Crude Drugs: Collection, Processing and Storage

COLLECTION AND PROCESSING OF CRUDE DRUGS

• After collection of the crude drugs, they are required to be processed prior to marketing. The reasons for the preparation of drugs are to stabilize them in transport and storage and to ensure the absence of foreign organic matter and substitutes. Market preparation of crude drugs also takes care of pharmaceutical elegance.
• While preparing a drug for commerce, several methods are adopted to meet the standard pharmacopoeial requirements.
• Generally, these methods include proper methods of collection and harvesting, drying and garbling. Sometimes, coating and bleaching are also necessary for converting the drug into suitable form for the market.
• While doing so, it should be taken care of that neither the action of the drug lowers nor does it change, due to the additives used in the process.

COLLECTION

• Irrespective of the type of crude drug and area of collection, there cannot be two opinions that the drugs are collected suitably when they contain maximum concentration of active ingredients.
• The advantage of existing environmental conditions is also taken into consideration while collecting the crude drugs.
• While collecting the natural drugs on commercial scale, attention should be paid for the use of skilled labour.
• As skilled Jabour will collect the pure drugs without any admixture as they are trained for the purpose. In the early stages of development, plants do not produce active ingredients, hence age of the plants should be given due consideration for collection, say for instance Boswellia does not produce sallaki up to five years of its age; similarly, mentha herb produces pulegone but no menthol (the chief active constituent) in the early stages.
• As far as possible diseased plants or plants treated with pesticides are to be avoided for medicinal use and should be rejected during collection.
• At times the season of collecting the medicinal plants is also very specific i.e. Rhubarb rhizomes aconite roots contain their respective active constituents at the maximum, on the commencement of the warmer season only.
• In general rhizomes and underground parts of the plants are to be collected when their aerial growth has ceased. The drugs which constitute leaf and the flowering tops of plants are collected just before they reach their flowering stage (maturity) e.g. senna, digitalis, vinca, belladonna, etc. while the leaves of aloe are collected when they are sufficiently thick.
• Flowers need to be collected just before pollination or many a time, before their full expansion, c.g. saffron, clove buds, chamomile, arnica, etc. They are collected in dry weather and preferably during morning hours.
• Barks are generally collected in spring or early summer when cambium is active, as it is easy to detach them from the stem. Sometimes, they are collected in autumn (wild cherry) or in rainy season (cinnamon).
• Three different methods for collecting barks are (a) felling, (b) uprooting and (c) coppicing. In felling method, the tree is cut at base and bark is peeled off. In uprooting technique, the roots are dug out and bark is stripped off from roots and branches.
• In coppicing method, the plant is allowed to grow for a definite period and then it is cut off at specific distance from soil.
• The stumps which remain in ground are allowed to send shoots, which develop further independently yielding aerial parts. These new parts are cut off and bark is collected from shoots. As compared to other methods of collection of bark, this technique is more economical and less time-consuming. It is, therefore, the method of choice for collecting barks commercially. Cascara and cinnamon are collected by this method.
• The fruits are collected depending upon the part of fruits used. They are collected either ripe or half ripe, but full-grown. For example, cardamom fruits are collected just before their dehiscence; bael and tamarind, after their maturity, while caraway, fennel and coriander are collected, when they are full ripe.
• The roots are collected in spring, before the vegetative process stops. Usually, the roots are sliced transversely or longitudinally to facilitate drying. Rhizomes are collected, when they have stored ample of reserve food material and contain maximum content of chemical constituents.
• The unorganized drugs such as resins, gums, latices are collected, as soon as, they ooze out of the plant. Acacia gum is collected 2-3 weeks after making incisions on the bark of the tree and when it is sufficiently hard.
• Opium and papaya latices are collected after coagulation of latex. Turpentine oleoresin and balsam of peru are collected when the plant is about 8 – 10 years old.

