Hydrogen peroxide scavenging activity was measured using the method of Bahorun et al. (1996) with slight modification.
Appropriate amount of the 80% ethanol extract was added to a test tube.
The solvent was removed by evaporation under reduced pressure or with nitrogen gas stream. The dried sample (5.0 mg D.W. of shrimp paste) was well mixed with 50 lL of 80% ethanol, and then was incubated with 0.45 mL of 0.1 M phosphate buffer (pH 7.0) containing 89 mM NaCl and 50 lL of 23 mM hydrogen peroxide for 10 min at 37 C.
To the mixture, 0.5 mL of 0.1 M phosphate buffer (pH 7.0) containing 0.05 mg HRPO and 0.1 mg phenol red was added and kept at room temperature for
15 min. Then, 50 lL of 1.33 M NaOH was added to the mixture.
After 10 min, the absorbance was read at 610 nm. When the insoluble substances were observed in the sample mixture, they were removed by centrifugation before reading the absorbance.
The hydrogen peroxide scavenging activity (%) was calculated from the decrease of absorbance at 610 nm by the addition of 80% ethanol sample extract toward that of control (without antioxidant).