0.2 mL of MeOH and 0.3 mL of various sample concentrations (10-100 g/mL) dissolved in MeOH were mixed in a10 mL test tube. DPPH (2.5 mL of 75 M in MeOH) was then added to achieve a final volume of 3.0 mL. The solution was kept at room temperature for 30 min, and the absorbance at 517 nm was measured.