2.3.1. Antioxidant Activity

The antioxidant capacity of SE was estimated using the DPPH· free radical scavenging assay [28], with some modifications. SE (10 mg) was dissolved in 1 mL of methanol. Thereafter, 100 μL of the appropriate diluted solution was mixed with 1.9 mL of a DPPH methanolic solution (0.094 mM). A control sample was prepared by adding 100 μL of methanol to 1.9 mL of the DPPH solution. The free radical· scavenging ability was determined by measuring the absorbance at 517 nm after incubation in dark at room temperature for 30 min. An UV/Vis spectrophotometer (model 4000, Dinko instruments, Barcelona, Spain) was used. Percentage of DPPH· inhibition was calculated following Equation (1):

$$\mathrm{I}(\%) = \frac{\mathrm{Ac} - \mathrm{As}}{\mathrm{Ac}} \times 100 \tag{1}$$

where Ac is the absorbance of the control and As is the absorbance of the sample. Trolox (0–1000 μM) was used as a standard to prepare calibration curve. The antioxidant activity was determined from the calibration curve and expressed as mM Trolox equivalents (TE)/g SE.
