Ever since the beginning of human civilization, plants have been one of the main sources of medication. Despite significant advances in the field of allopathy during the 20th century, plants remain one of the world's major sources of drugs in modern as well as conventional medicinal systems.
Approximately one-third of all pharmaceuticals are derived from the plants as well as from fungi and bacteria but over 60% are plant-based. Plants can have bioactive components such as alkaloids, glycosides, hormones, phenols, tannins, antioxidants and other classes of compounds that have anti-cancer, anti-malarial, anti-helminthic or anti-dysenteric medicinal behaviour, etc.
Many of the essential oils are often commonly used as medicines and even dyes, latex and vegetable oils. Only a small proportion of the approximately 4,50,000 higher plant species available have been investigated for medicinal properties and even a smaller percentage of plants develop well-defined medicines. The same is true of smaller plants and plants of marine origin.
Thus, given the huge number of species available in the world, the awareness of plant constituents obtained so far is still meager. Approximately, only 10% of the organic constituents of plants are reported to be known and the remaining 90% are yet to be explored.
Lower plants such as lichens, ferns, algae, etc. are just a very limited proportion of Indian medicinal plants. The bulk of medicinal plants are higher plants. Fabaceae, Euphorbiaceae, Asteraceae, Poaceae, Rubiaceae, Cucurbitaceae, Apiaceae, Convolvulaceae, Malvaceae, and Solanaceae are the main families in which medicinal plants occur.
Drugs are obtained from trees, shrubs, herbs, and also from primitive plant forms that do not fall into the categories above. They are produced from fruits (Senna, Solanum viarum, Datura, etc.), flowers (Butea monosperma, Bauhinia variegata), leaves (Senna, Datura, Periwinkle, Tylophora, etc.), roots (Rauvolfia, Periwinkle, Ginseng, etc.), seeds (Isabgol, Abrus, Nux vomica) and also bark (Liquorice, Ginger, Dioscorea, Costus, Cinchona).
Since time immemorial, plants have been connected with humanity's wellbeing. Archaeological findings in Iraq from 60,000-year-old Neanderthal burial grounds point to the use of many plants that still occur in folk medicine, such as marshmallow, yarrow and groundsel.
Mexican Indians have been known to have used peyote cactus for thousands of years because of its hallucinogenic and probably also its healing properties. This plant is now known to have antibiotic properties as well. The use of opium, liquorice, thyme, mustard and the chemical element Sulphur as medicine was recorded in cuneiform writing on clay tablets by the Sumerians of the Tigris and Euphrates (present day Iraq) around 4000 BC. In their formulations, the Babylonians, who apparently followed the Sumerians in this region, added Senna, Coriander, Saffron, Cinnamon and Garlic among the other herbs.
The practices of indigenous systems of medicine in India are based mainly on the use of plants. Charaka Samhita (1000 BC-100 AD) records the use of 2000 plants for remedies. ‘Ephedra’ a plant used in China 4000 years ago is still mentioned in modern pharmacopoeias as the source of an important drug, ephedrine.
The plant Sarpagandha (Rauvolfia serpentina) which was well known in India as a remedy for insanity is in existence today for curing mental ailments. Quinine, another important anti-malarial drug of modern medicine, was obtained from the cinchona tree. The ancient Egyptian Ebers Papyrus lists over 800 plant medicines such as aloe, cannabis, castor bean, garlic, juniper and mandrake.
From ancient times to the present, Ayurvedic medicine as documented in the Atharva Veda, the Rig Veda and the Sushruta Samhita has used hundreds of pharmacologically active herbs and spices such as turmeric, which contains curcumin. The Chinese pharmacopoeia, the Shennong Ben Cao Jing records plant medicines such as chaulmoogra for leprosy, ephedra, and hemp. In around 60 AD, the Greek physician Pedanius Dioscorides, working for the Roman army, documented over 1000 recipes for medicines using over 600 medicinal plants in De materia medica.
In the Islamic Golden Age, scholars translated many classical Greek texts including Dioscorides into Arabic, adding their own commentaries. The Early Modern period saw the flourishing of illustrated herbals across Europe, starting with the 1526 Grete Herball. John Gerard wrote his famous The Herball or General History of Plants in 1597.
The place of plants in medicine was radically altered in the 19th century by the application of chemical analysis. Alkaloids were isolated from a succession of medicinal plants, starting with morphine from the poppy in 1806, and soon followed by ipecacuanha and strychnos in 1817, quinine from the cinchona tree, and then many others.
Synthesis of a substance first discovered in a medicinal plant began with salicylic acid in 1853. Drug discovery from plants continued to be important through the 20th century and into the 21st, with important anti-cancer drugs from Yew and Madagascar periwinkle.
