pharmacology, University of Michigan, 2301 MSRB III,
1150 West Medical Center Drive,Ann Arbor, MI 48109-0632 United States
Carcinogenesis ( CARCINOGENESIS ) (United Kingdom) 1996, 17/4 (821-828)
Ellagic acid (EA), a naturally occurring plant polyphenol possesses
broad chemoprotective properties. Dietary EA has been shown to reduce
the incidence of N-2-fluorenylacetamide-induced hepatocarcinogenesis
in rats and N-nitrosomethylbenzylamine (NMBA)-induced rat esophageal
tumors. In this study changes in the expression and activities of
specific rat hepatic and esophageal mucosal cytochromes P450 (P450)
and phase II enzymes following dietary EA treatment were investigated.
Liver and esophageal mucosal microsomes and cytosol were prepared
from three groups of Fisher 344 rats which were fed an AIN-76 diet
containing no EA or 0.4 or 4.0 g/kg EA for 23 days. In the liver total
P450 content decreased by up to 25% and P450 2E1-catalyzed p-nitrophenol
hydroxylation decreased by 15%. No changes were observed in P450 1A1,
2B1 or 3A1/2 expression or activities or cytochrome h$D5 activity,
P450 reductase activity decreased by up to 28%. Microsomal epoxide
hydrolase (mEH) expression decreased by up to 85% after EA treatment,
but mEH activities did not change. The hepatic phase II enzymes glutathione
transferase (GST), NAD(P)H:quinone reductase (NAD(P)H:QR) and UDP
glucuronosyltransferase (UDPGT) activities increased by up to 26,
17 and 75% respectively. Assays for specific forms of GST indicated
marked increases in the activities of isozymes 2-2 (190%), 4-4 (150%)
and 5-5 (82%). In the rat esophageal mucosa only P450 1A1 could be
detected by Western blot analysis and androstendione
was the only P450 metabolite of testosterone detectable. However,
there were no differences in the expression of P450 1A1, the formation
of androstendione or
NAD(P)H:QR activities between control and EA-fed rats in the esophagus.
Although there was no significant decrease in overall GST activity,
as measured with 1-chloro-2,4-,dinitrobenzene (CDNB), there was a
significant decrease in the activity of the 2-2 isozyme (66% of control).
In vitro incubations showed that EA at a concentration of 100 muM
inhibited P450 2E1, 1A1 and 2B1 activities by 87, 55 and 18% respectively,
but did not affect 3A1/2 activity. Using standard steady-state kinetic
analyses, EA was shown to be a potent non-competitive inhibitor of
both liver microsomal ethoxyresorufin O-deethylase and p-nitrophenol
hydroxylase activities, with apparent K(i) values of ~55 and 14 muM
respectively. In conclusion, these results demonstrate that EA causes
a decrease in total hepatic P450 with a significant effect on hepatic
P450 2E1, increases some hepatic phase II enzyme activities (GST,
NAD(P)H:QR and UDPGT) and decreases hepatic mEH expression. It also
inhibits the catalytic activity of some P450 isozymes in vitro. Thus
the chemoprotective effect of EA against various chemically induced
cancers may involve decreases in the rates of metabolism of these
carcinogens by phase I enzymes, due to both direct inhibition of catalytic
activity and modulation of gene expression, in addition to effects
on the expression of phase II enzymes, thereby enhancing the ability
of the target tissues to detoxify the reactive intermediates. |
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Antimutagenicity
of ellagic acid against aflatoxin Binf 1 in the Salmonella microsuspension
assay |
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Loarca-Pina G.; Kuzmicky P.A.; Gonzalez de Mejia
E.; Kado N.Y.; Hsieh D.P.H.
