[49]. 3.2.4. Gardenin B = Demethyltangeretin (5-Hydroxy 6,7,eight,four -Tetra Methoxy Flavone) (four) (DMSO-d6 , 500

[49]. 3.2.4. Gardenin B = Demethyltangeretin (5-Hydroxy 6,7,eight,four -Tetra Methoxy Flavone) (four) (DMSO-d6 , 500 MHz): 12.51(1H, s
[49]. three.two.four. Gardenin B = Demethyltangeretin (5-Hydroxy 6,7,8,4 -Tetra Methoxy Flavone) (4) (DMSO-d6 , 500 MHz): 12.51(1H, s, 5-OH), eight.01 (2H, d, J = eight.five Hz, H-2 , H-6 ), 7.13 (2H, d, J = 8.5 Hz, H-3 , H-5 ), 6.78 (1H, s, H-3), three.84 (3H, s, 7-OCH3 ), 3.83 (3H, s, 4 -OCH3 ), 3.75 (3H, s, 8-OCH3 ), 3.74 (3H, s, 6-OCH3 ). Positive HRMS: 359.1135 (C19 H19 O7 + ) [49]. 3.two.five. Hispidulin (5) (DMSO-d6 , 500 MHz): 13.05(1H, s, 5-OH), 10.68 (1H, s, 7-OH), ten.33 (1H, s, 4 -OH), 7.91 (2H, d, J = eight.5 Hz, H-2 , H-6 ), six.89 (2H, d, J = 8.five Hz, H-3 , H-5 ), 6.76 (1H, s, H-8), 6.56 (1H, s, H-3), 3.71 (3H, s, 6-OCH3 ). Unfavorable HRMS: 299.0905 (C16 H11 O6 – ) [50]. 3.three. Molecular Docking Study The molecular docking study was performed utilizing the MOE 2019.012 suite [51,52] for the isolated and identified five flavonoids from A. hierochuntica, K. aegyptiaca, and citrus peels, namely taxifolin (1), pectolinarigenin (two), tangeretin (three), gardenin B (four), and hispidulin (5), to propose their mechanism of action as SARS-CoV-2 Mpro inhibitors according to their binding scores and interactions. In addition, they had been in comparison with the co-crystallized inhibitor of SARS-CoV-2 Mpro (KI) as a reference standard.1 H-NMR 1 H-NMR 1 H-NMR 1 H-NMR 1 H-NMRMolecules 2021, 26,7 of3.3.1. Preparation on the Isolated and Identified 5 Flavonoids (1) The 2D chemical structures from the isolated five flavonoids–taxifolin (1), pectolinarigenin (two), tangeretin (three), gardenin B (four), and hispidulin (5)–were sketched utilizing ChemDraw Expert. Each chemical structure was introduced separately into the MOE window, converted to the 3D orientation, adjusted for partial charges, and energy minimized to be ready for docking according to the default preparation steps described earlier [536]. Right after saving each prepared compound separately using the (.moe) extension, the co-crystallized native inhibitor of SARS-CoV-2 Mpro (KI) was extracted and saved inside a separate MOE file as well. Additionally, all the aforementioned prepared compounds (1) were imported within the exact same database file and saved as (.mdb) Laurdan web extension to be uploaded in the course of the docking step. three.3.2. Target Mpro of SARS-CoV-2 Preparation The target Mpro enzyme (as a dimer) of SARS-CoV-2 was extracted from the Protein Data Bank (PDB code: 6Y2G) [57]. In addition, it was subjected for the detailed preparation steps described just before [581] to become prepared for the docking course of action. 3.three.3. Docking from the Database Compounds (1) to the Dimer Mpro of SARS-CoV-2 The previously discussed database, containing the KI along with the five isolated and identified flavonoids (1), was uploaded in spot on the ligand for the duration of a basic docking course of action. The binding site in the co-crystallized -ketoamide inhibitor was identified as the docking web-site. Additionally, the program specifications had been adjusted as follows: triangle matcher for the placement methodology, London dG for the first scoring methodology, GBVI/WSA dG for the final scoring o-Phenanthroline Epigenetic Reader Domain methodology to pick the most beneficial ten poses from 30 unique poses for each docked compound, and rigid receptor for the refinement methodology [614]. Finally, the best pose for each and every tested compound, depending on the score and RMSD values, was chosen for additional research. Moreover, a MOE program validation procedure was carried out ahead of applying the previously described docking method by redocking the co-crystallized KI alone at its binding website of Mpro. The obtained low RMSD values (2) among the native co-crystallized along with the redocked.