Cytotoxic Diterpenoids from the Stem Bark of Annona squamosa L.

Three new ent ‐kaurane diterpenoids, (4 α )‐19‐nor‐ ent ‐kaurane‐4,16,17‐triol ( 1 ), (4 α ,16 α )‐17‐(acetyloxy)‐19‐nor‐ ent ‐kaurane‐4,16 ‐ diol ( 2 ), and 17‐hydroxy‐ ent ‐kaur‐15‐en‐19‐al ( 3 ), together with 11 known compounds, were isolated from the stem bark of Annona squamosa L. The structures of 1 – 3 were identified by analysis of their spectroscopic data. All compounds were evaluated for cytotoxic activity against human lung cancer (95‐D) and ovarian cancer (A2780) cell lines, and compounds 3, 5, 7, 11 – 14 exhibited promising antiproliferative activities with IC 50 values ranging from 0.38 to 34.66 μ M .