Antimutagenic activities of acetone and methanol fractions of Terminalia arjuna

Food and Chemical Toxicology 40 (2002) 1475–1482 www.elsevier.com/locate/foodchemtox

Antimutagenic activities of acetone and methanol fractions of Terminalia arjuna K. Kaura, S. Aroraa,*, S. Kumarb, A. Nagpala a

Department of Botanical Land Environmental Sciences, Guru Nanak Dev University, Amritsar 143 005, India b Department of Chemistry, Guru Nanak Dev University, Amritsar 143 005, India Accepted 6 January 2002

Abstract The antimutagenic effect of benzene, chloroform, acetone and methanol fractions from Terminalia arjuna, a well-known medicinal plant, was determined against Acid Black dye, 2-aminofluorene (2AF) and 4-nitro-o-phenylenediamine (NPD) in TA98 Frameshift mutagen tester strain of Salmonella typhimurium. Among the different fractions, the antimutagenic effect of acetone and methanol fractions was more than that observed with other fractions. Co-incubation and pre-incubation modes of experimentation did not show much difference in the antimutagenic activity of the extracts. Moreover, these fractions inhibited the S9-dependent mutagens, 2AF and Acid Black dye more effectively than the direct-acting mutagens. Studies are under way to isolate and elucidate the nature of the antimutagenic factor in acetone and methanol fractions. # 2002 Published by Elsevier Science Ltd. Keywords: Antimutagenicity; Salmonella typhimurium; Terminalia arjuna; Polyphenols; Acid Black dye

1. Introduction Cancer has become the number one cause of death in the world since infectious diseases are now more or less under control (Tominaga et al., 1994). Chemical carcinogenesis, or cancer induced or aided by chemically defined substances, was of great interest in scientific investigation. But less attention had been given to substances in the environment or in diet that may serve to protect against chemical mutagens or carcinogens acting as initiators in the carcinogenesis process. These are chemical substances present in plants that may act as anticarcinogens or antimutagens by blocking or trapping ultimate carcinogen electrophiles in a nucleophilic chemical reaction to form innocuous products. A continuous input of these could serve as a buffer against DNA damage. A wide array of phenolic substances, particularly those present in dietary and medicinal plants, have been

reported to possess substantial antimutagenic and anticarcinogenic activities (Okuda et al., 1991; Kaur et al., 1997; Zhu et al., 1997; Ebringer et al., 1999; Lopes et al., 1999; Surh, 1999). The bark of Terminalia arjuna (Combretaceae) is rich in polyphenols (about 60–70%), including flavones, flavonols, phenylpropanoids and tannins (20–24%), and is used in the treatment of fractures, ulcers, blood diseases, anaemia and asthma. It also has the ability to cure hepatic, congenital, venereal and viral diseases (Kumar and Prabhakar, 1987). Keeping in mind the great medicinal value of T. arjuna and high content of polyphenols in its bark, the present investigation was planned to study the antimutagenic effect of benzene, chloroform, acetone and methanol fractions using the Salmonella microsome assay.

2. Materials and methods Abbreviations: 2AF; 2-aminofluorene; B(a)P; benzo[a]pyrene; DMSO; dimethyl sulfoxide; NPD; 4-nitro-o-phenylenediamine; TPA; 12-O-tetradecanoyl-phorbol-13-acetate. * Corresponding author. Tel.: +91-183-451048; fax: +91-183258820. E-mail address: [email protected] (K. Kaur).

