Anti-diabetes constituents in leaves of Smallanthus sonchifolius.

The inhibitory effect of smallanthaditerpenic acids A, B, C and D previously isolated from leaves of Smallanthus sonchifolius (yacon) on alpha-glucosidase were examined and their IC50 were determined to be 0.48 mg/mL, 0.59 mg/mL, 1.00 mg/mL, and 1.17 mg/mL respectively. In addition, a rapid, reliable RP-HPLC method for the analysis of chlorogenic acid, caffeic acid, and smallanthaditerpenic acids A and C in yacon leaves was established, and the variation in their contents in leaves from plants cultivated in different places and collected at different times of the year were compared. The established analytical method for determining smallanthaditerpenic acids A and C, chlorogenic acid and caffeic acid presented good results and could be used as a method for the quality control of S. sonchifolius leaves.