The world is facing Covid19; it is caused by coronavirus SARSCoV2. Coronaviruses (CoVs) are single-stranded positive-sense RNA viruses; these were first reported in 1960. Only seven types of human-CoVs (HCoVs) exist that can infect humans- Middle East Respiratory Syndrome-CoV (MERS-CoV), Severe Acute Respiratory Syndrome-CoV (SARS-CoV), HCoV-229E, HCoV-OC43, HCoV-NL63, HCoV-HKU1, and latest novel SARS-CoV-2.
CoVs can infect mammals including humans, and cause respiratory, hepatic, neurological and gastrointestinal diseases. Covid19 is characterized in several cases by severe pneumonia. SARS-CoV-2 infection (COVID-19) is destroying the world economy, social life, and human lives with an increased mortality rate each day.
The increased mortality and hospitalization rates for COVID-19 worldwide are due to several factors such as the deficiency of immuno-modulatory vitamin D due to low ultraviolet exposure of humans, temperature variation, air pollution, especially particulate matter (PM), and relative humidity condition which allow the virus to survive longer outside the human body.
Plants are a source of antiviral bioactive compounds
There is no specific drug currently available to cure COVID-19 infection. But, the medicinal plants and their bioactive molecules with antiviral properties are a ray of hope to develop drugs against SARS-CoV-2 infection. Bioactive compounds of several medicinal plants have excellent ability to work against coronaviruses because these compounds are known to act on viral protein targets, namely ACE-2 (Angiotensin-converting enzyme-2) receptor, 3CLpro (3 chymotrypsin-like proteases), PLpro (Papain-like protease), RdRp (RNA-dependent RNA polymerase) enzyme and other known factors through which coronaviruses gain entry into the human cell and complete the life cycle.
Many plants have bioactive compounds like coumarin, saikosaponins, glycosides, phenols, tannins, flavonoids, carotenes, lycorine, quercetine, flavonoid, polyphenols, triterpenes, sterols, saponins, polysaccharides, caffeoylquinic acid, chlorogenic acid, mangiferin, astragalin, trifolin, indirubin, sinigrin, β-sitosterol, hesperetin, vitamin C, isoquinoline alkaloids, sesquiterpene lactones, emodin, alliin, allicin, ajoenes, vinyldithiins, catechol, p-hydroxybenzoic acid, caffeine, catechin, pyrogallol, gallic acids, resveratrol, naringin, rutin, sterols, caffeic acid, Tomentin E, cinnamon amides etc.
The above antiviral bioactive compounds have the capacity to block ACE-2 receptors, 3CLpro, PLpro and RdRp enzymes through which coronaviruses gain entry into the human cells.
Role of trees in controlling Covid-19 cases in South Italy
In northern Italy, COVID-19 disease provoked the highest number of victims in the country and one of the most worrying situations worldwide in 2020. In northern Italy, particulate matter (PM) played an important role in spreading Covid-19, where PM concentrations of ≥ 50 µg/m3 as PM10 daily averages were often recorded. Fine PM penetrating into the respiratory system can easily provoke inflammatory responses as well as cardiovascular and pulmonary diseases, thus resulting in respiratory distress.
A study on lower COVID-19 mortality in Italy’s forested areas by Valentina Roviello & Giovanni N. Roviello, published in Environmental Chemistry Letters on 2021-02-14, explains a surprising role of immunoprotection by Mediterranean plants. In southern Italy, the Mediterranean plants played a protective role and reduced the graph of Covid-19 cases. In South Italy, the forested areas mitigated air pollution by intercepting PM onto plant surfaces and bolstered the human immune system by emitting bioactive volatile organic compounds (VOCs). These trees act as unique sources of useful metabolites and volatile organic compounds (VOC), displaying positive effects against various pathogens, including virus and positive effect on the human immune system. Persons living in southern Italy received positive effects on the human immune system.
It was found that the pandemic’s severity was generally lower in southern regions, especially those with more than 0.3 hectares of forest per capita. The lowest mortality rates were found in southern Italy, mainly in regions like Molise (0.007%) and Basilicata (0.005%), where the forest per capita ratio is higher than 0.5 Ha/person.
Nevertheless, the mild climate, higher average sunlight exposure and the Mediterranean diet, which includes the consumption of foods containing polyphenols and natural compounds with potential antiviral activities, all contributed to the defence against the pandemic.
These findings suggest that evergreen Mediterranean forests and shrubland plants have protected the southern population by emission of immuno-modulating VOCs and provision of dietary sources of bioactive compounds.
The study found that Mediterranean trees Laurus nobilis, Quercus ilex, Olea europaea, Daucus virgatus, Onopordum Illyricum, Pistacia vera, and Nerium oleander played important roles in releasing VOCs. Important VOCs released by these trees are oleuropein, lauricides, ethyl acetate, methanol extracts, monoterpenes, sesquiterpene, Kaempferol, flavonoids, phenolics, terpenes, β-pinene, 1,8-cineole, β-caryophyllene, sabinene and megastigmanes. These all VOCs were found to have a significantly high affinity for SARS-CoV-2 main protease Mopar, one of the most important targets in the anti-COVID-19 therapeutic strategies.
Recently in India, the CIMAP (Central Institute of Medicinal and Aromatic Plants) has developed immunity-booster “CIM-MEG19” from Andrographis paniculata, which is able to block ACE-2 receptors and helpful in defeating Covid-19. There should be such International initiatives to prepare antiviral medicines from bioactive compounds.
Last but not least; our duty towards trees
Trees mitigate air pollution, emit bioactive volatile organic compounds (VOC) and make strong the body’s immune system. The biodiversity of such medicinal plants serves as an excellent source of new antiviral drugs that can act on various biochemical pathways and lead to the development of novel and effective therapeutic drugs against viral diseases, including Covid-19. Researchers and the global scientific community should consider the treatment of SARS-CoV-2 infection through natural plant-based compounds from ethnomedicinal plants. These findings highlight the importance of nature conservation and the search for natural antivirals.
According to Global Forest Watch, the tropics lost 12.2 million hectares of tree cover in 2020. Of that, 4.2 million hectares, an area the size of the Netherlands, humid tropical primary forests are important for carbon storage and biodiversity. The resulting carbon emissions from this primary forest loss are equivalent to the annual emissions of 570 million cars (2.64 Gt CO2), more than double the number of cars on the road in the United States. Primary forest loss was 12% higher in 2020 than the year before, and the second year in a row that primary forest loss worsened in the tropics.
According to a study, just 3% of the world’s ecosystems remain intact with healthy populations of all its original animals and undisturbed habitat. This is really worrisome and not good for our future. Forests are our hope for life; land biodiversity totally depends on forests. Forests are sequesters of carbon dioxide and climate change warriors. Save them.
Nature loves you and works for you; it is our fundamental duty and fundamental right to work for nature and better earth, where all biodiversity lives with love, peace and unity.