Abstract
The World Health Organization declared the severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 virus outbreak as a pandemic on May 27, 2020. Since then, more than 5 488 825 cases across the world have been recorded at the time of revising this article. Governments around the world have imposed serious containment measures, meanwhile, the healthcare system is overburdened due to large increases in COVID-19 cases. However, no specific anti-SARS-CoV-2 virus drugs or vaccines have yet been shown to be effective to fight this causative virus of acute infectious pneumonia. The current review was conducted to look for potential natural and synthesized drugs for the treatment of COVID-19 patients. Previously published data in journals, textbooks, periodicals, websites, and sources, including data about the treatment of human coronavirus with natural and synthesized drugs, were taken from the online bibliographical databases. The results showed that syndic drugs approved for other human diseases have been used to improve the symptoms of patients infected with SARS-CoV-2. Several clinical trials across the world evidenced beneficial effects of natural and synthesized drugs in the treatment of SARS-CoV-2 infections. On the other hand, many studies have provided a deep understanding of the therapeutic effects of conventional and traditional medicine in identifying naturally occurring drugs effective against the SARS-CoV-2 virus. Both natural and synthesized drugs should come together to fight the SARS-CoV-2 virus and other potential emerging dangerous viral diseases since they have shown promising findings in clinical trials conducted with COVID-19 patients.
COVID-19, also known as 2019-nCoV and severe acute respiratory syndrome (SARS)-coronavirus (CoV)-2 virus, belongs to the family Coronaviridae. As SARS-CoV-2 belongs to the genus Betacoronavirus, it is closely related to MERS-CoV and SARS-CoV and thus is a positive-strand RNA virus with the largest viral genome of all RNA viruses which have been reported to cause severe symptoms of pneumonia in previous pandemics. 1 The genetic structure of SARS-CoV-2 virus has been characterized and previously published. 2,3 The main proteins in this virus and those previously identified in SARS-CoV and MERS-CoV showed a high similarity between them. Coronavirus infection is commonly induced by the virus rapidly integrating its genetic material into the host cell and multiplying, depending on the host organism for its development. 4
The first research on human coronaviruses (HCoVs) was carried out in the mid-1960s. 5 After 40 years a CoV was declared as the responsible agent for SARS, which caused a global health burden. 6 The novelty of this strain of virus means that many uncertainties are surrounding its behavior, and, therefore, it is too early to determine natural and synthetic drugs that could contribute to society as prophylactic agents or as suitable substances as anti-coronavirus drugs against COVID-19 virus. However, due to the high similarity between the COVID-19 virus and the previously reported SARS-CoV and MERS-CoV viruses, previously published research on natural compounds proven to exert anti-coronavirus effects may be a valuable guide to finding natural agents which may be active against the SARS-CoV-2 virus.
Currently, COVID-19 disease cases are growing very quickly worldwide. 7 In the United States, Brazil, Spain, Italy, and other countries, the COVID-19 pandemic is overburdening the healthcare system. 8 In real time, even though a series of potential drugs have been reported to improve the disease, there are no approved or recommended antiviral drugs for COVID-19.
To contribute to society as prophylactic agents against COVID-19, the current review was undertaken to look for the potential for the intervention of both synthetic and natural drugs to fight COVID-19.
Material and Methods
Data Collection
Previously published data in journals, textbooks, periodicals, websites reporting the treatment of coronavirus with conventional and traditional medicine were taken from the online bibliographical databases such as Google, Google Scholar, PubMed, Science Direct, and Springer Link. These data were searched using keywords related to natural and synthesized drugs used in coronavirus treatment. A list was established as a table including the medicinal plants declared to be used in the treatment of coronavirus around the world. The consulted sources were also searched for pharmacological studies giving supportive information on the detail of the involved plants such as the responsible compound classes as well as the mechanism of action.
