2.5. DPPH• scavenging activity assay
Antioxidant activities of the samples before and after the
gastric and duodenal phases of digestion were analyzed by investigating their abilities to scavenge the DPPH free radical
(Cai, Sun, & Corke, 2003). 3.9 mL of 60 M DPPH• solution in 80%
ethanol were added to 0.1 mL of the diluted sample, then the
tube was vortexed for 15 s and reacted for 2 h, and the decrease
in absorbance of DPPH• was measured at 515 nm using
a Rui Li U9600 UV–vis spectrophotometer. Ethanol (80%) was
used as a blank solution, and DPPH• solution without test
samples (3.9 mL of DPPH• 0.1 mL of 80% ethanol) served as the
control, inhibition (%) of DPPH• absorbance = (Acontrol − Atest) × 100/
Acontrol. Trolox was used as a reference standard, and the results
were expressed as mol Trolox/g dry weight of flower.