Determination of antioxidant activity
The antioxidant capacity of the lignin was studied by evaluating its free radical scavenging effect on the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical following the method of Dizhbite et al. [7] and De Ancos et al. [12] with slight modifications. In brief, a known aliquot (320 µl) of the extract (lignin solution, 1 µg ml−1 to 100 µg ml−1) in 2 different solvents, namely, 2-methoxy ethanol and dimethyl sulfoxide (DMSO) (90%) was mixed with 1180 µl of 6.1 × 10−5 mol/l DPPH (pre dissolved in 80% methanol solution) at 25 ◦C for 16 min. The mixture was thoroughly vortexmixed and the absorbance was measured at 515 nm against a blank. Results expressed as percentage of inhibition of the DPPH radical, was calculated according
to the following equation:
Exploring the antioxidant potential of lignin isolated from black liquor of oil palm waste