Nine minor new tirucallane (1-7) and euphane (8 and 9) triterpenoids including five hydroperoxides, together with 18 known compounds, have been isolated from an ethanolic extract of the roots of Euphorbia micractina. Their structures including absolute configurations were elucidated by spectroscopic and chemical analysis. In the in vitro assays, betulin (10) showed a selective cytotoxic activity against A2780 ovarian cells with an IC(50) value of 6.1 microM and inhibitory activity against protein tyrosine phosphatase 1B (PTP1B) with an IC(50) value of 15.3 microM. Jolkinol B (11) showed a potent activity against HIV-1 replication with an IC(50) value of 12.6 muM. However, compounds 1-9 and the other known compounds were inactive in the three assays used.
