Medicinal & Aromatic Plants :

February 17, 2014
By Krishiworld

MEDICINAL PLANTS

During the past seven or eight decades, there has been a rapid extension of the allopathic system of medical treatment in India. It generated a commercial demand for pharmacopoeial drugs and products in the country, Thus efforts were made to introduce many of these drug plants into Indian agriculture, and studies on the cultivation practices were undertaken for those plant which were found suitable and remunerative for commerical cultivation. In general, agronomic practices for growing poppy, isabgol, senna, cinchona, ipecac, belladonna, ergot and a few others have been developed and there is now localized cultivation of these medicinal plants commercially. The average annual foreign trade in crude drugs and their phytochemicals is between 60 and 80 million rupees and this accounts for a little over 0.5 per cent of the world trade in these commodities.

The curative properties of drugs are due to the presence of complex chemical substances of varied composition (present as secondary plant metabolites) in one or more parts of these plants. These plant metabolites in one, according to their composition, are grouped as alkaloids, glycosides, corticosteroids, essential oils, etc. The alkaloids form the largest group, which includes morphine and codein (poppy), strychnine and brucine(nux vomica), quinine(cinchona), ergotamine(ergot), hypocyamine,(beeladona) ,scolapomine(datura), emetine(ipecac), cocaine(coco), ephedrine(ephedra), reserpine(Rauwolfia), caffeine(tea dust), aconitine(aconite), vascine(vasaca). santonin(Aremisia), lobelin(Lobelia) and a large number of others. Glycosides form another important group represented by digoxin(foxglove), stropanthin(strophanthus), glycyrrhizin(liquorice), barbolin (aloe), sennocides (senna),etc. Corticosteroids have come into prominence recently and diosgenin(Dioscorea), solasodin(Solanum sp.),etc. now command a large world demand. Some essential oils such as those of valerian kutch and peppermint also possess medicating properties and are used in pharmaceutical industry. However, it should be stated in all fairness that our knowledge of the genetic and physiological make-up of most of the medicinal plants is poor and we know still less about the biosynthetic pathways leading to the formation of active constituents for which these crops are valued.

During the last two decades, the pharmaceutical industry has made massive investments on pharmacological, clinical and chemical researches all over the world in an effort to discover and still more potent plant drugs ; in fact, a few new drug plant have suceessfully passed the tests of commercial screening. However, benefits of this labour would reach the masses when the corresponding support for agricultural studies for commercial cultivation is provided. Infact, agricultural studies on medicinal plants, by its very nature, demand an equally large investment and higher priority. India, in particular, has a big scope for the development of the pharmaceutical and phytochemical industry.

The Indian Pharmacopoeia(1966) recognizes eighty five drug plants whose ingredients are used in various pharmaceutical preparations. We shall, however, confine our treatment to a few important commercially grown medicinal plants whose cultivation deserves priority in out national economy.

CINCHONA (cinchona ledgeriana Linn.and allied spp.). Sixty-five species distributed in the Andes at elevations of 800 to 2,800 m, occur mainly in Peru, Bolivia, Columbia and Ecuador. Commercial supplies of the bank are obtained from C.ledgeriana, c.officinalis, C.calisaya, C.succirubra and their numerous hybrids. The cinchona bark yields quinine which is used as a treatment against malaria. Quinine salts are now increasingly used in soft drinks as bittters and quinidine sulphate is use in the treatment of heart troubles, such as auricular fibrillation and venticular trachycardia. Cinchona plantations cover about 1,600 ha in the Nilgiris and the Annamalais Hills(Tamil Nadu). India, Indonesia and Zaire(the Congo) are major suppliers of quinine products to the world market ; the Indian export of quinine salts earns about Rs 10 million annually.

