New lupane triterpenoids from Solidago canadensis that inhibit the lyase activity of DNA polymerase β

Bioassay-directed fractionation of a methyl ethyl ketone extract of Solidago canadensis L. (Asteraceae), using an assay to detect the lyase activity of DNA polymerase β, resulted in the isolation of the four new lupane triterpenoids 1-4 and the seven known compounds lupeol, lupeyl acetate, ursolic acid, cycloartenol, cycloartenyl palmitate, α-amyrin acetate, and stigmasterol. The structures of the new compounds were established as 3β-(3R-acetoxyhexadecanoyloxy)-lup-20(29)-ene (1), 3β-(3- ketohexadecanoyloxy)-lup-20(29)-ene (2), 3β-(3R-acetoxyhexadecanoyloxy)-29- nor-lupan-20-one (3), and 3β-(3-hetohexadecanoyloxy)-29-nor-lupan-20-one (4), respectively, on the basis of extensive 1D and 2D NMR spectroscopic interpretation and chemical modification studies. All 11 compounds were inhibitory to the lyase activity of DNA polymerase β.