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 α-methano bridge.