Sesquiterpenes from the roots of Illicium oligandrum

Two new sesquiterpenes, oligandrin (1) and oligandric acid (2), together with three analogues, tashironin A (3), tashironin (4), and oplodiol (5), were isolated from the roots of Illicium oligandrum. The structures of new compounds were determined based on 1D and 2D NMR experiments and X-ray diffraction. Compound 1 represents a presumed biosynthetic precursor of seco-prezizaane sesquiterpenes which consists of a novel 6/6/5 tricarbocyclic skeleton. Compound 2 is the first example of chamipinene-type sesquiterpene possessing a 6/4/6 tricyclic system from the genus Illicium. Compounds 1-5 were evaluated in vitro for their activity against coxsackie virus B3 (CVB3), influenza virus A/Hanfang/359/95 (H3N2), and influenza virus A/FM/1/47 (H1N1). Compound 1 showed selective antiviral activity against CVB3 with IC50 value of 11.11 mu M.