INTRODUCTION, CLASSIFICATION AND QUALITY CONTROL OF NATURAL ORIGINATED DRUGS.
1.1.1 Definition
Plants from the natural sources are serves for the benefits of man kinds. The drugs that are procured from natural sources belong to the branch of Pharmacognosy. Earlier only the external morphological characters were used to identify a drug. At the beginning, Pharmacognosy had developed mainly on the botanical side, being particularly concerned with the description and identification of drugs, both in their whole state and in powder form. Modern aspects of Pharmacognosy include not only the crude drugs but also their natural constituents and derivatives. The word Pharmacognosy is derived from the Greek words “Pharmakon” (drug), and “gnosis” (knowledge). The term Pharmacognosy was used for the first time by the Austrian physician Schmidt in 1811 and 1815 by Crr. Anotheus Seydler, who first coined this term in his dissertation entitled ‘Analecta
pharmacognostica’. Pharmacognosy is closely allied to medicine, developed during early 19th century as a branch of Materia Medica and applied biology. Pharmacognosy is the study of drugs having their origin in plant and animal kingdom. The subject Pharmacognosy can also be expressed as an applied science that deals with biological, biochemical, therapeutic and economic features of natural drugs and their constituents. Pharmacognosy is a subject in which plant parts are identified or authenticated using macroscopical anatomical phytochemical characters. Therefore Pharmacognosy is “the science of medicines from natural sources”. In other way, Pharmacognosy is knowledge of the history, distribution, cultivation, collection, selection, preparation, commerce, identification, evaluation, preservation and use of drugs and economic substances that affects the health of men and other animals. During the 19th century and the beginning of the 20th century, “Pharmacognosy” was used to define the branch of medicine or commodity sciences, which deals with drugs in their crude, or unprepared form. Crude drugs are the dried, unprepared material of plant, animal or mineral origin and they are used as such as they occur in nature without any processing except, drying and size reduction for medicines. Plant originated crude drugs consist of entire plants or their parts. For example, Ephedra and datura are entire plants, senna leaves and podes, nux-vomica seeds, cinnamon and cinchona bark, Rauwolfia roots, clove is a flower bud. Crude drugs may also be obtained by physical processes like drying (opium) or extracting with water (catechu, agar). Several other useful substances affecting the health of animals and human being are also included along with crude drugs in the study of Pharmacognosy but have no pharmacological action. These substances include allergens, flavoring agents, colors, pesticides, immunizing agents, vehicles disintegrants, stabilizers, filtering and supporting media and diagnostic aids. Animal source originated crude drugs include beeswax, gelatin, wool fat, silk, vitamins etc. Some of the mineral originated crude drugs like talc, chalk, bentonite etc. are used in various pharmaceutical preparations. In addition, antibiotics, hormones etc. may also be involved. Marine organisms (plants and animals), which have special potent pharmacological actions, are recent focus in the search for new drugs. Study of the materials obtained from natural sources in pharmakognosie was first developed in Europe especially in German populated areas, while other language areas often used in the book named Materia Medica that taken from the works of Galen and Dioscorides. Drogenkunde (“science of crude drugs”), the German term is also used in the same way. As late as the beginning of the 20th century, Pharmacognosy is still in growing importance, particularly for identification and quality control purposes and resulted rapid development in all other areas in the subject. With above discussion, finally a brief definition of Pharmacognosy is described as: “It is a branch of science and a tool for crude drug standardization which deals with the scientific and systematic study of structural, physical, chemical and biological characters and evaluation of crude drugs along with geographical sources, history, method of cultivation, collection and preparation for the market, their proper storage and their application in the improvement of health.”
Hence, Pharmacognosy science is concerned with studying the following subjects:
1. Taxonomy of plants and the natural sources of drugs.
2. Distribution of natural products worldwide.
3. Description of plants such as Trees (Cinnamon, cinchona, Salix), shrub, (Vinca), Perennials (Peppermint).
4. The active constituents from natural sources (active groups) like (glycosides, alkaloids, volatile oils, tannins, etc.).
5. The biosynthesis and storage places of the active constituents in organisms (plants, animals etc.).
6. The part used from the natural sources in medicine and pharmacy such as leaf (Senna, Mint, Digitalis), roots (Liquorice), seeds (Nux Vomica, Coffee bean), bark (Cinnamon).
7. Collection and Storage of the part used. To understand the basic concept of Pharmacognosy, some general functions of Pharmacognosist is:
• Identification of the drug sources.
• Determination of the morphological character.
• Investigation of potency, purity, and admixture
. • Planning and designing of the cultivation of medicinal plants
. • Prescription of the detail processes of collection, drying and preservation
. • Knowledge about extraction and isolation procedures.
