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

Phytochemical investigation of the aerial parts of Vernonia solanifolia resulted in the isolation of 23 new highly oxidized bisabolane-type sesquiterpenoids ( 1 - 23 ). Structures were determined by interpretation of spectroscopic data, single-crystal X-ray diffraction analysis, and time-dependent density 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 are isomerized at C-11 and C-2, respectively. The anti-inflammatory effect in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages was evaluated for pure compounds. Compound 9 inhibited LPS-stimulated NO production at the concentration of 80 μ M. It showed an anti-inflammatory effect by suppressing the activation of the NF-κB signaling pathway.