RHAMNETIN IS A BETTER INHIBITOR OF SARS-COV-2 2’-O-METHYLTRANSFERASE THAN DOLUTEGRAVIR: A COMPUTATIONAL PREDICTION

Background: The 2’-O-methyltransferase is responsible for the capping of SARS-CoV-2 mRNA and consequently the evasion of the host’s immune system. This study aims at identifying prospective natural inhibitors of the active site of SARS-CoV-2 2’O-methyltransferase (2’-OMT) through an in silico approach. Materials and Method: The target was docked against a library of natural compounds obtained from edible African plants using PyRx - virtual screening software. The antiviral agent, Dolutegravir which has a binding affinity score of -8.5 kcal mol−1 with the SARS-CoV-2 2’-OMT was used as a standard. Compounds were screened for bioavailability through the SWISSADME web server using their molecular descriptors. Screenings for pharmacokinetic properties and bioactivity were performed with PKCSM and Molinspiration web servers respectively. The PLIP and Fpocket webservers were used for the binding site analyses. The Galaxy webserver was used for simulating the time-resolved motions of the apo and holo forms of the target while the MDWeb web server was used for the analyses of the trajectory data. Results: The Root-Mean-Square-Deviation (RMSD) induced by Rhamnetin is 1.656A0 as compared to Dolutegravir (1.579A0). The average B-factor induced by Rhamnetin is 113.75 while for Dolutegravir is 78.87; the Root-Mean-Square-Fluctuation (RMSF) for Rhamnetin is 0.75 and for Dolutegravir is 0.67. Also at the active site, Rhamnetin also has a binding affinity score of -9.5 kcal mol−1 and forms 7 hydrogen bonds as compared to Dolutegravir which has -8.5 kcal mol−1 and forms 4 hydrogen bonds respectively. Conclusion: Rhamnetin showed better inhibitory activity at the target’s active site than Dolutegravir

Hemozoin formation in malaria: a two-step process involving histidine-rich proteins and lipids

Major blood stage antimalarial drugs like chloroquine and artemisinin target the heme detoxification process of the malaria parasite. Hemozoin formation reactions in vitro using the Plasmodium falciparum histidine-rich protein-2 (Pfhrp-2), lipids, and auto-catalysis are slow and could not explain the speed of detoxification needed for parasite survival. Here, we show that malarial hemozoin formation is a coordinated two component process involving both lipids and histidine-rich proteins. Hemozoin formation efficiency in vitro is 1-2% with Pfhrp-2 and 0.25-0.5% with lipids. We added lipids after 9h in a 12h Pfhrp-2 mediated reaction that resulted in sixfold increase in hemozoin formation. However, a lipid mediated reaction in which Pfhrp-2 was added after 9h produced only twofold increase in hemozoin production compared to the reaction with Pfhrp-2 alone. Synthetic peptides corresponding to the Pfhrp-2 heme binding sequences, based on repeats of AHHAAD, neither alone nor in combination with lipids were able to generate hemozoin in vitro. These results indicate that hemozoin formation in malaria parasite involves both the lipids and the scaffolding proteins. Histidine-rich proteins might facilitate hemozoin formation by binding with a large number of heme molecules, and facilitating the dimer formation involving iron-carboxylate bond between two heme molecules, and lipids may then subsequently assist the mechanism of long chain formation, held together by hydrogen bonds or through extensive networking of hydrogen bonds