Antiviral anthraquinones from the roots of Knoxia valerianoides

Three new anthraquinones, (2S)-8-carboxy-9-hydroxy-2-(2-hydroxypropan-2-yl)-1,2-dihydroanthra[2,1-b]furan-6,11-dione (1), 1,2,3,6-tetrahydroxy-9,10-anthraquinone (2), and 1,2,3,5,6-pentahydroxy-9,10-anthraquinone (3), as well as four known 9,10-anthraquinones (4–7) and five known triterpenes (8–12), were isolated from the roots of Knoxia valerianoides. Their structures and the absolute configuration of 1 were determined through interpretation of spectroscopic data, including UV, IR, NMR and CD spectra. The isolates were evaluated for their antiviral activities, and compounds 1 and 4 showed inhibitory effects on Coxsackie virus B3 replication with IC50 values of 19.24 μM and 11.11 μM, respectively. Compound 4 showed activity against influenza virus A/Hanfang/359/95 with an IC50 value of 11.11 μM.