In a study to establish whether green tea has anti-cancerous potential in human stomach and colon cancers, six cancerous and six non-cancerous adjacent human gastric tissues and seven cancerous and seven non-cancerous adjacent colon tissues were obtained from patients who underwent surgery for stomach and colon cancer in the Ankara University Faculty of Medicine, Department of General Surgery, Turkey. The tissues were treated with aqueous green tea extract at three different final concentrations (0.05%, 0.5%, and 1.25%) for one hour. Activity assays were performed on the same samples without green tea extract. Protein levels of the tissues were studied and adjusted to equal concentrations.
Xanthine oxidase (XO) and reduced adenosine deaminase (ADA) enzyme activities were measured before and after the incubation period. Percentage changes for the three different concentrations of green tea extract versus no green tea extract were calculated.