HMOX1 and Alzheimer disease: In general, the regulatory roles of polyphenols in the context of AD-related oxidative stress mechanisms are mainly based on the direct elimination of ROS; the regulation of SOD, CAT, and GSH levels; and the reduction of an oxidative stress injury in the brain through regulation of Nrf2/HO-1 and Nrf2/Keap1 pathways (Figure 2).