HPGDS and Alzheimer disease: Curcumin has been shown to exert protective effect against neuronal degeneration by scavenging ROS and neutralizing NO induced free radicals. In vivo study on Alzheimer's disease (AD) transgenic mouse model by Lim et al. demonstrated that curcumin reduces neuronal oxidative stress by inducing expression of cytoprotective proteins or antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), glutathione peroxidase (GPx), heme oxygenase 1 (HO-1), and glutathione-S-transferase (GST) [43].