Table of Contents Author Guidelines Submit a Manuscript
Journal of Toxicology
Volume 2011, Article ID 467305, 12 pages
http://dx.doi.org/10.1155/2011/467305
Review Article

Research Strategies in the Study of the Pro-Oxidant Nature of Polyphenol Nutraceuticals

Department of Biology, Stern College for Women, Yeshiva University, 245 Lexington Avenue, New York, NY 10016, USA

Received 10 January 2011; Accepted 12 April 2011

Academic Editor: P. J. O'Brien

Copyright © 2011 Harvey Babich et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Linked References

  1. R. Béliveau and D. Gingras, “Role of nutrition in preventing cancer,” Canadian Family Physician, vol. 53, no. 11, pp. 1905–1911, 2007. View at Google Scholar · View at Scopus
  2. S. Nair, W. Li, and A. N. T. Kong, “Natural dietary anti-cancer chemopreventive compounds: redox-mediated differential signaling mechanisms in cytoprotection of normal cells versus cytotoxicity in tumor cells,” Acta Pharmacologica Sinica, vol. 28, no. 4, pp. 459–472, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  3. H. Pelicano, D. Carney, and P. Huang, “ROS stress in cancer cells and therapeutic implications,” Drug Resistance Updates, vol. 7, no. 2, pp. 97–110, 2004. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  4. H. U. Simon, A. Haj-Yehia, and F. Levi-Schaffer, “Role of reactive oxygen species (ROS) in apoptosis induction,” Apoptosis, vol. 5, no. 5, pp. 415–418, 2000. View at Publisher · View at Google Scholar · View at Scopus
  5. J. O. Moskaug, H. Carlsen, M. C. Myhrstad, and R. Blomhoff, “Polyphenols and glutathione synthesis regulation,” The American Journal of Clinical Nutrition, vol. 71, supplement, pp. 16985–17025, 2005. View at Google Scholar · View at Scopus
  6. E. A. Decker, “Phenolics: prooxidants or antioxidants?” Nutrition Reviews, vol. 55, no. 11, pp. 396–398, 1997. View at Google Scholar · View at Scopus
  7. L. R. Fukumoto and G. Mazza, “Assessing antioxidant and prooxidant activities of phenolic compounds,” Journal of Agricultural and Food Chemistry, vol. 48, no. 8, pp. 3597–3604, 2000. View at Publisher · View at Google Scholar · View at Scopus
  8. R. Vittal, Z. E. Selvanayagam, Y. Sun et al., “Gene expression changes induced by green tea polyphenol (−)-epigallocatechin-3-gallate in human bronchial epithelial 21BES cells analyzed by DNA microarray,” Molecular Cancer Therapeutics, vol. 3, no. 9, pp. 1091–1099, 2004. View at Google Scholar · View at Scopus
  9. J. D. Lambert and R. J. Elias, “The antioxidant and pro-oxidant activities of green tea polyphenols: a role in cancer prevention,” Archives of Biochemistry and Biophysics, vol. 501, no. 1, pp. 65–72, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  10. C. S. Yang, J. D. Lambert, Z. Hou, J. Ju, G. Lu, and X. Hao, “Molecular targets for the cancer preventive activity of tea polyphenols,” Molecular Carcinogenesis, vol. 45, no. 6, pp. 431–435, 2006. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  11. P. C. Chai, L. H. Long, and B. Halliwell, “Contribution of hydrogen peroxide to the cytotoxicity of green tea and red wines,” Biochemical and Biophysical Research Communications, vol. 304, no. 4, pp. 650–654, 2003. View at Publisher · View at Google Scholar · View at Scopus
  12. J. H. Weisburg, D. B. Weissman, T. Sedaghat, and H. Babich, “In vitro cytotoxicity of epigallocatechin gallate and tea extracts to cancerous and normal cells from the human oral cavity,” Basic and Clinical Pharmacology and Toxicology, vol. 95, no. 4, pp. 191–200, 2004. View at Google Scholar · View at Scopus
