Nature is full of a plethora of herbs that people all over the planet have used to heal for thousands of years. Traditional use of plant medicines was based mostly on the observation of the effects these plants had when given to people with particular conditions and illnesses. Today, these same plants have to stand up to the rigor of scientific scrutiny to prove what our ancestors already knew.
Many of these herbs have antiviral properties due to the compounds or active chemical constituents they contain, which can help with the symptoms and hasten common cold and influenza. These plants and their compounds have been found to be effective against various other viruses as well. With pandemics becoming more and more prevalent, more money must be invested in researching plant medicines.
This is especially true since there are currently few drugs on the market today that can effectively treat most new and emerging viral infections. The only challenge that stands in the way to having medicinal plants tested as thoroughly as pharmaceutical drugs are the inability to patent natural substances and financial gain as pharmaceutical companies do.
Pharmaceutical companies spend billions of dollars researching drugs every year because they are able to get a return on investment from doing so, via patents which prevent others from profiting off of their drug that they’ve invested big money in researching. Herbal products, left in a gray zone because of the inability to patent them, get comparatively minuscule dollars volunteered for their research because of the lack of financial incentive.
The majority of studies on herbs available today are done by the commercial manufacturers of herbal products since they can at least recoup their costs in part by selling the products they are researching. This conundrum can lead to poor quality studies due to lack of funding for high quality, high-cost research, and experimental bias of the herbal product manufacturer similar to what we see when pharmaceutical companies do research on their own products.
Top 10 Antiviral Herbs
Below are ten of the most well-studied plants for viral illnesses, and a synopsis of the research performed on each one, that serves as a starting point to future independent research potentially funded by industry, and government. These studies, in the long run, could potentially serve to lower overall healthcare and workplace costs, as well as morbidity and mortality due to viral illness.
1. Sumbucus Nigra (Black Elderberry)
It is used for the treatment of colds and influenza. Sambucol, a standardized black elderberry extract, has shown antiviral properties. The extract showed antiviral activity against 10 strains of influenza virus and reduced flu duration by 3 to 4 days in a double-blind placebo-controlled, randomized study.
Compounds the flower contains that account for this activity are known as triterpenes, fixed oils, and phenolic acids (Hoffmann, 2003). Compounds the berries contain, namely anthocyanidins, act by directly inhibiting viral entry into the cell, and then viral replication within the cell (Torabian et al., 2019). These compounds also help strengthen the immune response to the virus.
2. Baptisia Tinctoria (Wild Indigo)
The plant was used traditionally by the Native Americans to treat pneumonia, TB, and influenza, amongst other things. The part traditionally used is the root. The constituents contained in the plant responsible for its activity are isoflavones, flavonoids, alkaloids, coumarins, and polysaccharides.
Wild indigo helps to clear infections and mucous in the ears, nose, and throat. Particularly it is useful for laryngitis, tonsillitis, pharyngitis and catarrhal infections of the nose and sinuses. The herb is also purported to reduce the swelling of enlarged lymph nodes and help lower fevers. Other traditional uses were for typhoid and scarlet fevers, which are now exceedingly rare illnesses.
3. Andrographis Paniculata (Creat or Green Chireta)
This herb has a long history of use as an antimicrobial for sore throats, URTIs, and flu in Asian cultures. In one study, it was deemed useful for shortening the duration of acute respiratory tract infections in adults and children. The primary active constituent andrographolide has anti-inflammatory effects and has been studied for its benefits in treating cancer, asthma, stroke, and arthritis.
Andrographolide also has antiviral and antibacterial properties. It was shown in a mouse study to stimulate the innate immune response, including macrophage activity, phagocytosis of bacteria, and replication of lymphocytes. Two other studies have demonstrated the compound’s immunostimulatory activity and shown it increases the proliferation of lymphocytes and the production of IL-2 an immune signaling molecule. In addition to its immune-enhancing properties, andrographolide is capable of killing Herpes Simple Virus Type 1 (HSV1) without causing damage to our cells. A whole-plant extract and andrographolide have been shown to inhibit the epstein barr virus as well.
4. Echinacea sp. (Purple Coneflower)
Traditionally in North America Echinacea sp. extracts have been used to treat colds, flus and other diseases. Viruses exhibiting sensitivity to a standardized extract of Echinacea purpurea known as Echinaforce include human and avian influenza A and B viri (including viri resistant to Tamiflu), herpes simplex virus, respiratory syncytial virus, and rhinoviruses (Hudson & Vimalanathan, 2011).
