*2.3. Antioxidant Activity of P. lapathifolia EO*

The EO of *P. lapathifolia* was tested for antioxidant activity via the reduction of the free radicals DPPH and ABTS, and it showed a substantial antioxidant activity compared to ascorbic acid as a standard antioxidant (Figure 3). By increasing the concentration of the EO, the reduction of radicals was increased. At the highest concentration of the EO (400 mg L<sup>−</sup>1), the DPPH and ABTS were reduced by 70.68 and 67.23%, respectively. The EO showed IC50 values of 159.69 and 230.43 mg L−1, respectively (Figure 3a), while ascorbic acid exhibited IC50 values 47.49 and 56.68 mg L<sup>−</sup>1, respectively (Figure 3b).

**Figure 3.** Antioxidant activity of *Persicaria lapathifolia* essential oil (**a**) and ascorbic acid as a standard antioxidant (**b**). Different letters mean a significant difference in values after Tukey's HSD test (*p* < 0.05).

The antioxidant activity of the EO is usually correlated to the oxygenated compounds in the EO profile [8,12,41]. Thereby, the substantial antioxidant activity of EO of *P. lapathifolia* could be attributed to its high content of oxygenated components (> 70%), especially oxygenated hydrocarbons. Additionally, terpenoid compounds have been stated to have important functions as free radical scavengers, especially the oxygenated derivatives [12,40]. In the present study, about 38% of the EO mass consisted of terpenoids, including 15% oxygenated derivatives that could be responsible for the scavenging of free radicals. Many EOs of plants have been proven to exhibit significant antioxidant effects via different methods

because of their high percentages of terpenoids, such as those of *Euphorbia mauritanica* [1], *Deverra tortuosa* [3], and *Launaea* species [40].

#### **3. Materials and Methods**

#### *3.1. Plant Materials Collected and Preparation*

The aerial parts of *Persicaria lapathifolia* were collected in May from a population growing on the canal bank habitat of an irrigation canal near the city of Mansoura, Egypt (31.0708553N 31.4394701E). The collected aerial parts were air dried at room temperature (25 ± 3 ◦C), crushed gently by hand, and packed in a paper bag till further analyses. A plant voucher specimen was deposited in the herbarium of the Department of Botany, Faculty of Science, Mansoura University, Egypt.