Results and Discussion
Evidence of Conventional Treatment of Human Coronaviruses
Although there is active research to develop efficient drugs to fight COVID-19, no specific antiviral therapeutics have been developed, and the main adopted treatment strategy is a combination of antibiotics, antivirals, corticosteroids, and convalescent plasma from recovered patients. 9 COVID-19 patients have been treated with a combination of antibiotics and the HIV protease inhibitors ritonavir and lopinavir. 10 Ribavirin, an analog of ritonavir, 11 may present promising efficacy on COVID-19 since this drug was used in the treatment of the respiratory syncytial virus. Moreover, ribavirin was approved for treating the SARS and MERS outbreak. 11 -13 However, earlier data reported that ribavirin induced severe secondary effects such as anemia; its efficacy on SARS-CoV-2 was also not clear. 12 The RNA polymerase of RNA viruses, such as the influenza virus, may be inhibited by the nucleoside analog favipiravir. 14 Literature shows that it possessed an anti-SARS-CoV-2 effect, but its in vivo efficacy was elusive. Remdesivir could be a promising treatment for the treatment of COVID-19 patients. This drug showed in vitro and in vivo effects on an array of RNA viruses including SARS as well as MERS 15 and reduced viral loads sufficiently in treated animals. 16 As reported earlier, remdesivir had a significant effect on SARS-CoV-2 in Vero E6 cells, and patients affected by SARS-CoV-2 recovered after they received remdesivir intravenously. 10,17 At present, remdesivir is under clinical trial assessment for COVID-19 patients. 18 Even though oseltamivir has been used to treat COVID-19 patients, its efficacy has not been confirmed. 10
Other drugs previously approved for the treatment of human diseases have been tested against SARS-CoV-2, which may lead to a potential treatment for COVID-19 patients. Chloroquine and hydroxychloroquine showed potential broad-spectrum antiviral effects on SARS-CoV-2, 19 and their efficacy is currently under clinical trials. Available data have recommended the use of IFNα atomization inhalation to treat COVID-19 patients, 9 and clinical trials have been conducted on the potential of IFNα-2b treatment of COVID-19 since it was approved to treat HCV infection. 20 However, its efficacy has not been well shown. Earlier published data showed that corticosteroids were used to reduce the cytokine elevation in patients affected by SARS-CoV 21 as well as MERS-CoV. 22,23 However, the effect on these patients was unclear, and the clearance of the viruses was delayed by the treatment with corticosteroids. 24,25 Corticosteroids have not been recommended for systematic use in the treatment of COVID-19 patients.
Convalescent plasma could be a promising tool to fight COVID-19 since it significantly decreased the viral load in severe influenza and SARS-CoV patients and, therefore, reduced the mortality. 24,26 COVID-19 patients treated with convalescent plasma in China showed promising results, although the efficacy needs further evaluation 16.
Medicinal Plants or Their Constituents for the Treatment of Coronavirus Infection
Since natural products have been used to treat infectious diseases for many years, there is potential for the intervention of such products for the complementary or alternative treatment of coronavirus infection. Literature from across the world has reported the history of the intervention of traditional medicine in the treatment of coronavirus infection that occurred in humans and animals. Plant products or their constituents could be a promising weapon for the treatment of COVID-19 since early patients with SARS-CoV infection have benefited from alternative medicine (Table 1).
Medicinal Plants Used for the Treatments of Coronavirus Infection.
ERK, extracellular signal-related kinase; HCoV, human coronavirus; MHV-A59, mouse hepatitis virus A59; PEDV, porcine epidemic diarrheavirus; SARS-CoV, severe acute respiratory syndrome coronavirus; TGEV, transmissible gastroenteritis coronavirus.
Conclusion
The current review summarizes a range of natural and synthesized products that have been shown previously to have beneficial antiviral properties and may have potential as prophylactic agents against COVID-19. Further studies involving both traditional and conventional medicine may lead to identifying novel agents that could be promising weapons to fight COVID-19 or any other potential emerging dangerous viral diseases. The safety of traditional medicine in the treatment of COVID-19 patients has not been investigated in the current work, and, therefore, the toxicological assessment of any natural medicine would need to be meticulously evaluated. Any potential toxicity or interference of the product with either traditional or conventional medicine induced by herb-drug interaction should be understood.
Footnotes
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding
The authors received no financial support for the research, authorship, and/or publication of this article.