Dept. of Environmental Toxicology, University of California,Davis,
CA 95616 United States
Mutation Research - Environmental Mutagenesis and Related Subjects
(Netherlands) 1996, 360/1 (15-21)
Ellagic acid (EA) is a phenolic compound with antimutagenic and anticarcinogenic
properties. It occurs naturally in some foods such as strawberries,
raspberries, grapes, black currants and walnuts. In the present study,
we used the Salmonella microsuspension assay to examine the antimutagenicity
of EA against the potent mutagen aflatoxin Binf 1 (AFBinf 1) using
tester strains TA98 and TA100, Further, we used a two-stage incubation
procedure that incorporates washing the bacterial cells free of the
incubation mixture after the first incubation to investigate EA and
AFBinf 1 interaction. Three different concentrations of AFBinf 1 (2.5,
5 and 10 ng/tube) were tested against five different concentrations
of EA for TA98 and TA100. EA significantly inhibited mutagenicity
of all doses of
AFBinf 1 in both tester strains with the addition of S9. EA alone
was not mutagenic at the concentrations tested. The greatest inhibitory
effect of EA on AFBinf 1 mutagenicity occurred
when EA and AFBinf 1 were incubated together. Lower inhibition was
apparent when the cells were first incubated with EA followed by a
second incubation with AFBinf 1, and also when the cells were first
incubated with AFBinf 1 followed by a second incubation with EA alone.
The results of the sequential incubation studies support the hypothesis
that one mechanism of inhibition could involve the formation of a
chemical complex between EA and AFBinf 1. |
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Organ
specific, protocol dependent modulation of 7,12-dimethylbenz[a]anthracene
carcinogenesis in rainbow trout (Oncorhynchus mykiss) by dietary ellagic
acid |
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Harttig, U; Hendricks, J D; Stoner, G D; Bailey,
G S *
Dep. Food Sci. and Technol., Wiegand Hall, Oregon State Univ.,
Corvallis, OR 97331-6602, USA
Carcinogenesis "CARCINOGENESIS", vol. 17, no. 11, p. 2403-2409,
Nov 1996
This study investigated pre-initiation and post-initiation effects
of dietary ellagic acid (EA) on 7,12-dimethylbenz[a]anthracene (DMBA)
multi-organ carcinogenesis in rainbow trout (Oncorhynchus mykiss).
EA at 100, 250 (study 2), 1000 and 2000 (study 1) p.p.m. suppressed
stomach adenopapilloma incidence by 33, 60, 70 and 78% (P less than
or equal to 0.001), respectively, as well as tumor multiplicity (P
< 0.01) and size (P < 0.001) when fed continuously following
DMBA initiation. However, continuous EA feeding also produced modest
(250 p.p.m.) to extensive (1000, 2000 p.p.m.) growth rate suppression
in these studies. Retrospective logistic regression modeling of the
data allowed separation of growth-related from non-growth-related
inhibitory effects. By this approach: (i) tumor development showed
a similarly strong dependence (same regression slope) on animal growth
rate in all treatment groups; (ii)
EA-mediated reduction in mean population growth contributed to suppressed
stomach tumor response above 250 p.p.m. EA; and (iii) even at high,
toxic doses EA displayed inhibitory mechanisms additional to, and
distinct from, growth suppression effect. The effects of post-initiation
EA were organ specific. Chronic EA treatment significantly suppressed
swim-bladder as well as stomach tumor incidence at doses greater than
or equal to 1000 p.p.m., but increased liver tumor incidence at doses
greater than or equal to 250 p.p.m. Three protocols examined EA effects
on the initiation process. EA fed at 1000 p.p.m. concurrently with
750 p.p.m. dietary DMBA for 7 weeks modestly reduced stomach tumor
incidence (from 85 to 78%, P < 0.05) and multiplicity (from 6.3
plus or minus 4.3 to 4.9 plus or minus 2.9, P < 0.01), but did
not alter swim-bladder or liver response. The effect of EA pretreatment
prior to DMBA single-dose initiation by gill uptake was also examined.
