With the increasing enthusiasm of the public for pursuing healthier and more sustainable dietary patterns, a trend of using natural plant pigments instead of synthetic pigments is quietly emerging. Phycocyanin, a pure blue natural pigment derived from spirulina, is gradually becoming a new favorite in the food industry. Its uniqueness lies not only in adding natural color to food, but also in its multiple biological activity advantages, such as significant free radical scavenging ability, mild regulatory effect of the immune system, and enhanced function of lipid peroxidase activity. It is widely used in the fields of food, cosmetics, and even pharmaceuticals as a nutritional supplement and health supplement.
However, a significant challenge in the widespread application of phycocyanin in the aforementioned fields is its extremely high chemical sensitivity. Specifically, when phycocyanin is exposed to a series of adverse environmental factors such as high temperature, strong light irradiation, acidic environment, high-pressure treatment, the presence of heavy metal cations, or contact with denaturing agents, its structure is highly susceptible to damage, leading to pigment degradation and subsequently affecting its effectiveness and stability in use. Therefore, how to overcome the limitations of chemical sensitivity while maintaining the natural advantages of phycocyanin has become an important topic in current research and development.
The structure and biological activities of the phycocyanin
The phycobilisome, a complex supermolecular protein structure, serves as a vital energy transfer station in photosynthesis, conveying collected light energy to the reaction centers of eukaryotic red algae and prokaryotic cyanobacteria. At its heart lies the allophycocyanin core, surrounded by rods made up primarily of phycocyanin.
Within the phycobiliprotein family, three primary pigments each exhibit their distinctive hues: phycocyanin with its characteristic blue (λmax = 617 nm), phycoerythrin shining red (λmax = 565 nm), and the bluish-green allophycocyanin (λmax = 650 nm). Among them, phycocyanin dominates the scene.
The enchanting blue color of phycocyanin stems from its chromophore, phycocyanobilin, which is tightly bound to the protein via thioether bonds, forming a unique molecular architecture. As an open-chain tetrapyrrole chromophore, phycocyanobilin’s specific arrangement of conjugated double bonds not only contributes to the vivid color of phycocyanin but also endows it with remarkable radical scavenging and antioxidant properties.
Remarkably, phycocyanin has also demonstrated significant potential in biomedical applications. By harnessing its unique γ-glutamyl-cysteinyl-glycine mechanism, phycocyanin can effectively neutralize reactive oxygen species and free radicals within the body, thereby safeguarding tissues from damage. This characteristic underscores the promising avenues for phycocyanin in preventing and treating diseases such as hepatorenal and hematological disorders.
anin from cyanobacterium S. platensis in form of hexamer, image from PDB (https://www.rcsb.
org/structure/1GH0). (B) Phycocyanin exists as (αβ) 6 hexamer and both chains have the α-helix structure.
(Green, brown and pink represent α subunit. Grey, yellow and dark brown represent β subunit). (C) (D)
Three-dimensional and secondary structure of phycocyanobilin. (For interpretation of the references to
color in this figure legend, the reader is referred to the Web version of this article.)
Strategies to improve the stability of phycocyanin