  13. H. Babich, N. J. Ackerman, F. Burekhovich, H. L. Zuckerbraun, and A. G. Schuck, “Gingko biloba leaf extract induces oxidative stress in carcinoma HSC-2 cells,” Toxicology in Vitro, vol. 23, no. 6, pp. 992–999, 2009. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  14. J. H. Weisburg, A. G. Schuck, M. S. Silverman et al., “Pomegranate extract, A prooxidant with antiproliferative and proapoptotic activities preferentially towards carcinoma cells,” Anti-Cancer Agents in Medicinal Chemistry, vol. 10, no. 8, pp. 634–643, 2010. View at Google Scholar
  15. T. Lapidot, M. D. Walker, and J. Kanner, “Can apple antioxidants inhibit tumor cell proliferation? Generation of H2O2 during interaction of phenolic compounds with cell culture media,” Journal of Agricultural and Food Chemistry, vol. 50, no. 11, pp. 3156–3160, 2002. View at Publisher · View at Google Scholar · View at Scopus
  16. L. H. Long, M. V. Clement, and B. Halliwell, “Artifacts in cell culture: rapid generation of hydrogen peroxide on addition of (−)-epigallocatechin, (−)-epigallocatechin gallate, (+)-catechin, and quercetin to commonly used cell culture media,” Biochemical and Biophysical Research Communications, vol. 273, no. 1, pp. 50–53, 2000. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  17. H. Babich, M. E. Krupka, H. A. Nissim, and H. L. Zuckerbraun, “Differential in vitro cytotoxicity of (−)-epicatechin gallate (ECG) to cancer and normal cells from the human oral cavity,” Toxicology in Vitro, vol. 19, no. 2, pp. 231–242, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  18. H. Babich, H. L. Zuckerbraun, and S. M. Weinerman, “In vitro cytotoxicity of (−)-catechin gallate, a minor polyphenol in green tea,” Toxicology Letters, vol. 171, no. 3, pp. 171–180, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  19. A. G. Schuck, M. B. Ausubel, H. L. Zuckerbraun, and H. Babich, “Theaflavin-3,3-digallate, a component of black tea: an inducer of oxidative stress and apoptosis,” Toxicology in Vitro, vol. 22, no. 3, pp. 598–609, 2008. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  20. H. Babich, R. T. Gottesman, E. J. Liebling, and A. G. Schuck, “Theaflavin-3-gallate and theaflavin-3-gallate, polyphenols in black tea with prooxidant properties,” Basic and Clinical Pharmacology and Toxicology, vol. 103, no. 1, pp. 66–74, 2008. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  21. T. Lapidot, M. D. Walker, and J. Kanner, “Antioxidant and prooxidant effects of phenolics on pancreatic β-cells in vitro,” Journal of Agricultural and Food Chemistry, vol. 50, no. 25, pp. 7220–7225, 2002. View at Publisher · View at Google Scholar · View at Scopus
  22. K. W. Lee, H. J. Hur, H. J. Lee, and C. Y. Lee, “Antiproliferative effects of dietary phenolic substances and hydrogen peroxide,” Journal of Agricultural and Food Chemistry, vol. 53, no. 6, pp. 1990–1995, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  23. H. Nakagawa, K. Hasumi, J. T. Woo, K. Nagai, and M. Wachi, “Generation of hydrogen peroxide primarily contributes to the induction of Fe(II)-dependent apoptosis in Jurkat cells by (−)-epigallocatechin gallate,” Carcinogenesis, vol. 25, no. 9, pp. 1567–1574, 2004. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  24. S. G. Rhee, T. S. Chang, W. Jeong, and D. Kang, “Methods for detection and measurement of hydrogen peroxide inside and outside of cells,” Molecules and Cells, vol. 29, no. 6, pp. 539–549, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  25. G. Y. Yang, J. Liao, K. Kim, E. J. Yurkow, and C. S. Yang, “Inhibition of growth and induction of apoptosis in human cancer cell lines by tea polyphenols,” Carcinogenesis, vol. 19, no. 4, pp. 611–616, 1998. View at Publisher · View at Google Scholar · View at Scopus