When fed for 1 week prior to initiation, 2000 p.p.m. EA again imposed
a small reduction in stomach adenoma incidence (from 88 to 78%; P
< 0.05) and multiplicity (from 5.5 plus or minus 3.2 to 4.4 plus
or minus 3.2; P < 0.01). However, when EA was pre-fed for 3 weeks
instead of 1 week, protection in the stomach
was lost and response in liver and swim-bladder significantly increased.
In sum, these studies demonstrate that EA influence on DMBA tumorigenesis
in this multi-organ model is highly protocol dependent and organ specific.
Post-initiation dietary EA consistently suppressed stomach tumor development
in trout, at EA doses far lower than those required for protection
in rodents. At higher doses, however, EA also displayed toxicity and
a potential in some protocols to enhance tumor response in other organs. |
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Inhibitory
effects of vitamin E and ellagic acid on 8-hydroxydeoxyguanosine formation
in liver nuclear DNA of rats treated with 2-nitropropane |
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Takagi A.; Sai K.; Umemura T.; Hasegawa R.; Kurokawa
Y.
Division of Toxicology, National Institute Health Sciences, 1-18-1
Kamiyoga,Setagaya-ku, Tokyo 158 Japan
Cancer Letters ( CANCER LETT. ) (Ireland) 1995, 91/1 (139-144)
The effects of five naturally occurring antioxidants, beta-carotene
(BC), vitamin C (VC), vitamin E (VE), ellagic acid (EA) and epigallocatechin
gallate (EGCG) on 8-hydroxydeoxyguanosine (8-OH-dG) formation by 2-nitropropane
(2-NP), a hepatocarcinogen in rats, were studied. Four days oral administration
of VE (100 mg/kg BW/day) or EA (100 mg/kg BW/day) significantly inhibited
8-OH-dG formation in the liver nuclear DNA of male F-344 rats injected
with 2-NP (100 mg/kg BW, i.p., killed 6 h later). The same treatment
with EGCG (100 mg/kg BW/day) showed slight, but not significant, inhibition.
In contrast, 4 days' oral administration of BC (100 mg/kg BW/day)
or VC (300 mg/kg BW/day) and 3 weeks' feeding of the two (either at
0.5% in the diet) did not produce any inhibitory effects on 8-OH-dG
formation. Thus, it is expected that VE and EA may have anticarcinogenic
effects towards 2-NP. |
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Taurine
and ellagic acid: Two differently-acting natural antioxidants |
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Cozzi R.; Ricordy R.; Bartolini F.; Ramadori L.;
Perticone P.; De Salvia R.
Dipartimento di Genetica, Universita 'La Sapienza', P.le A. Moro
5,00185 Rome Italy
Environmental and Molecular Mutagenesis ( ENVIRON. MOL. MUTAGEN. )
( United States) 1995, 26/3 (248-254)
Naturally occurring antimutagenic compounds are extensively analyzed
for their capacity to protect cells from induced damage. We selected
two agents, taurine and ellagic acid, treated in the literature as
antioxidants, but whose activity is insufficiently known. This paper
reports on the ability of these agents to act against damage induced
by mitomycin-C and hydrogen peroxide in Chinese hamster ovary cells
cultivated in vitro. Cytogenetic and cytofluorimetric analyses were
performed. Ellagic acid proved to have more than one mechanism of
action, probably as a scavenger of oxygen species
produced by Hinf 2Oinf 2 treatment, and as a protector of the DNA
double helix from alkylating agent injury. In our experimental conditions,
taurine seems able to scavenge oxygen species. |
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Polyphenols
as cancer chemopreventive agents |
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Stoner GD, Mukhtar H
Department of Preventive Medicine, Ohio State University, Columbus
43210, USA.
J Cell Biochem Suppl 1995;22:169-80
This article summarizes available data on the chemopreventive efficacies
of tea polyphenols, curcumin and ellagic acid in various model systems.
