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

In this study, the antibacterial and antioxidant properties of C-phycocyanin (C-PC) from Spirulina platensis 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 Escherichia coli, Staphylococcus aureus, Listeria monocytogenes, Streptococcus iniae and Yersinia ruckeri. 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 activities of 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 L. monocytogenes and S. iniae 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 S. platensis had high potential of antioxidant activity in vitro 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).