Plants vs. Pandemics: The Search for Potential COVID-19 Treatments

by Hanz Benedict Aguilar (Ikirara)

Rising COVID-19 cases have struck the world with an increasing number of deaths every single day, with an accumulated 143 million cases and 3 million deaths. Serious Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) still has the full capacity to be a threat as there is no official medication that can ultimately treat the disease. However, due to the high demand of medical research, plant-based medical studies have opened numerous possibilities for treatment on most of the deadly diseases including COVID-19.

These medical studies employ plant omics, a broad field which investigates plants on a cellular and molecular level through genomic, transcriptomic, proteomic, metabolomic, glycomic, and lipidomic means. Researchers in this field use bioinformatic and machine learning tools to search for medically important sequences and/or compounds found in plants and predict their interactions with the human cell or organs. After in silico analyses, the compounds should undergo the drug development process. The first phase, drug developers test the compound in vitro, i.e., outside a living organism, and in vivo, within a living organism. Then, the developers should submit an Investigational New Drug (IND) application to start human clinical trials, which consists of three phases. If these clinical trials were successful, they should submit a New Drug Application (NDA), then let the Food and Drug Administration review the drug for approval. Once approved, the drug developers and the government should cooperate in forming means to monitor and regulate the drug in the market.

Plant omics vs. COVID-19

Bhoomika Patel and their colleagues examined the underlying antiviral activity of edible medicinal plant materials against the RNA of SARS-CoV-2 which also can potentially improve immunity. The group reviewed the mechanism as to how the virus can be targeted by edible plants in relation to their structure. They have identified that two groups of proteins contribute to their unique characteristics: structural and non-structural proteins. The researchers reported that non-structural proteins were the primary target for drug development. Also, they have discussed that the transfer of viral contents will not be possible without the viral spike glycoprotein that attaches to cell receptors, thus making the spike glycoprotein a relevant target in the prevention of initial entry to host cells.

In relation to the spike protein, plant-derived compounds enable defense mechanisms against the initial entry of viruses with the help of their natural flavonoids. One of the inhibiting agents is emodin from the plants of family Polygonaceae, which is known to block the interaction of the spike protein. Likewise, plants’ natural proteins known as lectins target the sugar components of the spike which interferes with viral attachment and early entry. 

Through experimentation in the study, the flavonoids extracted from medicinal plants not only can prevent viral entry, but can also potentially stop the virus from replicating. Antiviral activity of edible plants Aloe barbadensis, Ginkgo biloba, Olea europaea, and Mangifera indica has the capability to target SARS-CoV-2. Recent studies reported that natural chemical inhibitors exhibited by plants can interrupt viral replication by targeting the replicating features of the virus. This includes myricetin and scutellarein that inhibits SARS-CoV helicase. Studies can also be done to plants such as Eugenia jambolana, Areca catechu, Ocimum sanctum, Phaseolus vulgaris, and Phyllanthus emblica which were known to contain antiviral activity.

Additionally, recent studies published in the Journal of Biological Chemistry reported that amino acid-derived defense metabolites from plants reveal potential sources to facilitate novel antimicrobial development, with the novel plant compounds found to exhibit biological activity, bioavailability, and chemical stability. These metabolites have therapeutic potential to treat a wide variety of viral pathogens, including SARS-CoV-2. 

Why is there a need to study plants?

It has been known that over 219 plants from 83 families were found to exhibit antiviral activity. Most of them have not been further investigated. This expresses that limitless possibilities await for future researchers in order to develop natural therapeutics that demonstrate absence of harmful toxicity. There is a rising need for these plants to be rigorously studied for the purpose of treating infectious diseases and preventing another lethal pandemic.

Should we consume these plants as treatment or prevention against COVID-19?

Even though the plants mentioned showed promising results in plant omics studies, everyone must keep in mind that these plants and their phytochemicals should undergo rigorous testing and processes before we can conclude that they are safe and effective against COVID-19. Drug developers should isolate the compound of interest from other compounds or metabolites, which may be harmful in large doses. In fact, the compound of interest may be toxic in large quantities or without certain modifications done within the laboratory. So, while we are in dire need of a cure for COVID-19, Filipinos need not to rush in prescribing themselves these plants to treat or prevent the disease.

Nevertheless, the field of plant omics offers promise in finding an effective treatment for COVID-19. These types of researches would definitely flourish in the country, where the richness in plant biodiversity is prominent. In alleviating our current public health crisis, plants may just hold the key. All it takes is progressing the research and discourse on the field here in the Philippines.