Therapy Against COVID-19: Medicinal Plant Extracts Can Be a Solution

: Coronavirus disease 2019 (COVID-19) was declared by the World Health Organization (WHO) as a pandemic on March 11, 2020. Despite the development of anti-COVID-19 vaccine, the disease continues to kill thousands of people, mainly due to a lack of sufficient doses for all populations and to the prioritization of populations to be vaccinated. According to epidemiological data from April 06, 2022, the COVID-19 pandemic has already killed more than 6,184,299 people around the world with nearly 494,286,073confirmed cases. To date, no antiviral drug has been officially approved to fight this pandemic. Medical professionals and researchers all over the globe are in pursuit for the discovery therapies against this disease. One of the strategies is the use of medicinal plants. Indeed, plant extracts can inhibit viral growth and their effectiveness has been demonstrated on many viruses encountered in human pathology including SARS-CoV-1, poliovirus, varicella-zoster virus, HIV, human papillomavirus, HSV-1, HSV-2, influenza virus, cytomegalovirus and many others. Besides, it has been shown that plant extracts can regulate immune system and make the body able to prevent the establishment of viral infection or to fight against its deleterious effects. The exploration of plant extracts with anti-viral and immunostimulatory properties could be exploitable in the development of drug against COVID-19. This review promotes medicinal plant extracts as potential anti-COVID-19 drugs.


Introduction
Coronavirus disease 2019 (COVID- 19) was declared a Public Health Emergency of International Concern by the World Health Organization (WHO) on 30 January 2020.The disease gradually spread across the world and was subsequently declared a pandemic on March 11, 2020.According to epidemiological data from January 25, 2021, the COVID-19 pandemic has already killed more than 6,184,299 people around the world with nearly 494,286,073 confirmed cases.It is an infectious disease with severe acute respiratory syndrome caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a new type of coronavirus first discovered in the city of Wuhan, China, at the end of December 2019.The SARS-CoV-2 infects the lower respiratory system induce a severe pneumonia.It can develop other disorders in the digestive system, heart, liver, kidneys, and nervous system, causing multi-organ failure.COVID-19-infected pneumonia is characterized by flu-like symptoms including fever, cough, and severe acute respiratory distress syndrome [1][2][3][4].
Since the outbreak of COVID-19, there has been no specific antiviral medication for treatment of the infection where supportive care and prevention of complications is the current management strategy.Despite the approval of the anti-COVID-19 vaccine by WHO, the disease continues to kill thousands of people, mainly due to a lack of sufficient doses for all populations and to the prioritization of populations to be vaccinated.No antiviral drug is available to fight COVID-19 although there are many efforts around the world to develop one as quickly as possible.Enormous efforts have been made to protect, alleviate and cure the disease, though no specific treatment has been approved.Many countries infected by this virus, have done various proceedings such as distraction of traveling, isolation of patients and continuous medical care to reduce and prevent coronavirus spreading.The lack of treatment options for COVID-19 has led to many attempts to find alternative options to prevent the transmission of the disease or to alleviate the progression of the infection, including focusing more on preventive measures and the use of natural products and herbal extracts to increase immunity and decrease the probability of getting infected.Historically, the use of natural products was known to be the only treatment method against many infections and diseases.Medicinal plant species can provide a solution as a source of natural antiviral compounds by the accumulation of secondary metabolites and lectins as well as acting as a platform to express the viral immunogenic proteins [6][7][8][9][10].
The elderly patients or people who have existing chronic medical conditions such as heart failure, cancer, type 2 diabetes, severe obesity, chronic kidney disease, sickle cell disease, weakened immune system from solid organ transplants have a higher risk of serious illness from COVID-19.This can be due to the lower immune system.In order to combat SARS-CoV-2, many drug and vaccine development studies at experimental and clinical levels are currently conducted worldwide.Some traditional herbal medicines prevented SARS-CoV-2 infection of healthy persons and improved the health state of patients with mild or severe symptoms.Herbal drugs can effectively relieve symptoms, such as fever, cough, and fatigue, and reduce the probability of patients developing severe conditions.The contribution of traditional medicine in the management of Covid-19 may complement healthcare prevention and medical care services [14].In China for example, the National Health Commission of China had recommended to use Chinese herbal medicine like QingfeiPaidu Decoction (QPD) to treat COVID-19 patients.Medicinal plants such as Artemisia annua are being considered by WHO as possible treatments for COVID-19 and should be tested for efficacy and adverse side effects.Furthermore, medicinal herbs have become an essential purpose to determine, isolate and purify the natural compounds for treatment of viral diseases.Most recent in silico studies revealed that natural compounds like myricitrin, methyl rosmarinate, calceolarioside B, myricetin3-O-β-Dglucopyranoside, licoleafol, and amaranthin could be potential leads to develop novel anti-SARS-CoV-2 drugs.WHO recognises that traditional, complementary and alternative medicine has many benefits.Medicinal plants have great prospect in the ultimate search for the cure against the dreaded coronavirus [2,[11][12][13][14][15][16][17][18][19][20].The traditional medicinal system based on herbal therapies has always played a pivotal role in the health systems [20].This review presents herbal remedies as a potential drug solution against COVID-19.

