Total inhibition of 1O2-induced oxidative damage to guanine bases of DNA/RNA by turmeric extracts

The guanine base of nucleic acids is known to be very reactive towards degradation by 1O2-induced oxidative stress. Oxidative reactions of DNA are linked to many human diseases including cancer. Among the various forms of reactive O2 species (OH, 1O2 or O2-), the oxidative stress caused by 1O2 is of particular physiologic importance because of its selectively long life in aqueous medium and its ability to diffuse through a cell membrane. In this study we investigated the degradation of a model compound guanosine (Guo) by 1O2, which was generated by riboflavin-induced photosensitization and by molybdate ion catalyzed disproportionation of H2O2. We observed the remarkable ability of an aqueous and alcoholic extracts of Turmeric (Curcuma longa) as an extraordinary scavenger of 1O2 to completely inhibit the degradation of Guo. The alcoholic extracts were more effective in their antioxidant activity than the corresponding water extract. This naturally occurring antioxidant offers a most economical supplement to protect biologically significant molecules from the oxidative stress induced by 1O2.