to these parameters in cadmium-intoxicated rats as well as lead-intoxicated animals by reducing various oxidative stress parameters such as malondialdehyde, conjugated diene and hydroperoxide.38,39 Extract of S. fusiformis provided protection against oxidative damage induced by mercuric chloride.40

Spirulina and Exercise-Induced Oxidative Damage

Spirulina supplementation prevents skeletal muscle damage in untrained human beings. Sixteen students were volunteered to take S. platensis in addition to their normal diet for 3 weeks. Blood samples were taken after finishing the Bruce incremental treadmill exercise before and after treatment. The results showed that plasma concentrations of malondialdehyde were significantly decreased after supplementation with Spirulina.41 The activity of blood superoxide dismutase (SOD) was significantly raised after supplementation with Spirulina. Both the blood glutathione peroxide (GP(x)) and LDH levels were significantly different between Spirulina supplementation analysis41 (Figure 5.6).

Spirulina and Nitrosative Stress

Peroxynitrite (ONOO(-)) is known to inactivate important cellular targets and also mediate oxidative damage in DNA. Phycocyanin, a biliprotein from S. platensis, and its chromophore, phycocyanobilin, efficiently scavenge ONOO(-), a potent physiological inorganic toxin. Scavenging of ONOO(-) by phycocyanin and PCB was established by studying their interaction with ONOO(-) and quantified by using competition kinetics of pyrogallol red bleaching assay. The relative antioxidant ratio and IC5o value clearly indicate that phycocyanin is a more efficient ONOO(-) scavenger than PCB. Increasing role of peroxynitrite species in different pathological conditions suggest that phycocyanin can be a potential therapeutic target for different disorders.26

The interaction of phycocyanin and its bilin chromophore with peroxynitrite (ONOO(-)) was studied spectroscopically by Bhat and Madyastha.31 They demonstrated that the addition of increasing concentrations of ONOO(-) (0-200 mM) to phycocyanin (10 mM) significantly decreased its absorption at 618 nm, with no change in the absorption at 360 nm. Nearly, 50% of absorption at 618 nm was lost in the presence of 200 mM ONOO(-), although there was no shift in the absorption maxima. The spectra of bilin chromophores are characterized by absorption maxima at 610 and 365.5 nm. The addition of ONOO(-) (0-125 mM) to bilin chromophores (10 mM) decreased the absorbance peak at 610 nm and 365.5 nm, with a shift towards lower wavelength (563 and 329.5 nm) at lower concentrations of ONOO(-). At higher concentration of ONOO(-) (125 mM), there was no further shift in the absorption maxima and the chromophore was almost completely bleached. The scavenging of ONOO(-) by phycocyanin and its bilin chromophore was also evaluated using competitive kinetics of pyrogallol red bleaching assays.31 Pyrogallol red is one of the more efficient dyes that can be used to evaluate the ONOO(-) scavenging activity of any compound in aqueous solution. Phycocyanin is an efficient scavenger of ONOO(-); at 70 mM concentration it inhibited pyrogallol red bleaching to the extent of nearly 90%. However, both bilin chromophore and glutathione (a known ONOO(-) scavenger) appeared to be more efficient scavengers of ONOO(-) at lower concentrations than phycocyanin. It was also noticed that phycocyanin, its bilin chromophore, and glutathione, inhibited bleaching of pyrogallol red in a concentration-dependent manner with an IC50 value of 21.8±2.6 mM, 30.5±0.8 mM and 4.8 ± 1.2 mM respectively. The relative antioxidant activity ratios calculated for phycocyanin, its bilin group and glutathione were 3.9, 1.8, and 5.2 respectively. The relative antioxidant ratio as well as IC50 value clearly suggested that phycocyanin is more efficient ONOO(-) scavenger than its bilin chromophore. This result was attributed to the interaction of ONOO(-) with tyrosine and tryptophan residues present g> 100

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