Plants with Antiviral and Immunomodulatory Properties
To date, medical professionals and researchers all over the globe are in pursuit for the discovery of prophylactic or anaphylactic remedy against COVID-19.One of the strategies employed is the exploration of traditional medicine as a potential source of an effective anti-COVID-19 drug.Plant extracts have long been used in the treatment of viral infections and their efficacy has been the subject of numerous scientific publications.Indeed, plant extracts can via several mechanisms inhibit viral growth and their effectiveness has been demonstrated on many viruses encountered in human pathology including SARS-CoV-1, poliovirus, varicella-zoster virus, HIV, human papillomavirus, HSV-1, HSV-2, influenza virus, cytomegalovirus and many others.By their antiviral properties, these plant extracts could also act on SARS-CoV-2, the viral agent responsible for COVID-19.It has also been shown that plant extracts can act at several levels of the body and regulate various mechanisms including the expression of the immune system.As with any other microbial infection, the immune system plays an important role in controlling COVID-19 infection.The immunocompromised are the most at risk.By boosting the immune system, plant extracts with immunostimulating properties make the body able to prevent the establishment of infection or to fight against its deleterious effects.Plant extracts can enhance immune reactions via the stimulation of non-specific systems, such as granulocytes, macrophages, complement, certain T-lymphocytes and various effector substances.The selection of plant extracts proven to be safe and possessing anti-SARS-CoV-2 and immunostimulatory properties could be exploitable in the development of an effective anti-COVID-19 drug.Plant extracts provide a rich resource for novel antiviral drug development and can improve the immunity against virsuses or other pathogen.In several countries around the world, drug formulations made from medicinal plants are used to prevent and fight COVID-19.This is the case with Qing FeiPai Du Tang (QFPDT), a Chinese medicine formula which has been reported to be efficacious on COVID-19 in China.The main herbs of QFPDT have been shown to have antiviral effects via different mechanisms.It can direct effect on virus replication and autophagy, and promotes the human defense system via T and B cell functions [21][22][23].Table 1 below presents some plants with antiviral which can also act on immune system.

Conclusion
The advent of the COVID-19 pandemic has totally changed global habits both economically and socially.To date, no antiviral drug has been approved to fight this disease.Traditional medicine once held pride of place as the premier treatment for emerging diseases.Several plant species are known there for their therapeutic and anti-infectious properties in particular.Since the advent of COVID-19 many potions made from herbal remedies have been proposed as drugs to fight this infection.However, no scientific studies demonstrating the efficacy and safety of these drugs for approval have been performed.Clinical studies on these drug potions and an exploration of other therapeutic possibilities offered by traditional medicine would help to overcome this pandemic.

Table 1 .
Plants with antiviral and immunomodulatory properties.