Study On The Interaction And Physicochemical Properties Of Phycocyanin-Different Bioactive Molecule Complexes

Phycocyanin（PC）is a natural pigment-protein complex in food dye applications.Phycocyanin is not only one of the few natural blue pigments in nature,but also has a series of biological activities beneficial to the human body.In order to enrich the basic theoretical research of phycocyanin and expand the potential applications of phycocyanin in food industry,a phycocyanin-pigallocatechin gallate（EGCG）complex（PE）was prepared and the effects of EGCG on the structure and color stability of PC were evaluated.Finally,phycocyanin-quercetin-folic acid complex were prepared by non-covalent binding of phycocyanin with multiple ligands to investigate the potentiation between phycocyanin and each ligand.Phycocyanin（PC）is a natural pigment-protein complex in food dye applications.In this study,a phycocyanin-epigallocatechin gallate（EGCG）complex（PE）was prepared and the effects of EGCG on the structure and color stability of PC were evaluated.The fluorescence results showed that the binding number n was 62.1±3.41（EGCG/PC）and the binding constant K was 4.39（±0.2）×10⁵M^-1,indicating a weak-binding interaction.Fourier transform-infrared analysis showed that EGCG caused structural changes in PC by partially uncoilingα-helix and increasingβ-sheet content.The EGCG induced a PC association at a reaction molar ratio above 40:1（EGCG/PC）.Moreover,EGCG protected phycocyanobilin against color fading,making PE more stable relative to PC under 8-days storage in light.This study provides a novel scheme to stabilize PC by forming a complex with polyphenols,which will facilitate the PC application as a natural blue pigment in food.Phycocyanin was selected as the reaction substrate to interact with two small molecular active substances with different properties（hydrophilic folic acid and hydrophobic quercetin）to study the synergistic protective effect of phycocyanin on ligands.Fluorescence spectra showed that the binding number n of the protein to folic acid and quercetin were 38.8±1.98（FA/PC）and 18.6±2.38（Quercetin/PC）,respectively.It has little effect on the structure of phycocyanin.In studies of the binding sequence of ligand-protein reactions,proteins tended to bind to folic acid first and then to quercetin.At the same time,the first combination of folic acid with the complex will reduce the binding ability of quercetin and phycocyanin;the first combination of quercetin with the complex will also reduce the binding ability of folic acid and phycocyanin.The stability test showed that after the two active substances were combined with phycocyanin,the thermal stability of phycocyanin was increased;the stability of folic acid under ultraviolet light irradiation was improved.In this study,the non-covalent compounding of phycocyanin with epigallocatechin gallate improves the storage stability of phycocyanin under light conditions,which opens up new ideas for the application of phycocyanin.At the same time,the preparation of phycocyanin-multiligand complex in the order of addition of quercetin and folic acid provides a new idea for phycocyanin as a carrier that can simultaneously bind and protect different biologically active components.