Melampolides from the leaves of Smallanthus sonchifolius and their inhibitory activity of LPS-induced nitric oxide production

Abstract

Two new melampolide-type sesquiterpene lactones, 8 beta-epoxyangeloyloxy-9 alpha-ethoxy-14-oxo-acanthospermolide (1) and 8 beta-angeloyloxy-9 alpha-ethoxy-14-oxo-acanthospermolide (2), were isolated from the leaves of yacon [Smallanthus sonchifolia (POEPP. et ENDL.) H. Robinson] along with eleven known melampolides, allo-schkuhriolide (3), enhydrin (4), polymatin A (5), fluctuanin (6), 8 beta-angeloyloxy-9 alpha-acetoxy-14-oxo-acanthospermolide (7), 8 beta-angeloyloxy-14-oxo-acanthospermolide (8), 8 beta-methacryloyloxymelampolid-14-oic acid methyl ester (9), uvedalin (10), polymatin B (11), 8 beta-tigloyloxymelampolid-14-oic acid methyl ester (12), and sonchifolin (13). Their structures were established on the basis of spectroscopic evidence including 1D- and 2D-NMR experiments. All isolates were evaluated for inhibition of LPS-induced nitric oxide production in murine macrophage RAW 264.7 cells.