3.10. DPPH Assay

To determine antioxidant activity by inhibition of the DPPH radical, the DPPH solution was prepared by dissolving 7.8 mg of 1,1-diphenyl-2-picrylhydrazyl radical (D9132, Sigma-Aldrich, St. Louis, MO, USA) in 80% methanol (PQ06121, Fermont, Monterrey, Mexico). The solution was agitated for 2 h in the dark [70]. Then, 2.5 mL aliquots of 6.1 × 10-5M methanolic DPPH solution were added to glass tubes and reacted with 0.5 mL of sample. The tubes were left to stand in the dark for 30 min. Subsequently, the samples were measured at 515 nm using a spectrophotometer (JENWAY, Model 6705, Dunmow, UK). The blank was an 80% methanol (PQ06121, Fermont, Monterrey, Mexico) aqueous solution. The percent inhibition was calculated using Equation (1).