The protective effect of hydroxyl-substituted Schiff bases on the radical-induced oxidation of DNA

The protective effects of 18 hydroxyl-substituted Schiff bases (SchOHs) on the oxidative damage of naked DNA induced by 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) were reported, in which SchOHs were prepared by condensing hydroxyl-substituted aromatic aldehydes and anilines. The extent of the oxidative damage of DNA was followed by measuring the formation of thiobarbituric acid reactive substance (TBARS). Some SchOHs bearing only one hydroxyl group (prepared by salicylic aldehyde) protected DNA by decreasing the formation rate of TBARS. Other SchOHs inhibited the oxidation of DNA for a period, resulting in an inhibition period (t(inh)) that was proportional to the concentration of SchOH, viz., t(inh) = (n/R-i)[SchOH]. Thus, the stoichiometric factor (n) can be calculated if the initiation rate (R-i) was known. The n value of an SchOH was closed to the summation of the n from every structural feature in this SchOH, indicating that the antioxidant activity of SchOH was contributed from every structural feature in the molecule. Furthermore, the large conjugative system and para-hydroxyl at benzilidene were good for the antioxidant activity of SchOHs. Copyright (C) 2009 John Wiley & Sons, Ltd.