This paper proposes natural drug candidate compounds for the treatment of coronavirus disease 2019 (COVID-19). We investigated the binding properties between the compounds in the Moringa oleifera plant and the main protease (Mpro) of severe acute respiratory syndrome coronavirus 2 using molecular docking and ab initio fragment molecular orbital calculations. Among the 12 compounds, niaziminin was found to bind the strongest to Mpro. We furthermore proposed novel compounds based on niaziminin and investigated their binding properties to Mpro. The results reveal that the introduction of a hydroxyl group into niaziminin enhances its binding affinity to Mpro. These niaziminin derivatives can be promising candidate drugs for the treatment of COVID-19.

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<div>COVID-19 which is caused by the virus SARS-CoV-2, has now been declared a global pandemic by the World Health Organization. At present, no specific vaccines or drugs are available to treat COVID-19. Therefore, there is an urgent need for the identification of novel drug lead compounds</div><div>to treat COVID-19. The SARS-CoV-2 main protease (Mpro also known as 3CLpro) and RNA-dependent RNA polymerase (RdRp also known as nsp12) are the best-characterized drug targets among corona viruses. In order to discover the natural lead compounds for SARS-CoV-2, we</div><div>performed molecular docking with the compounds from <i>Moringa Oleifera</i> that target the Mpro and RdRp. The molecular docking studies were carried out using AutoDock Vina through PyRx. Drug-likeness property of the selected compounds was checked by applying the ‘Lipinski’s rule of five’ using Swiss ADME. The top four compounds with most favourable binding affinity were selected for each of the targets. The results indicated that the compounds kaempferol, pterygospermin, morphine and quercetin exhibited best binding energy towards Mpro and RdRp. This study suggests that these natural compounds could be promising candidates for further evaluation of COVID-19 prevention.</div>

Monocarboxylate transporter-8 (MCT8) is a specific thyroid hormone transporter, essential for the uptake of thyroid hormone into target tissues. Mutations in the MCT8 gene have been identified as the cause of Allan-Herndon-Dudley syndrome (AHDS). It has been reported that soy isoflavones influence thyroid hormone system and can interact with thyroid hormone transporter proteins. Therefore, the present study aimed to find out whether soy isoflavones (genistein, daidzein and glycitein) can be used as a natural inhibitor to target MCT8 in AHDS. Docking studies were performed for soy isoflavones in order to evaluate their binding affinity to MCT8 protein using AutoDock4 (version 4.2.6) and AutoDock Vina. After docking, the ligands were ranked according to their binding energy and the best lead compound was selected based on the least binding energy. The docking results indicated that daidzein possesses the lowest binding energy against MCT8. Moreover, it was found that the residues PRO-338, HIS-341, and GLU-348 were involved in hydrogen bond interactions with genistein and daidzein. This study suggests that daidzein is a promising natural inhibitor to target MCT8 in AHDS.

Intrinsically Disordered Proteins (IDPs) lack a stable, three-dimensional structure under physiological conditions, yet they exhibit numerous biological activities. Protean segments (ProSs) are the functional regions of intrinsically disordered proteins that undergo disorder-to-order transitions upon binding to their partners. Example ProSs collected from the intrinsically disordered proteins with extensive annotations and literature (IDEAL) database. The interface of protean segments (ProSs) is classified into core, rim, and support, and analyzed their secondary structure elements (SSEs) based on the relative accessible surface area (rASA). The amino acid compositions and the relative solvent accessible surface areas (rASAs) of ProS secondary structural elements (SSEs) at the interface, core and rim were compared to those of heterodimers. The average number of contacts of alpha helices and irregular residues was calculated for each ProS and heterodimer. Furthermore, the ProSs were classified into high and low efficient based on their average number of contacts at the interface. The results indicate that the irregular structures of ProSs and heterodimers are significantly different. The rASA of irregular structures in the monomeric state (rASAm) is large, leads to the formation of larger ΔrASA and many contacts in ProSs.