A new cyanogenio glycoside, sarmentosin, has been isolated from the whole herb of Sedum sarmentosum Bunge which belongs to the family Crassulaceae. This compound showed signifioant effect in lowering the serum glutamio-pyruvio transaminase level of the pationts with chronic virus hepatitis. Dilute aqueous alkaline treatment of sarmentosin results in a quantitatively isomerization to give iso-sarmentoain, which is ineffective in clinical trials. By means of spectral analysis and chemical degradation, the structures of sarmentosin and iso-sarmentosin are shown to be 1 and 4, respectively.