Cytotoxic Constituents of Piper sintenense

A new pyridone alkaloid, 5,6‐dihydro‐5‐hydroxy‐1 H ‐pyridin‐2‐one ( 1 ), and a new ester, sintenin (=3‐(3,4‐dimethoxyphenyl)propyl 3‐(3,4‐dimethoxyphenyl)propanoate 2 ), together with three known compounds, 5,6‐dihydro‐1 H ‐pyridin‐2‐one ( 3 ), d ‐sesamin (=5,5′‐(3a,4,6,6a‐tetrahydro‐1 H ,3 H ‐furo[3,4‐ c ]furan‐1,4‐diyl)bis[1,3‐benzodioxole]; 4 ), and ( E )‐phytol (=3,7,11,15‐tetramethylhexadec‐2‐en‐1‐ol; 5 ) have been isolated from the whole plant of Piper sintenense. The structures of the two new compounds were determined through spectral analyses. Among twenty isolates obtained so far, four compounds exhibited effective cytotoxicities against P‐388, HT‐29, or A549 cell lines in vitro.