C.ledgerianna Moens is a small tree grown at elevations between 1,000 and 1,900 m, mainly in West Bengal. The average total alkaloid content in the root, stem and branch (of plants 10-12 years old) is 7.21, 6.01 and 4.0 per cent of which the quinine content is 5, 4 and 1.98 per cent respectively. Under less favourable conditions, a hybrid (ledgerianna X succirubra) is preffered ; the hybrid has a lower quinine content, but it produces a more robust tree, growth. C.officinalie Linn. is a weak straggling tree, about 6m high. It grows at altitudes ranging from 2,000-2,600 m mainly in the Nilgris. The root, stem and branch contain 1.75-4.16,2.56-4.42 and 1.44-2.35 per cent of quinine respectively. A hybrid, called robusta (officinalisX succirubra) is a hardy type and, as such, is adapted to a wider range of elevations (1,2000-3,000 m) and temperatures ; another hybrid(officinalisX ledgeriana) is grown in Mungpoo (Darjeeling District).

C.calisaya Wedd. is a large tree which is not suitable for growing under excessive cold and humid conditions, is grown at lower altitudes of 400 to 1,000 m in the Moyar Valley (Nilgiris). The total alkaloids in the stem bark range from 3.89 to 7.24 per cent, of which quinine and cinchonidine are 0.78 to 5.57 and 0.03 to 1.56 per cent respectively.

C.succirubra Pavon is a hardy tree which grows between elevations of 1,200 and 2,000 m in some parts of Annamalais and attain a heught of 18-20 meters. This species possess a remarkable ability to withstand both high humidity and drought. Its main alkaloid is cinchonidine. The total Alkolid in the root ,stem and bark is 7.6,5.5 and 3.3 per cent respectively. Out of these amounts, quinine constitutes 0.76-1.42, 1.1-1.74 and 0.8-1.76 per cent respectively in the root, stem and bark.

Cinchona prefers deep, well drained rich loamy to clayey loam, acidic soils(pH 4.5-6) on sloping sheltered locations. Most species prefer high humidity, a well- distributed rainfall of about 150 cms,and only minor variation in the maximum and minimum temperatures during their growing seasons. All species are susceptible to frost and succumb to water-logged conditions.

Cinchona is usually propogated through seeds. The seeds are small and light (350 – 400 seeds per gramme) and loose viability soon. About 50g of fresh seeds sown per square meter during February-May produce about 10,000 seedlings in the nursery-beds, prepared with a mixture of leaf-mould and sand. The nursery is provided with partial shade and kept moist and free from weeds. Germination takes 25 to40 days to be completed and the seedlings grow 4 pairs of leaves in 4 to 6 months when they are transplanted in another nursery at 10 cm X 10 cm spacing. The seedling grow 30-50 cm high in the next 4 to 5 months and are planted in the field at a spacing of 2 m x 2m ; the young-growing plants are provided with shade. The plantation is thinned when 4 to 6 years old and thus about 50 per cent of the stock is uprooted and debarked in two years. More bark is obtained in the 8th year by coppicing when only one strong stump is allowed to grow. The left-over trees are finally uprooted when 12-years old. The bark is moved by ringing the stem at a height of 60 cm from the ground and is dried in the open. The drying reduces its weight to 60-70 per cent.

In Indonesia, the vegetable propagation of selected clones has helped to maintain a high quinine content, thereby upgrading the average quinine content from 4 to 7.5 per cent . Several methods of vegetative propogation, as patch and slit-budding, cincturing, layering and mould-layering, are recommended. Vegetative propagation is done during the monsoon, when root initials are produced in 40 to 60 days and the shoot is then cut off and planted.

The cinchona bark has 30 chemically related alkaloids, of which quinine (C20H24O2N2) is the most important. The alkaloids are formed during the descent of the sap and, therefore, its percentage is lowest in the twigs and it rises in the stem and is maximum in the root bark ; the collar portion of about 30-45 cm in length is the richest portion. The percentage of total alkaloids increases till the age of 8 to 12 years and then begins to decline.

Damping-off is reported both from nursery and fields, particularly at lower elevations . The disease is controlled by fumigation with chloropicrin. Root-rot due to Fomeslamayensis (Murr.)Sacc. and Trott. has also been reported in nurseries; a better drainage of the nursery-beds and spraying with Bordeaux mixture help to prevent it.

