[Studies on triterpenoids of Populus yunnanensis Dode]

Three triterpenoids (I, II and III) were isolated from the roots of Populus yunnanensis Dode, which has been used as a folk remedy for the treatment of urinary tract infection and calculus in Yunnan Province. Compound I and III were identified as friedelin and 21 alpha-hydroxyfriedelan-3-one and compound II as 21 alpha-acetoxyfriedelan-3-one which is a new triterpenoid. 13C NMR data of II showed that the presence of an alpha-acetoxy group at C-21 does not affect the boat conformation of ring E similar to the results in the study of some other D:A-friedo-oleananes.