Sesquiterpenoids from the aerial parts of Pogostemon cablin

Six sesquiterpenoids including three previously undescribed ones (1-3) were isolated from the essential oil of the aerial parts of Pogostemon cablin. Their structures were determined to be (+)-(1S,4R,6S,7R,10S)-1-hydroxycadinan-12-ene-5-one (1), 11-dehydroxy-cinnamosin A (2), and 1-methoxy-senecrassidiol (3) by extensive spectroscopic analyses. This is the first report of cadinane-, cyperane-, and caryolane-type sesquiterpenoids from the genus Pogostemon. Particularly, compound 2 was a rare cyperane-type sesquiterpenoid, compound 3 was a caryolane-type sesquiterpenoid with an unusual cis fusion of A/B ring and an unusual alpha-methano bridge.