Studies on chemical constituents of the leaves of Smallantus sonchifolius (yacon): Structures of two new diterpenes

The extract from the leaves of Smallantus sonchifolius (yacon) was found to show potent anti-diabetic activity. Two new diterpenes, named ent-kaurane-3 beta,16 beta,17,19-tetrol (1) and ent-kaurane-16 beta,17,18,19-tetrol (2), were isolated from the extract, together with six known compounds. The structures of the new compounds were determined on the basis of chemical and physicochemical evidence.