Exploring the Potential of Natural Products to Combat COVID-19

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ABSTRACT As of August 2021, the coronavirus disease COVID-19, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), has infected more than 200 million people across the globe, causing more than 600,000 deaths in the USA and 4.2 million worldwide. Though vaccines have become available, vaccinated individuals can still spread the disease to unvaccinated and vulnerable populations. As vaccination rates in the United States remain low, emerging variants that may evade the vaccine are a new risk. Identifying novel preventative agents from traditional medicine could lead to the development of a readily available, cost-effective, and safe dietary intervention against COVID-19. During the pandemic, individuals have turned to herbal supplements to prevent COVID-19. There are published in silico studies and a few in vitro studies on these extracts, but the science to support natural products’ (NPs) use to prevent viral infection is still incomplete. The Quave Natural Product Library (QNPL) is a collection of over 2,000 botanical and fungal extracts, including the 40 most used natural supplements in the USA. Viral entry, in which SARS-CoV-2 attaches to the Angiotensin-Converting Enzyme 2 (ACE2) cell surface receptor found on endothelial cells, pneumocytes (type 1 and 2), and ciliated bronchial epithelial cells, presents an attractive option for preventatives. I have screened 2,000 extracts from the QNPL against SARS-CoV- 2 pseudotyped virus system to test which extracts inhibit viral entry. Mammalian cell cytotoxicity assays measuring Lactate Dehydrogenase (LDH) formation were run in parallel to ensure inhibition was not due to cell death. This proposal employs a multi-faceted approach to identify agents with direct-acting antiviral properties using a one-of-a-kind natural product library. Three extracts with potent bioactivity as direct-acting antiviral agents without apparent toxicity were selected after screening the QNPL. Bioassay guided fraction coupled to LC- MS/MS molecular networking analysis will be used for the identification of compounds with direct-acting antiviral activity. Compounds will be further isolated using preparative HPLC and structurally elucidated by NMR and X- crystallography to determine the absolute structure of the viral inhibitor. The fractions and isolated compounds will be tested across emerging variants in relevant cell lines and in live virus to further understand activity. Additionally, I will undertake mechanism of action studies utilizing biolayer interferometry and ELISA assays. These studies will result in the identification of NPs with the potential to block SARS-CoV-2 viral entry in relevant human cells, enhancing understanding of the preventative value of plant NPs for COVID-19 and other viruses. This will enable formulation of a bioactive dietary supplement, prioritization of leads for a medicinal chemistry campaign, and identification of tool compounds to query these pathways.