2.1. Chemicals 2-aminofluorene (2AF) and 4-nitro-o-phenylenediamine (NPD) were purchased from Sigma Chemical Co. (St. Louis, MO, USA). Acid Black dye used in the

0278-6915/02/$ - see front matter # 2002 Published by Elsevier Science Ltd. PII: S0278-6915(02)00078-9

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present study was procured from a dye manufacturing industry (Punjab Rang Udyog, Amritsar, India). 2.2. Bark The bark used to make the extracts was collected from a tree growing on the campus of Guru Nanak Dev University, Amritsar, which was washed with distilled water, dried in oven at 40
C and ground to a fine powder. 2.3. Preparation of extract Finely powdered bark of T. arjuna was extracted successively with benzene, chloroform, acetone and methanol by a Soxhlet apparatus to obtain benzene, chloroform, acetone and methanol fractions, respectively (Fig. 1). The solvents from the extracts were evaporated to dryness and the residual dissolved in dimethyl sulfoxide (DMSO). 2.4. Antimutagenicity test The Ames Salmonella/mammalian-microsome mutagenicity test (Maron and Ames, 1983) was used to test the antimutagenic activity of the extracts, with some modifications (Grover and Bala, 1993). The media and S9 mix were prepared according to the procedure of Maron and Ames (1983). In the co-incubation method, the order of addition, to 2 ml of molten top agar, was

0.1 ml of bacterial culture, 0.1 ml of mutagen and 0.1 ml of non-toxic concentration of test compound. In the pre-incubation experiment, a mixture of test compound and mutagen, each having a volume of 0.1 ml, was preincubated at 37
C with rapid shaking for 30 min before addition to the bacterial culture. For the experiments with metabolic activation, the order of addition was 0.1 ml of bacterial culture, 0.1 ml of mutagen, 0.5 ml of S9 mix and 0.1 ml of test compound. The combined solutions were vortex-mixed and poured onto minimal glucose plates. The plates were incubated at 37
C for 48 h, after which the number of histidine-independent (His+) revertant colonies were scored. Bacterial survival was routinely monitored for each experiment. To check the toxicity of the test sample, parallel controls were run with fractions alone at all concentrations tested with mutagens. The concentrations of the test sample and for investigating the antimutagenicity were 2.5103, 1103, 0.5103, 0.25103, 0.1103 and 0.01103 mg/0.1 ml/ plate. These were tested against Acid Black dye (500 mg/ 0.1 ml/plate) in TA98 tester strain. All the test samples and mutagens/promutagens were dissolved in DMSO. In each case, there was no overt toxicity observed and the number of spontaneous revertants was identical to the DMSO vehicle control. Non-toxic concentrations were categorized as those where there was a well-developed lawn, almost similar size of colonies and no statistical difference in the number of spontaneous revertants in test and control plates. Triplicate plates were set up with each concentration and the entire

Fig. 1. Schematic representation of extraction of various fractions from bark powder of Terminalia arjuna.

Table 1 Effect of acetone fraction of Terminalia arjuna on the mutagenicity of Acid Black dye, NPD and 2AF in TA 98 strain of Salmonella typhimurium Treatment

Dose (mg/0.1 ml)

Acid Black dye +S9

S9 MeanSE Spontaneous

–

Positive controls

% Inhibition

MeanSE

NPD (Direct-acting mutagen)

2AF (S9-dependent mutagen)

MeanSE

MeanSE

% Inhibition

% Inhibition

% Inhibition

–

47.22 1.79

–

58.000.37

–

33.441.12

–

0.50103 20.00

722.563.62a –

– –

708.00 6.86a –

– –

– 1216.78 21.55

– –

– 1097.33–25.16a

– –

Negative control

2.50103 1.00103 0.50103 0.25103 0.10103 0.01103

47.781.08 47.000.91 44.110.87 52.890.79 49.000.91 44.890.95

– – – – – –

49.00 0.82 46.00 1.08 41.00 1.01 45.00 1.22 44.00 0.91 47.00 0.75

– – – – – –

58.891.02 53.110.79 55.001.39 46.564.03 50.442.33 50.891.82

– – – – – –

– 35.001.76 31.111.61 41.893.22 40.561.99 33.112.32

– – – – – –

Co-incubation

2.50103 1.00103 0.50103 0.25103 0.10103 0.01103

407.0010.06b 453.7614.05c 471.565.76cd 482.2211.14cde 503.1111.91def 547.444.67g

46.76 39.79 37.00 35.89 32.58 25.84

335.89 15.90b 446.00 28.85c 446.22 11.36cd 482.00 12.03cde 500.11 19.16cdef 542.67 7.11efg