ISABGOL (plantago ovata Forks.).It is an annual stem-less herb, a native of Persia, now grows as a cash crop on about 16,000 ha in the Mehsana, Palampur and Banaskantha districts of Northern Gujrat, India is the largest producer of isabgol and exports seed and huskworth Rs 25 million annually. The husk is the rosey-white membranous covering of the seed which constitutes the drug and is given as a safe laxative, particularly beneficial in habitual constipation, chronic diarrhoea and dysentery.

Isabogal is an irrigated rabi crop which remains in the field for about 4 months. The crop is grown in marginal, light, well-drained sandy-loam to loamy soils having pH between 7 to 8. It requires a cool climate and dry sunny weather or light showers cause seed shedding.

After harvesting the kharif crops,e.g. jowar(Sorghum vulgare),
the land is brougt to fine tilth and laid out into
beds of convinient size for irrigation. It is preferable to mix
with the soil 15 cartloads of well-rotted farmyard mannure
per hectare during the preparation of the land.The
optimum sowing time is early November ; sowing however,
is extended till the end of December, but the delayed sowing
decreases the yield. The seed rate is 7.8 kg per hectare.
Seeds are small and light about 6000 to a gramme and are
sown by broadcast. They are covered thinly by raking
the soil. A light irrigation is given immediately. Germination
starts in 6 to 10 days and the crop is given the
second irrigation after 3 weeks and a third one at the time
of the formation of the spikes ; thus the crop needs 6 to 7
irrigations.

Isabgol makes a moderate demand for nutrients. Usually,25 kgof each N and P per hectare is given at plantation.The crop is given 1 or 2 hand-weedings during the entire growing period. The plants are about 50 cm high andeach plants gives out between 25 to 100 tillers,depending upon tje fertility of soil and wheather conditions. The plant bears the flowering spikes in about 60 days after sowing and matures in the next 2 months.The yellowing of the lower leaves is an indication of maturity,confirmed by pressing a spike between two figers when the mature seeds come out. The crop is harvested close to the ground in the early morning hours to avoid looses owing to seed shedding.The harvested material is stacked for 1 or 2 days,made to be trampled by bullocks, winnowed,and the seperated seed crop is collected . A boldseeded crop fetches a better price.

The seeds are processed through a series of grinding mills to seperate the husk, and about 30 per cent husk by weight is thus recovered . The husk contains a mucilaginous substance.

Powdery mildew sometimes attacks the crop and is brought under control by spraying the crop with wettable sulphur, e.g. ‘Karathen’ and ‘Sulfex’ two or three times at 15-day intervals after the apperance of infection. White grubs are reported to damage the roots ; soil treatment with 5 per cent Aldrin or Lindane to protect the crop is given at the time of the last ploughing during the preparation of the field.

OPIUM POPPY (papaver somniferum Linn).Poppy is a native of the western Mediterranean region,introduced into India in the early sixteenth century.India produces about 70 per cent of the world’s production and 90 per cent of it is exported annually.The crop can be grown under a licence issued by the Excise Department and, as such, its cultivation is restricted to about 24,000 hectares in the districts of Neemuch,Mandsaur and Ratlam in Madhya Pradesh ; in Faizabad,Bara Banki,Bareilly and Shahjahanpur in Uttar Pradesh,and in Chittoor,Jhalawar and Kota in Rajasthan.

Poppy is an annual erect plant, 60-120 cm in height, rarely branching,with ovate-oblong leaves;it bears large showy flowers and nearly globose to spherical capsules, containing small white or black kidney-shaped seeds.It is a rabi crop,and remains for about 150-160 days in the fields .It is mainly(90%)self-pollinated ,since the dehiscence of anthers takes place before the opening of the flower. A large number of the forms of variety album DC. are cultivated inIndia; it has ovate globose capsules devoid of apertures.

