Identification of water-soluble Monascus yellow pigments using HPLC-PAD-ELSD, high-resolution ESI-MS, and MS-MS

Water-soluble Monascus yellow pigment (WSMYP) prepared from monascorubin is widely used in the food industry. However, the structure and composition of this pigment has been unclear until now. In the present study, the components of WSMYP has been identified by means of HPLC coupled with a photodiode-array detector (PAD) and an evaporative light scattering detector (ELSD), HPLC/ESI-MS-MS, and high resolution ESI-MS (HR-ESI-MS). Eight compounds have been separated from WSMYP and unambiguously structurally characterized; namely, monascin, ankaflavin and six novel compounds with molecular weights/structural formulae of 356/C21H24O5, 376/C21H28O6, 384/C23H28O5, 404/C23H32O6, 437/C21H27NO7S, and 465/C23H31NO7S. Compounds 3 (376/C21H28O6), 7 (437/C21H27NO7S), and 8(465/C23H31NO7S) are the main components in WSMYP with contents of 55.8%, 16.5%, and 10.1%, respectively. These results provide useful information for further bioactivity studies and industrial application of WSMYP.