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CULTIVATION, COLLECTION & PREPARATION
OF CRUDE DRUGS
Phcog-1.4.
Crude drugs cultivated or uncultured plants
Processing of crude drugs
Some cases: pharmacopoeias specify cultivated spp. Such as
Fennel, ginger, cinnamon & opium
Opium: only official growers may legally produce herbs.
Other herbs: senna, tragacanth etc, may be collected from
By Abdul Ghani Karimi wild or cultivated species.
Department of Pharmacognosy, Faculty of Pharmacy
Date: 13.01.1390
DISADVANTAGES OF WILD PLANT COLLECTION ADVANTAGES OF CULTIVATED HERBS
Only desired spp are collected uniform quality.
Sparse distribution e.g. Sceletium tortuosum
Potentially difficult to transport herb to area of processing. Collection, transport & access to processing facilities
Difficult access (e.g. Forests, Mountains etc) is improved.
Collector ignorance admixture of other plants, collection of Better control of soil quality, pests & plant disease.
undesired plant parts or stage of development or during an Supply: Constant & Regular (Controlled).
incorrect season loss of medicinal activity.
Herb collectors – trained.
1. Collecting of medicinal plants B. Rules for collection
The following general rules are based on
A. Suitable time for collection assuming that the material is best collected
when the organ in question has reached its
The amount of a constituent is usually not constant
optimal state of development:
throughout the life of a plant. 1. Roots and rhizomes are collected at the end of the vegetation period,
The stage at which a plant is collected or harvested is, i.e. usually in the autumn. In most cases they must be washed free of
therefore, very important for maximizing the yield of the adhering soil and sand.
2. Bark is collected in the spring.
desired constituent.
3. Leaves and herbs are collected at the flowering stage.
The differences are sometimes not only quantitative but
4. Flowers are usually gathered when fully developed.
also qualitative.
5. Fruits and seeds are collected when fully ripe.
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C. Methods of collection 2. Preservation of plant material
Medicinal plants must be largely collected by • The plant material must first be preserved so that
the active compounds will remain unchanged
hand. This is especially true in the case of wild during transport and storage.
plants. • The cells of living plants contain not only low
molecular-weight compounds and enzymes, but
With cultivation on a large scale, it may be they also have many kinds of barriers that keep
these constituents apart.
possible to use modern agricultural harvesters, • When the plant dies, the barriers are quickly broken
but in many cases, e.g. barks, manual collection is down and the enzymes then get the opportunity to
promote various chemical changes in the other cell
unavoidable. Thus, the cost of drug production is constituents, e.g. by oxidation or hydrolysis.
• Preservation aims at limiting these processes as
largely the cost of the labor involved. far as possible.
• To stop the enzymic processes, the water content must be brought
A. Drying
down to about 10 %.
The most common method for preserving plant
material is drying. • Drying must be done quickly, in other words at raised temperatures
Enzymic processes take place in aqueous solution. and with rapid and efficient removal of the water vapor.
Rapid removal of the water from the cell will,
therefore, largely prevent degradation of the cell • The most efficient drying is achieved in large driers of the tunnel type.
constituents. • The plant material is spread out on shallow trays, which are placed on
Drying also decreases the risk of external attack, e.g. by mobile racks and passed into a tunnel where they meet a stream of
moulds.
warm air.
Living plant material has a high water content: leaves may contain
60-90% water, roots and rhizomes 70-85%, and wood 40-50%.
60-90% 70-85% 40-50% • The air temperature is kept at 20-40 °C for thin materials such as
The lowest percentage, often no more than 5-10%, is found in
10% leaves, but is often raised to 60-70 °C for plant parts that are harder to
seeds.
seeds dry, e.g. roots and barks.
B. Freeze-drying
Freeze-
• When the crude drug has been collected under primitive
Freeze-drying (lyophilization) is a very mild method.
conditions, without access to a drier, it must be dried in the open.
Frozen material is placed in an evacuated
• The material should be spread out in shallow layers with good apparatus which has a cold surface maintained at -
ventilation to facilitate the drying. 60 to -80 °C. Water vapor from the frozen material
then passes rapidly to the cold surface.
