A genuine triterpenoid saponin, platyconic acid A (1) was isolated from the roots extract of Platycodon grandiflorum, together with five known saponins: deapioplatycoside E (2), platycoside E (3), platycodin D(3) (4), platycodin D(2) (5) and platycodin D (6). The structure of 1 was determined on the basis of spectral analysis and chemical evidence.