Isolation and structure determination of one new metabolite isolated from the red fermented rice of Monascus purpureus

The n-BuOH-soluble portion of the 95% EtOH extract of red fermented rice fermented with the yellow mutant of the fungus Monascus purpureus BCRC 38113 (Monascaceae) led to the isolation of one new pyran-2-one derivative, namely peroxymonascuspyrone (1), along with nine known compounds, monasfluore A (2), monasfluore B (3), 3-epi-betulinic acid (4), 3-epi-betulinic acid acetate (5), -tocospiro A (6), friedelan-3-one (7), -cadinol (8), anticopalol (9), and spathulenol (10). Interestingly, this is the first report of a naturally occurring pyran-2-one skeleton isolated from Monascus sp. Their structures and relative configurations were elucidated by spectroscopic methods, including 1D- and 2D-NMR (1H,1H-COSY, HMQC, HMBC and NOESY), as well as low- and high-resolution mass spectrometric analyses. In addition, cytotoxicities against MCF-7, NCI-H460 and SF-268 cancer cell lines were measured in vitro; the results revealed that these metabolites have no cytotoxicity against the selected tumour cells.