Abstract
The rapid outbreak of coronavirus disease 2019 (COVID-19) has demonstrated the need for development of new vaccine candidates and therapeutic drugs to fight against the underlying virus, severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2). Currently, no antiviral treatment is available to treat COVID-19 as treatment is mostly directed to only relieving the symptoms. Retrospectively, herbal medicinal plants have been used for thousands of years as a medicinal alternative including for the treatment of various viral illnesses. However, a comprehensive description using various medicinal plants in treating coronavirus infection has not to date been described adequately, especially their modes of action. Most other reports and reviews have also only focused on selected ethnobotanical herbs such as Traditional Chinese Medicine, yet more plants can be considered to enrich the source of the anti-viral compounds. In this review, we have screened and identified potential herbal medicinal plants as anti-coronavirus medication across major literature databases without being limited to any regions or ethnobotanic criteria. As such we have successfully gathered experimentally validated in vivo, in vitro, or in silico findings of more than 30 plants in which these plant extracts or their related compounds, such as those of Artemisia annua L., Houttuynia cordata Thunb., and Sambucus formosana Nakai, are described through their respective modes of action against specific mechanisms or pathways during the viral infection. This includes inhibition of viral attachment and penetration, inhibition of viral RNA and protein synthesis, inhibition of viral key proteins such as 3-chymotrypsin-like cysteine protease (3CLpro) and papain-like protease 2 (PLpro), as well as other mechanisms including inhibition of the viral release and enhanced host immunity. We hope this compilation will help researchers and clinicians to identify the source of appropriate anti-viral drugs from plants in combating COVID-19 and, ultimately, save millions of affected human lives.
Highlights
Coronaviruses are known to infect various hosts such as mice, pigs, birds and even human (human coronavirus, HCoV including severe acute respiratory syndrome coronavirus (SARS-CoV), SARSCoV-2, Middle East Respiratory Syndrome-CoV (MERS-CoV), HCoV-OC43, HCoV-NL63 and HCoV-229E) with different disease severity (Vellingiri et al, 2020; Zhu et al, 2020)
The zoonotic source of COVID-19 is yet to be verified, sequence-based analysis of isolates from infected patients has indicated that bats may serve as the primary reservoir, of which over 80% of the viral genome sequences is identical to the previous human SARS-coronavirus (Wu et al, 2020)
Most COVID-19 patients initially suffered from fever, cough, and fatigue while developing other symptoms including muscle pain, headache, shortness of breath, and diarrhea, of which, in extreme cases, severe inflammatory responses may lead to fatality (Chen et al, 2020)
Summary
Coronaviruses are known to infect various hosts such as mice (mouse hepatitis virus, MHV), pigs (porcine epidemic diarrhea virus, PEDV), birds (avian coronavirus, IBV) and even human (human coronavirus, HCoV including severe acute respiratory syndrome coronavirus (SARS-CoV), SARSCoV-2, Middle East Respiratory Syndrome-CoV (MERS-CoV), HCoV-OC43, HCoV-NL63 and HCoV-229E) with different disease severity (Vellingiri et al, 2020; Zhu et al, 2020). Most previous publications including review papers have mainly focused on the use of TCM and other ethnobotanical herbs (Dudani and Saraogi, 2020; Khanna et al, 2020; Ling, 2020; Vellingiri et al, 2020) or the use of drugs and other dietary supplements that are currently in clinical trials (Di Matteo et al, 2020; Kumar et al, 2020; Stahlmann and Lode, 2020) This may not cover most, if not all, potential plant species or extracts available globally. This review highlights the potential use of herbal plants and related compounds in treating the coronavirus infection, in the hope that it could lead to a potential source of anti-viral drugs for curbing the COVID-19 outbreak.
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