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    Pharmacognostical characterization of some selected medicinal plants.
    By Ashwani Kumar | November 5th 2009 04:01 AM | Print | E-mail | Track Comments
    About Ashwani

    Professor Emeritus ,Former Head of the Department of Botany, and Director Life Sciences, University of Rajasthan, Jaipur. 302004, India At present...

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    Pharmacognostical characterization of some selected medicinal plants. History of Pharmacognosy: In the early period primitive man went in search of food and ate at random plants or parts of plants like tubers, fruit, leaves etc. If the found that no harmful effects were observed he considered it as edible and used as food. If he found that by eating other actions were found it was considered inedible and according to the action he used in treating symptoms or diseases. If it caused diarrohea it was used as purgative, if vomitting it was used as emetic and if it was found poisonous and death was caused he used it as arrow-poison. The knowledge was empirical and obtained by trial and error. He used drugs as such or as infusions and decoction of the drugs. The results were passed from one generation to another generation and new knowledge was added in the same way. In India knowledge of medicinal plants is very old and medicinal properties of plants are described in Rigveda and in Atharvaveda (3500-1500 B.C.) from which Ayurveda is developed. In Ayurveda the ancient well-known treatises are Charak Sanhita dealing mostly with plants and Susrut Sanhita in which surgery is also mentioned. In Egypt people were familiar with medicinal properties of plants and animals. They were familiar with human anatomy and knew of embalming the dead and preserving their bodies as described in Papyrus Ebers (1550 B.C.) an ancient book found in one of the mummies. Greek scientists contributed much to knowledge of natural history. Hippocrates (460-370 B.C.) is referred to as father of medicine and is remembered for his famous oath which is even now administered to doctors. Aristotle (384-322 B.C.) was a student of Plato and philosopher and is known for his writing on animal kingdom which are considered authoritative even in twentieth century. Theophrastus (370-287 B.C.) a student of Aristotle wrote about plant kingdom. Dioscorides a physician living in first century A.D. described medicinal plants some of which like Belladonna, Ergot, Opium, Colchicum are used even today. Pliny wrote 37 volumes of natural history and Galen (131-200 A.D.) devised methods or preparations of plant and animal drugs known as ‘galenicals’ in his honour. Pharmacy starting from medicine, separated and materia medica the science of material medicines describing collection, preparation and compounding emerged. As mentioned earlier in 1815 Seydler introduced the name pharmacognosy. Even up to the begining of 20th century pharmacognosy was more a descriptive subject mainly of botanical science and consisted of identification of drugs both in entire and powdered condition and their history, commerce, collection, preparation and storage. Period 1934-1960 : The development of modern pharmacognosy book place later during the period 1934-1960 by simultaneous application of disciplines like organic chemistry, biochemistry, biosynthesis, pharmacology and modern methods and techniques of analytic chemistry including paper, thin layer and gas chromatography and spectrophotometry. The substances from the plants were isolated, their structure elucidated and pharmacologically active constituents studied. The development was mainly due to following four events: (i) Isolation of penicillin in 1928 by Fleming and large scale production in 1941 by Florey and Chain. (ii) Isolation of reserpine from Rauwolfia roots and confirming its hypotensive and tranquillising properties. (iii) Isolation of Vinca alkaloids especially vincristine and vinblastine. Vincristine was found useful in the treatment of leukeemia. These alkaloids have also anticancer properties. (iv) Steroid hormones like progesterone were isolated by partial synthesis from diosgenin and other steroid saponins by Marker’s method. From progesterone by microbial reactions, cortisone and hydrocortisone are obtained. Progress from 1960 onwards: During this period only a few active constituents mainly antibiotics, hormones and antitumour drugs were isolated or new possibilities for their production were found. From 6- amino penicillianic acid which has very little antibiotic action of