A new dammarane-type triterpene saponin was isolated from the aerial parts of Gynostemma pentaphyllum (Thunb.) Makino. Its structural elucidation was accomplished mainly on the basis of the interpretation of spectroscopic data, such as IR, HR-TOF-MS and NMR. Its cytotoxic activity was evaluated against one human cancer cell line HL-60 using MTT assay.