56.47 39.57 39.25 34.09 31.31 25.01

637.67 13.62b 808.00 14.88c 908.22 20.22d 979.78 15.94de 999.33 16.63ef 1017.56 18.12efg

50.01 35.13 26.56 20.25 18.64 17.09

– 44.334.18b 51.672.94bc 108.677.88d 527.0010.45e 803.899.78f

– 99.12 98.07 93.67 53.97 27.57

Pre-incubation

2.50103 1.00103 0.50103 0.25103 0.10103 0.01103

294.3315.11b 381.449.77bc 415.678.09bcd 456.6711.49cde 470.1110.10cdef 512.2215.83defg

63.46 50.49 45.23 39.70 37.48 31.04

275.00 12.44b 368.22 18.70c 411.44 11.36cd 446.00 12.03 464.78 15.79def 507.89 18.47efg

65.71 51.33 44.47 39.40 36.61 30.27

561.67 10.16b 772.78 16.35c 846.89 14.52d 963.44 13.21e 1039.67 19.12f 1049.11 14.38fg

56.58 38.16 31.84 21.65 15.19 14.38

– 10.445.06b 44.893.70bc 61.674.59bcd 178.226.75e 709.2224.95f

– 99.12 98.71 98.13 86.97 36.47

One-way ANOVA Positive control and co-incubation Positive control and pre-incubation

F(6,56)=109.53*; HSD=42.33 F(6,56)=126.03*; HSD=126.03

F(6,56)=31.38*; HSD=77.24 F(6,56)=91.59*; HSD=60.87

F(6,56)=108.46*; HSD=75.12 F(6,56)=179.36*; HSD=69.34

F(5,48)=1274.37*; HSD=52.43 F(5,48)=874.86*; HSD=63.10

Two-way ANOVA Co-incubation and pre-incubation Treatment Dose TreatmentDose

F(1,96)=68.86* F(5,96)=52.45* F(5,96)=4.17*

F(1,96)=34.42* F(5,96)=28.37* F(5,96)=2.64*

F(1,96)=4.81* F(5,96)=221.27* F(5,96)=4.69

F(1,80)=238.32* F(4,80)=1849.95* F(4,80)=103.06*

K. Kaur et al. / Food and Chemical Toxicology 40 (2002) 1475–1482

58.000.53

Data shown are mean SE of two repeated experiments. NPD: 4-nitro-o-phenylenediamene; 2AF: 2-aminofluorene; -S9:without S9; +S9: with S9. Means followed by the same letter are not significantly different using HSD multiple comparison test. * P40.05. 1477

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experiment was repeated twice. Inhibitory activity was expressed as percentage decrease of reverse mutation: Percent inhibition=[(a–b)/(a–c)]100, where a=number of histidine revertants induced by mutagen, b=number of histidine revertants induced by mutagen in the presence of fractions and c=number of revertants induced in negative control. 2.5. Statistical analysis The results are presented as the average and standard error of three experiments with triplicate plates/dose/ experiment. The data were further analyzed for statistical significance using analysis of variance (one-way and two-way ANOVA) and the difference among means was compared by high-range statistical domain (HSD) using Tukey’s test (Meyers and Grossen, 1974). A level of probability < 0.05 was taken as indicating statistical significance.

3. Results The antimutagenic potential of acetone and methanol fractions isolated from T. arjuna against Acid Black dye, NPD and 2AF (promutagen) is presented in Tables 1 and 2, and Figs. 2 and 3.The inhibitory effect at different concentrations of the fractions was found to be more or less same in pre-incubation as well as in the co-incubation mode of experiments. It was observed that both fractions inhibited 2AF-induced revertants more significantly than those induced by direct-acting mutagens. Acetone and methanol fractions exhibited maximum inhibition of 99.49 and 99.80%, respectively, in the pre-incubation mode of treatment against the mutations induced by 2AF. The methanol fraction exhibited more inhibition of revertants induced by Acid Black dye in the presence of S9 than those by acetone fraction. On the whole, the acetone and methanol fractions both showed relatively more antimutagenicity in

