Antioxidative and antimutagenic effects of theaflavins from black tea

Shiraki, Mayumi; Hara, Yukihiko; Osawa, Toshihiko; Kumon, Hiroki; Nakayama, Tsutomu; Kawakishi, Shunrô

doi:10.1016/0165-7992(94)90041-8

Cited by 161 publications

(74 citation statements)

References 16 publications

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“…EGCG contains multiple hydroxyl groups, particularly in the B-rings, and it significantly increases the production of ROS. High dosages of EGCG can induce DNA damage [41,103,124] due to the generation of hydrogen peroxide. A recent study showed that EGCG neither directly scavenges hydrogen peroxide nor mediates other antioxidant activities, but instead increases hydrogen-peroxide-induced oxidative stress and DNA damage in vitro [19].…”

Section: Possible Prooxidant Activity and Carcinogenicity Of Some Polmentioning

confidence: 99%

The roles of polyphenols in cancer chemoprevention

2006

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Abstract.Oxidative stress imposed by reactive oxygen species (ROS) plays a crucial role in the pathophysiology associated with neoplasia, atherosclerosis, and neurodegenerative diseases. The ROS-induced development of cancer involves malignant transformation due to altered gene expression through epigenetic mechanisms as well as DNA mutations. Considerable attention has been focused on identifying naturally occurring antioxidative phenolic phytochemicals that are able to decrease ROS levels, but the efficacies of antioxidant therapies have been equivocal at best. Several studies have shown that some antioxidants exhibit prooxidant activity under certain conditions and potential carcinogenicity under others, and that dietary supplementation with large amounts of a single antioxidant may be deleterious to human health. This article reviews the intracellular signaling pathways that respond to oxidative stress and how they are modulated by naturally occurring polyphenols. The possible toxicity and carcinogenicity of polyphenols is also discussed.

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Section: Possible Prooxidant Activity and Carcinogenicity Of Some Polmentioning

confidence: 99%

The roles of polyphenols in cancer chemoprevention

2006

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“…These effects of catechins are due to the radical scavenging and antioxidant activities inherent in polyphenolic compounds. [3][4][5] To date, many attempts not only to take advantage of their desirable bioactivities, but also to enhance those activities, have been made. [6][7][8][9][10][11] We found that epigallocatechin gallate (EGCG) showed hepatoprotective activity against hepatotoxins, bromobenzene (BB) and rubratoxin B (RB) (to be reported elsewhere).…”

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confidence: 99%

Enhancing Effect of Zinc on Hepatoprotectivity of Epigallocatechin Gallate in Isolated Rat Hepatocytes.

Kagaya

Kawase

Maeda

et al. 2002

Biological & Pharmaceutical Bulletin

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“…The most abundant TFs in black tea are theaflavin (TF), theaflavin-3-O-gallate (TF-3-g), theaflavin-3'-O-gallate (TF-3'-g) and theaflavin-3,3'-di-Ogallate (TFDg) (Figure 1). The dry weight of TF, TF-3-g, TF-3'-g and TFDg in black tea are 0.08, 0.3, 0.2 and 0.4%, respectively (Davies et al, 1999;Hara et al, 1987;Shiraki et al, 1994;Tanaka et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

“…It has been reported that TFs show health benefits such as antioxidant effects (Shiraki et al, 1994), antimutagenic effects (Shiraki et al, 1994), anti-inflammation effects (Lin et al, 1999), cancer prevention (Leone et al, 2003), reduction of blood cholesterol levels (Ikeda et al, 2010) and anti-hyperglycemic effects (Matsui et al, 2007). However, the distinctive bitter taste, insolubility in water, and easy oxidation of tea polyphenols such as catechins and/or TFs are problematic for their use as food and/or beverage additives.…”

Section: Introductionmentioning

confidence: 99%