Over 35 per cent of medicines available in the market are estimated to have originated directly or indirectly from natural products. Natural products are obtained from plants, animals, microorganisms, insects, and minerals. It is known that more than 8,000 species of medicinal plants are found in different parts of India. The use of medicinal plants in the treatment of diseases in humans and animals began in the early phase of an ancient civilisation.
One or several parts of a plant (root, stem, leaves, flowers, fruits, seeds, and bark) may contain different phytochemicals which are naturally produced in the plants as secondary metabolites for their defense against pathogens, harmful environmental conditions, the attraction of pollinators, etc. Alkaloids, flavonoids, saponin, tannin, glycosides, etc. are common phytochemicals known to possess medicinal properties. Nevertheless, some plants are sources of potent poisonous compounds (phytotoxins). Abrin is a potent poisonous compound present in the seeds of the rosary pea plant (Abrus precatorius). The toxin can inhibit protein synthesis and cause cell death. This plant is also available in many parts of Northeast India.
Ancient medicine and other known alternative medicines are primarily based on the use of medicinal plants. The medicinal value of a plant extract may be from a single bioactive constituent or a combined effect of several chemically different constituents. This gives a reason for the difficulty in deciding an exact dose of a crude extract in a patient as compared to a pure compound.
With the advancement in biomedical science and technology, scientists have succeeded in extraction, isolation as well as structural and chemical characterisations of several bioactive compounds from plants, microorganisms, animals, and other natural sources. This enables pharmacologists and other scientists to determine the therapeutic applicability of a pharmacophore (the main structural component in a compound attributed to a pharmacological effect). Studies of pharmacodynamic (drug action) and pharmacokinetics (drug movement inside the body) profiles of any compound reveal any potential for the improvement of the efficacy and safety of the compound through the production of semi-synthetic and/ or synthetic compounds.
Many plant-derived compounds are popularly being utilised in modern medical treatments and veterinary medicine. Opium is derived from an extract of the dried milky exudates from the unripe seed of poppy plants. Morphine is a potent pain reliever isolated and crystallised in pure form from opium. Unfortunately, many people illegally obtain morphine and its derivatives and misuse these important drugs for their euphoric and other effects often leading to increased morbidity and mortality from the overdose of the drugs across the globe.
Quinine, an important antimalarial drug used in the treatment of chloroquine-resistant and multidrug-resistant Plasmodium falciparum is an alkaloidal drug obtained from the bark of the South American Cinchona tree. The tree is also available in different states of India. Plants are the sources of many classes of anti-cancer drugs. Vincristine and other alkaloidal anticancer compounds are obtained from a flowering plant – the Periwinkle plant (Catharanthus roseus). Paclitaxel and docetaxel (from the bark of the Pacific yew tree), etoposide, teniposide (semisynthetic derivatives of podophyllotoxin from the rhizome of the wild mandrake), etc. are also important anticancer drugs. Bleomycin (a glycopeptide), dactinomycin (a peptide), etc. are important bioactive metabolites from microbes found in soil and water, clinically useful as anticancer drugs.
Atropine is one of the important preanaesthetic agents for its anticholinergic effects (increase heart rate, reduce GIT motility, reduce salivary, bronchial and other GIT secretions, etc.) during surgery. The compound is obtained from the Atropa belladonna plant commonly known as the deadly nightshade. This alkaloidal drug is also effectively used in the treatment of poisoning with pesticides (e.g. organophosphates, carbamates) and other toxic agents to reduce the excessive cholinergic effects of the poison such as sweating, vomiting, diarrhea, abdominal pain, decrease heart rate, difficulty in breathing due to respiratory tract obstruction with excessive secretion. However, the incidences of intoxication due to consumption of belladonna contaminated fodder is rarely reported in livestock and other animals.
Animals and microorganisms are also potential sources of therapeutic agents. Many vaccines, antivenoms, vitamins, hormones, minerals, and other clinically useful compounds are obtained from different species of animals. Antibiotics are secondary metabolites naturally synthesized in certain microorganisms to defend against other competing organisms.
