Two new eudesmane sesquiterpenoids with neuroprotective activity from Pogostemon cablin

Two new eudesmane sesquiterpenoids [(−)-(1R,5S,6R,8S)−1-hydroxy-nor-eudesm-11-ene-2-one (1) and (−)-(1S,5S,6R,8R)−6-hydroxyeudesm-11-ene-2-one (2)] were isolated from the aerial parts of Pogostemon cablin. Compound 1 is an unusual 1-nor-eudesmane, and its skeleton structure is similar to that of compound 2. The molecular structures and absolute conformations of the two new sesquiterpenoids were determined by NMR spectroscopy, X-ray diffraction analysis, NMR data calculations and electronic circular dichroism (ECD) calculations. The neuroprotective activity of the isolates in an H2O2-induced PC12 cell model was also assessed, and the results show that both compounds exhibit good neuroprotective effects.