Seven new monacolins, monacolins Q-S (1-3), α,β-dehydromonacolin S (4), 3α-hydroxy-3,5-dihydromonacolin L (5), 3β-hydroxy-3,5-dihydromonacolin L (6), and α,β-hydromonacolin Q (7) were isolated and characterized from the methanol extract of red yeast rice. In addition, six known monacolins, α,β-dehydrodihydromonacolin K (8), dehydromonacolin K (9), dehydromonacolin L (10), monacolin K (11), dihydromonacolin K (12), dihydromonacolin L (13) and two compounds other than monacolins (14, 15) were also isolated. Structure elucidation of the isolates was achieved by means of NMR and mass spectroscopic data analyses. Compounds 1-5, 8, 9, 11, and 13 were evaluated for their cytotoxic activity against four cancer cell lines (SK-MEL, KB, BT-549, SK-OV-3) and two noncancerous kidney cell lines (LLC-PK1 and Vero). Monacolin Q (1), monacolin R (2) α,β-dehydrodihydromonacolin K (8), dehydromonacolin K (9), and monacolin K (11) showed cytotoxicity to most of these cell lines in terms of inhibition of cell proliferation. The cytotoxicity of monacolin K (11) was the most potent among all the tested monacolins.
Keywords: Cytotoxicity; Monacolins; Red yeast rice.
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