Fig. 2. Effect of acetone fraction isolated from Terminalia arjuna on Acid Black dye (S9), acid black dye (+S9), NPD- and 2AF-induced mutagenicity in TA98 tester strain of Salmonella typhimurium. *Positive control. % of control ¼

Hisþ revertants=plate with mutagen and antimutagen  100: Hisþ revertants=plate with mutagen alone

Table 2 Effect of methanol fraction of Terminalia arjuna on the mutagenicity of Acid Black eye, NPD and 2AF in TA98 strain of Salmonella tryphirium Treatment

Dose (m/0.1 ml)

Acid Black dye +S9

S9 MeanSE –

Positive controls

Negative control

Co-incubation

Pre-incubation

Mean SE

2AF (S9-dependent mutagen)

MeanSE

MeanSE

% Inhibition

% Inhibition

& Inhibition

38.89 1.95

–

49.441.46

–

33.111.70

–

49.781.96

–

0.50103 20.00

658.11 11.10a –

– –

396.222.35a –

– –

– 1035.0015.24

– –

– 2286.56–22.30a

– –

2.50103 1.00103 0.50103 0.25103 0.10103 0.01103

47.56 1.77 47.00 1.32 41.56 3.08 44.56 2.32 41.22 2.03 35.44 2.44

– – – – – –

48.112.35 45.001.75 47.331.58 44.113.58 44.443.66 50.782.31

– – – – – –

42.441.32 36.781.88 37.222.37 33.441.83 44.002.90 33.671.91

– – – – – –

–

– – – – – –

46.672.64 46.562.73 44.111.38 46.221.66 46.441.89

2.50103 1.00103 0.50103 0.25103 0.10103 0.01103

323.67 9.20b 394.11 19.10c 518.78 10.96d 603.89 17.15a 550.44 12.64ade 679.56 9.97af

54.78 46.20 22.60 8.84 17.46 3.44

288.561.67b 259.8910.80bc 306.6711.72bcd 285.6711.72bcde 314.8913.82bcdef 398.3312.90ag

30.93 38.81 25.67 31.67 23.12 0.61

477.441.44b 561.2217.41c 658.1124.71d 658.8910.20de 764.3312.49ef 847.4411.00g

56.17 47.46 37.77 37.55 27.31 18.73

–

2.50103 1.00103 0.50103 0.25103 0.10103 0.01103

458.56 12.45b 588.76 17.65bc 659.89 9.78ad 538.00 14.07ce 604.78 12.98acdf 602.78 13.46acdfg

32.68 11.36 0.29 19.58 8.64 8.96

43.782.43b 48.783.49bc 57.892.79bcd 72.003.31bcde 50.441.45bcdef 59.679.58bcdefg

101.24 98.86 96.97 92.87 98.29 97.43

409.0011.46b 578.1112.96c 630.339.21d 637.5610.75de 745.338.26f 859.337.57g

63.07 45.77 40.56 39.68 29.23 17.54

–

71.332.14b 132.373.16c 277.8914.60d 1639.3310.37e 1776.3311.15f

51.221.79b 65.112.29bc 87.003.44bcd 930.8910.99e 1295.6716.38f

– 98.90 96.16 89.57 28.89 22.77 – 99.80 99.15 98.09 60.51 44.23

One-way ANOVA Positive control and co-incubation Positive control and pre-incubation

F(6,56)=105.12*; HSD=56.02 F(6,56)=28.22*; HSD=57.41

F(6,56)=14.80*; HSD=61.45 F(6,56)=297.41*; HSD=32.51

F(6,56)=131.11*; HSD=70.49 F(6,56)=337.28*; HSD=47.89

F(5,48)=6016.01*; HSD=53.07 F(5,48)=5399.99*; HSD=51.65

Two-way ANOVA Co-incubation and pre-incubation Treatment Dose TreatmentDose

F(1,96)=67.61* F(5,96)=87.64* F(5,96)=36.08*

F(1,96)=1785.10* F(5,96)=12.16* F(5,96)=9.85*

F(1,96)=5.16* F(5,96)=216.54* F(5,96)=2.54

F(1,80)=2483.24* F(4,80)=11828.59* F(4,80)=494.91*

K. Kaur et al. / Food and Chemical Toxicology 40 (2002) 1475–1482

Spontaneous

% Inhibition

NPD (Direct-acting mutagen)

