Sesquiterpenes and neolignans from the roots of Illicium dunnianum.

Two new sesquiterpenes, dunnianoside I (1) and 8'-oxo-6-hydroxy-dihydrophaseic acid methyl ester (2), a new glycoside, dunnianoside J (3), two new neolignans, dunnianeolignans A-B (4, 5), together with 10 known compounds (6-15), were isolated from the roots of Illicium dunnianum. The structures of these new compounds were elucidated by spectroscopic methods including 1D and 2D NMR, HR-ESI-MS, and chemical methods. Compounds 7, 8, and 13-15 exhibited potent antioxidant activities against Fe2+-cystine-induced rat liver microsomal lipid peroxidation, with IC50 values ranging from 4.2 +/- 0.4 to 38.4 +/- 2.6 mu M.