## 3 Results and Discussion
### In Silico Investigations (Molecular Docking)  
Free radicals are produced endogenously through several enzymes, such as NADPH oxidase (NOX) [97], nitric oxide synthase (NOS) [98], myeloperoxidase (MPO) [99], 5-lipoxygenase (5-LOX) [100], monoamine oxidase B (MAOB) [101], xanthine oxidase [102], and cyclooxygenase [103]. However, free radical production by various enzymes is necessary for the physiological and biological functions; overproduction of such substances could produce harmful oxidative stress, which should be neutralized through antioxidant defense mechanisms or nutraceutical antioxidants [104]. In silico studies were performed to realize the antioxidant effects of the extracted oil from white mahaleb seed through the prediction of binding interactions and inhibitions of the enzymes that have a critical role in intracellular oxidations, such as NOX, NOS, MPO, 5-LOX, and MAOB [105; 106]. The seed  
Figure 3: Antioxidant activity of quercetin, PMSOENH, and PMSOEPE using DPPH free radical scavenging rate. oil composition of PMSOENH and PMSOEPE was mainly FAs, but four phthalate derivatives were also extracted from PMSOENH (Tables 3 and 5). In addition to the verifiable antioxidant activity of FAs [107], natural phthalate derivatives were recorded as inhibitors of the oxidative enzymes [35]. Binding free energies between the compounds and the selected enzymes were represented by \(\Delta\)G values (kcal/mol). In this study, the 12 extracted compounds (eight UFAs and four phthalate derivatives) and the positive control were docked against the five selected enzymes; therefore, the total calculated \(\Delta\)G values were 70. As presented in Table 6. The positive control had the highest binding free energies to 5-LOX (\(-\)7.81 kcal/mol) and MAOB (\(-\)8.65 kcal/mol), and the second highest binding free energies to NOX (\(-\)6.87 kcal/mol) and MPO (\(-\)8.38 kcal/mol), after **C10**. However, it had the fifth rank to NOS (\(-\)6.59 kcal/mol). The most promising results of docking were for **C10**, which had the highest \(\Delta\)G to NOX (\(-\)7.27 kcal/mol), MPO (\(-\)8.6 kcal/mol), and NOS (\(-\)7.98 kcal/mol), and the second highest binding affinity to 5-LOX and MAOB (\(-\)7.5 and \(-\)8.52 kcal, respectively). According to exploring the binding free energy of each compound, the highest \(\Delta\)G of **C01**, **C03**, **C05**, **C06**, **C07**, **C08**, and quercetin were to MAOB; the highest \(\Delta\)G of **C09**, **C10**, **C02**, and **C04** were to MPO. Finally, the highest \(\Delta\)G of the remaining compounds (**C11** and **C12**) were to NOS (\(-\)7.21 and \(-\)7.5 kcal/mol, respectively). Small molecules (MW \(<\) 500 Da) are the preferred form of biomolecules and therapeutics because of their favorable pharmacokinetic features and oral bioavailability [108]. The oral bioavailability of the compounds can be determined through [PERSON]'s rule of five criteria [109; 110]. This rule is based on the physicochemical properties of the compounds and states that the compounds to be orally absorbed and permeated through intestinal membranes should have the following criteria: MW \(\leq\) 500 Da, logP \(\leq\) 5, H-bond donors and acceptors \(\leq\)5 and 10, respectively. Any molecule that violates more than one of the mentioned criteria could appear to have absorption or permeation issues and eventually may not be orally bioavailable [111]. Moreover, rotatable bonds (RB) or molecular flexibility, is one of the parameters used to predict drug-like properties because exceeding 10 RB may limit oral bioavailability [112]. Lastly, topological polar surface area (TPSA) of the molecule is another indicator of the compound's absorption because the TPSA of orally bioavailable drugs should not exceed 120 A [113]. In the current study, the physicochemical properties, or drug-likeness properties, of all the PMSOE compounds were calculated through Molinspiration software (Molinspiration v2022.08) to explore the correlations between antioxidant activity and oral bioavailability of the compounds [114].