Development and biochemical characterization of proprotein convertase-furin/TMPRSS2 inhibitor from Nigerian medicinal plants traditionally used in viral infectious diseases management

The world is facing a deadly novel beta coronavirus-severe acute respiratory syndrome (SARS)-coronavirus (CoV) -2 infection that causes a serious debilitating disease called Covid-19 in some individuals. It has wrecked unprecedented havoc in world economy and caused great human casualty. Viral disease of this nature is difficult to contain or eradicate necessitating an urgent need to develop drugs for its cure or vaccination to prevent it. In search of suitable chemotherapy for the cure, Nigeria in particular is blessed with a diverse species of medicinal plants. In south-western Nigeria, many herbal products exist which have traditionally been used to effectively treat viral diseases including HIV/AIDS, measles, jaundice, yellow fever etc. The problem with the usage of such herbal products is that they contain cocktail of many compounds, in addition to the main active ingredient(s). By virtue of their off-target activities, such compounds often cause unintended adverse health consequences, sometimes resulting in permanent damage. Some have been reported to be teratogenic. This thus necessitates the need for isolation, purification and determining the mechanism of action of the active ingredients, present in such plants. Most of these medicinal plants contain many bioactive ingredients, including phenolics, glycosides, alkaloids, coumarins, diterpenoids, essential oils and peptides suggesting that a bioactivity-guided fractionation should be adopted when searching for novel drug leads from such herbal plants. Phenolics are broadly distributed in the plant kingdom and are the most abundant secondary metabolites of plants. Flavonoids have received a lot of attention because they are powerful antioxidants with anti-inflammatory and immune system benefits. They are thus associated with cancer, neurodegenerative and cardiovascular disease prevention by virtue of the fact that they scavenge reactive oxygen radicals (ROS). Of recent however, evidences have started to emerge that some of the flavonoids are nonpeptide protease inhibitors, suggesting that some of the health benefits may in fact be due to inhibition of some proteases which have been implicated in many diseases including different types of cancer, HIV, influenza, Ebola and the new SARS-CoV-2 disease. Even though synthetic protease inhibitors exist, many of which are modified oligopeptides, therapeutic use of non-peptide protease inhibitors (especially of natural origin) has many advantages over peptide inhibitors. SARS-CoV-2 differs from other coronaviruses in that the spike protein S which is essential for infectivity contains a proprotein convertase (furin)- cleavage site which increases the efficiency of the spread of SARS-CoV-2 compared to other beta coronaviruses suggesting that furin inhibitors will be suitable as potential drugs for Covid-19. T cells expressing trans membrane protease serine 2 (TMPRSS2) are more susceptible to SARS-CoV-2 attack than those without, in cell line studies. Therefore, targeting TMPRSS2 inhibition could also have a therapeutic value. Recombinant human furin and TMPRSS2 will be commercially sourced. Medicinal plants with established antiviral activity will be selected and sourced locally. Using bioassay-guided fractionation, their phytochemicals will be screened and purified using standard protocols. Those with potent anti-furin/ anti-TMPRSS2 activity will be used to carry out detailed inhibition studies on the kinetics of furin/TMPRSS2 both in dilute and crowded solutions. Promising compounds thus obtained will be subjected to toxicity tests. SARS-CoV-2 replication/multiplication inhibition assay will be carried out using either of VeroE6, Calu3, Huh7 or human airway epithelial cells infected with SARS-CoV-2. Chemical structure of the most promising compounds will be determined using 1H NMR, 13C NMR, IR, UV and MS spectra analysis. The proposed investigation will generate an array of chemical compounds that are candidate drugs for the cure of SARS-COV-2 disease in particular, and many other diseases whose mechanism involves activation by furin/TMPRSS2 or other proteases. Expected Outputs 1. An array of compounds, of natural origin, with high chemotherapeutic potentials for the management of Covid-19, ovarian and prostate cancer, hypertension and seasonal influenza will be obtained for further development and clinical trials. 2. The chemical structure, toxicity, efficacy and mechanism of action of some novel antiviral compounds from African medicinal plants will be established. 3. At least three publications in high impact Journal will come out of the study. The work will be published open-access for wide accessibility. 4. At least two students who will be research assistants will have sufficient research exposure and data for the award of PhD degree in Biochemistry. Many more undergraduate (B.Sc.) degrees will also be awarded in the course of the research.