Two new Monascus metabolites with strong blue fluorescence isolated from red yeast rice.
Red yeast rice obtained as cultures of Monascus AS3.4444 on rice was extracted and analyzed by high-performance liquid chromatography (HPLC). Two new Monascus metabolites with similar fluorescence spectra (lambda ex = 396 nm, lambda em = 460 nm) and UV absorption spectra (lambda max = 386 nm) were detected. They were isolated by rechromatography on a silica gel column and semipreparative HPLC, and two strong blue fluorescent compounds were obtained. Their structures were elucidated by electrospray ionization mass spectrometry (ESI-MS), electrospray ionization tandem mass spectrometry (ESI-MS/MS), intensive ESI-MS, and nuclear magnetic resonance spectroscopy ( (1)H NMR, (13)C NMR, COSY, and HMBC) studies. High-resolution mass spectrometry indicated the molecular formulas C 21H 24O 5 and C 23H 28O 5. The two new compounds, named monasfluore A and monasfluore B, respectively, contain a alkyl side chain, gamma-lactone, and propenyl group, whereas the more lipophilic compound, monasfluore B, is a higher homologue of monasfluore A, with the more lipophilic octanoyl instead of the hexanoyl side chain.
Huang
Zhibing
Z
Sino-Germany Joint Research Institute, Key Laboratory of Food Science, Ministry of Education, and Center of Analysis and Testing, Nanchang University, Nanchang, Jiangxi, PR China.
Xu
Yang
Y
Li
Laisheng
L
Li
Yanping
Y
D002851:Chromatography, High Pressure Liquid; D005285:Fermentation; D009682:Magnetic Resonance Spectroscopy; D032741:Monascus / Q000378:metabolism*; D012275:Oryza / Q000737:chemistry* / Q000382:microbiology*; D013050:Spectrometry, Fluorescence; D021241:Spectrometry, Mass, Electrospray Ionization