4.3. DPPH Free Radical Scavenging Activity Assay

The free radical scavenging activity of the sample was measured by the DPPH scavenging photometric assay [51]. Chemically, the odd electron of the nitrogen atom in 2,2-diphenyl-1-picrylhydrazyl (DPPH) is reduced by receiving a hydrogen atom from antioxidants to the corresponding hydrazine. When DPPH is added to the reaction mixture, the rate of reduction is used as an indicator of the antioxidant capacity. The reaction mixture was prepared by adding 100 µL of the sample to 900 µL of the DPPH solution (12.5 µg/mL (31.7 µM) DPPH in DMSO, 40 mM Tris-HCl, pH 7.4). Samples used were ARC lysate (2 mg/mL), and DBY (inactive dry brewer’s yeast, 2 mg/mL) and quercetin (1 µg/mL) and ascorbic acid (100 µM, 17.6 µg/mL) as the reference and the positive control. The reaction mixture was vortexed thoroughly and left in dark at room temperature for 30 min. Absorbance was measured with a UV-VIS spectrophotometer at 517 nm. DPPH inhibition (%) or DPPH radical scavenging activity (%) was calculated according to the formula below.

where C and C₀ are absorbances of the DPPH and water without sample, and S and sample S₀ are absorbances of the DPPH and water with sample, respectively.