A new cycloartane-type triterpenoid saponin named riparsaponin (1) was isolated from the stem of Homonoia riparia Lour together with six known compounds. The structure of riparsaponin was determined by using NMR and mass spectroscopy and X-ray crystallography techniques. Additionally, riparsaponin has a significant inhibitory effect on xanthine oxidase in vitro, and the IC50 was 11.16 nmol/mL.