HARVESTING

• Harvesting is an important operation in cultivation technology, as it reflects upon economic aspects of the crude drugs. An important point which needs attention over here is the type of drug to be harvested and the pharmacopoeial standards which it needs to achieve.
• Harvesting can be done efficiently in every respect by the skilled workers. Selectivity is of advantage in that the drugs other than genuine, but similar in appearance can be rejected at the site of collection.
• It is, however, a laborious job and may not be economical. In certain cases, it cannot be replaced by any mechanical means, e.g. digitalis, tea, vinca and senna leaves.
• The underground drugs like roots, rhizomes, tubers, etc. are harvested by mechanical devices, such as diggers or lifters.
• The tubers or roots are thoroughly washed in water to rid earthy-matter of. Drugs which constitute all aerial parts are harvested by binders for economic reasons.
• Many a time, flowers, seeds and small fruits are harvested by a special device known as seed stripper. The technique of beating plant with bamboos is used in case of cloves.
• The cochineal insects are collected from branches of cacti by brushing. The seaweeds producing agar are harvested by long handled forks. Peppermint and spearmint are harvested by normal method with mowers, whereas fennel, coriander and caraway plants are uprooted and dried.
• After drying, both they are thrashed or beaten and the fruits are separated by winnowing. Sometimes, reaping machines are also used for their harvesting.

DRYING

• Before marketing a crude drug, it is necessary to process it properly to preserve it for a longer time and also to acquire better pharmaceutical elegance.
• This processing includes several operations or treatments, depending upon the source of the crude drug (animal or plant) and its chemical nature.
• Drying consists of removal of sufficient moisture content of crude drug to improve its quality and make it resistant to the growth of microorganisms. Drying inhibits partially enzymatic reactions.
• Drying also facilitates pulverizing or grinding of a crude drug. In certain drugs, some special methods are required to be followed to attain specific standards, e.g. fermentation in case of Cinnamomum zeylanicum bark and gentian roots.
• The slicing and cutting into smaller pieces is done to enhance drying, as in case of Glycyrrhiza, squill and Calumba. The flowers are dried in shade so as to retain their colour and volatile oil content.
• Depending upon the type of chemical constituents, a method of drying can be used for a crude drug; drying of flowers can be achieved by (1) Natural (sun drying) and (2) Artificial means.

1. Natural Drying (Sun-drying)

In case of natural drying, it may be either direct sun-drying or in the shed. If the natural colour of the drug (digitalis, clove, senna) and the volatile principals of the drug (peppermint) are to be retained, drying in shed is preferred. If the contents of the drugs are quite stable to the temperature and sunlight, the drugs can be dried directly in sunshine (gum acacia, seeds and fruits).

2. Artificial Drying

Drying by artificial means includes drying the drugs in (a) an oven; i.e. tray-dryers; (b) vacuum dryers, and (c) spray dryers.

(a) Tray dryers: The drugs which do not contain volatile oils and are quite stable to heat or which need deactivation of enzymes are dried in tray dryers. In this process, hot air of the desired temperature is circulated through the dryers and this facilitates the removal of water content of the drugs (belladonna roots, cinchona bark, tea and raspberry leaves and gums are dried by this method).

(b) Vacuum dryers: The drugs which are sensitive to higher temperature are dried by this process. e.g. tannic acid and digitalis leaves.

(c) Spray dryers: Drugs which are highly sensitive to atmospheric conditions and also to temperature of vacuum drying are dried by spray drying method. The technique is followed for quick drying of economically important plant or animal constituents, rather than the crude drugs. Examples of spray drying are papaya latex, pectin, tannins, etc.