This standardized extract shows virucidal activity against rhinovirus during the initial stage of infection and during transmission from infected cells. Echinaforce has been shown to be a very active virucidal against all enveloped viruses. The extract appears to inhibit receptor binding activity of the influenza A virus and inhibit its entry into the cell. Other extracts have been shown to inhibit glycoproteins and enzymes specific to the influenza virus. Extracts of various species of Echinacea have shown weak antiviral activity against vesicular stomatitis and herpes simplex viruses.
The most potent antiviral activity was achieved by extracts of E. purpurea . In another study, E. purpurea, in a water extracted form, showed potent activity against HSV and influenza virus . E. angustifolia, in the same study, showed moderate antiviral activity against HSV, rhinovirus and influenza virus. E. pallida extracts have demonstrated the ability to kill and inhibit the replication of HSV-1 and HSV-2. Echinaforce, has the added benefit of decreasing mucin secretion leading to less mucus is produced during rhinovirus infections. The extract also inhibits pro-inflammatory cytokines which are normally released by the body in response to infection by rhinovirus, HSV-1, Influenza A, Adenovirus type II and III and RSV.
A study done this year on Echinaforce that is undergoing the peer review process found evidence that respiratory cell cultures pre-treated with Echinaforce were less likely to be infected with human coronavirus strain 229E (Cov-29E). It was found that this extract inactivated the virus and may serve as an effective prophylactic agent).
The main active constituents in Echinacea responsible for its antimicrobial, immunomodulatory, anti-inflammatory, and anticatarrhal activity are Caffeic acid esters, including echinacoside contained in E. Angustifolia, and cichoric acid contained in E. purpurea, alkyl amides, and polysaccharides including echinacin B. Echinachea spp. It also contains compounds known as polyacetylenes and essential oils.
5. Hydrastis Canadensis (Goldenseal)
The main active constituent in goldenseal that is responsible for the plants’ antimicrobial activity is berberine, which is classified as an isoquinoline alkaloid. Berberine is also found in barberry (Berberis vulgaris), Coptis (Coptis chinensis), and Oregon grape (Mahonia aquifolium).
When isolated, berberine has shown the ability to strongly inhibit the growth of H1N1 influenza A strains in vivo. Similarly, berberine-containing ethanol extract of goldenseal has also been shown to inhibit the growth of influenza A and the production of inflammatory mediators. Goldenseal helps remove excess mucous from the body, especially when a sinus disorder is causing excessive mucous production (Hoffmann, 2003). It also has broad-spectrum antibiotic activity, although not to the level of pharmaceutical antibiotics.
6. Ligustrum Porterii (Osha)
Traditionally, in Native American ad Hispanic cultures, Osha was used for pneumonia, colds, bronchitis, influenza, tuberculosis, hay fever, and coughs (Natural Medicines Database as cite in Cervoni, 2019). A closely related species of Ligustrum known as Ligustrum lucidum (glossy privet) has antiviral effects against RSV and parainfluenza type 3 virus (Para 3).
These effects are thought to be due to compounds contained in the fruit of the plant known as secoiridoid glucosides. One of these compounds known a Oleuropein showed significant antiviral effects against RSV and Para3. Three other of these compounds known as Lucidumoside C, oleoside dimethylester and ligustroside showed moderate to potent antiviral activity against Para3. Used early on in a cold or flu, it can treat the symptoms of coughing, sneezing, sinus congestion, sore throat and bronchial inflammation .
Other viral conditions, osha has been found to be effective against are Herpes, and AIDS/HIV (Therapeutic Research Facility, 2018). One of the active ingredients in osha is ligustilide. This compound has antimicrobial and antiviral properties. Though the mechanisms have not yet been determined, this compound is able to inhibit viral proteases and has direct inhibitory activity against influenza. Another active ingredient, the furanocoumarins (inc. psoralen ad bergapten) have antibiotic, antitumor, and antiviral activity by way of intercalating with DNA and RNA molecules.
7. Usnea sp. (Old man’s Beard)
Classified as a fruticose lichen, this plant is fungus and alga symbionts found growing on the bark of wood of conifers and deciduous hardwood trees. In, Traditional Chinese Medicine (TCM) it has been used for thousands of years for lung infections and upper respiratory tract infections. It can also be applied topically for skin infections and ulcers and is still used to treat tubercular lymphadenitis.