its own but from which important broad spectrum semi-synthetic penicillins like ampicillin and amoxicillin were developed. From ergocryptine alkaloid of ergot, bromocryptine has been sybnthesised. Bromocryptine is a prolactine inhibitor and also has activity in Parkinson's disease. By applications of several disciplines pharmacognosy from a descriptive subject has developed into an integral, important discipline of pharmaceutical sciences. Diseases are born with man and drugs came into existence since a very early period to remove the pain of diseases and to cure them. Thus, the story or history of drugs is as old as mankind. Drugs used in medicine today are either obtained from nature or are of synthetic origin. Natural drugs are obtained from plants, animals or mineral kingdom. Drugs made from micro-organisms like antibiotics were not known in the early period. Synthetic drugs (or syntheticals) like aspirin, sulpha drugs, some vitamins and some antibiotics are synthesized in laboratories from simple chemical (or chemicals) through various chemical reactions. Natural drugs obtained from plants and animals are called drugs of biological origin and are produced in the living cells of plants or animals. Pharmacognosy is the study of crude drugs obtained from plants, animals and mineral kingdom. Even though the science of pharmacognosy is practised since a very early period, the term pharmacognosy was first used by Seydler, a German scientist, in 1815 in his book Analecta Pharmacognostica. It is derived from two Latin words pharmaka (a drug) and gignosco (to acquire a knowledge of). It means a knowledge or science of drugs. Crude drugs are plants or animals or their parts which after collection are subjected only to drying or making them into transverse or longitudinal slices or peeling them in some cases. Most of the crude drugs used in medicine are obtained from plants and only a small number comes from animal and mineral kingdom. Drugs obtained from plants consist of entire plants or their parts. Ergot, ephedra and datura are entire plants while senna leaves and pods, nux vomica seeds, ginger rhizomes and cinchona bark are parts of the plants. Though in few cases as in lemon and orange peels and in colchicum corm drugs are used in fresh condition, most of the drugs are dried after collection. Crude drugs may also be obtained by simple physical processes like drying or extraction with water. Thus the aloe is dried juice of leaves of aloe species, opium is the dried latex from poppy capsules and black catechu is the dried aquous extract from the wood of Acacia catechu. Further drugs used by doctors or pharmacists, directly or indirectly, like cotton, silk, jute, nylon in surgical dressings or kaolin, diatomite used in filtration of turbid liquids or gums, wax, gelatin, agar used as pharmaceutical auxiliaries or flavouring or sweetening agents or drugs used as vehicles or insecticides are treated in pharmacognosy. Drugs obtained from animals are either glandular products, like thyroid organ or extracts like liver extract. Simlarly, fish liver oils, musk, bees’ wax, certain hormones, enzymes and antitoxins are products obtained from animal sources. Drugs from mineral kingdom are kaolin, chalk, diatomite, the well- known Makardhwaj and other bhasmas of Ayurveda. A systematic and complete study of the drugs is done in pharmacognosy. In the systematic study of crude drugs (a). origin, common names, biological source and family; (b). geographical source; (c) history; (d). cultivation, collection, preparation for market and storage; (e) macroscopical, sensory and microscopical characters; (f). chemical constituents; (g). uses; (h). substitutes and adulterants and (i). evaluation are described. Each drug is always obtained from the same plant or animal. The Latin name of the plant or animal is called its botanical or zoological source. The family to which this plant or animal belongs is also mentioned, e.g. Vasaka leaves are obtained from Adhatoda vasica plant; family Acanthaceae. Vasaka leaves are included in the Indian pharmacopoeia and are called official leaves. Their botanical source is called official source. Geographical source or habitat gives us information about the country or place where the drug is produced. Ginger is produced in Jamaica and nux vomica and ispaghula in India. In some cases the original native place of a drug is not the same as the present geographical source, e.g. cinchona is a native of South America and is at present cultivated in Indonesia, India and Congo. History of the drugs gives