World is facing Covid19; it is caused by the coronavirus SARSCoV2. Coronaviruses (CoVs) are single-stranded positive sense RNA viruses and were first reported in 1960. In humans, only seven types of human-CoVs (HCoVs) exist that can infect humans; these are- 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. SARS-CoV-2 infection (COVID-19) is destroying the world economy, social life, and human lives with an increased mortality rate each day. 

Plants are source of antiviral bioactive compounds 

There is no specific drug currently available to cure COVID-19 infection. But, there are many medicinal plants which have bioactive molecules having antiviral properties. 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 protease), 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. The bioactive compounds of these medicinal plants are a ray of hope to develop drugs against SARS-CoV-2 infection. 

The antiviral bioactive compounds includes coumarin, saponins, glycosides, phenols, tannins, flavonoids, carotenes, lycorine, quercetine, polyphenols, terpenes, sterols, chlorogenic acid, mangiferin, astragalin, trifolin, sinigrin, β-sitosterol, hesperetin, vitamin C, isoquinoline alkaloids, emodin, alliin, allicin, ajoenes, vinyldithiins, catechol, p-hydroxybenzoic acid, caffeine, catechin, pyrogallol, gallic acids, resveratrol, rutin, caffeic acid, Tomentin E, cinnamon amides etc. 

These antiviral bioactive compounds have been reported from many plants especially Radix bupleuri, Lycoris radiata, Artemisia annua, Pyrrosia lingua, Isatis indigotica,  Torreya nucifera, Lindera aggregate, Rheum palmatum, Polygonum multiflorum, Cerasus avium, Alcea digitata, Citrus aurantium, Allium sativum, Quercus infectoria, Onopordum acanthium, Berberis integerrima, Crataegus microphylla, Andrographis paniculata, Alnus japonica, Psoralea corylifolia, Paulownia tomentosa, Tribulus terrestris, Sambucus nigra, Eleutherococcus senticosus, Salvia miltiorrhiza, Acacia arabica, Ocimum sanctum, Ocimum basilicum, Theobroma cacao, Pelargonium sidoides, Taraxacum officinale, Illicium oligandrum, Glycyrrhiza glabra, Angelica keiskei, Polygala karensium, Calophyllum brasiliense, Cimicifuga foetida, Boerhavia diffusa, Terminalia chebula, Caesalpinia sappan etc. 

Role of trees in controlling Covid-19 cases in South Italy, in the year 2020

In northern Italy, particulate matter (PM) played important role in spreading Covid-19 where COVID-19 disease provoked the highest number of victims in the country, as well as one of the most worrying situations worldwide, and 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 into respiratory distress. 

In a recent study on lower COVID-19 mortality in Italy’s forested areas 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 viruses and positive effects on the human immune system. Persons living in southern Italy received positive effects on the human immune system. 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 VOC reported from South Italy’s forests were Borneol, bornyl acetate, 1,8-cineole, terpineol, α-pinene, β-caryophyllene, β-pinene, oleuropein, lauricides, ethyl acetate, methanol extracts, monoterpenes, sesquiterpene, Kaempferol, flavonoids, phenolics, sabinene and megastigmanes.

It was also found that the pandemic’s severity was generally lower in southern regions, especially those areas which have 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. 

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. 

According to the study, the 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. 

Antiviral Bioactive Compounds From Indian Trees 

Many Indian flora have shown antiviral bioactive compounds and VOCs; some of the important one are: Aglai roxburghiana, Vicoa indica, Acacia auriculiformis, Cassia fistula, Olex polyama, Senecio tenuifolius, Zingiber capitatum, Phyllanthus amarus, Picrorhiza kurroa, Adansonia digitata, Aloe vera, Andrographis paniculata, Aglai odorata, Atlantia, Curcuma longa, Acacia nilotica, Acacia tortilis, Alpinia galanga, Ailanthus allisima, Anisomeles indica, Glycyrrhiza glabra, Agrimonia eupatoria, Alpinia officinarium, Avicennia marina, Azadirachta indica, Hibiscus sabdariffa, Aristolochia bracteolate, Alstonia scholaris, Cassia fistula, Eucalyptus sp., Ficus benghalensis, Ficus religiosa, Mangifera indica, Melia azedirach, Syzygium jambolanum, Psidium guajava, Morus alba, Lantana camara, Hibiscus rosasinensis, Ficus glomerata, Dalbergia sissoo, Casuarina equisetifolia, Adhatoda vasica & Aegle marmelos. 

Several Indian mangrove plants including Ceriops decandra, Excocaria agallocha, Rhizophora lamarckii, Rhizophora mucoranata, Rhizophora spiculata have been reported to exhibit potent antiviral activity.

So, Protect Earth’s Biodiversity

Trees release life saving antiviral bioactive compounds and VOCs. Foliar emission of VOC has been reported in many plants of angiosperms, bryophytes, ferns and gymnosperms (conifers). But anthropogenic activities are destroying the ecosystem of Earth, forests and biodiversity.

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. This is really worrisome and not good for our future. Forests are our hope for life; land biodiversity totally depends on forests. Forests are biosequesters 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 a better earth, where all biodiversity lives with love, peace and unity. Trees are the soul and source of life on Earth, save trees.

Note: This article has been written only to cause awareness.