NQO1 and brain disorder: Following the hormetic paradigm, natural polyphenolic substances at low doses act as antioxidants in a wide range of brain diseases, this occurring through upregulation of Nrf2 signaling pathway and increased expression of vitagenes, such as NAD(P)H-quinone oxidoreductase (NQO1), glutathione transferase (GT), GPx, heme oxygenase-1 (HO-1), sirtuin-1 (Sirt1), and thioredoxin (Trx) system.