Anti-neuroinflammatory sesquiterpene lactones from Achillea millefolium L

Abstract

Achillea millefolium L. is a medicinal plant traditionally used in the treatment of inflammation-related diseases. Sixteen sesquiterpene lactones, including twelve previously undescribed ones were isolated from the whole plant of A. millefolium. Their structures were established using spectroscopic techniques, including HRMS and NMR, and by comparing with literature. The absolute configuration of these compounds was determined by means of single-crystal X-ray crystallography, ¹³C NMR calculations with DP4+ probability analyses, and ECD calculations. Millefoliumine R (1), millefoliumine S (2), millefolacton H (6), millefolacton B12 (11), and achalplide a (13) displayed inhibitory activity against NO release in LPS-induced BV2 microglial cells, and millefoliumine S (2) presented the most significant activity with IC₅₀ value close to that of the positive control, dexamethasone. Furthermore, enzyme-linked immunosorbent assay disclosed that millefoliumine S (2) inhibited the release of TNF-α, IL-6, and PGE₂ from LPS-induced BV2 cells in a dose-dependent manner. Western blot and immunofluorescence assays revealed that millefoliumine S (2) inhibited the expression of iNOS/COX2 signaling-related proteins (iNOS and COX2), NF-κB signaling-related proteins (NF-κB and IκB), MAPK signaling-related proteins (MAPK, JNK, and ERK), and pyroextinction signaling-related proteins (NLRP3, cleavaged-caspase 1, ASC and IL-1β). Additionally, the potential mechanisms of NO inhibition of millefoliumine S (2) were investigated by molecular docking and molecular dynamics simulation.