  26. T. Nakazato, K. Ito, Y. Miyakawa et al., “Catechin, a green tea component, rapidly induces apoptosis of myeloid leukemic cells via modulation of reactive oxygen species production in vitro and inhibits tumor growth in vivo,” Haematologica, vol. 90, no. 3, pp. 317–325, 2005. View at Google Scholar · View at Scopus
  27. T. Nakazato, K. Ito, Y. Ikeda, and M. Kizaki, “Green tea component, catechin, induces apoptosis of human malignant B cells via production of reactive oxygen species,” Clinical Cancer Research, vol. 11, no. 16, pp. 6040–6049, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  28. T. Yamamoto, J. Lewis, J. Wataha et al., “Roles of catalase and hydrogen peroxide in green tea polyphenol-induced chemopreventive effects,” Journal of Pharmacology and Experimental Therapeutics, vol. 308, no. 1, pp. 317–323, 2004. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  29. G. Y. Yang, J. Liao, C. Li et al., “Effect of black and green tea polyphenols on c-jun phosphorylation and H2O2 production in transformed and non-transformed human bronchial cell lines: possible mechanisms of cell growth inhibition and apoptosis induction,” Carcinogenesis, vol. 21, no. 11, pp. 2035–2039, 2000. View at Google Scholar · View at Scopus
  30. M. M. Chan, K. J. Soprano, K. Weinstein, and D. Fong, “Epigallocatechin-3-gallate delivers hydrogen peroxide to induce death of ovarian cancer cells and enhances their cisplatin susceptibility,” Journal of Cellular Physiology, vol. 207, no. 2, pp. 389–396, 2006. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  31. T. Atsumi, K. Tonosaki, and S. Fujisawa, “Induction of early apoptosis and ROS-generation activity in human gingival fibroblasts (HGF) and human submandibular gland carcinoma (HSG) cells treated with curcumin,” Archives of Oral Biology, vol. 51, no. 10, pp. 913–921, 2006. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  32. S. Yeu, C. M. Sun, H. H. Chuang, and P. T. Chang, “Studies on the cytotoxic mechanisms of ginkgetin in a human ovarian adenocarcinoma cell line,” Naunyn-Schmiedeberg's, vol. 362, no. 1, pp. 82–90, 2000. View at Publisher · View at Google Scholar · View at Scopus
  33. J. M. Feugang, F. Ye, D. Y. Zhang et al., “Cactus pear extracts induce reactive oxygen species production and apoptosis in ovarian cancer cells,” Nutrition and Cancer, vol. 62, no. 5, pp. 692–699, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  34. H. Babich, A. R. Selevan, and E. R. Ravkin, “Glutathione as a mediator of the in vitro cytotoxicity of a green tea polyphenol extract,” Toxicology Mechanisms and Methods, vol. 17, no. 6, pp. 357–369, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  35. H. Babich, S. M. Pinsky, E. T. Muskin, and H. L. Zuckerbraun, “In vitro cytotoxicity of a theaflavin mixture from black tea to malignant, immortalized, and normal cells from the human oral cavity,” Toxicology in Vitro, vol. 20, no. 5, pp. 677–688, 2006. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  36. J. Lu, C. T. Ho, G. Ghai, and . Kuan Yu Chen, “Differential effects of theaflavin monogallates on cell growth, apoptosis, and Cox-2 gene expression in cancerous versus normal cells,” Cancer Research, vol. 60, no. 22, pp. 6465–6471, 2000. View at Google Scholar · View at Scopus
  37. H. Babich, A. Sedletcaia, and B. Kenigsberg, “In vitro cytotoxicity of protocatechuic acid to cultured human cells from oral tissue: involvement in oxidative stress,” Pharmacology and Toxicology, vol. 91, no. 5, pp. 245–253, 2002. View at Publisher · View at Google Scholar · View at Scopus