Data shown are meanSE of two repeated experiments. NPD: 4-nitro-o-phenylenediamene; 2AF: 2-aminofluorene; S9:without S9; +S9: with S9. Means followed by the same letter are not significantly different using HSD multiple comparison test. * P40.05. 1479

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Fig. 3. Effect of methanol fraction isolated from Terminalia arjuna on Acid Black dye (S9), Acid Black dye (+S9), NPD- and 2AF-induced mutagenicity in TA98 tester strain of Salmonella typhimurium. *Positive control. % of control ¼

Hisþ revertants=plate with mutagen and antimutagen  100: Hisþ revertants=plate with mutagen alone

the S9-dependent mutagens, namely 2AF and Acid Black dye, than the direct-acting mutagen, NPD. The results obtained with benzene and chloroform extracts were insignificant (data not shown).

4. Discussion The results of the present study demonstrate that both acetone and methanol fractions contained some antimutagens capable of inhibiting the mutagenicities of Acid Black dye, NPD and 2AF. On the basis of results obtained, it is therefore suggested that antimutagens present in these fractions may interact with some specific enzyme system of microsomal cytochrome P-448/P-450 in the liver homogenates which are necessary for activation of chemical mutagens. These enzymes catalyse a range of oxidative reactions, each with broad substrate specificity: aromatic and aliphatic

hydroxylations; N-, O- and S-dealkylations; sulfoxidation; deamination; epoxidation; desulfuration; and dehalogenation. Over 1000 chemicals are already known to be transformed by this system and many additional chemicals may serve as substrates (West, 1980). The activation of 2AF involves the formation of N-hydroxy2-aminofluorene, a reaction catalyzed by the cytochrome P450 enzyme system. There are reports in the literature that lettuce and string bean extracts as well as some natural compounds inhibit the mutagenicities of benzo[a]pyrene (B(a)P) and smoke condensate, and the mechanism of inhibition was suggested to be the interaction between antimutagen and enzymes in liver homogenate (Van der Hoeven et al., 1986). Yen and Chen (1995) reported that tea extracts showed a strong antimutagenic action against five indirect mutagens in TA98 and TA100 tester strains of S. typhimurium. The probability is that polyphenols, which are important constituents, may be one of the prime factors for the

K. Kaur et al. / Food and Chemical Toxicology 40 (2002) 1475–1482

observed antimutagenicity, since they have been reported as antimutagens in a number of systems (Sayer et al., 1982; Wood et al., 1985; Teel, 1986; San and Chang, 1987; Calomme et al., 1996; Daner et al., 1998; Kirzkova et al., 1998; Shih et al., 2000). Triterpenoids have also been found to exert potent antimutagenic/anticarcinogenic activity. Shao et al. (1997) obtained triterpenoid saponins from Aster lingulatus and showed them to exhibit inhibitory activity on DNA synthesis in human leukemia HL-60 cells. The increased antimutagenic activity of methanol fraction may be due to its more oligomeric nature. Gali et al. (1992) reported hydrolyzable tannins to be potent inhibitors of tumor promotion in mouse skin treated with 12-O-tetradecanoylphorbol-13-acetate (TPA) in vivo and observed that tannic acid, ellagic acid and gallic acid, which had decreasing molecular masses, also had decreasing inhibitory effects, suggesting that oligomeric hydrolyzable tannins have more antitumor-promoting activities than monomeric hydrolyzable tannins. Studies by some workers on antimutagenic, antitumor and anticarcinogenic activities of plant phenolics revealed that these biochemical constituents do not act via a single mechanism (Sayer et al., 1982; Huang et al., 1983, 1985; Wood et al., 1985; Newmark, 1987; Mukhtar et al., 1988). They interfere with the metabolic activation of promutagens, act as blocking agents, form adducts with ultimate metabolite and scavenge free radicals, but the exact mechanism by which the antimutagens present in acetone and methanol fractions inhibited the mutagenicities of Acid Black dye and 2AF is not known. Further characterization of these fractions has been undertaken and success has been obtained in isolating ellagic acid and triterpenes in purified form. These have been confirmed by the standards. Work is in progress to unravel their antimutagenic effect.

