Antioxidant Capacity of PGBE Complex

The antioxidant capacity of the PGBE complex was investigated using ABTS cation radical scavenging activity assay, as described by Cai et al [13 (link)]. ABTS radical cations generated by reacting 7.2 millimolar (mM) ABTS and 2.6 mM potassium persulfate for 24 h in a dark room were diluted with phosphate-buffered saline (pH 7.4) so as to give 20% to 30% inhibition of the blank absorbance at 734 nm with a spectrophotometer (Biotek Instruments, Inc., Winooski, VT, USA). Subsequently, 10 μL of PGBE complex or L-ascorbic acid was added into 190 μL of ABTS solution to get a final PGBE concentration of 0.16% to 0.01% (vol/vol) or L-ascorbic acid (1.0, 0.1 and 0.01 mg/mL; Sigma-Aldrich, St. Louis, MO, USA) in a 96-well plate (Thermo Fisher, USA), and reacted for 10 min in a dark room. The optical density (OD) of the resulting mixture was measured at 734 nm, and radical scavenging activity was calculated using the following formula: 1 – (OD blank – OD sample)/OD blank.