Monascus purpureus NTU 568 was a mutant strain from M. purpureus HM105. The methanol extract of red mold rice fermented by this strain exhibited four major yellow pigment signals on HPLC profile. By repeated chemical chromatography methods, three new azaphilone derivatives, namely, monaphilone A (1), B (2) and C (3), along with the known pigments ankaflavin (4) and monascin (5), were isolated and characterized. Based on spectroscopic analyses, mainly 1D and 2D NMR data, the structures of compounds 1-3 were completely elucidated; in addition, 1-3 were determined to be new azaphilone structures, due to the decrease of carbon monoxide for producing a gamma-lactone ring, compared with other azaphilone derivatives. Biological evaluations showed that monaphilone A (1) and B (2) exhibited an antiproliferative effect against HEp-2 (human laryngeal carcinoma cell line) and WiDr (human colon adenocarcinoma cell line), and none of the five compounds had toxicity to normal human lung cell lines (WI-38 and MRC-5) at 70 muM.