Acknowledgements We are grateful to Professor B.N. Ames, Department of Biochemistry, University of California, Berkeley, USA, for supplying the TA98 strain of S. typhimurium for the present investigation. We are also highly thankful to Professor A.K. Thukral, Department of Botanical Sciences, Guru Nanak Dev University, Amritsar, India, for the help rendered to us in the statistical analysis of the results.

References Calomme, M., Pieters, L., Vlientinct, A., Vanden-Berghe, D., 1996. Inhibition of bacterial mutagenesis by citrus flavonoids. Planta Medica 62, 222–226. Daner, A., Metzner, P., Schimmer, U., 1998. Proanthocyanidins from the bark of Hamamelis virginiana exhibit antimutagenic properties against nitroaromatic compounds. Planta Medica 64, 324–327.

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Ebringer, L., Krizkova, L., Polomyi, J., Dobias, J., Lahitona, N., 1999. Antimutagenicity of lignin in vitro. Anticancer Research 19, 569–572. Gali, H.U., Perchellet, E.M., Klish, D.S., Johnson, J.M., Perchellet, J.-P., 1992. Hydrolyzable tannins: potent inhibitors of hydrogen peroxide production and tumor promotion in mouse skin treated with 12-O-tetradecanoylphorbol-13-acetate in vivo. International Journal of Cancer 51, 425–432. Grover, I.S., Bala, S., 1993. Studies on antimutagenic activity of Terminalia bellerica (myroblan) in Salmonella typhimurium. Mutation Research 300, 1–3. Huang, M.-T., Chang, R.L., Wood, A.W., Newmark, H.L., Sayer, J.M., Yagi, H., Jerina, D.M., Conney, A.H., 1985. Inhibition of the mutagenicity of bay region diol epoxides of polycyclic aromatic hydrocarbons by tannic acid, hydroxylated anthraquinones and hydroxylated cinnamic acid derivatives. Carcinogenesis 6, 237–241. Huang, M.-T., Wood, A.W., Newmark, H.L., Sayer, J.M., Yagi, H., Jerina, D.M., Conney, A.H., 1983. Inhibition of the mutagenicity of bay region diol epoxides of polycyclic aromatic hydrocarbons by phenolic plant flavonoids. Carcinogenesis 4, 1631–1637. Kaur, S.J., Grover, I.S., Kumar, S., 1997. Antimutagenic potential of ellagic acid isolated from Terminalia arjuna. Indian Journal of Experimental Biology 35, 478–482. Kirzkova, L., Nagy, M., Polomyi, J., Ebringer, L., 1998. The effect of flavonoids on ofloxacin induced mutagenicity in Euglena gracilis. Mutation Research 416, 85–92. Kumar, D.S., Prabhakar, Y.S., 1987. On the ethnomedical significance of the arjun tree, Terminalia arjuna (Roxb.) Wight & Arnot. Journal of Ethnopharmacology 20, 173–190. Lopes, G.K., Schulman, H.M., Hermes-Lima, M., 1999. Polyphenol tannic acid inhibits hydroxyl radical formation from Fenton reaction by complexing ferrous ions. Biochimica et Biophysica Acta 1472, 142–152. Maron, D.M., Ames, B.N., 1983. Revised methods for Salmonella mutagenicity test. Mutation Research 113, 173–215. Meyers L.S., Grossen N.E., 1974. Analysis of independent group designs. In: Behavioural Research, Theory, Procedure and Design. W.H. Freeman, San Francisco, pp. 237–252. Mukhtar, H., Das, M., Khan, W.A., Wang, Z.Y., Bik, D.P., Bickers, D.R., 1988. Exceptional activity of tannic acid among naturally occurring plant phenols in protecting against 7,12-dimethyl-benz(a)anthracene, benzo(a)pyrene, 3-methylcholanthrene and Nmethyl-N-nitrosourea-induced skin tumorigenesis in mice. Cancer Research 48, 2361–2365. Newmark, H.L., 1987. Plant phenolics as inhibitors of mutational and pre-carcinogenic events. Canadian Journal of Physiology and Pharmacology 65, 461–466. Okuda, T., Yoshida, T., Hatano, T., 1991. Economic and Medicinal Plant Research. In: Wagner, H., Farnsworth, N.R. (Eds.), Vol. 5. Farnsworth Academic Press, London, pp. 129–165. San, R.H.C., Chang, R.I.M., 1987. Inhibitory effect of phenolic compounds on aflatoxin B1 metabolism and induced mutagenesis. Mutation Research 177, 229–239. Sayer, J.M., Yagi, H., Wood, A.W., Conney, A.H., Jerina, D.M., 1982. Extremely facile reaction between the ultimate carcinogen benzo(a)pyrene-7,8-diol-9,10-epoxide and ellagic acid. Journal of the American Chemical Society 104, 5562–5564. Shao, Y., Ho, C.T., Chin, C.K., Poobrasert, O., Yang, S.W., Cordell, G.A., 1997. Asterlingulatosides C and D, cytotoxic triterpenoid saponins from Aster lingulatus. Journal of Natural Products 60, 743–746. Shih, H., Pickwell, G.V., Quattrochi, L.C., 2000. Differential effects of flavonoid compounds on tumor-promoter induced activation of the human CYP1A2 enhancer. Archives of Biochemistry and Biophysics 373, 287–294. Surh, Y., 1999. Molecular mechanisms of chemopreventive effects of

