Monascorubrin and rubropunctatin: Preparation and reaction characteristics with amines

Production and Characterization of Anti-Inflammatory Monascus Pigment Derivatives

“…This result is in agreement with previous reports in which large amounts of orange pigments were obtained under acidic fermentation conditions [ 50 , 51 ], red pigments were mainly produced at pH 6.5, and orange pigments were observed in pH 2.5 media [ 44 , 49 ]. The increase in orange pigment yield under low-pH conditions can be caused by inhibition of the transformation of orange to red pigments [ 28 , 52 ]. As red pigments are known to be synthesized by amination reaction from orange pigments [ 29 , 52 ], inhibition of this transformation can result in a substantial increase in orange pigments during the fermentation process.…”

“…For further purification, the condensed solution was mixed with silica gel, and a pigment–silica gel complex with dark red color was obtained. To remove hydrophobic impurities from the orange pigments, the pigment–silica gel complex was extracted by n-hexane, a lipophilic volatile organic solvent that could dissolve undesirable hydrophobic substances but poorly extract orange pigments [ 28 ]. After completion of the n-hexane extraction, pure ethyl acetate was again used to obtain an orange pigment solution with enhanced purity from the pigment–silica gel complex.…”

“…The purified orange pigments were used as the basic building blocks for the synthesis of many types of Monascus pigment derivatives. As shown in Figure 1 a, each derivative was synthesized by aminophilic reaction, in which the pyranyl oxygen in the orange pigments was replaced with the nitrogen of the amino group of primary amines or amino acids [ 28 , 30 ]. This synthetic method can induce the production of diverse Monascus pigment derivatives with novel molecular structures and increase the possibility of each derivative having different functionalities, such as antimicrobial, antiviral, anticholesterol, antiobesity, and antimelanogenesis effects [ 31 , 58 ].…”

“…nitrogen of the amino group of primary amines or amino acids [28,30]. This synthetic method can induce the production of diverse Monascus pigment derivatives with novel molecular structures and increase the possibility of each derivative having different functionalities, such as antimicrobial, antiviral, anticholesterol, antiobesity, and antimelanogenesis effects [31,58].…”

“…Monascus pigments are a complex mixture of compounds with an azaphilone skeleton, which is a class of a typical fungal polyketide pigment [ 26 , 27 ]. Monascus pigments have been used as food additives in Asian countries for thousands of years [ 28 ]. They are traditionally classified as red, orange, and yellow pigments based on their maximum absorbance [ 29 ].…”