Protective actions of 5′-n-alkylated curcumins on living cells suffering from oxidative stress

Abstract To elucidate the roles of 5′- n -alkyl chains of curcumin derivatives in their protective actions on cells against oxidative stress, we compared the efficacy of curcumin and 5′-alkylated curcumins to inhibit the peroxidation of linoleic acid and to protect rat thymocytes suffering from H 2 O 2 -induced oxidative stress with their permeation into cells. The inhibitory action of 5′- n -alkylated curcumins on lipid peroxidation increased as the length of hydrocarbon chains of 5′- n -alkylated curcumins was prolonged. This potency order was not confirmed for the protective actions of 5′- n -alkylated curcumins on cells against oxidative stress. Among 5′-alkylated curcumins, the most potent protective action was observed for 5′- n -C 3 H 7 -curcumin because it had the greatest permeation into the cells. Further increases in the length of hydrocarbon chains (up to n -C 19 H 39 ) of 5′- n -alkylated curcumins greatly attenuated their protective actions by reducing their permeation into the cells.