Design and synthesis of trolline derivatives with Nrf2 pathway-associated anti-inflammatory activity

Activation of nuclear factor erythroid-2-related factor 2 (NRF2) has been proven to be an effective means to prevent the development of inflammatory diseases. In this study, series of trolline derivatives (4 -25) were designed and synthesized as potential anti-inflammatory agents. Among them, compound 5 showed the best activity, with an IC₅₀ value of 7.86 μM, by evaluation of the inhibition of NO production in LPS-stimulated RAW264.7 macrophages. Chiral separation of compound 5 further gave 5-S and 5-R, and 5-S proved to be the more active enantiomer in the NO assay (IC₅₀ = 5.89 μM), while 5-R was less active (IC₅₀ = 13.71 μM). Moreover, 5-S significantly reduced the production of TNF-α, IL-1β, and IL-6 in LPS-stimulated RAW264.7 cells. Western blot analysis showed that 5-S increased Nrf2 expression and promoted its nuclear translocation, accompanied by upregulation of the downstream target proteins HO-1 and NQO1. These results suggest that the anti-inflammatory effect of 5-S is associated with activation of the Nrf2 pathway. Overall, 5-S may serve as a potential lead for further development of trolline-based anti-inflammatory agents.