Akademik Veri Yönetim Sistemi
Hacettepe University Journal of the Faculty of Pharmacy, cilt.34, sa.2, ss.133-146, 2014 (Scopus)
Phenolic substances in natural products play an important role in protecting the organism against harmful effects of reactive oxygen species. Tannic acid (TA), water-soluble polyphenol, is present in many plant beverages and foods, such as herbal teas, beer, walnut, hazelnut, and berries. Tannins have been reported to exert some physiological effects, such as to accelerate blood clotting, reduce blood pressure, decrease the serum lipid level, cause liver necrosis, and modulate immunoresponses. It acts as an antioxidant or a prooxidant, depending on the concentrations of TA and the number and position of hydroxyl groups on TA. It has been suggested that tannins might be carcinogenic, as the incidences of certain cancers, such as esophageal cancer, are related to consumption of tannins-rich foods. In the present study, the antioxidant capacity of TA was determined by the trolox equivalent anti-oxidant capacity assay and the effect of TA on DNA damage induced by H2O2in human lymphocytes were investigated by the standard comet assay and the formamidopyrimidine-DNA-glycoslase (Fpg) modified comet assay. Our study showed that above the concentrations of 0.5 pM TA showed significant antioxidant capacity. It was determined that at all the concentrations studied (0.1-100 µM), TA alone did not cause DNA damage and even significantly reduced oxidative DNA damage induced by H2O2. It was also determined that within the concentration of 0.1-100 µM TA alone did not induce Fpg sensitive sites indicating the increased oxidized purine base levels, but TA treatment at all the concentrations studied significantly reduced the Fpg sensitive sites induced by H2O2 in a dose dependent. In conclusion, it seems that TA exerts a protective effect on oxidative DNA damage in human lymphocytes in vitro. In appropriate levels as a dietary supplement, TA may be used as a natural antioxidant however it is necessary to perform the further in vivo and in vitro studies to clarify the potential effects of TA on human health.