“…The DPPH reagent (100 μL, 0.3 mM in methanol) was added. After 30 min, the absorbance at 540 nm was recorded [ 62 , 63 ]. Butylhydroxytoluene (>99%, Sigma-Aldrich, St. Louis, MA, USA) was used as a standard, and was dissolved in methanol at concentrations of 10, 20, 30, 50, 100, 150, 175, and 225 μg/mL.…”