Emphasis is placed upon the anticarcinogenic activity of these polyphenols
and their proposed mechanism(s) of action. Tea is grown in about 30
countries and, next to water, is the most widely consumed beverage
in the world. Tea is anufactured as either green, black, or oolong;
black tea represents approximately 80% of tea products. Epidemiological
studies, though inconclusive, suggest a protective effect of tea consumption
on human cancer. Experimental studies of the antimutagenic and
anticarcinogenic effects of tea have been conducted principally with
green tea polyphenols (GTPs). GTPs exhibit antimutagenic activity
in vitro, and they inhibit carcinogen-induced skin, lung, forestomach,
esophagus, duodenum and colon tumors in rodents. In addition, GTPs
inhibit TPA-induced skin tumor promotion in mice. Although several
GTPs possess anticarcinogenic activity, the most active is (-)-epigallocatechin-3-gallate
(EGCG), the major constituent in the GTP fraction. Several mechanisms
appear to be responsible for the tumor-inhibitory properties of GTPs,
including enhancement of antioxidant (glutathione peroxidase, catalase
and quinone reductase) and phase II (glutathione-S-transferase) enzyme
activities; inhibition of chemically induced lipid peroxidation; inhibition
of irradiation- and TPA-induced epidermal ornithine decarboxylase
(ODC) and cyclooxygenase activities; inhibition of protein kinase
C and cellular proliferation; antiinflammatory activity; and enhancement
of gap junction intercellular communication. Curcumin is the yellow
coloring agent in the spice tumeric. It exhibits antimutagenic activity
in the Ames Salmonella test and has
anticarcinogenic activity, inhibiting chemically induced preneoplastic
lesions in the breast and colon and neoplastic lesions in the skin,
forestomach, duodenum and colon of rodents. In addition, curcumin
inhibits TPA-induced skin tumor promotion in mice. The mechanisms
for the anticarcinogenic effects of curcumin are similar to those
of the GTPs. Curcumin enhances glutathione content and
glutathione-S-transferase activity in liver; and it inhibits lipid
peroxidation and arachidonic acid metabolism in mouse skin, protein
kinase C activity in TPA-treated NIH 3T3 cells, chemically induced
ODC and tyrosine protein kinase activities in rat colon, and 8-hydroxyguanosine
formation in mouse fibroblasts. Ellagic acid is a polyphenol found
abundantly in various fruits, nuts and vegetables. Ellagic acid is
active in antimutagenesis assays, and has been shown to inhibit chemically
induced cancer in the lung, liver, skin and esophagus of rodents,
and TPA-induced tumor promotion in mouse skin.
|
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Ellagic
acid induces transcription of the rat glutathione S-transferase-Ya
gene |
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Barch DH, Rundhaugen LM, Pillay NS
Department of Medicine, Lakeside Veterans Affairs Medical Center,
Chicago, IL.
Carcinogenesis 1995 Mar;16(3):665-8
Induction of glutathione S-transferase (GST) enzymes can increase
detoxification of carcinogens and reduce carcinogen-induced mutagenesis
and tumorigenesis. To determine if the anticarcinogen ellagic acid
induces cellular enzymes which detoxify carcinogens, we examined the
effect of ellagic acid on the expression of glutathione S-transferase-Ya.
Rats fed ellagic acid demonstrated significant increases in total
hepatic GST activity, hepatic GST-Ya activity and hepatic GST-Ya mRNA.
To determine if the observed increase in GST-Ya mRNA was due to ellagic
acid inducing transcription of the GST-Ya gene, transfection studies
were performed with plasmid constructs containing various portions
of the 5' regulatory region of the rat GST-Ya gene. The transfection
studies demonstrated that ellagic acid increased GST-Ya mRNA by inducing
transcription of the GST-Ya gene and demonstrated that this induction
is mediated through the antioxidant responsive element of the GST-Ya
gene. 31. Ann N Y Acad Sci 1993 May 28;686:177-85 |
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