A new sesquiterpene, named neo-acorane A (1), and two known ones, acoric acid (2) and calamusin D (3), were isolated from a 95% ethanol extract of the rhizome parts of Acorus calamus L. Their structures were elucidated by spectroscopic methods, and the absolute configurations were determined by single-crystal X-ray diffraction analysis. Compounds 1 and 2 are nonisoprenoid sesquiterpenoids, likely biosynthesized from an acorane-type sesquiterpene by oxidative fission of the six- or five-membered ring. Moreover, compounds 1 (10 μM), 2 (5 μM and 10 μM) and 3 (10 μM) showed cell proliferation activity on the SK-N-BE (2) cell line.
Keywords: Acorus calamus L.; Araceae; acorane-type sesquiterpene; biosynthetic pathway; cell proliferation.