Precursor-directed production of water-soluble red Monascus pigments with high thermal stability via azaphilic addition reaction-based semi-synthesis

Linman He; Cai Liu; Suo Chen; Jialan Zhang; Mengxiang Gao; Li Li

doi:10.1016/j.fochx.2023.100940

Precursor-directed production of water-soluble red Monascus pigments with high thermal stability via azaphilic addition reaction-based semi-synthesis

Food Chem X. 2023 Oct 10:20:100940. doi: 10.1016/j.fochx.2023.100940. eCollection 2023 Dec 30.

Authors

Linman He¹, Cai Liu¹, Suo Chen¹, Jialan Zhang², Mengxiang Gao^{1

3}, Li Li^{1

3}

Affiliations

¹ College of Life Science, Yangtze University, Jingzhou 434025, China.
² College of Animal Science, Yangtze University, Jingzhou 434025, China.
³ Institute of Food Science and Technology, Yangtze University, Jingzhou 434025, China.

Abstract

Red Monascus pigments (MPs) are a large group of polyketides from the fungus Monascus which have been widely used as food colorants. In this study, a variety of red MPs congeners were prepared to explore promising water-soluble candidates for application in liquid food formulations. The results showed that by combining the two-stage, low-pH fermentation strategy with a downstream purification step of fractional crystallization, precursors of red MPs, namely monascorubrin and rubropunctatin, were obtained with a purity of 91.9%. Then, via the azaphilic addition reaction, 18 types of red MPs congeners carrying different amino acid moieties (MPs-aa) were semi-synthesized. Compared to rubropunctamine and monascorubramine, the water solubility, pH and thermal stability of MPs-aa were improved greatly. MPs-His, MPs-Phe, MPs-Tyr and MPs-Trp were identified to be the most resistant to pasteurization. These findings provide water-soluble red MPs candidates with high thermal stability and an attractive approach for their large scale production.

Keywords: Azaphilic addition reaction; Monascorubrin, PubChem CID: 12118084; Monascus pigments; Semi-synthesis; Thermal stability; Water solubility; ankaflavin, PubChem CID: 15294091; monascin, PubChem CID: 12118082; rubropunctatin, PubChem CID: 6452445.