• The choice of sunshine or shade is determined by the sensitivity
The method requires a relatively complicated
to light of the constituents. apparatus and is much more expensive than hot-airhot-
drying.
• In a dried drug the enzymes are not destroyed but only rendered
For this reason, it is not used as a routine method,
inactive due to the low water content. As soon as water is added, but it is very important for drying heat-sensitive
heat-
substances, e.g. antibiotics and proteins
proteins.
they become active again. Hence, dried drugs must be protected
from moisture during storage.
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C. Stabilization D. Fermentation
On long storage, enzymic reactions will slowly destroy the Enzymic transformation of the original plant constituents is
constituents, because the last traces of water can never be sometimes desirable.
removed. The fresh material is then placed in thick layers, sometimes
In order to avoid this degradation, the enzymes should be covered and often exposed to raised temperatures (30-40 °C)
destroyed before drying, a process usually called stabilization
stabilization.
and humidity, so as to accelerate the enzymic processes.
The most common method being brief exposure (a few
This treatment is usually called fermentation.
minutes only) of the plant material to ethanol vapor under
pressure (0.5 atm). The fermented product must, of course, be dried afterwards
Stabilization may be of value for the isolation of compounds to prevent attack by microorganisms, e.g. moulds.
that are very susceptible to enzymic degradation.
Fermentation is mostly used to remove bitter or 3. Standardization of Crude Drugs
unpleasant-tasting substances or to promote the
• Standardization of drug means adjustment of the quality and
formation of aromatic compounds with a pleasant smell
quantity of drugs according to standards.
or taste.
• Completion of drying of crude drugs
It is mainly applied to drugs used as spices or stimulants, • Wet of crud drugs
e.g. vanilla, tea and cacao.
cacao. • Removing foreign matters
• Removing of other parts of plant which does not important
• Removing of deteriorate parts
• Departing of unlimited particles
WHO Monograph for Herbal Drugs
4. Storage of crude drugs
• There are great differences in the stability of crude drugs
because of slow enzymic changes in the constituents.
• Drugs containing glycosides and esters are usually less
stable than those containing alkaloids.
• Drugs with essential oils deteriorate rather quickly
through evaporation, oxidation and polymerization of the
substances constituting the essential oil.
• Tannins on the other hand, have an almost unlimited
durability.
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• In order to keep crude drugs as long as possible:
5. Evaluation of Crude Drugs
• Evaluation of drug means confirmation of its identity and
1. It is essential to store them in a dry condition in determination of its quality and purity and detection of
carefully closed containers. nature of adulterant by various parameters like
morphological, microscopical, physical, chemical and
2. It is also advisable to exclude light, because - even biological observations.
if it does not affect the active constituents - it • The evaluation of crude drug is necessary because of 3
almost always causes changes in the appearance of
main reasons.
the drug, especially loss of color.
1. Biochemical variation in the drug.
3. It is also necessary to protect the drug against
insect attack. 2. Deterioration due to treatment and storage.
3. Substitution and adulteration, as a result of carelessness,
ignorance or fraud.
Morphological or Organoleptic Evaluation Microscopical Evaluation
• It refers to evaluation of drugs by colour, odour, • Diagnostic character of leaf
taste, size, shape and special features like touch,
texture, etc. • Stomata
• It is a technique of qualitative evaluation based on • Trichomes
the study of morphological and sensory profiles of
whole drugs.
Diagnostic Character of Leaves Types of Trichomes
Palisade Ratios of various leaf-drugs
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Stomata and stomatal index
Type of Glandular trichomes
Preliminary phytochemical screening
Chemical Evaluation
Preliminary Qualitative chemical
phytochemical screening examinations
Qualitative chemical examinations Physical Evaluation
1. Detection of Alkaloids • Physical standards are to be determined for
2. Detection of carbohydrates and glycosides
drugs, wherever possible.
