Characteristics of flavonoids as potent MERS-CoV 3C-like protease inhibitors

Area of Science:

• Virology
• Biochemistry
• Drug Discovery

Background:

• Middle East respiratory syndrome-coronavirus (MERS-CoV) is a zoonotic virus causing severe respiratory illness with high mortality.
• Currently, no specific vaccines or treatments are available for MERS.
• Flavonoids are known to possess antiviral properties, making them potential candidates for drug development.

Purpose of the Study:

• To identify flavonoid compounds that inhibit the enzymatic activity of MERS-CoV 3C-like protease (3CLpro).
• To elucidate the structural requirements of flavonoids for effective binding to MERS-CoV 3CLpro.
• To explore the potential of flavonoids as a basis for developing novel MERS-CoV inhibitors.

Main Methods:

• Screening of a flavonoid library against MERS-CoV 3CLpro.
• Enzymatic activity assays to determine inhibition.
• Tryptophan-based fluorescence method to confirm flavonoid binding.
• Induced-fit docking analysis to predict binding sites and interactions.

Main Results:

• Four flavonoids—herbacetin, isobavachalcone, quercetin 3-β-d-glucoside, and helichrysetin—were identified as inhibitors of MERS-CoV 3CLpro.
• Binding of these flavonoids to 3CLpro was confirmed experimentally.
• Flavonol and chalcone scaffolds were found to be favorable for binding to the 3CLpro catalytic site.
• Flavonoid derivatives with hydrophobic or carbohydrate moieties showed enhanced inhibitory effects.

Conclusions:

• Flavonoids, particularly those with flavonol and chalcone scaffolds, can effectively inhibit MERS-CoV 3CLpro.
• Specific structural features, such as hydrophobic or carbohydrate attachments, enhance inhibitory activity.
• Flavonoids with these characteristics represent promising templates for the development of new MERS-CoV therapeutics.