1482

K. Kaur et al. / Food and Chemical Toxicology 40 (2002) 1475–1482

selected dietary and medicinal phenolic substances. Mutation Research 428, 305–327. Teel, R.W., 1986. Ellagic acid binding to DNA as a possible mechanism for its antimutagenic and anticarcinogenic action. Cancer Letters 30, 329–336. Tominaga, S., Aoki, K., Fujimoto, I., Kurihara, M., 1994. Cancer Mortality and Morbidity. Japan Scientific Society Press, Tokyo. Van der Hoeven, J.C.M., 1986. Occurrence and detection of natural mutagens and modifying factors in food products. In: Hayashi, Y., Nagao, M., Sugimura, T., Takayama, S., Tomatis, L., Klattenberg, L.W., Wogan, G.N. (Eds.), Diet, Nutrition and Cancer. Japan Scientific Press, Tokyo, pp. 119–137. West, C.A., 1980. Hydroxylases, monoxygenases and cytochrome P450. In: Stumpf, P.K., Conn, E.E. (Eds.), The Biochemistry of

Plants. A Comprehensive Treatise, Vol. 2. Academic Press, New York, pp. 317–364. Wood, A.W., Huang, M.-T., Chang, R.L., Newmark, H.L., Lehr, R.E., Yagi, H., Sayer, J.M., Jerina, D.M., Conney, A.H., 1985. Inhibition of the mutagenicity of bay region diol epoxides of polycyclic aromatic hydrocarbons by naturally occurring plant phenols: exceptional activity of ellagic acid. Proceedings of the National Academy of Sciences of the USA 79, 5513–5517. Yen, G., Chen, H., 1995. Antioxidant activity of various tea extracts in relation to their antimutagenicity. Journal of Agricultural and Food Chemistry 43, 27–32. Zhu, M., Phillipson, J.D., Greengrass, P.M., Bowery, N.E., Cai, Y., 1997. Plant polyphenols: biologically active compounds or nonselective binders to protein? Phytochemistry 44, 441–447.