The main active component of this plant is known as usnic acid. Usnic acid from Usna longissima was shown to be significantly effective against epstein-barr virus and its tumor promoting capabilities . Usnic acid was also shown to be protective against HSV-1 and polio type 1 induced cell damage to the virally infected kidney cells of green monkeys (Ingolfsdottir, 2002 as cited in Guo, et al., 2008).
In a study on 100 women with HPV requiring radiosurgery, usnic acid and zinc sulfate helped significantly to promote re-epithelization (Scirpa, Scambia, Masciullo, Battaglia, Foti, et al., 1999, as cited in Guo et al, 2008).
8. Olea Europaea (Olive leaf)
Oleuropein is the main active constituent of the plant responsible for its antiviral activity. The plant has shown significant and potent antiviral activity against herpes, mononucleosis, hepatitis virus, rotavirus, bovine rhinovirus, canine parvovirus, feline leukemia virus, RSV and Para3 . It was also shown in another study to inhibit cell-to-cell transmission of HIV . A commercial olive leaf extract and the main active constituent oleuropein inhibited the ability of viral hemorrhagic septicemia virus to infect healthy cells in a study conducted by Micol et al (2005). The extract decreased the ability of the virus to infect other cells to 10% and oleuropein to 30%.
The proposed mechanism of decreased infectivity was that the extract and active constituent were thought to interfere with the viral membrane fusion process with healthy cells.Thirty-six hours after initial infection, the olive leaf extract was shown to have virucidal effects when added to the cell cultures.
The effect of these virucidal effects was dose-dependent. Another study found that a hydroalcoholic extract of olive leaves exhibited antiviral activity when it was incubated with the virus for an hour and add to cell culture (Nekooeian, Moatari & Motamedifard, 2006). The proposed mechanism of action was again by interfering with the membrane of the virus to prevent attachment and entry of the virus into healthy cells.
9. Thymus vulgaris (Thyme)
The main active constituents in thyme are Volatile oils such as thymol and carvacrol (Hoffmann, 2003). Some of the uses of thyme help to get rid of the body of stuck mucus via expectoration and decreasing bronchospasm. It is, therefore, useful for bronchitis, whooping cough, and asthma. It has also been found useful for helping with a sore throat and coughing and can be used as a gargle for laryngitis and tonsillitis.
One study found that essential oils of thyme and other plants were capable of inhibiting acyclovir-resistant Herpes Simplex Virus 1 (HSV-1) (Schnitzler, Schon, & Reichling, 2011 as cited in Swamy, Akhtar, Si& Sinniah, 2016). The postulated mechanism of action was the essential oils that possibly hindered virus replication by interfering with the genetic replication process.
Another study found similar antiviral activity against HSV-1 . Anti-influenza virus activity was also found against H1N1 in a 2014 study (Vimalanathan & Hudson, 014 as cited in Winska, Maczka, Lyczko, Grabarczyk & Szumny, 2019)
10. Origanum Minutiflorum (Oregano)
The active ingredients in oregano include carvacrol, thymol, and triterpenes. Generally, the oil of oregano, the most common commercially available preparation of the plant, is standardized to contain at least 70% or more of carvacrol. It is used today to treat cold and flu symptoms (Cronkelton, 2020).
According to research performed by Vimalanathan & Hudson, (2012), though 5 different dosing concentrations were shown to be antiviral against influenza, that they were less effective than a standardized extract of E. purpurea and more toxic to lung epithelial cells. Carvacrol alone was the most toxic to lung epithelial cells. Oregano oil, and isolated carvacrol when tested against nonenveloped murine norovirus (MNV) showed a significant decrease in infectivity within 15 minutes following exposure.
Carvacrol by itself proved to be much more effective alone versus the full spectrum oil. The mechanism of action was likely to direct action against the viral capsid and RNA, which lead to the disintegration of the capsid. Carvacrol actually inactivated MNV within an hour of exposure.
The 10 plants discussed above have evidence of their utility in treating viral infections. More research is needed to determine if these benefits apply to new and emerging viruses as well. Finding effective cures for existing and emerging viral illnesses has the potential to save the healthcare system and economy a substantial amount of money by reducing money spent on things like hospitalizations, and by reducing worker absences from work.
It may also help to reduce morbidity and mortality. Therefore, investing money into more rigorous research for herbs with antiviral properties may be an effective cost-saving measure for governments and employers globally.
Dr. Hayley, a licensed Naturopathic Physician graduated in 2013 from Boucher Institute of Naturopathic Medicine located in Vancouver, BC in 2013. She has been licensed and practicing in Arizona since 2014, and plans to also begin practicing in British Columbia this year(2020).