Antioxidant and antibacterial activities of C-phycocyanin from common name Spirulina platensis

Abstract

In this study, the antibacterial and antioxidant properties of C-phycocyanin (C-PC) from <em>Spirulina platensis</em> were evaluated. The extraction and purification of C-PC were carried out using lyzosyme and ammonium sulphate precipitation, respectively. DPPH radical-scavenging activity, ferric reducing antioxidant power (FRAP)and Fe²⁺-chelating activity were used for evaluation of antioxidant properties of C-PC. Antibacterial activity was also performed using agar well diffusion and microdilution [minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC)]. The selected bacteria were <em>Escherichia coli</em>,<em> Staphylococcus aureus</em>,<em> Listeria monocytogenes</em>,<em> Streptococcus iniae</em> and <em>Yersinia ruckeri</em>. The results showed that the biomass production was 1120 mg L^-1 and C-PC concentration in crude extracts and purified by (NH₄)₂SO₄ were also 1.815 and 3.75 mg ml^-1, respectively. The results of DPPH, FRAP and Fe²⁺-chelating activitiesof C-PC was 45.75%, 0.051 mg TAE g^-1 and 40.23% at zero time and 41.56%, 0.046 mg TAE g^-1 and 36.56% after 60 days at -18°C, respectively. The results of agar well diffusion indicated that <em>L. monocytogenes</em> and <em>S. </em><em>iniae</em> were the most sensitive and resistant, respectively among examined bacteria in different concentrations of C-PC (0- 25 µg ml^-1) and the mean of inhibition zones were also 7.50-22.11mm. The results of MIC and MBC of C-PC (as µg ml^-1) were 50-500 and 100-500, respectively. As a conclusion, C-PC from <em>S. platensis</em> had high potential of antioxidant activity <em>in vitro</em> and it can be used as natural antioxidants in variety of foods. Antibacterial activity of C-PC was lower than other algal pigments (such as astaxanthin and C-PC in other cyanobacteria).