1 1 diphenyl 2 picrylhydrazyl dpph free radical

The antioxidant activity of the essential oil based on the scavenging activity of the stable 1,1diphenyl-2-picrylhydrazyl (DPPH) free radical (Sigma Aldrich Co., St. Louis, USA) was determined by the method described by Robu et al. [15] with few modifications. Initially, four dilutions in DMSO (5 mg/mL; 7.5 mg/mL; 10 mg/mL and 12.5 mg/mL) were carried out. Briefly, an aliquot of each dilution (0.5 mL) was mixed with a solution of DPPH in Methanol (4 mg%) (1.5 mL) and the absorbance was measured at 517 nm for 30 min, using a Spectrophotometer Shimadzu UV-1800. Thymol (Merck KGaA, Darmstadt, Germany) were used as reference standards and dissolved in DMSO to make solutions within the same range of concentrations (12.5 mg/mL-0.05 mg/mL). Methanol (Merck KGaA, Darmstadt, Germany) was used as blank. The DPPH free-radical scavenging activity (%) was calculated as 100 x [(Acontrol -Asample)/Acontrol], where Acontrol is the absorbance of the solvent and Asample is the absorbance of the sample. The IC50 value (mg/mL), which is the concentration of the extract/standard that reduces 50% of the free-radical concentration, was calculated through linear interpolation between values above and below 50% activity.