GARBLING (DRESSING)

• The next step in preparation of crude drug for market after drying is garbling. This process is desired when sand, dirt and foreign organic parts of the same plant, not constituting drug are required to be removed.
• This foreign organic matter (extraneous matter) is removed by several ways and means available and practicable at the site of the preparation of the drugs.
• If the extraneous matter is permitted in crude drugs, the quality of drug suffers and at times, it doesn’t pass pharmacopoeial limits.
• Excessive stems in case of lobelia and stramonium need to be removed, while the stalks in case of cloves are to be deleted.
• Drugs constituting rhizomes need to be separated carefully from roots and rootlets and also stem bases. Pieces of iron must be removed with the magnet in case of castor seeds before crushing and by shifting, in case of vinca and senna leaves. The pieces of bark should be removed by peeling as in gum acacia.

PACKING

• The morphological and chemical nature of drug, its ultimate use and effects of climatic conditions during transportation and storage should be taken into consideration while packing the drugs.
• Aloe is packed in goat skin. Colophony and balsam of tolu are packed in kerosene tins, while asafoetida is stored in well closed containers to prevent loss of volatile oil.
• Cod liver oil, being sensitive to sunlight, should be stored in such containers, which will not have effect of sunlight, whereas, the leaf drugs like senna, vinca and others are pressed and baled.
• The expensive drugs which are very sensitive to moisture need special attention, e.g. digitalis, ergot and squill.
• Squill becomes flexible ergot becomes susceptible to the microbial growth, while digitalis looses its potency due to decomposition of glycosides, if brought in contact with excess of moisture during storage. Hence, the chemicals which absorb excessive moisture (desiccating agents) from the drug are incorporated in the containers.
• Colophony needs to be packed in big masses to control auto- oxidation. Cinnamon bark, which is available in the form of quills, is packed one inside the other quill to facilitate transport and prevent the volatilization of oil from the drug.
• The crude drugs like roots seeds and others do not need special attention and are packed in gunny bags while in some cases bags are coated with polythene internally. The weight of certain drugs in lots is also kept constant, e.g. Indian opium.

STORAGE AND PRESERVATION OF CRUDE DRUGS

• Preservation of crude drugs needs sound knowledge of their physical and chemical properties.
• Good quality of the drugs can be maintained if they are preserved well. The following illustrations shall help in understanding the factors to be considered while preserving the drug.
• All the drugs should be preserved in well-closed and, possibly, in the filled containers. They should be stored in the premises which are waterproof, fireproof and rodent-proof.
• A number of drugs absorb moisture during their storage and become susceptible to microbial growth. Some drugs absorb moisture to the extent of 25per cent of their weight.
• The moisture, not only increases the bulk of the drug, but also impairs the quality of the crude drug.
• The excessive moisture facilitates enzymatic reactions resulting in the decomposition of active constituents, e.g. digitalis leaves and wild cherry bark. Gentian and ergot receive mould infestation due to excessive moisture.
• Radiation due to direct sunlight also causes the destruction of active chemical constituents as in the case of ergot, cod liver oil and digitalis. Form or shape of the drug also plays a very important role in preserving the crude drugs.
• Colophony in the entire form (big masses) is preserved nicely, but if stored in powdered form, it gets oxidized or loses its solubility in petroleum ether.
• Squill, when stored in powdered form becomes hygroscopic and forms rubbery mass on prolonged exposure to air.
• The fixed oil in the powdered ergot becomes rancid on storage. To maintain a good quality of powdered ergot, it is required that the drug should be defatted with lipid solvent prior to storage.
• Lard, the purified internal fat of the abdomen of the hog, is to be preserved against rancidity by adding Siam benzoin. Atmospheric oxygen is also destructive to several drugs; hence, such drugs are filled completely in well-closed containers, or the air in the container is replaced by an inert gas like nitrogen, e.g. shark liver oil, papain, etc.
• Apart from protection against adverse physical and chemical changes, the preservation against insect or mould attacks is also essential.
• Different types of insects, nematodes, worms, moulds and mites infest the crude drugs during storage. Some of the more main pests found in drugs are Coleoptera (Stegobium paniceum and Calandrum granarium), Lepidoptera (Ephestia kuehniella and Tinea pellionella), and Arachnida or mites (Tyroglyphus farinae and Glyophagus domesticus