Anti-neuroinflammatory terpenes from Magnolia grandiflora

Six previously undescribed sesquiterpenes, magnogranoides A-F (1-6), along with 10 known terpenes, were isolated from the leaves of Magnolia grandiflora L. Six previously undescribed sesquiterpene derivatives ( 11a - 11e and 14a) were synthesized using chemical methods. Those structures were identified through extensive spectroscopic data and quantum chemical calculations. Notably, compound 1 represents the first sesquiterpene with a previously undescribed 8/5/5 tricyclic ring, and compound 2 was elucidated to be the first 13-norguaiane-type sesquiterpenoid with a 5/7/5 tricyclic ring system. Four compounds (3, 7 , 8 , and 16 ) exhibited better antineuroinflammatory activities in BV-2 cells with IC50 values ranging from 3.23 +/- 0.23 mu M to 15.98 +/- 1.79 mu M than the positive control, minocycline (IC50: 20.56 +/- 0.93). Furthermore, the chemotaxonomic significance of the isolates was also discussed.