Penicillin is the first antibiotic discovered serendipitously by Alexander Fleming in 1928 from the fungus Penicillium notatum. Consequently, many scientists started working on microorganisms and could succeed in discovering a few more novel classes of antibiotic, especially from the 1940s to the 1960s. The introduction of penicillin in 1945 followed by other classes of antibiotic for wide-scale use in the market marked the beginning of the golden era of antibiotics. Thereafter, a drastic shift that occurred in the production of drugs from new antibiotics to drugs used for chronic diseases like diabetes, cancer, hypertension, etc had resulted in less availability of different classes of antimicrobial agent for the treatment of infections. The consequent increase in the clinical application of antibiotic analogs popularly known as the ‘me too’ drugs has led to an acceleration in the development of antibiotic resistance.
Northeast regions of India are widely considered as potential sources of medicinal plants. Reports indicate the availability of more than 2,000 species of medicinal plants in different parts of Northeast India. Hilly regions are also popular for the availability of unique indigenous fruits and vegetables that are not and/or rarely available in other parts of the country. Initial findings from different
Research centers and Institutions in India indicated the richness in the contents of vitamins, minerals, antioxidants, and other useful phytochemicals in some of the indigenous vegetables and fruits. Black rice/ purple rice (Chakhao in manipuri) is a range of rice types of the species Oryza sativa, and is very popularly consumed in Northeast India, especially in the state of Manipur during traditional feasts. These varieties of rice are getting more attention recently from the scientific community because of their numerous health benefits. Black rice contains a high level of immune-boosting compounds. The level of anthocyanin (a type of flavonoid with an antioxidant effect) in black rice is reported to be even higher than in blueberries. Vitamins and minerals content in the rice are also known to be higher than most of the other rice varieties.
Scientific communities are now focusing on discovering any other potentially useful compounds in the rice. Similarly, Naga chili (Raja Mircha, also known as oo-morok in Manipuri) is getting attention from researchers for its medicinal values. This chili is a potential source of capsaicinoids –compounds known for their effectiveness in reducing body pain, swelling, obesity, etc.
Cannabis is a flowing plant commonly known only for its hallucinating and other psychotropic effects in man. Delta-9-tetrahydrocannabinol and cannabidiol are major components (cannabinoids) in the plant. The investigations on cannabinoids led to the discovery of the previously unknown important system- the endocannabinoid system (ECS) in our body in the early 1990s. This is a complex cell signaling system composed of endocannabinoids (endogenous compounds working as neurotransmitters) in the brain and peripheral tissues which are linked with several processes in our body.
Scientists across the globe have already reported the potentially useful effects of cannabinoids in neurodegenerative diseases in man and animals. There are hundreds of more compounds in the market that are clinically useful in the modern health care systems as well as other alternative medicines worldwide.
Until and unless the traditional knowledge (TK) and uses of medicinal plants are being brought to the scientific communities, and researchers, as well as research institutions are given access to the biodiversity for scientific research and innovations, it is less likely to explore any potentially useful active compounds in the plants. Exploration and identification of active constituents in plants are indispensable components of the drug discovery process.
Every community across the globe must cooperate sincerely and encourage scientific research activities to find any potentially useful medicinal plants. At the same time, proper acknowledgment of the associated region and community must be a part of any findings for the issues of geographical indications and other intellectual property rights. The rapidly changing environmental conditions of our planet are greatly influenced by human habitation and our developmental activities.
Destruction of nature and its resources has been occurring in a rapid manner which is evident in the form of deforestation for cultivation and habitation, construction of water dams in hilly regions for hydroelectric production that usually submerges vast forest areas, pollution of soil and water with industrial effluents, hospital waste, domestic sewage, etc. as well as pollution of atmospheric air with smokes containing thousands of toxic chemicals. Hence, there is a need to swiftly explore the rare plants, especially those plants indigenous to a specific geographical region for their medicinal values before they go extinct from the planet.
Equal importance needs to be paid to protecting microorganisms naturally found in the soil and water. The active compounds available in nature are mostly chemically and structurally complex and diverse and are either difficult to synthesize in laboratory conditions or time-consuming and expensive in production. So, it is judicious to continue exploring the compounds from natural products. Traditional medicines systems and other folk use of medicinal plants and other natural products still play an important role in modern drug discovery programmes.
Coordinated work between the two systems helps in shortening the time-gap between a drug discovery and its clinical application. Therefore, making people aware about the importance of natural products will definitely contribute greatly in discovering potential novel compounds from nature. More people will extend their hands in conserving medicinal plants and other natural sources only when they know about their medicinal values.
