The chemopreventive effects of Theaflavin-3,3'-digallate, a component of black tea

Abstract

Black tea, the type of tea consumed by the majority of the world, has been attributed chemopreventive properties. The polyphenols, catechins and theaflavins, within black tea are considered the active components and theaflavins are unique to black tea. Epidemiological studies have not conclusively accredited black tea with chemopreventive benefits but preliminary clinical studies as well as numerous in vivo studies have demonstrated a chemopreventive effect upon different human organs. In vitro studies h~ve shown the cytotoxicity of black tea polyphenol extract and black tea theaflavin mixture. Our studies were among the first to specifically analyze the effects of an individual theaflavin monomer, theaflavin-3,3'-digallate (TF-3). TF-3 was shown to be cytotoxic towards cancerous cells. Normal cells were less sensitive to TF-3. As a potential method of cytotoxicity, the prooxidant abilities of TF-3 were ascertained by measuring the generation of reactive oxygen species (ROS). The reduction of ROS in the presence of catalase and superoxide dismutase provided evidence that TF-3 generates hydrogen peroxide and superoxide ion. These studies showed TF-3 as an inducer of oxidative stress. Further studies indicated that TF-3 induced apoptosis as the method of killing cancerou\ cells but not normal cells. TF-3 thus acts as a prooxidant killing cancerous cells but acting as an antioxidant protecting normal cells. The

delivery and bioavailability of TF-3 along with other theaflavins is critical with regard to the effectiveness and holding black tea leaf extract in the mouth is sufficient to deliver high levels of theaflavins to the oral cavity.