Antioxidant activity optimisation of Spirulina platensis C-phycocyanin obtained by freeze-thaw, microwave-assisted and ultrasound-assisted extraction methods

In vitro antioxidant activities of C-phycocyanin extracts obtained from Spirulina platensis by freeze-thaw, microwave-assisted extraction (MAE) and ultrasound-assisted extraction (UAE) methods were evaluated according to 1,1-diphenyl-2-picryl-hydrazyl radical scavenging capacity. Full factorial design was used to optimise the extraction time and medium pH using multiple linear regression analysis. The third-order polynomial models with high R2 values (0.925, 0.946 and 0.858) were sufficiently fitted to the experimental antiradical activities of C-phycocyanin extracted by the three extraction methods. The optimised results showed that the lowest IC50 value for C-phycocyanin extracted by freeze-thaw extraction method (IC50 = 0.031 mg/ml) was obtained after 4 h of extraction at pH=8.00. While these values for MAE (IC50 = 0.021 mg/ml) and UAE (IC50 = 0.036 mg/ml) methods were 22.5 s at pH=8.00, and 6.71 min at pH=7.57, respectively. The models adequacy was confirmed by extracting the C-phycocyanin under the optimum values suggested by the models. Results showed that MAE could be a better method for C-phycocyanin extraction from S. platanssis in terms of antioxidant activity