Bioactive Sesquiterpenoids from the Rhizomes of <i>Acorus calamus</i>

Eight new sesquiterpenes (<b>1</b>–<b>8</b>) and one new norsesquiterpene (<b>9</b>) named calamusins A–I were isolated from the ethanol extract of <i>Acorus calamus</i> rhizomes. The absolute configuration of compound <b>8</b> was determined by comparing its experimental and calculated ECD spectra. The absolute configurations of the other compounds were determined from their CD spectra. Furthermore, in in vitro assays, compounds <b>3</b>, <b>4</b>, <b>7</b>, and <b>9</b> (10 μM) exhibited weak hepatoprotective activities against APAP-induced HepG2 cell damage