Phycocyanin is a bluish pigment used by blue-green algae ( or cyanobacteria) to photosynthesize. It accounts for as much as 20% of the protein in cyanobacteria, and attaches itself to photosynthesizing membranes. It acts as a nitrogen-storing molecule. There is no metal in phycocyanin and it is a very stable protein.
Phycocyanin may also act as an antioxidant. It appears to scavenge OH and RO radicals quite well. It may also work as well as some NSAIDs to treat inflammation, and seems to have positive effects on liver mocrosomal lipid peroxidation.
Pigments derived from phycocyanin such as C-phycocyanin and Allophycocyanin have fluorescent properties that are valuable to researchers in immuno assay kits. Phycocyanin is selective about which cells it attaches to, making it simple to track down.
It is also used as a colorant in biological research, and as a natural color in a number of foods and cosmetics because it is so safe.