4.4.3. DPPH Radical Scavenging Assay

The antioxidant activity was evaluated using 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) free radical scavenging activity according to the method modified from Paradee et al. [27]. Briefly, 200 µL of samples were mixed with 200 µL of 0.4-mM DPPH solution and incubated at room temperature for 30 min in the dark. Trolox was used as the positive control. Then, the absorbance was measured at a wavelength of 517 nm using a microplate reader (BioTek Synergy H4 Hybrid Reader, BioTek Instruments Inc., Winooski, VT, USA). The ability of DPPH radical scavenging was expressed as the percentage inhibition and calculated using the following equation:

where A₀ is the absorbance of the control, and A₁ is the absorbance of the sample.