Natural Flavonoids Found Effective in Inhibiting COVID-19
Recent efforts in battling the spread of SARS-CoV-2 and its newly emerged variants have been directed towards finding alternative therapy involving natural products. One comprehensive review investigates the effectiveness of natural flavonoids in targeting key SARS-CoV-2 enzymes. Flavonoids are secondary metabolites found in many plants and their products, such as tea or wine. They serve as a defense against harmful effects and are known for their antioxidant, antimicrobial and antiviral features, among others.
The research process involved collecting data from various published in silico and in vitro studies that have proven the antiviral effects of flavonoids. The authors identified potential targets in the virus itself and the patient who would inhibit the infection at various stages of its life cycle.
The team found over 69 flavonoids that have the strongest inhibitory potential against the most promising SARS-CoV-2 targeted proteases, 3CLpro and PLpro, which play a significant role in replicating the virus. Of the total number of flavonoids, the authors made a list of subclasses, including various flavonols, flavanonols, isoflavones, and flavones that are most effective against 3CLpro activity.
Flavonoids can also help prevent the binding of the viral spike (S) protein with the human angiotensin-converting enzyme 2 (ACE2), which represents the critical process in the viral entry stage. The review also includes a description of the antiviral effect of the flavonoids on under researched SARS-CoV-2 targets using cell-based methodologies.
Finally, the study discusses the relationship between the structure and how flavonoid subtypes — flavanols, flavanonols, flavones, flavanones, flavanols, and isoflavones — interact with 3CLpro, PLpro, the S protein, and the human ACE2 receptor. They concluded that the impact of the flavonoids mentioned above is enhanced if hydroxyl groups are present on all their phenolic rings. Specifically, myricetin was identified as the most potent flavonoid as it has six hydroxyl groups located on its three rings.
Specific flavonoids suggested for further investigation were quercetin, myricetin, and their derivatives – the flavones baicalin and baicalein, the flavan-3-ol EGCG, and tannic acid, as these were proven to be the most effective in battling SARS-CoV-2 targets.