Antioxidant activity: DPPH assay.

The antioxidant activities of the polysaccharide were assayed according to the methods adopted by Sagar (17). In this method, the algal extracts were dissolved in methanol, where the metabolic 2,2 diphenyl-1picryl hydrazyl (DPPH) was used as a control. A mixture of 5 mL DPPH solution (10, 20, and 40 mg/mL) was used, and the absorbance was measured spectrophotometrically at 517 nm after 30 min. The free radical scavenging activities of the algal extracts were indicated by the degree of decolonization of DPPH. The percentage of decolonization was calculated using the following equation: Free radical scavenging % = (Ac–As)/Ac × 100 where Ac is Absorbance of control and As is Absorbance of the sample. Ascorbic acid was used as a reference free radical scavenger.