Phycocyanin: From natural pigment to multifunctional bioactive substance

Phycocyanin, a blue-green pigment protein derived from algae such as Spirulina, belongs to the phycobiliprotein family and is responsible for capturing and transmitting light energy in photosynthesis. This natural substance has attracted attention because of its distinctive blue colour and diverse biological activities, and is widely used in various fields such as food, medicine and cosmetics. Basic Properties and Chemical Composition Algae blue protein appears as dark blue granules or powder, belongs to protein-binding pigments, and has the same properties as proteins. Its isoelectric point is 3.4, soluble in water but insoluble in alcohol and oil. This pigment is sensitive to heat, light and acid, and remains stable in weakly acidic and neutral environments (pH 4.5-8), precipitates under acidic conditions (pH 4.2), and decolourises in strong alkaline environments. In terms of chemical structure, phycocyanin consists of de-coordinated proteins covalently bound to phycobili...