Table

Summary of Studies on Antioxidant Effects of Spirulina

Reference

Manoj et al., 1992

Zhi gang et al., 1997

Miranda et al., 1998

Romay et al., 1998

Romay et al., 2000

Hirata et al., 2000

Bhat and Madyastha, 2000

Rimbau et al., 1999

Vadiraja et al., 1998

Miranda et al., 1998

Bhat and Madyastha, 2000

Type of study Summary of study

In vitro The alcohol extract of Spirulina inhibited lipid peroxidation more significantly than the chemical antioxidants like alpha-tocopherol, BHA, and beta-carotene. Water extract showed more antioxidant activity than gallic acid and chlorogenic acid.

In vitro Two fractions of hot water extracts showed marked scavenging of hydroxyl radical (the highly reactive oxygen radical); one of the fractions had significant activity in scavenging lipid radicals at low concentrations.

In vitro Peroxidation of rat brain homogenate was inhibited by almost 95% with 0.5 mg of the methanolic extract. The IC50 of the extract in this system was found to be 180 mcg.

In vitro Phycocyanin was able to scavenge hydroxyl

(IC50 = 0.91 mg/mL) and alkoxyl (IC50 = 0.76 M-g/mL) radicals. It also inhibited liver microsomal lipid peroxidation (IC50 = 12 mg/mL).

In vitro Phycocyanin inhibited 2,2'-azobis(2-amidinopropane)

dihydrochloride (AAPH), a free radical generator induced human erythrocyte haemolysis in the same way as trolox and ascorbic acid, two well-known antioxidants. On the basis of the values of IC50 phycocyanin was found to be 16 times more efficient as antioxidant than trolox and about 20 times more efficient than ascorbic acid.

In vitro The antioxidant activity of phycocyanobilin (a component of phycocyanin) was greater than that of alpha-tocopherol, zeaxanthin, and caffeic acid on the molar basis.

In vitro Phycocyanin showed a potent peroxyl radical scavenger capacity with a rate constant ratio of 1.54 compared to 3.5 for uric acid (a known peroxyl radical scavenger).

Animal (Rats) Oral administration of c-phycocyanin (100 mg/kg) in rats prevented kainic acid induced behavioral and glial reactivity in the rat hippocampus crossing the hematoencepphalic barrier.

Authors postulate potential use of phycocyanin in the treatment of neurodegenerative disease such as Alzheimer's and Parkinson's disease induced by oxidative stress-induced neuronal injury.

Animal (Rats) Carbon tetrachloride (0.6 mL/kg) and R-(+)-pulegone

(250 mg/kg) induced hepatotoxicity in rats was reduced significantly when phycocyanin was administered intraperitoneally to rats 1 or 3 h before the challenge.

Animal (Rats) Plasma antioxidant activity in brain homogenate incubated at 47° C showed that the antioxidant activity of plasma was 97% and 71% for the experimental group and 74% and 54% for the control group after 2 months and 7 months, respectively.

Animal (Rats) c-Phycocyanin from Spirulina effectively inhibited CCl4-induced lipid peroxidation in rat liver in vivo.

activity of a methanolic extract of Spirulina in vitro and in vivo. The in vitro antioxidant assay involved a brain homogenate incubated with and without the extract at 37°C. Peroxidation of rat brain homogenate was inhibited by almost 95% with 0.5 mg of the methanolic extract. The IC50 of the extract in this system was found to be 180 mcg. The in vivo antioxidant capacity was evaluated in plasma and liver of animals receiving a daily dose of 5 mg for 2 and 7 weeks.14 Plasma antioxidant activity in brain homogenate incubated at 47°C showed that the antioxidant capacity of plasma was 97% and 71% for the experimental group and 74% and 54% for the control group after 2 and 7 months of Spirulina treatment. The antioxidant effect was attributed to beta-carotene, tocopherol, and phenolic compounds working individually or in synergy.14,15 Different extracts from the microalga S. platensis were obtained using pressurized liquid extraction (PLE) and four different solvents (hexane, light petroleum, ethanol, and water). All extracts demonstrated a significant antioxidant activity as tested using electro-chromatography with diode array detection (MEKC-DAD).16 Chlorella (Chlorella vulgaris), another microalga, has also been reported to show antioxidant activity17 in exhibiting attenuating effects on oxidative stress and suppressing inflammatory mediators.18 In one study, Wu et al.,19 compared the antioxidant activity of Spirulina and chlorella extracts. Results of this study indicated that the total phenolic content of Spirulina was almost five times greater than that of chlorella (6.86 +/- 0.58 vs. 1.44 +/- 0.04 mg tannic acid equivalent/g of algae powder, respectively). The antioxidant activity of Spirulina determined by the ABTS*+ method was higher than chlorella (EC50: 72.44 +/- 0.24 ^mol of trolox equivalent/g of Spirulina extract vs. 56.09 +/- 1.99 ^mol of trolox equivalent/g of chlorella extract). Results of DPPH assay also showed a similar trend as the ABTS*+ assay (EC50: 19.39 +/-0.65 ^mol of ascorbic acid equivalent/g of Spirulina extract vs. 14.04 +/- 1.06 ^mol of ascorbic acid equivalent/g of chlorella extract).19

PHYCOCYANIN, A MAJOR ANTIOXIDANT CONSTITUENT OF SPIRULINA

Phycobiliproteins are a small group of highly conserved chromo proteins that constitute the phycobilisome, a macromolecular protein complex whose main function is to serve as a light harvesting complex for the photosynthetic apparatus of cyanobacteria and eukaryotic groups. The most common classes of phycobiliproteins are allophy-cocyanin, phycocyanin (Pc), and phycoerythrin all of which are formed by a and b protein subunits and carry different isomeric linear tetrapyrrole prosthetic groups (bilin chromophore) that differ in the arrangement of their double bonds. The bilin groups are attached to the polypeptides through thioether linkages to specific cysteinyl residues.20 Phycocyanin (Figure 5.3) is composed of two dissimilar a and b protein subunits of 17,000 and 19,500 Da, respectively, with one bilin chromophore attached to the subunit (a 84) and two to the b subunit (b 84, b 155).21 Phycocyanin exists as a complex interacting mixture of trimer, hexamer, and decamer aggregates. It is obtained from the microalgae cellular biomass by a freeze thawing process or by using a French pressure cell, and is purified by successive steps of ammonium sulphate precipitation and further DEAE-cellulose chromatography. Phycocyanin is considered

Hfci

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