Nrf2 activator-2 (compound O15), a Osthole derivative, is a potent Nrf2 agonist with an EC50 of 2.9 μM in 293 T cells. Nrf2 activator-2 effectively inhibits the interaction between Keap1 and Nrf2, thus showing the activation effect on Nrf2. Nrf2 activator-2 shows a marked decrease in the level of ubiquitinated Nrf2 in cells.