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Curcumin, a well-known antioxidant in a principal ingredient of turmeric, acted as a prooxidant causing a copper-dependent DNA damage and the induction of apoptosis. Treatment of DNA from plasmid pBR322 and calf thymus with curcumin plus copper ion caused strand scission and the formation of 8-hydroxy-2(')-deoxyguanosine in DNA. Addition of catalase protected DNA from the curcumin-dependent injuries, indicating that hydroxyl radical may participate in the DNA damage. Flow cytometry analysis showed that curcumin caused an apoptotic cell death of HL60 cells in a dose- and time-dependent manner. Curcumin-mediated apoptosis was closely related to the increase in intracellular reactive oxygen species. On the contrary, capsaicinoids, which have a ortho-methoxy phenolic structure without beta-diketone in the side chain, did not produce 8-hydroxy-2(')-deoxyguanosine. Capsaicin further did not induce apoptosis of HL60 cells, but rather protected cells from prooxidant-induced apoptosis. Curcumin can generate reactive oxygen species as a prooxidant in the presence of transition metals in cells, resulting in DNA injuries and apoptotic cell death. The prooxidant action of curcumin may be related to the conjugated beta-diketone structure of this compound.

Apoptosis of HL60 cells by gallic acid derivatives was analyzed in relation to their prooxidant action. Octyl- and laurylgallates showed a potent apoptosis-inducing effect on HL60 cells, whereas gallic acid, ethyl-, propyl- and butylgallates caused only a little apoptosis. Long hydrophobic alcoholic chain in gallic acid esters enhanced apoptotic activity. Octylgallate markedly inactivated aconitase sensitive to oxidative stress before the apoptotic cells appeared. Preincubation of HL60 cells with butylated hydroxyanisole inhibited apoptosis completely. Treatment of cells with TEMPOL, which crosses the cell membrane, inhibited the octylgallate-mediated apoptosis, whereas the cell-impermeable DTPA did not protect the apoptosis. These results suggest that gallic acid compounds with hydrophobic chains may enter the cell, and can generate reactive oxygen species through the redox cycling in cells, resulting in the induction of apoptosis.

Gallic acid and its alkylesters, polyphenolic compounds with antioxidative activity, acted as a prooxidant causing a copper-dependent DNA damage. Treatment of DNA from plasmid pBR322 and calf thymus with gallic acid plus copper ion caused strand scission and the formation of 8-hydroxy-2'-deoxyguanosine in DNA. Addition of catalase protected DNA from the gallic acid/copper-dependent strand breaks and the formation of 8-hydroxy-2'-deoxyguanosine, indicating that hydroxyl radical may participate in the DNA damage. Ethyl-, propyl- and butylgallates showed only a little DNA damage. Octyl- and laurylgallates caused negligible damage of DNA. DNA strand breaks and formation of 8-hydroxy-2'-deoxyguanosine were closely related to the reduction of copper by gallate compounds. These results imply that cuprous ion reduced by gallate derivatives may play a key role in the oxidative cleavage of DNA and the formation of base adduct. The cytotoxic effect of gallate compounds can be explained by their prooxidant action dependent on the reducing activity.

1. 1. Uricase was partially purified from livers of five mammals (dog, bovine, horse, house musk shrew and guinea pig), and its immunological properties were studied using anti-hog liver uricase prepared in rabbits. 2. 2. Results obtained by immunodiffusion suggest that hog uricase has four sites of partial antigens (a, b, c, d), while the enzyme of other mammals has only part of them, and a cladogram of these six mammals is presented showing development of partial antigens. 3. 3. Results obtained by immunoelectrophoresis suggest that the protein structure of house musk shrew uricase is considerably different from the other five mammals tested.