[49]. 3.two.four. Gardenin B = Demethyltangeretin (5-Hydroxy six,7,eight,4 -Tetra Methoxy Flavone) (4) (DMSO-d6 , 500 MHz): 12.51(1H, s
[49]. 3.two.4. Gardenin B = Demethyltangeretin (5-Hydroxy 6,7,8,four -Tetra Methoxy Flavone) (four) (DMSO-d6 , 500 MHz): 12.51(1H, s, 5-OH), 8.01 (2H, d, J = eight.5 Hz, H-2 , H-6 ), 7.13 (2H, d, J = 8.five Hz, H-3 , H-5 ), 6.78 (1H, s, H-3), 3.84 (3H, s, 7-OCH3 ), three.83 (3H, s, 4 -OCH3 ), three.75 (3H, s, 8-OCH3 ), three.74 (3H, s, 6-OCH3 ). Constructive HRMS: 359.1135 (C19 H19 O7 + ) [49]. 3.two.5. Hispidulin (5) (DMSO-d6 , 500 MHz): 13.05(1H, s, 5-OH), ten.68 (1H, s, 7-OH), 10.33 (1H, s, 4 -OH), 7.91 (2H, d, J = eight.5 Hz, H-2 , H-6 ), six.89 (2H, d, J = 8.5 Hz, H-3 , H-5 ), six.76 (1H, s, H-8), 6.56 (1H, s, H-3), three.71 (3H, s, 6-OCH3 ). Unfavorable HRMS: 299.0905 (C16 H11 O6 – ) [50]. three.three. Molecular Docking Study The molecular docking study was performed utilizing the MOE 2019.012 suite [51,52] for the isolated and identified 5 (R)-Albuterol Agonist flavonoids from A. hierochuntica, K. aegyptiaca, and citrus peels, namely taxifolin (1), pectolinarigenin (2), 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 were when compared 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.three.1. Preparation in the Isolated and Identified Five Flavonoids (1) The 2D chemical structures of the isolated 5 flavonoids–taxifolin (1), pectolinarigenin (2), tangeretin (3), gardenin B (4), and hispidulin (5)–were sketched working with ChemDraw Experienced. Every single chemical structure was introduced separately in to the MOE window, converted for the 3D orientation, adjusted for partial charges, and energy minimized to become ready for docking based on the default preparation measures described earlier [536]. Soon after saving every single ready compound separately applying the (.moe) extension, the co-crystallized native inhibitor of SARS-CoV-2 Mpro (KI) was extracted and saved within a separate MOE file also. In addition, all of the aforementioned prepared compounds (1) have been imported inside the same database file and saved as (.mdb) extension to become uploaded through the docking step. 3.3.two. Target Mpro of SARS-CoV-2 Preparation The target Mpro enzyme (as a dimer) of SARS-CoV-2 was extracted in the Protein Data Bank (PDB code: 6Y2G) [57]. Furthermore, it was subjected for the detailed preparation steps described prior to [581] to become ready for the docking course of action. 3.three.3. Docking with the Database Compounds (1) for the Dimer Mpro of SARS-CoV-2 The previously discussed database, containing the KI as well as the five isolated and identified flavonoids (1), was uploaded in spot from the ligand through a general docking procedure. The binding website in the co-crystallized -ketoamide inhibitor was identified because the docking site. Moreover, the program specifications had been adjusted as follows: triangle matcher for the placement methodology, London dG for the initial scoring methodology, GBVI/WSA dG for the final scoring methodology to pick the very best 10 poses from 30 distinctive poses for each docked compound, and rigid receptor for the refinement methodology [614]. Lastly, the top pose for every tested compound, based on the score and RMSD values, was chosen for additional research. Furthermore, a MOE system validation course of action was carried out before applying the previously described docking procedure by redocking the co-crystallized KI alone at its binding web page of Mpro. The obtained low RMSD values (two) between the native co-crystallized plus the redocked.