Four New Sesquiterpene Pyridine Alkaloids from the Roots of Tripterygium wilfordii Hook. f.

Investigation of the roots of Tripterygium wilfordii Hook. f. resulted in the isolation of nine sesquiterpene pyridine alkaloids (SPAs), including four previously undescribed compounds 1-4. The structures of all compounds were elucidated by extensive spectroscopic analysis, including NMR and HRESIMS. In particular, compound 1 was found to possess an unprecedented cage-like ether moiety, representing the first report of such a structural feature within this class of alkaloids. All isolated compounds were evaluated for their anti-inflammatory activity using a lipopolysaccharide (LPS)-induced RAW264.7 macrophage model. Compounds 1, 2, and 4 exhibited significant inhibition of nitric oxide (NO) production, with IC50 values of 7.14 ± 1.89, 8.55 ± 0.37, and 14.76 ± 0.39 μM. Furthermore, compounds 1 and 2 suppressed the secretion of key pro-inflammatory cytokines, including TNF-α, IL-6, and IL-1β, in the same cellular model. These results not only enhanced the structural diversity of SPAs identified from T. wilfordii, but also highlight their potential as promising anti-inflammatory lead compounds.