  38. A. Furukawa, S. Oikawa, M. Murata, Y. Hiraku, and S. Kawanishi, “(−)-Epigallocatechin gallate causes oxidative damage to isolated and cellular DNA,” Biochemical Pharmacology, vol. 66, no. 9, pp. 1769–1778, 2003. View at Publisher · View at Google Scholar · View at Scopus
  39. H. Babich, A. Stern, and E. Borenfreund, “Eugenol cytotoxicity evaluated with continuous cell lines,” Toxicology in Vitro, vol. 7, no. 2, pp. 105–109, 1993. View at Publisher · View at Google Scholar · View at Scopus
  40. B. R. You and W. H. Park, “Gallic acid-induced lung cancer cell death is related to glutathione depletion as well as reactive oxygen species increase,” Toxicology in Vitro, vol. 24, no. 5, pp. 1356–1362, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  41. S. C. Sahu, D. I. Ruggles, and M. W. O'Donnell, “Prooxidant activity and toxicity of nordihydroguaiaretic acid in clone-9 rat hepatocyte cultures,” Food and Chemical Toxicology, vol. 44, no. 10, pp. 1751–1757, 2006. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  42. S. H. Bhat, A. S. Azmi, and S. M. Hadi, “Prooxidant DNA breakage induced by caffeic acid in human peripheral lymphocytes: involvement of endogenous copper and a putative mechanism for anticancer properties,” Toxicology and Applied Pharmacology, vol. 218, no. 3, pp. 249–255, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  43. S. B. Sarikçioǧlu, G. Öner, and E. Tercan, “Antioxidant effect of EGb 761 on hydrogen peroxide-induced lipoperoxidation of G-6-PD deficient erythrocytes,” Phytotherapy Research, vol. 18, no. 10, pp. 837–840, 2004. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  44. H. Babich, A. G. Reisbaum, and H. L. Zuckerbraun, “In vitro response of human gingival epithelial S-G cells to resveratrol,” Toxicology Letters, vol. 114, no. 1–3, pp. 143–153, 2000. View at Publisher · View at Google Scholar · View at Scopus
  45. L. Elbling, R. M. Weiss, O. Teufelhofer et al., “Green tea extract and (−)-epigallocatechin-3-gallate, the major tea catechin, exert oxidant but lack antioxidant activities,” FASEB Journal, vol. 19, no. 7, pp. 807–809, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  46. Z. Hou, S. Sang, H. You et al., “Mechanism of action of (−)-epigallocatechin-3-gallate: auto-oxidation- dependent inactivation of epidermal growth factor receptor and direct effects on growth inhibition in human esophageal cancer KYSE 150 cells,” Cancer Research, vol. 65, no. 17, pp. 8049–8056, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  47. G. C. Yen, J. W. Ju, and C. H. Wu, “Modulation of tea and tea polyphenols on benzo(a)pyrene-induced DNA damage in Chang liver cells,” Free Radical Research, vol. 38, no. 2, pp. 193–200, 2004. View at Publisher · View at Google Scholar · View at Scopus
  48. S. M. Hadi, S. H. Bhat, A. S. Azmi, S. Hanif, U. Shamim, and M. F. Ullah, “Oxidative breakage of cellular DNA by plant polyphenols: a putative mechanism for anticancer properties,” Seminars in Cancer Biology, vol. 17, no. 5, pp. 370–376, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  49. A. Ishino, S. Mita, S. Watanabe, and H. Sakagami, “Effect of anticancer drugs, metals and antioxidants on cytotoxic activity of epigallocatechin gallate,” Anticancer Research, vol. 19, no. 5, pp. 4343–4348, 1999. View at Google Scholar · View at Scopus
  50. S. Fujisawa, T. Atsumi, M. Ishihara, and Y. Kadoma, “Cytotoxicity, ROS-generation activity and radical-scavenging activity of curcumin and related compounds,” Anticancer Research, vol. 24, no. 2, pp. 563–569, 2004. View at Google Scholar · View at Scopus
