Chrysanthevelides A−D, the Rearranged 5/5/5 Tricyclic Spiro-Guaianolides and 1, 3-Dioxolane-Containing Nor-Guaianolide Dimers from Chrysanthemum vestitum Target PKM2 to Mediate the Anti-Inflammatory Effect

Four unprecedented dimeric (1−2) and monomeric (3−4) sesquiterpenoids were isolated from the aerial part of Chrysanthemum vestitum. Chrysanthevelides A−B (1−2) represented the first example of the dimers with a special 1,3-dioxolane nor-guaianolide sesquiterpenoid unit, while chrysanthevelides C−D (3−4) were two pairs of unprecedented 1,10-seco rearranged 5/5/5 tricyclic spiro-guaianolide sesquiterpenoids. The undescribed structures of 1−4, including their absolute configurations, were determined through spectroscopic techniques combined with DP4+ NMR analysis and ECD calculations. Compound 1 displayed an NO production inhibitory effect with an IC50 value of 1.62 ± 0.21 μM. Primarily, western blotting and ELISA combined with the RNA-seq results indicated that 1 suppressed downstream-related inflammatory factors (IL-6 and TNF-α) and proteins (COX-2 and iNOS). Mechanistically, the α-methylene-γ-lactone (αMγL) moiety of 1 covalently binds to Cys423 of PKM2, promoting its tetramerization, which in turn regulates the HIF-1α/STAT3 axis and the glycolytic pathway. This ultimately suppressed the expression of inflammatory mediators, thereby achieving its anti-inflammatory function.