Use of hyphenated analytical techniques to identify the bioactive constituents of Gunnera perpensa L., a South African medicinal plant, which potently inhibit SARS-CoV-2 spike glycoprotein–host ACE2 binding

• Published in: Analytical and bioanalytical chemistry Vol. 414; no. 13; pp. 3971 - 3985
• Main Authors: Invernizzi, Luke, Moyo, Phanankosi, Cassel, Joel, Isaacs, Freddie J., Salvino, Joseph M., Montaner, Luis J., Tietjen, Ian, Maharaj, Vinesh
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2022; Springer; Springer Nature B.V
• Subjects: ACE2; Analytical Chemistry; Angiosperms; Angiotensin; Angiotensin-Converting Enzyme 2; Antibodies; Antiviral agents; Antiviral Agents - chemistry; Antiviral Agents - pharmacology; Binding; Biochemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; Constituents; Coronaviruses; COVID-19; COVID-19 - drug therapy; COVID-19 vaccines; Food Science; Glycoproteins; Gunnera perpensa; Herbal medicine; Laboratory Medicine; Mathematical analysis; Medicinal plants; Monitoring/Environmental Analysis; Morbidity; Peptidyl-dipeptidase A; Pharmacology; Plant Extracts - pharmacology; Plants, Medicinal; Receptors; Research Paper; SARS-CoV-2; Severe acute respiratory syndrome coronavirus 2; South Africa; Spike glycoprotein; Spike Glycoprotein, Coronavirus - chemistry; Vaccines; Viral diseases; South Africa; Antiviral; SARS-CoV-2; Punicalagin; UPLC-IMS-HRMS; Punicalin; Gunnera perpensa
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-022-04041-3

SARS-CoV-2, the causative agent of COVID-19, continues to cause global morbidity and mortality despite the increasing availability of vaccines. Alongside vaccines, antivirals are urgently needed to combat SARS-CoV-2 infection and spread, particularly in resource-limited regions which lack access to existing therapeutics. Small molecules isolated from medicinal plants may be able to block cellular entry by SARS-CoV-2 by antagonising the interaction of the viral spike glycoprotein receptor-binding domain (RBD) with the host angiotensin-converting enzyme II (ACE2) receptor. As the medicinal plant Gunnera perpensa L. is being used by some South African traditional healers for SARS-CoV-2/COVID-19 management, we hypothesised that it may contain chemical constituents that inhibit the RBD-ACE2 interaction. Using a previously described AlphaScreen-based protein interaction assay, we show here that the DCM:MeOH extract of G. perpensa readily disrupts RBD (USA-WA1/2020)-ACE2 interactions with a half-maximal inhibition concentration (IC 50 ) of < 0.001 µg/mL, compared to an IC 50 of 0.025 µg/mL for the control neutralising antibody REGN10987. Employing hyphenated analytical techniques like UPLC-IMS-HRMS (method developed and validated as per the International Conference on Harmonization guidelines), we identified two ellagitannins, punicalin (2.12% w/w) and punicalagin (1.51% w/w), as plant constituents in the DCM:MeOH extract of G. perpensa which antagonised RBD-ACE2 binding with respective IC 50 s of 9 and 29 nM. This good potency makes both compounds promising leads for development of future entry-based SARS-CoV-2 antivirals. The results also highlight the advantages of combining reverse pharmacology (based on medicinal plant use) with hyphenated analytical techniques to expedite identification of urgently needed antivirals.