  51. C. Chen, G. Shen, V. Hebbar, R. Hu, E. D. Owuor, and A. N. T. Kong, “Epigallocatechin-3-gallate-induced stress signals in HT-29 human colon adenocarcinoma cells,” Carcinogenesis, vol. 24, no. 8, pp. 1369–1378, 2003. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  52. K. A. Nath, H. Enright, L. Nutter, M. Fischereder, J. N. Zou, and R. P. Hebbel, “Effect of pyruvate on oxidant injury to isolated and cellular DNA,” Kidney International, vol. 45, no. 1, pp. 166–176, 1994. View at Google Scholar · View at Scopus
  53. R. T. Mallet, “Pyruvate: metabolic protector of cardiac performance,” Proceedings of the Society for Experimental Biology and Medicine, vol. 223, no. 2, pp. 136–148, 2000. View at Google Scholar · View at Scopus
  54. A. Shostak, L. Gotloib, R. Kushnier, and V. Wajsbrot, “Protective effect of pyruvate upon cultured mesothelial cells exposed to 2 mM hydrogen peroxide,” Nephron, vol. 84, no. 4, pp. 362–366, 2000. View at Google Scholar · View at Scopus
  55. H. Babich, E. J. Liebling, R. F. Burger, H. L. Zuckerbraun, and A. G. Schuck, “Choice of DMEM, formulated with or without pyruvate, plays an important role in assessing the in vitro cytotoxicity of oxidants and prooxidant nutraceuticals,” In vitro Cellular & Developmental Biology, vol. 45, no. 5-6, pp. 226–233, 2009. View at Google Scholar · View at Scopus
  56. C. K. Garcia, J. L. Goldstein, R. K. Pathak, R. G. W. Anderson, and M. S. Brown, “Molecular characterization of a membrane transporter for lactate, pyruvate, and other monocarboxylates: implications for the Cori cycle,” Cell, vol. 76, no. 5, pp. 865–873, 1994. View at Publisher · View at Google Scholar · View at Scopus
  57. R. Bunger, R. T. Mallet, and D. A. Hartman, “Pyruvate-enhanced phosphorylation potential and inotropism in normoxic and postischemic isolated working heart. Near-complete prevention of reperfusion contractile failure,” European Journal of Biochemistry, vol. 180, no. 1, pp. 221–233, 1989. View at Google Scholar · View at Scopus
  58. X. Wang, E. Perez, R. Liu, L. J. Yan, R. T. Mallet, and S. H. Yang, “Pyruvate protects mitochondria from oxidative stress in human neuroblastoma SK-N-SH cells,” Brain Research, vol. 1132, no. 1, pp. 1–9, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  59. F. M. Maiorino, R. Brigelius-Flohé, K. D. Aumann, A. Roveri, D. Schomburg, and L. Flohé, “[5] Diversity of glutathione peroxidases,” Methods in Enzymology, vol. 252, pp. 38–48, 1995. View at Publisher · View at Google Scholar · View at Scopus
  60. M. K. Eberhardt, C. Santos, and M. A. Soto, “Formation of hydroxyl radicals and Co3+ in the reaction of Co2+-EDTA with hydrogen peroxide. Catalytic effect of Fe3+,” Biochimica et Biophysica Acta, vol. 1157, no. 1, pp. 102–106, 1993. View at Publisher · View at Google Scholar · View at Scopus
  61. H. Babich, T. Gold, and R. Gold, “Mediation of the in vitro cytotoxicity of green and black tea polyphenols by cobalt chloride,” Toxicology Letters, vol. 155, no. 1, pp. 195–205, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  62. T. Sakagami, K. Satoh, M. Ishihara et al., “Effect of cobalt ion on radical intensity and cytotoxic activity of antioxidants,” Anticancer Research, vol. 20, no. 5, pp. 3143–3150, 2000. View at Google Scholar · View at Scopus
  63. H. Nakagawa, M. Wachi, J. T. Woo et al., “Fenton reaction is primarily involved in a mechanism of (3)-epigallocatechin-3-gallate to induce osteoclastic cell death,” Biochemical and Biophysical Research Communications, vol. 292, no. 1, pp. 94–101, 2002. View at Publisher · View at Google Scholar · View at Scopus
