4,5-seco-guaiane and a nine-membered sesquiterpene lactone from Holostylis reniformis

Root extracts of Holostylis reniformis (Aristolochiaceae) yielded three new natural sesquiterpenes, a sesquiterpene with an unusual carbon skeleton, 4,5-seco-guaiane (7-epi-11-hydroxychabrolidione A, 1), a nine-membered lactone with new carbon skeleton (holostylactone, 2), and a new megastigmane [(6S,7E)-6,9-dihydroxy-10-(2'-hydroxy-ethoxy)-4,7-megastigmadien-3-one, 3], together with bulnesol and sitosterol-3-O-β-D-glucopyranoside. The structures of these compounds were determined by spectroscopic analyses and B3LYP/STO-3G** theoretical studies.