2.8. Antioxidant Activity (AOA) Assays

For the AOA evaluation by DPPH method a 10-fold dilution was performed for PSM US, PND US, PSR US, PSV US, PSM M and PND M variants and a 20-fold dilution for the PSV M and PSR M variants. Of each sample 100 µL were treated with a 2.5 mL 0.1 mM DPPH solution. The mixture was shaken and then left in a dark room at room temperature for 30 min. The sample and DPPH solution absorbance were measured at 517 nm. Six measurements were performed for each variant. The inhibition percentage was calculated using the following formula [35]:

A₀—DPPH solution absorbance and A₁—sample absorbance

For the AOA evaluation by ABTS method, a procedure described previously with slight modifications, was used [36]. Briefly, this method consists in the treatment of 100 µL of tested sample with 100 µL of ABTS reagent. The mixture is shaken and left in a dark room for 5–6 min. For the measurement of sample and ABTS solution absorbance at 734 nm, an Epoch microplate reader (BioTek Instruments Inc., Winooski, USA) was used. Six measurements were performed for each variant. The inhibition percentage was determined with the formula mentioned at the DPPH method.