Enhanced antioxidant effect of caffeic acid phenethyl ester and Trolox in combination against radiation induced-oxidative stress

• An intermolecular interaction existed between CAPE and Trolox.
• CAPE and Trolox exerted synergistic antioxidant effects by scavenging ROS directly.
• CAPE and Trolox exerted synergistic antioxidant effects by inhibiting lipid peroxidation.
• CAPE used with Trolox promoted the redox cycle of GSH mediated by Nrf2 in cells.

Combinations of antioxidants are believed to be more effective than single antioxidant because when antioxidants are combined they support each other synergistically to create a magnified effect. Discovering the enhancer effects or synergies between bioactive components is valuable for resisting oxidative stress and improving health benefits. The aim of this study was to investigate a possible cooperation of natural antioxidant caffeic acid phenethyl ester (CAPE) with synthetic antioxidant Trolox in the model systems of chemical generation of free radicals, lipid peroxidation of microsomes and radiation-induced oxidative injury in L929 cells. Based on the intermolecular interaction between CAPE and Trolox, the present study shows a synergistic effect of CAPE and Trolox in combination on elimination of three different free radicals and inhibition of lipid peroxidation initiated by three different systems. CAPE and Trolox added simultaneously to the L929 cells exerted an enhanced preventive effect on the oxidative injury induced by radiation through decreasing ROS generation, protecting plasma membrane and increasing the ratios of reduced glutathione/oxidized glutathione and the expression of key antioxidant enzymes mediated by nuclear factor erythroid 2 p45-related factor 2 (Nrf2). Our results showed for the first time that administration of CAPE and Trolox in combination may exert synergistic antioxidant effects, and further indicate that CAPE and Trolox combination functions mainly through scavenging ROS directly, inhibiting lipid peroxidation and promoting redox cycle of GSH mediated by Nrf2-regulated glutathione peroxidase and glutathione reductase expression.