Plants have been used by the mankind since prehistoric times for getting relief from sufferings and ailments. Investigations in the field of pharmacognosy and pharmacology have provided valuable information on medicinal plants with regard to their availability, botanical properties, method of cultivation, collection, storage, commerce and therapeutic uses. In addition, no cumulative derogatory effect has been recorded in most medicinal plants and that is why many of the medicines obtained from plants are still widely used today depicting that the popularity of herbal medicines is gaining momentum.
Besides, following are some of the reasons that make the large scale cultivation of medicinal plants inevitable:
• Cultivation of medicinal plants enables us to obtain raw material of homogenous quality with high potency.
• It is easy to grow and fulfill the commitment of large-scale demand through cultivated sources.
• The increasing pressure of population and the development of roads into remote areas have resulted in deforestation and the eventual loss of natural plant resources.
• In many cases, the important plant parts used are roots or the entire plant, results in destructive collection/ extractive methods, which results in the extinction of many species and ecotypes.
• Despite the fact that our forests are the major resource base for medicinal plants as many of them appear in wild, the importance of conservation has not been clearly spelt out.
• The unauthorized collection of minor forest produces by persons who are led by the burgeoning demand for raw medicinal plant parts has led to the deprivation of the rights and opportunities of the forest-dwelling communities.
• Since government of India provides policy support for promoting Indian system of medicine, the pharma industries look for organized supply of quality raw materials in larger quantities.
• The World Health Organization (WHO) has emphasized the need for better utilization of the indigenous system of medicine, based on the locally available medicinal plants in the developing countries.
• Medicinal plants and their derivatives will continue to play a major role in medical therapy in spite of advances in chemical technology. For example, in Vitamin A, diosgenin and solasodine of plants, where stearic forms are possible, chemical synthesis yields a mixture of the isomers which may be difficult to separate and may therefore be toxic or have a different therapeutic effect than what is obtained in nature.
• Drug development out of medicinal plants is less costly than synthetic drug development.
• The vast range of agro climatic conditions in India, varying from alpine/mild temperate to tropical regions with abundant rains and sunshine make it an ideal place for the luxuriant growth of flora.
• There has been a tremendous upsurge in the demand for phytopharmaceutical raw medicinal herbs and vegetable drugs of Indian origin from the Western nations.
• India is the possessor of an impressive medical heritage which encompasses various systems of medicine, viz., Ayurveda, Siddha, Unani, folklore and grandma medicine. India has an invaluable treasure trove of various scriptures on diverse medical systems.
Although India is a leading exporter of medicinal plants in the world, the rate of growth of these crops in relation to their economic prospects is not at all satisfactory. The reasons for this apparent backwardness are many and varied like:
• So far, there has been no organized research set-up to continually recharge scientific inputs in order to make their cultivation not only economically viable but also more profitable, so that they can claim their due share in the cropping systems of the country.
• In spite of the thrust given by the government of India through the institutions like the Centre for Medicinal and Aromatic Plants (CIMAP), the Regional Research Laboratories (RRL), at Jammu, Bhubaneshwar and Jorhat, Directorate of Medicinal & Aromatic Plants (DMAPR), National Botanical Gardens, Forest Research Institutes, state Cinchona Directorates in Tamil Nadu and West Bengal, the replenishment of renewable inputs like quality planting material of improved varieties, developing extension literature, organizing training and quality testing, are very limited because of the number of medicinal plants as well as their divergent uses.
• The other major constraint is marketing of the cultivated raw material because of the quality considerations. Lack of testing facilities at the procurement and trading centres together with unscrupulous market handling, results in wide fluctuations in prices, often going down to uneconomic and unrealistic levels.
• The systematic cultivation of a few medicinal plants has been found to be a discouraging enterprise, mainly because of the uneconomical price they command.
• Although most of them are industry-oriented crops, the pattern of land-holdings does not lend itself for commercial cultivation on an extensive scale.
• Unstable market conditions have also kept farmers away from taking up cultivation of these crops.
• In the phytopharmaceutical industry, presently, no quality standards have been fixed, either for the raw material or the final product and, as such, one finds wide variation in the quality specifications.
• Difficulty in proper identification of medicinal plants has led to the use of adulterants or mimics.
• The package of practices for number of medicinal plants has not been standardized to suit different agro ecological conditions.
• In a number of cases the produce has to be used fresh for which instant transportation is a must, and in many cases, it cannot be stored for long periods as this would entail fumigation which at times, results in chemical contamination of the raw material and eventually the final product, because of its residual effect.