Diacetylenic Spiroacetal Enol Ethers from Chrysanthemum indicum Alleviates Inflammation in LPS-Induced RAW 264.7 Cells via Regulation of Nrf2 and MAPK Signaling Pathways

Five novel naturally occurring diacetylenic spiroacetal enol ethers, named chracetylespienoles A–E (1–5), along with five known analogues (6–10), were isolated from the aerial part of Chrysanthemum indicum. A combination of extensive spectroscopy, chemical derivatization, DP4+ NMR analysis, and ECD calculations was employed to determine the new compounds' structures and assign their absolute configurations. The anti-inflammatory activity of 1–10 was determined by measuring their suppression on NO production in lipopolysaccharide (LPS)-mediated RAW 264.7 cells, and 8 showed the best NO production inhibitory activity with an IC50 value of 7.42 ± 0.87 μM. Furthermore, compound 8 downregulated the expression of iNOS and COX-2 proteins by inhibiting the MAPK and activating the Nrf2 signaling pathways, thereby suppressing inflammatory cascades.