Chemical Constituents from the Aerial Parts of Artemisia iwayomogi and Their Anti-Neuroinflammatory Activities

Neuroinflammation, predominantly mediated by microglial activation, is a key immunological response in the pathogenesis of neurodegenerative disorders. In our preliminary study, the aerial part of Artemisia iwayomogi inhibits LPS-induced microglial activation. The present study aims to identify chemical constituents with anti-neuroinflammatory properties in the aerial parts of A. iwayomogi. Two new guaianolide sesquiterpenes, iwayomogins A and B (1 and 2), along with thirteen known sesquiterpene lactones (3-15), one diterpene glycoside (16), and nine phenolic compounds (17-25) were isolated from the aerial parts of A. iwayomogi by repeated chromatography. The structures of the isolates were elucidated by their spectroscopic data. All isolates were evaluated for their inhibitory activities on nitric oxide (NO) production in LPS-induced BV-2 microglial cells. 2,3-Dehydro-1-epi-asperilin (11) exhibited the strongest inhibitory effect on NO production (IC₅₀ value of 1.78 μM). In the molecular docking study, three compounds (1, 2, and 11) showed good binding affinities with iNOS. Additionally, compounds 1, 2, and 11 inhibit pro-inflammatory cytokines (TNF-α and IL-6) in dose-dependent manners. The present study demonstrates that the chemical constituents from A. iwayomogi inhibit NO production and pro-inflammatory cytokine release in BV-2 cells. However, further evaluation with biological experiments utilizing in vivo models is necessary.