2.8.1. Assay of DPPH• Radical Scavenging Activity

The DPPH• radical scavenging capacity of total flavonoid extracts of *P. cretica* was investigated on the basis of the method reported by Shukla et al. [28] with a minor modification. Briefly, 0.8 mL of the DPPH solution (0.1 mM in ethanol) was mixed with 2.4 mL of total flavonoid extract solution at different concentrations (25–250 μg/mL in ethanol). The reaction mixture was then shaken well and incubated at room temperature for 30 min. The absorbance of the reaction mixture was recorded at 517 nm. Ascrobic acid was used as a positive control in this work. The percentage of DPPH• radical scavenging was calculated using the following equation:

$$\text{Radical scavenging activity} \ (\%) = \frac{A\_0 - A\_1}{A\_1} \times 100 \tag{4}$$

where *A*<sup>0</sup> represents the absorbance of the reaction system without the extract and the *A*<sup>1</sup> represents the absorbance of the reaction system in the presence of the extract. The test was carried out in triplicate, and the IC50 was defined as the concentration of the extract that resulted in a 50% inhibition of DPPH• radical.