us useful information about how the drug was known, where it was growing originally and how it was introduced into the modern medicine. History of some drugs like cinchona bark, coca leaves, rauwolfia root and opium is very interesting. Politics play its part in the drugs also. Thus there is restriction on the import of buchu leaves growing in South Africa because of our political relations with that country. One of the requirements of the drugs is that they should possess maximum activity and thus should contain maximum percentage of active chemical constituents. For this reason many of the drugs like digitalis leaves, belladonna herb and roots, Ceylon cinnamon bark, linseed, fennel and other umbelliferous fruits are obtained from cultivated plants only. In cultivation attention is paid to the selection of proper strains of seeds, type of soil, optimum climatic factors like light, temperature, elevation, rainfall, etc. so that strong and sturdy plants rich in active chemical constituents would grow. The crude drugs obtained in this way are usually more active. Drugs are collected during definite season, time of the day and in special condition at a definite stage of development. Thus ephedra, wild cherry bark, most of the subterranean drugs consisting of roots and rhizomes are collected in autumn. Leaf drugs are collected during the flowering season. Solanaceous herbs like hyoscyamus, belladonna etc. are collected in the morning and during the dry weather. Clove is collected in bud condition, santonica when flower heads are closed, chamamile flowers when fully expanded and coriander fruits when completely ripe. However, some of the drugs, mostly because of economic considerations, are obtained from wild plants. Thus gentian root in Europe, nux vomica seeds in India and strophanthus seeds in Africa are obtained from wild plants. Crude drugs consist of definite parts of the plants, e.g. leaf, flower, fruit seed, wood bark, root etc. Morphological or macroscopical description of these parts is undertaken with naked eye or with magnifying lens. In this description general condition of the drug, size, shape, outer surface, inner surface, fracture etc. are described. Thus each part of the plant is described to a definite system characteristic of each group. Drugs can be identified as above only if they are in entire condition. Sensory or organoleptic characters describe colour, odour, taste, consistency etc. By the sensory characters often useful information is obtained. If leaf drugs are not thoroughly dried they are though, or flexible but if over-dried they become brittle. If leaves, flowers, and some herbs like lobelia are dried directly in the sunlight they become pale, bleached and yellow but retain green colour if dried in shade. Different species of mentha can be determined by an experienced worker by smell only. In ergot rancid and ammoniacal odour indicates inferior drug. Taste tells us about bitter drugs like nux vomica and pungent drugs like ginger and capsicum. If the drugs are in broken or even in powdered condition their microscopic characters are studied by use of microscope. In case of leaves, surface preparation and transverse section, preferably through mid-rib, are made and nature of epidermis, trichomes, stomata, arrangement of tissues like palisade cells, vascular bundles and nature of cell-contents are studied Similarly in case of barks, roots, rhizomes and wood, transverse and longitudinal sections are made and from characteristic arrangement of tissues of each drug and from diagnostic elements like stone cells, fibres, vessels etc. the drugs are identified. The diagnostic elements persist even when the drugs are in fine powdered condition and help in identification of the drugs. The sections or the powdered drug samples are cleared by clearing agents, mostly by chloral hydrate solution, before mounting on the slide. The basic chemical nature of cell-wall of almost all the plants is cellulosic. However, lignin, suberin, cutin or mucilage are deposited to the cellulose. Cellulose gives blue colour with chlor-zine iodine solution or with cuoxam (copper-oxide-ammonia) reagent. Lignin is present in the middle lamella and secondary cell-walls of many vessels, fibres and scleroids and gives red colour with phloroglucinol and concentrated hydrochloric acid. Suberin is present in cork and endodermis cells while cutin in the cuticle of leaf. Both are fatty in nature and when heated with Sudan red III give red colour. Mucilage gives red colour with ruthenium red. The chemical constituents present