The crop is grown on well-drained ,fertile,clayey loam to rich sandy-loam soils. It prefers moderately cool weather and open sunny locations;severely cold spells, frost dull cloudy weather ,high winds,and heavy rainfall during the lancing period adversely affect the yield.

Land is prepared to a fine tilth up to a depth of 20-25 cm during September and the fields are laid out into beds of convenient size. Twenty-five to thirty-seven cartloads of farmyard manure is mixed with the soil during the preparation of the land,penning of sheep or goats is preffered .Seed-rate is 2.5 to 3.5 kg per hectare.The seeds are minute weighing 0.25 to 3.5 kg per 100 .They are mixed with sand and sown thinly in rows 0.3m apart during mid-Octobor till early November(optimum temperature 9 -10 degree centigrade).The rows are covered with a thin layer of soil and are given a light irrigation,followed by another irrigation after 8-10 days when the seeds start germinating.Seed treatment with 1.0 %Agrosan protects it from seed-borne dieases.The crop is given about 15 irrigations in all,depending upon the texture of the soil and the variety sown;moisture defiency at the time of capsule formation affects the yield adversely.The crop needs a heavy nutrient supply and 50 kg N/ha is applied during the preparation of the land and another application of an equal quantity is given as top-dressing in two-split doses when the crop is one month old and at the time of the flag-leaf stage. The seedlings are thinned out to 20-25 cm apart when they grow 5-7 cm tall. The crop is weeded and hoed weekly till the plants are about 20 cm tall and thereafter ,weeding and hoeing are done once a month.The plants take 75-80 days (in Neemuch, Madhya Pradesh)and about 105 days(in Uttar Pradesh) to come into flower ,depending upon the variety sown. The petals fall in 3-4 days and the growing capsule is ready for lancing in the next 6 to 10 days. The green unripe capsules contain the maximum amount of morphine which diminishes with its ripening and yellowing; conversely, codeine and narcotine increases with age.

Lancing is done longitudinally in bright sunlight and the latex (crude opium)which oozes from the wounds dries during the following night and is scrapped with a sharp kitchen-knife in the early hours of the succeeding morning. Lancing is performed in the afternoon with a special knife, capable of making four incisions at a time ,each at about 1/12 cm apart. Each capsule is lanced for 4 to 6 times. A deep incision causes the collection of the latex inside the capsule and spoils the seeds. The crude opium is stored in earthen -pots and dried in the sun to obtain the raw opium of a uniform consistency.The dry produce should be stored in closed vessels. The entire produce goes to the Excise And Narcotics Department which pays according to its cosistency and purity.The average yield of raw opium varies from 13 to 33 kg per hectare,though much higher yields are recorded under good agronomic practices.The crop also yield 3 to 4 quintals of seeds per hectare.The seeds contain up to 50 per cent of a golden-yellow fatty oil which is devoid of narcotic properties.

There are 25 opium alkaloids identified in the raw opium.Of them,morphine, theabine,codeine,narcotine and papaverine are important; morphine is by far the most important.The Indian produce of raw opium contains,on an average,about 20% of the total alkaloids by weight.They,in turn,posses 9 to 14% of morphine,5-7% narcotine, 1.25 -3.75% codeine,0.4-1% papverine and 0.2-0.5% theabine. The produce obtained in Turkey and the Balkan countries is collected from one incision only and is therefore rich (10-21%) in morphine;conversely,the Indian opium is richer in codeine and narcotine.

The crop is attacked by the leaf-miner(phyllocnistis sp.),which can be kept under control by spraying with 0.2% Metasystox or Rogor.Sometimes ,cutworms {Agrotis suffura Hubn.)cause damage to the young plants;the flooding of the fields makes these worms float on the water and they are ultimately pickedby birds. Downy mildew(Peronospora arborescens(Berk)de Bary)sometimes causes serious damage to the crops at the time of capsule formation. It is controlled by the application of 0.2% Diathane Z-78. Root-rot due to Rhizoctonia is also reported on the crop.

 

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