Phycocyanin from Spirulina sp. and Galdieria sp.: A systematic review of bibliometric trends, bioactivities, and structural biology

Phycocyanin is a blue pigment-protein complex widely produced by cyanobacteria and red algae, including Spirulina and Galdieria sp. The complex has attracted considerable attention due to its potential as a natural colorant and bioactive compound with antioxidant, anti-inflammatory, and anti-cancer properties. This review presents a comprehensive analysis of research trends, structural characteristics, and biofunctional applications of phycocyanin based on a bibliometric study using Scopus data (1973–2025) and VOSviewer. We highlight the differences in the molecular composition and thermal stability between phycocyanin derived from Spirulina and Galdieria, with Galdieria demonstrating higher heat tolerance and industrial relevance. Various extraction and purification techniques, including ultrasonication, enzymatic hydrolysis, and chromatography, were compared to assess yield and purity. Despite extensive studies on Spirulina, significant knowledge gaps remain regarding the structural biology, production scalability, and application feasibility of phycocyanin from extremophilic algae. This review identifies underexplored study areas and suggests that future studies should focus on improving extraction efficiency, assessing industrial-scale production stability, and expanding its applications in the food, cosmetic, and pharmaceutical sectors. Advancing interdisciplinary research is crucial for unlocking the full potential of phycocyanin as a sustainable and functional biopigment.