in the drugs can be identified by chemical or micro-chemical tests. Cascara bark and rhubarb rhizome give with 5% potassium-hydroxide red colour because of anthraquinone derivatives. Strychnine present in nux vomica gives purplish-red colour with ammonium vanadate and concentrated sulphuric acid. Paper chromatography and thin layer chromatography are utilized in identification of drugs, their adulterants and their chemical constituents. Methods have been developed for quantitative estimation of the chemical constituents from paper and thin layer chromatography. Drugs contain chemical constituents in different proportions which give us information about active and other constituents. Thus quinine is an alkaloid present in cinchona bark; eugenol is a constituent of clove oil; wild cherry bark contains cyanogenetic glycosides; jalap and podophyllum contain resins and mucilage is the chemical constituent of ispaghula and linseed. The study of pharmacognosy also includes the use of drugs and the pharmacological action of their chemical constituents. Thus cinchona bark is used in malaria, rauwolfia root in high blood-pressure and in insanity, digitalis in cardiac diseases etc. Some drugs or their products have pharmaceutical applications, e.g. starch as distintegrating agent in tablets, gum as binding and suspending agent, agar as emulsifier and diatomite for filtration. Sometimes crude drugs are adulterated. An adulterant is the drug resembling the original or authentic drug but usually quite different or inferior, less effective, containing less percentage of active constituents and sometimes containing more extraneous matter than permitted.. Nature of adulteration can be determined by the study of pharmacognosy. Evaluation of the drugs means determining their identity, purity and quality or activity. According to Claus evaluation can be expressed through (a). orgamoleptic and morphological evaluation, (b). microscopical evaluation, (c). biological evaluation, (d) physical evaluation and (e) chemical evaluation. In organoleptic evaluation macroscopical and sensory characters are mentioned. In microscopical evaluation, microscopic characters of drugs are described. In biological, physical and chemical evaluation quality or activity of the drug is determined. In the study of pharmacognosy drugs are arranged according to the following systems of classification: (1) Morphological classification, (2) Biological (Taxonomical) classification, (3) Chemical classification, and (4) Pharmacological classification. In morphological classification drugs are arranged according to their morphological or external characters. Thus all leaves like digitalis, senna and vasaka are grouped under leaf drugs; and barks like cinchona, cinnamon and kurchi in bark drugs. Similarly seeds, fruits, subterranean parts are arranged. Dr. Wallis, a great exponent of this classification , says that if pharmacognosy is to be an independent science, drugs should be classified according to some inherent or intrinsic properties of the drug. This classification is useful in teaching of practical pharmacognosy. In modern pharmacognosy the importance of this classification is decreasing. In biological (taxonomical) classification, drugs are classified as plants and animals are classified. As the drugs are obtained from plants, it is suggested that they should be classified as plants. At first sight this classification looks appealing but many drugs are not entire plants but are parts of the plants which have been subjected to drying and sometimes peeling and even slicing. Thus from the drugs as they occur in commerce, say cinchona bark, it is difficult to identify the plant from which it is obtained. In chemical classification as the medicinal action of the drug is due to active chemical constituents, drugs are classified according to the chemical nature of active constituents. Thus alkaloid containing drugs like opium or solanaceous drugs or rauwolfia are arranged under alkaloidal drugs and even according to the chemical nature of alkaloids. Drugs containing anthraquinone glycosides like senna, cascara, rhubarb and those containing cardiac glycosides like digitalis, strophanthus and scilla are grouped together. Similarly, drugs containing volatile oils like clove, cardamom and umbelliferous fruits are put together. Biochemical classification which is more natural and takes into account the biogenetic relationship of natural order is followed. Thus in modern pharmacognosy more importance is given to chemical and biochemical classifications. In