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 beta-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.