Black Tea Polyphenols, Theaflavins, Prevent Cellular DNA Damage by Inhibiting Oxidative Stress and Suppressing Cytochrome P450 1A1 in Cell Cultures

Abstract

Tea polyphenols have been demonstrated as chemopreventive agents in a number of experimental models. However, less is known about the mechanism of chemoprevention by black tea compared with that of green tea. Some beneficial properties of theaflavins, the black tea polyphenols, were investigated in the present study. Theaflavins showed inhibitory effects on H(2)O(2)- and tert-butyl hydroperoxide (tBuOOH)-induced cytotoxicity (evaluated by tetrazolium bromide reduction), cellular oxidative stress (detected by oxidation of 2', 7'-dichlorofluorescin), and DNA damage (measured by amount of 8-OHdG and comet assay) in rat normal liver epithelium cell RL-34 cell lines. In addition, theaflavins also exhibited suppression of cytochrome P450 1A1 induced by omeprazole in the human hepatoma HepG2 cell line. Furthermore, when HepG2 cells were pretreated with omeprazole to induce CYP1A1, then exposed to benzo[a]pyrene (B[a]P), DNA damage was observed using the comet assay. However, theaflavins could inhibit this DNA damage. These results indicated that theaflavins could prevent cellular DNA damage by inhibiting oxidative stress and suppressing cytochrome P450 1A1 in cell cultures.

Antimutagenesis Studies: Where Have They Been and Where Are They Heading?

“…Notable among the literature on antioxidants are studies on various teas, especially green tea (51,52). For example, polyphenols in green tea include catechins (‰avan-3-ols) (53,54), while in black tea, thea‰avin formation may be important (54,55). Polyphenols from green and black tea are eŠective antioxidants in model test systems, while tea polyphenols may also chelate pro-oxidant metals (56).…”

“…Various types of anti-mutagen appear to act through inhibiting induction of these enzymes, or otherwise interfering with the activation process. For example, black tea polyphenol (thea‰avin) has been shown to be able to reduce the induction of CYP1A1, at least in a human cultured cell line, and this has been suggested as one mechanism by which this class of chemicals can reduce DNA damage, and possibly also reduce cancer risk (55). The activation of speciˆc groups of mutagens resides with other speciˆc classes of enzymes.…”

Efficacy of Toothpastes on Bacteria Isolated from Oral Cavity

“…15 Studies also demonstrated the anti-cancerous activity and suppression of oral squamous cell carcinoma by Curcuma longa 16 Mentha spicata, 17 Withania somnifera, 18 Nigella sativa 19 and Azadirachta indica. 20 Feng, et al 21 reported that Camellia sinensis protects buccal cells from DNA damage caused by reactive oxygen species. Flower sap of Echinacea sp.…”

Study on the Effect of Several Natural Products on Tyrosine Damage Induced by Peroxynitrite

“…Natural products are important ingredients for medicines, in recent years a variety of natural products have been found to inhibit ONOO¯ damage, a large number of studies have shown that flavonoids compounds have strong antioxidant activity [9][10][11][12], and also these compounds have obvious pharmacological effects on cardiovascular disease treatment and anti-tumor [13]. Studies have shown that the antioxidant effect of flavonoids is closely related to the phenol hydroxyl group in the adjacent position.…”