pharmacological classification, the important aspect of the drug is its activity and drugs are classified according to their pharmacological action. Thus purgative drugs like senna, aloe and cascara or cardiac drugs like digitalis and strophanthus are grouped together. Some drugs in which the action is known but the chemical constituents have not been investigated can be included in this classification. This classification also helps in finding out new drugs. In this chapter, however, the morphological classification will be followed. Pharmacognosy of Tinospora cordifolia Botanical origin: Tinospora cordifolia (Willid.) Miers Family : Menispermaceae Sanskrit synonyms : Amrita, Amritalata, Amritavallari, Amritavalli, Bhishakapriya, Chakralakshna, Chakrangi, Chandrahasa, Dhira, Guduchi, Jivanthika, Madhuparni, Pittaghni. Regional names: Bengali : Gadancha, Giloe, Gulancha, Guluncho, Nimgilo. Bombay : Ambarvel, Gharol, Giroli, Guloe, Gulwel. Gujarati : Gado, Galo, Gulo, Gulvel. Hindi : Giloe, Gulancha, Gulbel, Gurach, Ambarvel. English : Gulancha, Tinospora Marathi : Ambervel, Gharol, Giroli. Parts used: Root, stem and leaves. Properties and uses: The drug Guduchi has been in use in the indigenous system of medicine since remote past. The leaves of Guduchi are mentioned under Tikta-saka varga which is claimed to be salutary and useful in treating kushta, meha jwara, svasa, kasa and aruchi (Susruta). It has been indicated in Ayurvedic treatises in various ailments like kamala (Jaundice), Jvara(fever), vatarakta and so on. The fresh plant is said to be more efficacious than the dry and the stem is the part which is mostly used, from which a kind of starch is prepared known as Giloe-Ke-Sat or Guduchi- Satva. According to Bhavamisra (1969) Guduchi is considered as bitter, tonic astringent, diuretic and a potent aphrodisiac and curative against skin infections, jaundice, diabetes and chronic diarrohea and dysentery. Dhanvantari Nighantu mentions other properties and uses such as cure for bleeding piles, promoting longevity, curing itching and erysipelas (Aiyer and Kolammal, 1963). Its use has been indicated in heart diseases, hypertension, leprosy, helminthiasis and rheumatoid arthritis (Kirtikar and Basu, 1933; Misra, 1969; Sharma, 1969 and Shah, 1968). It has been in extensive use in India as a valuable tonic, alterative and antipyretic. It caught the notice of European physicians in India as a specific tonic, antiperiodic and diuretic (Watt, 1893; Pendse and Bhatt, 1932). The drug itself as well as a tincture prepared from it are now official in the Indian Pharmacopoeia. Tinospora cordifolia is mentioned in Ayurvedic literature as a constituent of several compound preparations used in general debility, dyspepsia, fever and urinary diseases. (The plant attracted the early notice of European physicians in India). Fleming remarked on its use as a febrifuge and as a drug in gout. Ainslie described the root as a powerful emetic. Gulancha was included in the Bengal Pharmacopoeia of 1844 and the Indian Pharmacopoeia of 1868. Gulancha which grow on Neem trees is considered to be most efficacious for remedial purpose (Watt, 1972). Botanical description: This is a glabrous, succulent, climbing shrub, often attaining a great height and sending down long thread like aerial roots. The plant seems to be particularly found climbing up the trunks of large Neem trees. The aerial roots that arise from the mature branches or cut bits of stems grow downward and by continuously lengthening some times reach the ground. They thicken gradually and resemble the stems, except for the absence of nodal swellings. The fresh or tender stems are greenish, longitudinally striated ribbed. The bark is grey of creamy-white in colour, deeply cleft with spiral and longitudinal clefts, the space between the clefts being usually dotted with large rosette like lenticels. The branches bear smooth heart shaped leaves. Leaves: Simple, alternate, ex-stipulate, fairly long petiolate and are articulated to short tumid nodal projections on the stem, petiole slender, rounded, basal part pulvinate for a short length and this thickened portion is slightly twisted. Lamina broadly ovate to roundish cordate, thin, entire, glabrous on both surfaces, tip acute or shortly acuminate and base with a broad sinus and five to seven –nerved. Inflorescence: The plants are dioecious, male and female developing on separate plants. Racemose, simple or panicled. Staminate inflorescences are usually dropping, longer than the leaves and bear the flowers in fascicles of two to six. The