The generation of reactive oxygen species in all organisms is associated with the damage of biologically relevant molecules such as DNA, proteins, carbohydrates and lipids. These highly reactive species include the hydroxyl radical, the superoxide anion radical, hydrogen peroxide and singlet molecular oxygen as well as hypochlorite, the nitric oxide radical and peroxynitrite. A variety of biological processes and diseases e.g., inflammation, photobiological effects, antimicrobial defence, radiation damage, carcinogenesis, neurodegenerative diseases, atherosclerosis and aging involve reactive oxygen species. Our organism processes
various defence mechanisms against the highly reactive oxygen species including the action of endogenous or exogenous antioxidant molecules. Exogenous antioxidants of dietary origin include vitamin C, vitamin E, carotenoids and polyphenols.
The antioxidant properties of Spirulina are mainly related to the strong antioxidant and free radical scavenging activities of phycocyanin, although other antioxidant constituents contribute to the total antioxidant potential of the microalga. In this respect, it has been shown:
The potent peroxyl radical scavenging activity of phycocyanin. In this respect, the covalently linked chromophore phycocyanobilin is involved in this antioxidant activity,
The scavenging of peroxynitrite by phycocyanin. Peroxynitrite is an inorganic toxin of biological importance, which can be generated in vivo from nitric oxide and superoxide,
The strong selective inhibition of cyclooxygenase-2 (COX-2) by phycocyanin, with a very low COX-2/COX-1 ratio (0.04). The capacity of phycocyanin to inhibit COX-2 is much higher than those of the non-steroid anti-inflammatory drugs celecoxib and rofecoxib, the well-known selective COX-2 inhibitors; thus, anti-inflammatory
properties of phycocyanin reported in the literature may be due, in part, to its selective COX-2 inhibitory property, although its ability to scavenge free radicals may also be involved,
The scavenging of hydroxyl and alcoxyl radicals by phycocyanin (phycocyanobilin moiety is the main part of phycocyanin involved in scavenging hydroxyl radicals), and (e). The scavenging of stable free radicals by a variety of Spirulina extracts.
It has been also demonstrated that phycocyanin exhibits antihyperalgesic activity by suppression of iNO synthase and COX-2 induction Cell-free and cell-based assays were also used to examine the antioxidant and antiinflammatory properties of Spirulina preparations. The results showed inactivation of free superoxide radicals as well as an anti-inflammatory effect which is related to the
reduction of metabolic activity of neutrophils.
A limited number of clinical trials have been also carried to evaluate the antioxidant and/or anti-inflammatory activities of Spirulina in healthy humans or patients with type 2 diabetes. Intake of Spirulina (7-8 g/day for 8-16 weeks) has shown significant decrease of serum interleucin IL-6 levels and rise in plasma IL-2 concentrations,
increase in superoxide dismutase activity and reduction of the oxidative marker MAD (malondialdehyde), thus demonstrating the antioxidant and anti-inflammatory activities of Spirulina in vivo.
Animal experiments have shown that Spirulina is able to protect the organism from drug-induced oxidative damages (nephrotoxicity and cardiotoxicity), from metalinduced oxidative damages (lead, cadmium, mercury) and from hepatotoxin-induced oxidative damage (hepatotoxicity from carbon tetrachloride) as well as from neuronal
oxidative damages. In the last case it has been proposed that phycocyanin may be useful for the treatment of neurodegenerative disorders such as Alzheimer’s,
Parkinson’s and Huntington’s diseases. In this respect, among various food extracts tested as aggregation blockers of amyloid-β for Alzheimer’s disease therapy,
Spirulina extract was the most active. Phycocyanobilin chromophore of phycocyanin that constitutes up to 1% of the dry weight of spirulina, has recently been shown to be a potent inhibitor of NADPH oxidase. Some of the central physiological effects of phycocyanobilin may also reflect inhibition of neuronal NADPH oxidase, which is now known to have a modulatory impact on neuron
function, and can mediate neurotoxicity in certain circumstances. The possibility that orally administered phycocyanobilin could reach the brain parenchyma in sufficient concentrations to influence microglial function and to preserve a healthful function of the central nervous system has been proposed.
Among the various bioactivities of Spirulina polysaccharide extracts, a strong inhibitory effect on inflammation-induced corneal neovascularization can also be included. These experimental results suggest the potential use of Spirulina polysaccharide extracts in the treatment of inflammatory neovascularization-related corneal diseases.