• Knowledge about active constituents, phytoconstituents, chemical nature and uses.
• Knowledge about physical, chemical, biological and microbial evaluation of drugs.
1.1.2 History
The early man sought to alleviate his sufferings of illness and injuries by using plants. They acquired knowledge of medicinal properties of plants by guesswork or trial and error, while searching for food, by superficial resemblance between the plant parts and the affected organs, i.e., by examining the “Signature of Nature”, by observing other animals, instinctive discrimination between toxic and palatable plants or by accidental discovery. In course of time a group of people emerged in each community who acquired expertise in collecting, testing and using medicinal plants for treating diseases. These people later became known as `Medicine Men’. They transferred this secret knowledge only to their trusted predecessors of the successive generations, who gradually increased the volume of knowledge about drugs and their medicinal uses. Initially the transfer of the acquired knowledge from generation to generation used to be done verbally by the use of signs and symbols. As civilization progressed, transfer and recording of the knowledge were done in writing. According to Old History: The history of herbal medicine is from the beginning of human civilization. In that era, maximum plant based medicines were used. Before the beginning of Christian era, many ancient documents revealed that plants were used largely by the Asian namely China, India, Egypt and Greece. In China, medicinal plants had been in use since 5000 BC. In around 3000 BC, Shen Nung wrote a book on herbal document “Pentaso”which is very old documentary book. During the same period, meticulous efforts had been progressing in India, for classification of herbs through proper examination. Finally, Charaka made 50 groups of 10 herbs, each of which was meant for specific diseases whereas Sushrutha enlisted only 760 herbs in 7 groups, based on their common properties.
In India, the medicinal properties of the plants are first described in two Vedas, Rigveda and in Atharvaveda (3500-1500 B.C) from which Ayurveda has developed. The earliest plant medicines used in the Ayurvedic system were described with a list of 127 plants. The binomial classification of plants, introduced by Swedish botanist Carl Linnaeus in 1700s, was further developed by Bentham and Hooker (1862-1863). Gregor Mendel’s important observations on plant hybrids came in 1865. Soon microscope was introduced as an important analytical tool; techniques like clearing, staining, mounting etc. came in to focus. Thus, anatomical atlas of crude drugs was published in 1865. In the 20th century, tremendous work was been done in this field and Phytochemistry evolved as a distinct branch in science. Constituents isolated from the plants were not only used as such, but they were also used for semi-synthetic and synthetic drugs. This section has tried to give basic information about origination of Pharmacognosy so that readers can get an idea about the history of the same.
Contribution of the Scientists in Significant Development of Pharmacognosy: Hippocrates (460-370 B.C), a Greek scientist, is known as the father of medicine. He worked on human anatomy and Physiology, particularly circulatory system and nervous system. He prepared famous oath for physicians, which is still taken by them. Further Aristotle (384-322 B.C) and Theophrastus (370-287 B.C), well known philosopher and scientist are known for their writing animal and plant kingdom respectively. Dioscorides (1st
Century AD), a Greek Physician, published five volumes of a book, entitled “De Materia Medica” in 78 AD, in which the described more than 600 medicinal plants with their collection, storage and uses. Pliny de Elder (23-70 AD), a Greek botanist, collected and described a large number of medicinal plants with their uses.