3. Detection of saponins
4. Detection of phenolic compounds and tannins
• These are rarely constant for crude drugs, but
5. Detection of gum and mucilage may help in evaluation, specifically with
6. Detection of volatile oils reference to moisture content, specific gravity,
7. Detection of phytosterols
density, optical rotation, refractive index and
8. Detection of fixed oil and fats
solubility in different solvents.
9. Detection of protein and free amino acids
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Moisture Content
Volatile oil
Content
Physical Optical rotation
evaluation
Crude Drugs with Limit For Moisture Content
Moisture Refractive
content index
Foreign organic
Ash content Solubility
matter
Ash soluble in Water-soluble Alcohol-soluble
General Ash
HCl extractives extractives
Sulphated Ash Ether-soluble
extractives
OPTICAL ROTATION Refractive index
• Optically active compounds have the property of rotating • When a ray of light passes from one medium to another of
the plane of polarized light.This property is known as different density, then the ratio of velocity of light in vacuum
optical rotation. to its velocity in substance is termed as refractive index of
second medium.
• Normally, the optical rotation is determined at 25˚c using
sodium lamp as the source of light. • It is constant for a pure drug and varied with wavelength of
incident light, temperature and pressure.
• E.g. :
• E.g. :
Extractives Alcohol soluble extractive
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Ash contents
Ether-soluble Extractives
Volatile Oil Content Foreign organic matter
• The parts of the organ or organs other than those
named in the definition and description of the drug
are defined as foreign organic matter.
• The maximum limit for the foreign matter is defined
in the monograph of crude drugs.
• If it exceeds the limits, deterioration in quality of the
drug takes place.
Diagrams of HPLC & GC
Chromatographic Techniques
• Thin Layer Chromatography (TLC)
• Column Chromatography
• High Performance Chromatography (HPLC)
• Gas Liquid Chromatography (GLC)
• Spectroscopic Methods
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W.H.O. Guidelines for General limits
Biological Evaluation (Contaminants in herbal drugs)
• Hepatoprotective activity
• Hypoglycemic activity
• Anti fertility testing
• Anti inflammatory activity
• Neuropharmacological activity
• Testing for anti ulcer activity
• Anti-insect activity
• Microbiological Assays
6. Classification of Plant Drugs Alphabetical Classification
• Alphabetical • Latin/vernacular names
• Taxonomic • Advantage: quick reference
• Morphological • Disadvantage: no indication of the
• Pharmacological/Therapeutic interrelationships between plants (drugs)
• Chemical/Biogenic • Used in
– Dictionaries
– Pharmacopoeias
Taxonomic Classification Morphological Classifications
• Plants classified based on their botanical classification.
• (Plant) Drugs are divided into organized and
• (Plant) Drugs are arranged according to the plants they unorganized drugs.
– Based on plant morphology
are derived from (class, order, family, genera & species).
• Advantage: Precise & ordered arrangement (no • Advantage
– Practical application to the study of plant drugs.
ambiguity)
• Disadvantage: Botanical knowledge decreases over the • Disadvantage
– Microscopical studies are needed to identify powdered
years in students.
herbs.
• < popular with teaching
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Morphological Classification Pharmacological/Therapeutic
Classification
• Organized drugs • Unorganized drugs • Plant drugs are grouped according to their
pharmacological action of the most important active
– Leaves – Dried latices constituent in the plant.
– Flowers – Extracts
– Fruits – Gums – OR
– Seeds – Resins
– Herbs – Oils • According to the drug’s therapeutic use.
– Whole organisms – Fats
• Disadvantage: The constituents of one drug may
– Woods – waxes have more than one therapeutic action (fall into
– Barks numerous groups. E.g. Flavonoids).
– Rhizomes
– Roots
Biogenic/Chemical Classification
• Drugs are classified according to the main active
chemical constituent available in the plant.
– OR
• The biosynthetic pathways of the main active
constituent.
• Advantage: Popular for teaching when
Pharmacognosy is phytochemically based.
• Disadvantage: Ambiguities: Plants contain more
than one group of active constituents each with
different actions.
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