Journal of Biosciences and Medicines, 2021, 9, 42-51 https://www.scirp.org/journal/jbm ISSN Online: 2327-509X ISSN Print: 2327-5081 DOI: 10.4236/jbm.2021.911005 Nov. 15, 2021 42 Journal of Biosciences and Medicines Morinda citrifolia (Noni) Fruit Juice Inhibits SARS-CoV-2 Spike Protein Binding of Angiotensin-Converting Enzyme 2 (ACE2) Brett J. West, Shixin Deng Research and Development, NewAge, Inc., American Fork, Utah, USA Abstract COVID-19 is a global pandemic that has claimed millions of lives. This dis- ease is caused by a coronavirus, SARS-CoV-2, which requires the binding of its spike protein to angiotensin-converting enzyme 2 (ACE2) for infection of the host cell. Morinda citrifolia (noni) fruit juice has antiviral activity that involves enhancement of immune system function. SARS-CoV-2 spike-ACE2 interaction experiments were carried out to further investigate the antiviral properties of noni juice and its major iridoids. Noni juice inhibited binding by approximately 69%. Scandoside was the most active of the three iridoids evaluated, reducing average spike protein-ACE2 interaction by 79.25%. The iridoids worked synergistically towards inhibiting spike protein binding when assayed together, improving activity by more than 22% above the expected level. But the modest activity of the most abundant iridoid, deacetylasperulo- sidic acid, indicates that other phytochemicals (i.e. scopoletin, quercetin, ru- tin and kaempferol) are also involved. Our results suggest that the presence of several biological active phytochemicals in noni juice enhances resistance to SARS-CoV-2 by interfering with its ability to bind ACE2. This is a new and significant anti-viral mechanism of noni juice that does not directly involve its immunomodulatory properties. Keywords Coronavirus, COVID-19, SARS-CoV-2, Spike Protein, Morinda citrifolia, Noni, Iridoid 1. Introduction Coronaviruses are a group of viruses known for the characteristic glycoprotein How to cite this paper: West, B.J. and Deng, S. (2021) Morinda citrifolia (Noni) Fruit Juice Inhibits SARS-CoV-2 Spike Protein Binding of Angiotensin-Converting Enzyme 2 (ACE2). Journal of Biosciences and Medicines, 9, 42-51. https://doi.org/10.4236/jbm.2021.911005 Received: October 11, 2021 Accepted: November 12, 2021 Published: November 15, 2021 Copyright © 2021 by author(s) and Scientific Research Publishing Inc. This work is licensed under the Creative Commons Attribution International License (CC BY 4.0). http://creativecommons.org/licenses/by/4.0/ Open Access