What this work is about, in plain words
The blue pigment-proteins of spirulina are known as antioxidants in animal cells. The authors tested how they act in plant tissues, using potato as an example.
Phycobiliproteins are colored proteins of the cyanobacterium Arthrospira platensis (spirulina), the main one being the blue C-phycocyanin. They are known to protect animal cells from oxidative stress. How they act in plant cells has been little studied. That became the authors' task.
A protein extract with a high share of phycocyanin was obtained from spirulina biomass by cold extraction. Its antioxidant properties were tested on potato extracts in which hydrogen peroxide is formed. Separately, the effect of the extract on the work of mitochondria — the cell's "power plants" — isolated from potato was studied.
According to the authors, the extract reduced hydrogen peroxide formation more strongly the higher its concentration, and at 0.25 mg/mL prevented it completely. At the same concentration, potato mitochondria switched to a mild "uncoupling" mode: they respired more actively but stored energy less efficiently. The authors consider the mechanism of this effect unclear.
The authors conclude that spirulina pigments help the plant cell maintain the balance between oxidants and antioxidants and affect the work of mitochondria.
Limitations. The experiments were carried out in vitro, on tissue extracts and isolated potato mitochondria. The effect on whole plants was not tested, and the conclusions do not carry over to humans or animals.