Bisabolane-Type Sesquiterpenoids with a Tetrahydrofuran or Tetrahydropyran Ring from Vernonia solanifolia

Phytochemical investigation of the aerial parts of Vernoniasolanifolia resulted in the isolation of 23 new highly oxidizedbisabolane-type sesquiterpenoids (1-23). Structures were determined by interpretation of spectroscopicdata, single-crystal X-ray diffraction analysis, and time-dependentdensity functional theory electronic circular dichroism calculations.Most compounds possess a rare tetrahydrofuran (1-17) or tetrahydropyran ring (18-21). Compounds 1/2 and 11/12 are pairs of epimers isomerized at C-10, while compounds 9/10 and 15/16 areisomerized at C-11 and C-2, respectively. The anti-inflammatory effectin lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages was evaluatedfor pure compounds. Compound 9 inhibited LPS-stimulatedNO production at the concentration of 80 mu M.It showed an anti-inflammatory effect by suppressing the activationof the NF-kappa B signaling pathway.