Abstract

The emergence of viral pneumonia caused by a novel coronavirus (CoV), known as the 2019 novel coronavirus (2019-nCoV), resulted in a contagious acute respiratory infectious disease in December 2019 in Wuhan, Hubei Province, China. Its alarmingly quick transmission to many countries across the world and a considerable percentage of morbidity and mortality made the World Health Organization recognize it as a pandemic on March 11, 2020. The perceived risk of infection has led many research groups to study COVID-19 from different aspects. In this literature review, the phylogenetics and taxonomy of COVID-19 coronavirus, epidemiology, and respiratory viruses similar to COVID-19 and their mode of action are documented in an approach to understand the behavior of the current virus. Moreover, we suggest targeting the receptors of SARS-CoV and SARS-CoV-2 such as ACE2 and other proteins including 3CLpro and PLpro for improving antiviral activity and immune response against COVID-19 disease. Additionally, since phytochemicals play an essential role in complementary therapies for viral infections, we summarized different bioactive natural products against the mentioned respiratory viruses with a focus on influenza A, SARS-CoV, MERS, and COVID-19.Based on current literature, 130 compounds have antiviral potential, and of these, 94 metabolites demonstrated bioactivity against coronaviruses. Interestingly, these are classified in different groups of natural products, including alkaloids, flavonoids, terpenoids, and others. Most of these compounds comprise flavonoid skeletons. Based on our survey, xanthoangelol E (88), isolated from Angelica keiskei (Miq.) Koidz showed inhibitory activity against SARS-CoV PLpro with the best IC50 value of 1.2 μM. Additionally, hispidulin (3), quercetin (6), rutin (8), saikosaponin D (36), glycyrrhizin (47), and hesperetin (55) had remarkable antiviral potential against different viral infections. Among these compounds, quercetin (6) exhibited antiviral activities against influenza A, SARS-CoV, and COVID-19 and this seems to be a highly promising compound. In addition, our report discusses the obstacles and future perspectives to highlight the importance of developing screening programs to investigate potential natural medicines against COVID-19.

Highlights

  • The emergence of viral pneumonia caused by a novel coronavirus (CoV), known as the 2019 novel coronavirus (2019-nCoV), resulted in a contagious acute respiratory infectious disease in December 2019 in Wuhan, Hubei Province, China (Zhu et al, 2020)

  • The insights provided in this study indicate that natural products isolated from plants and microorganisms with activity against respiratory viruses support further exploration of such sources for anti-COVID-19 agents

  • angiotensin-converting enzyme 2 (ACE2) is a functional receptor for SARS coronavirus (SARS-CoV) and SARS-CoV-2 to enter the host target cells (Hoffmann et al, 2020), and ACE2 inhibition can be considered for development of antiviral agents against SARS-CoV and SARSCoV-2

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Summary

INTRODUCTION

The emergence of viral pneumonia caused by a novel coronavirus (CoV), known as the 2019 novel coronavirus (2019-nCoV), resulted in a contagious acute respiratory infectious disease in December 2019 in Wuhan, Hubei Province, China (Zhu et al, 2020). As of November 2, 2020, the number of total confirmed COVID-19 infections in the world is over 46 million, and the number of deaths is reportedly more than one million individuals These numbers are continually increasing with no sign of respite (WHO Coronavirus Disease, 2020). Analysis of phylogenetic results has shown that SARS-CoV-2 is genetically related to bat-SL-CoVZC45 and bat-SL-CoVZXC21 (89% identity), but has less similarity to SARS-CoV (79%) and MERS-CoV (50%) (Lai et al, 2020) In this regard, analysis of protein sequences showed that SARS-CoV-2 was evolutionarily most related to SARS-CoV. Evaluation of structural proteins indicated that the envelope, nucleocapsid and spike protein have 96%, 89.6%, and 77% sequence identity, respectively, compared to SARS-CoV (Lan et al, 2020). This review will exclusively focus on influenza viruses and coronaviruses, both of which are known to cause respiratory infections

Influenza Virus
NATURAL PRODUCTS AGAINST RESPIRATORY VIRUSES
Natural Products Against Influenza Virus
Natural Products Against Coronaviruses
Influenza subtype
Blocking the virus receptor
HA inhibitor
In silico In silico Alpinia officinarum and ginger In silico
Under evaluation
Isatis indigotica Fortune ex Lindl
CONCLUSION AND FUTURE PERSPECTIVES
Findings
AUTHOR CONTRIBUTIONS
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