pistillate inflorescence is often shorter with flowers borne singly but densely packed on the rachis. Flower: Small, numerous, very early deciduous, greenish-yellow with short slender pedicels. Bract lanceolate, subulate, the lower ones occasionally somewhat leafy. Sepals: Six , free, deciduous in two series of which the outer are small, ovate, oblong, acute and the inner three larger and membraneous. Petals: Six, in one whorl free, smaller than the sepals being about half the length of the calyx. In staminate flowers each petal loosely embraces or encloses a stamen and its limb finally gets reflexed. In pistillate flowers, petals are cuneate, oblong with the limb entire and not getting reflexed. Staminate flowers: Stamens six, filaments free, spreading, slightly longer than and wrapped in petals, anther cells oblong. Pistillate flower: Have six clavate staminodes in addition to the gynoecium. Gynoecium superior of three free carpels. Styles very short, simple, stigma dilated and forked. Fruit: An aggregate of one to three sessile drupelets. Seed, solitary in each drupelets. Distribution : Indigenous and found distributed throughout most parts of tropical India from Kumaon to Assam, in north extending through Bengal, Bihar, Deccan, Konkan, Karnataka and Kerala. It is a fairly common wild plant of the deciduous and dry forests of most districts growing over hedges and small trees. Cultivation: The plant is sometimes cultivated for ornament and is propagated by cuttings. It is perfectly suited to and grows well in almost any type of soil and under varying climatic conditions. It is specially trained to grow on Neem and mango trees, thereby it is supposed to possess increase in its medicinal virtue. Pharmacognostical characters of the different parts of the plant Stem: The drug occurs as long, cylindrical, glabrous, soft wooded pieces which show characteristic nodal swelling. The fresh stems are greenish with a smooth surface but the older stems have a warty surface due to the presence of circular lenticels. Fracture is fibrous, taste bitter and odourless. Aerial root: In commerce the aerial roots are usually seen associated with the pieces of stem. The young roots are thread like, whereas the mature ones resemble the young stem except for the presence of nodal swellings. The surface is light grey, fracture short, taste bitter, odourless. Leaf: The leaves are simple, alternate and exstipulate. The petiole is slender and fairly long ranging between 3 to 7 cms. The base of the petiole is pulvinate and slightly twisted at base. The blade is broadly ovate to roundish, cordate with a diameter of 5 to 9 cms The surface is smooth. Lower surface is pale coloured; the upper surface is glaucous. The tip is acute or sharply acuminate the base has a broad sinus. Venation is reticulate with a number of principal veins. Veins are multicostate and prominent on dorsal side. The leaves when seen in bulk look intensely green. Over-mature leaves show yellowish green to yellow colour. The leaves are bitter and have an indistinct odour. Physical constant values: Table- 9a Ash, extractive and moisture content of the stem of Tinospora cordifolia. Percentage Total ash 6.55 Acid insoluble ash 0.80 Water insoluble ash 3.20 Sulphated ash 3.80 Water soluble ash 3.35 Alcohol soluble extractive 10.32 Water soluble extractive 20.80 Moisture content 8.40 Table – 9b Mucilage percentage of dry root, fresh and dry stems of Tinospora cordifolia. Percentage Fresh stem 12.0-1.33 Dry stem 3.75-4.40 Dry root 1.08 Table – 9c Active constituents present in the stem bark and wood of Tinospora cordifolia . Solvent Active constituents present Stem bark Wood Pet. ether (60-80°C) Sterols and carbohydrates Sterols, Carbohydrates Alcohol (95%) Alkaloids, carbohydrates and tannin Carbohydrates Water Carbohydrates Carbohydrates Diagnostic characters: The stem is characterised by the presence of bicollateral vascular bundles surrounded by pericycle fibres. The cork arises in the sub-epidermal layers and gives rise to 2 to 3 layers of cork. Starch is present throughout the parenchyma of the stem. The aerial root is characterised by tetra to pentarch primary structure. The cortex is divided into outer thick-walled zone representing the velamen and inner parenchymatous zone containing secretory canals. Starch is present throughout the parenchyma of the aerial root. Microscopically the leaves are simple, alternate and exstipulate. The petiole is slender and fairly long ranging between 3 to 7 cms. The base of the petiole is pulvinate and slightly twisted at base.