The major pigment components in the crude Monascus pigments
were yellow Monascus pigments and orange ones. The aminophilic
reaction between orange Monascus pigments and MSG
was carried out followed a similar procedure as reported in the literatures
[18]. The crude Monascus pigments was re-dissolved in
24 ml ethanol aqueous solution (70% (V/V), pH = 7) to prepare
Monascus pigments ethanol aqueous solution with 46 AU (absorbance
unit, multiplication of the absorbance with its dilution ratio
of a sample) at 410 nm and 39 AU at 470 nm. Then excess MSG
(1.5 g) was added into the Monascus pigment ethanol aqueous
solution, which was shaken at 30 C and 200 rpm. The residual
orange Monascus pigments in the ethanol aqueous solution were
monitored by thin layer chromatography (TLC) analysis. After the
aminophilic reaction for 10 h, 190 ml cyclohexane was added into
the reaction solution. The mixture solution was separated into a
cyclohexane phase and an ethanol aqueous solution phase.
Yellow Monascus pigments were partitioned into the cyclohexane
phase, which was recovered by air stripping off solvent.
The yellow Monascus pigments were further purified by silica
gel column chromatography. The yellow Monascus pigments in
the washing solution were monitored by TLC analysis. The detailed
information was presented in supplementary materials of Fig. S3.
The washing solution was subjected to air stripping off solvent
and yellow Monascus pigments had been crystallized.