<jats:title>Abstract</jats:title><jats:p>Investigation of the 95% EtOH extract of red yeast rice fermented with the fungus <jats:italic>Monascus purpureus</jats:italic> BCRC 31615 has led to the isolation and structure elucidation of four new compounds, including one new azaphilone analog, monascuspurpurone (<jats:bold>1</jats:bold>), a new isocoumarin, monaschromone (<jats:bold>2</jats:bold>), a new furan‐3‐one derivative, 2‐dodecyl‐5‐(2‐methoxyethyl)‐2‐methylfuran‐3(2<jats:italic>H</jats:italic>)‐one (<jats:bold>3</jats:bold>), and a new alkaloid, methyl 4‐[(<jats:italic>E</jats:italic>)‐2‐acetyl‐4‐oxoundec‐1‐enyl]‐6‐propylnicotinate (<jats:bold>4</jats:bold>), together with seven known compounds. The structures of all isolates were elucidated on the basis of extensive spectroscopic analyses and comparison with literature data. Compounds <jats:bold>1</jats:bold>–<jats:bold>4</jats:bold> were tested for their cytotoxicity against the MCF‐7, NCI‐H460, and SF‐268 cell lines using the MTT (=3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2<jats:italic>H</jats:italic>‐tetrazolium bromide) assay. Among them, compounds <jats:bold>1</jats:bold> and <jats:bold>4</jats:bold> were found to have moderate cytotoxic effects against these three cell lines <jats:italic>in vitro.</jats:italic>