Phycocyanin, as a cyanobacterial antioxidant: structure, function and applications

Phycobilins, as open-chain tetrapyrrole pigment molecules, serve as accessory photosynthetic light-harvesting pigments in red algae and cyanobacteria. Phycobilin pigments are covalently linked with proteins which form phycobiliproteins organized into large macromolecular complexes called phycobilisomes on the top of the thylakoid membranes. In deep water, only green light is available, thus phycobilisomes are able to absorb this part of light very efficiently and allowing cyanobacteria to survive. Cyanobacteria are capable of adjusting the quantitative pigment composition of phycobilisomes in response to changes in environmental conditions. Phycocyanin is a kind of phycobiliproteins which is characterized by an intense blue color and has been widely used as most important natural dye and antioxidant. The free radical scavenging properties of cyanobacterial phycocyanin are well documented. Phycocyanin eliminates reactive oxygen and nitrogen species and therefore prevents oxidative stress that leads to major damage in the structure of biomolecules of the cell. The variety of applications, from its involvement in the prevention of free radical-related diseases including cancer and Alzheimer's, to its antimicrobial effects, from its use in research laboratories and industry to its significant financial turnover, highlights the importance of reviewing studies on phycocyanin. Hence, this review describes recent findings about the sources, structure, function, production, extraction techniques and different applications of phycocyanin.