Modern Pharmacognosy:
The development of modern Pharmacognosy began during the period of 1930-1960 by the application of a broad spectrum of biological and socio-scientific subjects, including botany, ethno botany, medical anthropology, marine biology, microbiology, herbal medicine, chemistry, biotechnology, phytochemistry, pharmacology, pharmaceutics, clinical pharmacy and pharmacy practice along with modern analytical techniques like paper and thin layer chromatography (TLC), gas chromatography (GC), High performance liquid chromatography (HPLC), Extreme and ultra-pressure liquid chromatography (XLC, UPLC), high pressure thin layer chromatography (HPTLC), Mass spectroscopy, Liquid chromatography combined with mass spectroscopy (LC/ MS), High Resolution Mass Spectroscopy (HRMS) etc. During this period isolation, structure elucidation and various pharmacological activity of different phytoconstituents were studied. Examples like isolation of penicillin in 1928 by Alexander Fleming from microorganisms and later on commercial production of the same in 1941 by Florey and Chain. Gradually, other antibiotics were isolated and their chemistry was studied and among them streptomycin, chloramphenicol, tetracycline are most important. Some of the important isolated constituents are reserpine from Rauwolfia root (responsible for anti-hypertension action), vincristine and vinblastine from vinca plant (responsible for treatment of leukemia), digitoxin from digitalis plant (only one potent cardiac drug which is used directly as an allopathic medicine), morphine (a potent analgesic) and codeine (a potent antitussive) isolated from dried latex of Opium poppy, ergotamine from ergot (have potent oxytocic activity) etc. Several steroidal hormones were also isolated from plants. E.g., progesterone from diosgenin (from dioscorea plant). Gradually biosynthetic pathways were also identified with the help of radioisotopes for the study of accumulation and synthesis of primary and secondary metabolites. Some of the important pathways are Calvin’s cycle for photosynthesis (biosynthesis of carbohydrate, a primary metabolite), shikimic acid pathway for synthesis of aromatic compounds, acetate pathway for anthracene glycoside synthesis, isoprenoid pathway for synthesis of terpenes and steroids etc. Development of structure activity relationship of the phytoconstituents helped in the identification of the structure of the constituents, as well as effects of addition or deletion of the organic or inorganic groups in the mother structure. This tracer study is also useful to make derived plant products through biotransformation which shows more therapeutic
1.1.3 Scope of Pharmacognosy
India also has a diverse cultural heritage due to its biodiversity. Though at present Indian health care delivery consists of both traditional and modern systems of medicines, both organized traditional systems of medicine like Ayurveda, Siddha and Unani and unorganized systems like folk medicine have been flourishing well. Ayurveda and Siddha are of Indian origin and account for about 60% health care delivery in general, and 85% of rural Indian population depends on these traditional systems. It is estimated that roughly 1500 to 1600 plant species in Ayurveda and 1200 to 1500 plant species in Siddha have been used for drug preparation. In Indian folk medicine use, about 7500 to 9,000 plant species are recorded as medicinal plants. In 1998 the latest figures available for Europe, the total OTC market for herbal medicinal products reached about $ 6 billion, with consumption for Germany of $ 2.5 billion, France $ 1.6 billion and Italy $ 600 million. In the US, the market for all herb sales reached a peak in 1998 of $ 700 billion. Medicines became a huge business with an annual growth of 6-9% and it is presently estimated that global sales of pharmaceuticals will top in 2017 with $ 1.5 trillion. Hence the demand of herbals is increased gradually in the world market especially in India. The scope of Pharmacognosy has expanded from the traditional morphological description of plants and other organisms, to encompass the most modern aspects of molecular science relating to the exploration of naturally occurring bioactive compounds, their mode of action and their applications in world market and to the social activities. Nature is a source of bioactive products from which new drugs have been developed and marketed. Hence by understanding and exploiting the biodiversity, it is essential to establish integrative programs like conservation of species, bioactivity, chemical analysis, chemical synthesis and their proper storage. This is clearly mentioned in the below Fig. 1.1.
The extraction of active compounds from various plants and parts of plants and their utilization has revolutionized the health sciences.
(c) In the pharmaceutical industry, various herbal drugs are used in drug manufacture process includes:
• Aloe Vera used for healing burns and wound healing.
• Blackberry (Rubus fruticosus) reduces the wrinkling of skin, aging effect.
• Digitoxin (Digitalis purpures) used for the cardiac diseases.
• Calendula (Calendula officinalis) used for the treatment of constipation and cramps.
• Echinacea (Echinacea angustifolia) used for action against rhinovirus colds.
• Grapefruit (Naringenin) used for obesity treatment.
• Green tea (Camelia sinensis) cures the breast cancer.
(d) The revolution in herbal medicine has increased the demand for research in Pharmacognosy with concern to:
• Quality Control to assure the identity, purity and uniform consistency of drug substances
. • Efficacy to determine the therapeutic effects, indications, clinical aspects and pharmacological effects.
• Safety research to study the adverse toxic reactions, drug interactions, contraindications and precautions. With the view of above applications of Pharmacognosy is linked with various allied sciences.
Link between Pharmacology and Medicinal Chemistry Pharmacognosy gives a sound knowledge of the vegetable drugs under botany and animal drugs under zoology. It also includes taxonomy, breeding, pathology and genetics of plants. Pharmacognosy knowledge helps to improve the cultivation methods for both medicinal and aromatic plants. Now-a-days photochemistry (plant chemistry) has undergone significant improvement. This includes a variety of substances that are accumulated by plants and synthesized by plants. Newly detected plant drugs (purified phytochemicals) are converting into medicines. Pharmacognosy is essential for drug discovery because crude drugs are used for the preparation of galanicals or as sources of therapeutically active metabolites. Phytopharmaceuticals, i.e., synthesized drugs are finally formed in a suitable dosage forms and in which the crude drugs can act as an intermediates (Fig. 1.2).
0 टिप्पणियाँ