Terpenoids with anti-influenza activity from the leaves of Euphorbia leucocephala

Two rearranged terpenoids with a rare 3,4,5-trimethyl-cyclohexa-2,5-dien-1-one moiety, namely leucocephins A (1) and B (2), and a megastigmane, namely leucocephin C (3), as well as three known compounds, hollongdione (4), 3-acetoxy-lup-12,20(29)-diene (5), and β-amyrin acetate (6) were isolated from the leaves of Euphorbia leucocephala. Their structures and absolute configurations were determined by spectroscopic methods and comparing with literature data. Compounds 4–6 exhibited potent anti-influenza A virus activity comparable to the positive control, betulinic acid.