Invalidation of geraniin as a potential inhibitor against SARS-CoV-2 main protease

Abstract

Recently, geraniin has been identified as a potent antiviral agent targeting SARS-CoV-2 main protease (Mpro). Considering the potential of geraniin in COVID-19 treatment, a stringent validation for its Mpro inhibition is necessary.Herein, we rigorously evaluated the in vitro inhibitory effect of geraniin on Mpro using the fluorescence resonance energy transfer (FRET), fluorescence polarization (FP), and dimerization-dependent red fluorescent protein (ddRFP) assays. Our data indicate that geraniin is not a potential inhibitor against Mpro based on the results from a set of in vitro assays. These results suggest a stringent in vitro validation with diverse biochemical assays is essential for the discovery of Mpro inhibitors, and the fluorescence quenching effect caused by natural products should be considered when evaluating Mpro inhibitors.

Improved fluorescence‐based assay for rapid screening and evaluation of SARS‐CoV‐2 main protease inhibitors

“…After denaturing, 20 μL sample was loaded into the sample wells for SDS-PAGE analysis. 17 The final concentrations of Mpro or PLpro were 0.5, 1, and 2 μM.…”

“…[13][14][15] Moreover, natural products that quench the fluorescence signal of peptide substrates will inevitably lead to false positive results. 16,17 The fluorescence polarization (FP) assay is more homogeneous, robust, and economical for a large-scale screening, but the unstable fluorogenic peptides still serve as substrates in this assay. [18][19][20] With these assays, numerous compounds have been identified as potent Mpro inhibitors by measurement of the change of relative fluorescence unit (RFU) or millipolarization unit (mP), whereas only one single indicator is available in each assay.…”

Carbene-Catalyzed Enantioselective Petasis-Like Alkenylation

“…NHC-catalyzed transformation has proven to be a powerful class of synthetic tools that can be used to assemble numerous biologically important or medicinal skeletons. − Among NHC-bounded intermediates, α,β-unsaturated acyl azoliums are classified as electrophilic cationic species − due to their LOMO activation. , As shown in Figure a, a number of nucleophiles have been reported to react with α,β-unsaturated acyl azoliums to achieve diversified β-functionalizations. Within this context, the α-Csp 3 contained carbonyls − or imines ,− and benzylic-type ,, nucleophiles were widely explored.…”

Geraniin Alleviates Inflammation in Caco-2 Cells and Dextran Sulfate Sodium-Induced Colitis Mice by Targeting IL-1β

“…23 Many studies have recently shown that the elevation of intestinal TJ permeability by IL-1β induction is caused by upregulated MLCK expression, which in turn is regulated by NF-kB and MAPK signaling pathways. 24−26 Geraniin, the main polyphenolic component found in extracts of various plants, such as Geranium, Nephelium, and Phyllanthus, 27 has been reported to have a variety of bioactive properties, such as anti-inflammatory, 28 antioxidant, 29 antihypertensive, 30 antiviral, 31 and antitumor activities. 32 Geraniin has previously shown a chemo-protective effect on azoxymethane-induced colorectal cancer by the reduction of inflammatory cytokines.…”

“…Geraniin, the main polyphenolic component found in extracts of various plants, such as Geranium , Nephelium , and Phyllanthus , has been reported to have a variety of bioactive properties, such as anti-inflammatory, antioxidant, antihypertensive, antiviral, and antitumor activities . Geraniin has previously shown a chemo-protective effect on azoxymethane-induced colorectal cancer by the reduction of inflammatory cytokines .…”