Anti-Coxsackie virus B diterpenes from the roots of Illicium jiadifengpi

Nine new diterpenes, named jiadifenoic acids A–I (1–9), together with 10 known analogues were isolated from the roots of Illicium jiadifengpi. Their structures were elucidated by extensive spectroscopic analysis and circular dichroism (CD) experiments. Jiadifenoic acid A (1) is a novel dimeric diterpene with a rare spiro[bicyclo[2.2.2]-oct-5-ene-2,1′-cyclopentan]-3-one motif. A plausible biosynthetic pathway of compound 1 was also postulated. All isolated compounds were evaluated in vitro for their antiviral activities against Coxsackie virus B2, B3, B4, and B6. Among them, 2, 3, and 15 were the most potent inhibitors. Structure–activity relationship (SAR) was also discussed in this paper.