Antioxidant Properties and PC12 Cell Protective Effects of a Novel Curcumin Analogue (2E,6E)-2,6-Bis(3,5- dimethoxybenzylidene)cyclohexanone (MCH)

The antioxidative properties of a novel curcumin analogue (2E,6E)-2,6-bis(3,5-dimethoxybenzylidene)cyclohexanone (MCH) were assessed by several in vitro models, including superoxide anion, hydroxyl radical and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging and PC12 cell protection from H(2)O(2) damage. MCH displayed superior O(2)(•−) quenching abilities compared to curcumin and vitamin C. In vitro stability of MCH was also improved compared with curcumin. Exposure of PC12 cells to 150 μM H(2)O(2) caused a decrease of antioxidant enzyme activities, glutathione (GSH) loss, an increase in malondialdehyde (MDA) level, and leakage of lactate dehydrogenase (LDH), cell apoptosis and reduction in cell viability. Pretreatment of the cells with MCH at 0.63–5.00 μM before H(2)O(2) exposure significantly attenuated those changes in a dose-dependent manner. MCH enhanced cellular expression of transcription factor NF-E2-related factor 2 (Nrf2) at the transcriptional level. Moreover, MCH could mitigate intracellular accumulation of reactive oxygen species (ROS), the loss of mitochondrial membrane potential (MMP), and the increase of cleaved caspase-3 activity induced by H(2)O(2). These results show that MCH protects PC12 cells from H(2)O(2) injury by modulating endogenous antioxidant enzymes, scavenging ROS, activating the Nrf2 cytoprotective pathway and prevention of apoptosis.