Structure and bioassay of triterpenoids and steroids isolated from Sinocalamus affinis.

Five triterpenoids with a new 25-norfern carbon skeleton (1-5), a lupane triterpenoid (6), and four 20-hydroxyprogesterone acyl esters (7-10), together with 23 known compounds, were isolated from the stem (with skin removed) of Sinocalamus affinis. The absolute configuration of compound 1 was confirmed by single-crystal X-ray crystallographic analysis using anomalous scattering of Cu Kα radiation. Compounds 1-5 exhibited inhibitory activity against protein tyrosine phosphatase 1B.