Monoterpenoids and Triterpenoids from Pterocephalus hookeri with NF-κB inhibitory activity

Abstract In this study, we isolated two new monoterpenoids hookerinoids A and B ( 1 and 2 ; rare arranged nonglycosidic bis-iridoids) and hookerinoid C ( 3 ; a novel norursane-type triterpenoid) in addition to two known compounds, 11,12-epoxy-2,6-dihydroxy-24-norursa-1,4-dien-3-on-2-on-(28 → 13)-olide ( 4 ) and rivularicin ( 5 ), from Pterocephalus hookeri . The structures of 1–3 were established using one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy and high-resolution electrospray ionisation mass spectrometry. All compounds were isolated from this plant for the first time. Bis-iridoids isolated from P. hookeri possessed secoiridoid/iridoid subtype skeletons. Therefore, bis-iridoids can be considered chemotaxonomic markers of P. hookeri . The origins of the new compounds ( 1–3 ) were postulated and their inhibitory activities on a nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway were assayed; 1 and 2 showed obvious activity in inhibiting NF-κB.