FRAP was determined by the method described by Ganesan
et al. [18]. To 1 mL algal extracts at different concentrations
(7.81–1000mg/L) were added 2.5 mL phosphate buffer (0.2 M,
pH 6.6) and 2.5 mL potassium ferricyanide (1%). This mixture
was incubated at 50
C for 20 min, cooled in ice-water and
then added of 2.5 mL trichloroacetic acid (10%). After stirring,
2.5 mL were taken and mixed with 2.5 mL distilled water and
0.5 mL ferric chloride (0.1%). After 10 min incubation at room
temperature, the absorbance was read at 700 nm in a microplate
reader (Biochrom Asys UVM 340). The BHA was used as a
positive control at the same concentrations of algal extracts. The
increase in absorbance indicated increase of FRAP, that is, the
higher the absorbance, the greater the FRAP.