Hygienic Studies on Monascus Pigments (II)

Fractionation of Monascus Pigments and Quantitative Analysis of Monascin

Abstract

The mold Monascus is used for brewing of red rice wine (an-tyiiu) and the production of monascus pigments which is added to foodstuff as a natural food dye.
In the present paper, the fundamental methods for fractionation and quantitative analysis of monascus pigments were described.
The principle for the fractionation of monascus pigments is as follows: a mixture of purple, orange and yellow pigments was applied to a silica gel column. Purple pigments were adsorbed on the column with ether, but orange and yellow pigments were eluted with ether. The purple pigmetns remained on the column were eluted with methanol. Ether saturated with ammonia was added to the eluate which contains a mixture of orange and yellow pigments. Orange pigments in the mixture were converted to purple pigments by the reaction with ammonia in ether. Then the mixture was applied again to the silica gel column. Yellow pigments were eluted with ether, and orange pigments, which have been converted to purple pigments, were eluted with methanol.
For the determination of monascin, test solution was heated at 100°C for 10min with concentrated sulfuric acid and produced fluorescence was determined at 453nm for excitation and 507nm for emission.
The above method was applied to red rice wine, and 9.0-11.1ppm of water-soluble pigments, 2.2-3.1ppm of purple pigments, and 0.9-1.9ppm of yellow pigments were determined. Orange pigments were not detected in red rice wine.