  64. S. Inoue, K. Ito, K. Yamamoto, and S. Kawanishi, “Caffeic acid causes metal-dependent damage to cellular and isolated DNA through H2O2 formation,” Carcinogenesis, vol. 13, no. 9, pp. 1497–1502, 1992. View at Google Scholar · View at Scopus
  65. S. Oikawa, A. Furukawa, H. Asada, K. Hirakawa, and S. Kawanishi, “Catechins induce oxidative damage to cellular and isolated DNA through the generation of reactive oxygen species,” Free Radical Research, vol. 37, no. 8, pp. 881–890, 2003. View at Publisher · View at Google Scholar · View at Scopus
  66. M. C. W. Myhrstad, H. Carlsen, O. Nordström, R. Blomhoff, and J. Ø. Moskaug, “Flavonoids increase the intracellular glutathione level by transactivation of the γ-glutamylcysteine synthetase catalytical subunit promoter,” Free Radical Biology and Medicine, vol. 32, no. 5, pp. 386–393, 2002. View at Publisher · View at Google Scholar · View at Scopus
  67. B. A. Arrick, C. F. Nathan, O. W. Griffith, and Z. A. Cohn, “Glutathione depletion sensitizes tumor cells to oxidative cytolysis,” The Journal of Biological Chemistry, vol. 257, no. 3, pp. 1231–1237, 1982. View at Google Scholar · View at Scopus
  68. H. Raza and A. John, “Green tea polyphenol epigallocatechin-3-gallate differentially modulates oxidative stress in PC12 cell compartments,” Toxicology and Applied Pharmacology, vol. 207, no. 3, pp. 212–220, 2005. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  69. Y. D. Hsuuw and W. H. Chan, “Epigallocatechin gallate dose-dependently induces apoptosis or necrosis in human MCF-7 cells,” Annals of the New York Academy of Sciences, vol. 1095, pp. 428–440, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  70. G. X. Li, Y. K. Chen, Z. Hou et al., “Pro-oxidative activities and dose-response relationship of (−)-epigallocatechin-3-gallate in the inhibition of lung cancer cell growth: a comparative study in vivo and in vitro,” Carcinogenesis, vol. 31, no. 5, pp. 902–910, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  71. J. D. Lambert, M. J. Kennett, S. Sang, K. R. Reuhl, J. Ju, and C. S. Yang, “Hepatotoxicity of high oral dose (−)-epigallocatechin-3-gallate in mice,” Food and Chemical Toxicology, vol. 48, no. 1, pp. 409–416, 2010. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus
  72. N. Li, Z. Sun, C. Han, and J. Chen, “The chemopreventive effects of tea on human oral precancerous mucosa lesions,” Proceedings of the Society for Experimental Biology and Medicine, vol. 220, no. 4, pp. 218–224, 1999. View at Google Scholar · View at Scopus
  73. A. Halder, R. Raychowdhury, A. Ghosh, and M. De, “Black tea (Camellia sinensis) as a chemopreventive agent in oral precancerous lesions,” Journal of Environmental Pathology, Toxicology and Oncology, vol. 24, no. 2, pp. 141–144, 2005. View at Publisher · View at Google Scholar · View at Scopus
  74. C. S. Yang, M. J. Lee, and L. Chen, “Human salivary tea catechin levels and catechin esterase activities: implication in human cancer prevention studies,” Cancer Epidemiology Biomarkers and Prevention, vol. 8, no. 1, pp. 83–89, 1999. View at Google Scholar · View at Scopus
  75. M. J. Lee, J. D. Lambert, S. Prabhu et al., “Delivery of tea polyphenols to the oral cavity by green tea leaves and black tea extract,” Cancer Epidemiology Biomarkers and Prevention, vol. 13, no. 1, pp. 132–137, 2004. View at Publisher · View at Google Scholar · View at Scopus
  76. J. D. Lambert, S. J. Kwon, J. Hong, and C. S. Yang, “Salivary hydrogen peroxide produced by holding or chewing green tea in the oral cavity,” Free Radical Research, vol. 41, no. 7, pp. 850–853, 2007. View at Publisher · View at Google Scholar · View at PubMed · View at Scopus