July 23, 2020
The coronavirus outbreak caused by severe acute respiratory syndrome coronavirus2 (SARS-CoV-2) happened in Wuhan, Hubei, China in December 2019. It was transmitted from humans to humans so quickly that it has become the pandemic responsible for the current global crisis. In May 2020, as was reported by the WHO, there have been approximately 5 million confirmed cases of COVID-10 and more than 30 thousand deaths worldwide.
Since there is also no effective pharmacologic treatment against COVID-19, determining the drug target requires an understanding of the viral lifecycle.
While many clinical trials aimed at discovering a potential effective COVID-19 drug are ongoing, using herbal medicines with well-known antiviral activity might be a complementary SARS-CoV-2 preventive therapy.
Since treating influenza with very large amounts of vitamin C has been practiced for decades, nutrition can be used for prevention and treatment of coronavirus. Both COVID-19 and SARS are caused by coronaviruses. The virus that causes SARS is known as SARS-CoV, while the virus that causes COVID-19 is known as SARS-CoV-2. Since the common cold, SARS-CoV-1, and SARS-CoV-2 fall under the same coronavirus family, they are regarded as the same viral type. Therefore, vitamin C may be effective against COVID-19; clinical studies are required.
Evidence supporting the role of vitamin D in reducing risk of COVID-19 includes that the outbreak occurred in winter, a time when 25-hydroxyvitamin D (25(OH)D) concentrations are lowest. Thus, vitamin D intake may reduce the risk of influenza and COVID-19 infections and related deaths.
Many foods and herbs are known to display antiviral and immunomodulatory activities. Aloe vera, Angelica gigas (Korean angelica), Astragalus membranaceus (Mongolian milkvetch), Ganoderma lucidum (lingzhi mushroom), Panax ginseng (ginseng), and Scutellaria baicalensis (Chinese skullcap) have been reported to exhibit immunomodulatory properties. Their activities are based on selectively stimulating cytokines, activating lymphocytes, increasing natural killer cell counts, and enhancing macrophage actions. Rice bran, wheat bran, Lawsonia alba (hina), Echinacea purpurea (eastern purple coneflower), Plumbago zeylanica (Ceylon leadwort), and Cissampelos pareira Linn (velvetleaf) also exhibit immunomodulatory properties by stimulating phagocytosis. Eucalyptus essential oil is reported to improve the innate cell-mediated immune response that can be used as an immunoregulatory agent against infectious diseases. Collectively, using these immunomodulatory foods and herbs could enhance the immune system and protect the body against COVID-19. However, these observations must be verified through scientific or clinical studies.
Numerous studies have reported about the bioactive components of foods and herbs against the influenza virus and SAR-CoV-1. The most clinical studies have been done on food and herb combinations, or the traditional Chinese formulas against the influenza virus and SAR-CoV-1.
The extracts or bioactive compounds of garlic, ginger, Korean red ginseng, eucalyptus, tea tree, Tianmingjing, Machixian, fish mint, Chinese mahogany, cape jasmine, zhebeimu have been shown to exhibit antiviral activity against the influenza virus.
Some essential oils also have been shown to exhibit anti-influenza activities. These include Cinnamomum zeylanicum leaf oil (cinnamon), Citrus bergamia (bergamot), Cymbopogon flexuosus (lemongrass) and Thymus vulgaris (Red Thyme). A blend of essential oils also inhibits the infectivity of influenza virus via inactivating viral binding ability and viral protein translation in MDCK cells. Tea tree oil and eucalyptus oil capturing on the fiber coating materials are capable of inactivating influenza virus A.
Current literature carries strong evidence in support of dietary therapy and herbal medicine as potential effective antivirals against SARS-CoV-2 and preventive agents against COVID-19. Dietary therapy and herbal medicine could be used against COVID-19 in the following four ways: (1) diet or supplement for infection prevention and immunity strengthening; (2) application as antiviral agent on masks; (3) air disinfection agent to stop aerosol transmission of the virus; and (4) surface sanitizing agent to afford a disinfected environment.
Surgical masks are good at preventing virus spread into the air and transmission to humans. However, after mask removal, the virus remains on the mask and is probably re-aerosolized, increasing the risk of human infection. Mask coating with an antiviral compound could be advantageous, but disinfectant toxicity to humans must be considered.
Aromatherapy has been used for thousands of years in Egypt and India to treat various diseases, and the antimicrobial and antiviral activity of essential oils have been confirmed by numerous studies. However, most of these studies only investigated the effect of their liquid formula, limiting their administration to only via the oral route. Using essential oils vapors could increase their application against airborne bacteria and viruses. The anti-influenza virus activity of some essential oil vapors, such as that of Citrus bergamia (bergamot), Eucalyptus globulus (eucalyptus), Pelargonium graveolens (geranium), Cinnamomum zeylanicum leaf oil (cinnamon), and Cymbopogon flexuosus (lemongrass), has been reported. Their inhibitory mechanism is based on the inactivation of the principal external proteins of the influenza virus. The hemagglutinin protein of the virus appeared to be a major target of most of these oil vapors, and this may provide therapeutic benefits for people suffering from influenza or other respiratory viral infections. Aerosolized tea tree oil reportedly inhibits airborne viral particles of H11N9 subtype avian influenza virus. There are currently very few studies on the potential of the vapor form of essential oils.
Air sterilization without human health damage using essential oils could be a good way to prevent COVID-19. However, the minimum essential oil concentration needed for SARS-CoV-2 inhibition should be investigated.
Many restaurants use cleaning detergents for surface sanitization; however, their safety and disinfection efficiency need further consideration. Natural antiviral extracts from herbs could be added to cleaning detergents to increase their anti-SARS-CoV-2 activity.
Current studies provide obvious evidence supporting dietary therapy and herbal medicine as potential effective antivirals against SARS-CoV-2 and as preventive agents against COVID-19. Thus, dietary therapy and herbal medicine could be a complementary preventive therapy for COVID-19. However, these hypotheses require experimental validation in SARS-Cov-2 infection models and COVID-19 patients.