Investigation of hypoglycemic activity of major saponin constituents from "gymnemic acid", a crude saponin fraction of G. sylvestre, exposed not only two new saponins, gymnemosides a (1) and b (2), but also gymnemoside b and gymnemic acid V (7) as active principles. Furthermore, an acetyl group linked 16- or 22-hydroxy group in 1 and 2 was found to migrate easily to primary 28-hydroxyl group, while acyl migration from 28-hydroxy group in 3 was little observed.