<jats:title>Abstract</jats:title><jats:p>A new pyridone alkaloid, 5,6‐dihydro‐5‐hydroxy‐1<jats:italic>H</jats:italic>‐pyridin‐2‐one (<jats:bold>1</jats:bold>), and a new ester, sintenin (=3‐(3,4‐dimethoxyphenyl)propyl 3‐(3,4‐dimethoxyphenyl)propanoate <jats:bold>2</jats:bold>), together with three known compounds, 5,6‐dihydro‐1<jats:italic>H</jats:italic>‐pyridin‐2‐one (<jats:bold>3</jats:bold>), <jats:italic>d</jats:italic>‐sesamin (=5,5′‐(3a,4,6,6a‐tetrahydro‐1<jats:italic>H</jats:italic>,3<jats:italic>H</jats:italic>‐furo[3,4‐<jats:italic>c</jats:italic>]furan‐1,4‐diyl)bis[1,3‐benzodioxole]; <jats:bold>4</jats:bold>), and (<jats:italic>E</jats:italic>)‐phytol (=3,7,11,15‐tetramethylhexadec‐2‐en‐1‐ol; <jats:bold>5</jats:bold>) have been isolated from the whole plant of <jats:italic>Piper sintenense.</jats:italic> 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 <jats:italic>in vitro.</jats:italic>