Cultivation, Collection of Crude drugs
AS per PCI Syllabus
(S.
Y. B. Pharm Sem IV) Unit -I
Cultivation of crude
drugs:
Cultivation of
medicinal plants requires intensive care and management.
The conditions and
duration of cultivation required vary depending on the quality of medicinal
plant materials required.
Methods of Propagation
A. Vegetative
Propagation (Asexual Propagation)
Vegetative propagation
can be defined as regeneration or formation of a new individual from any
vegetative part of the plant body. The method of vegetative propagation involves
separation of a part of plant body, which develops into a new plant.
Methods of Vegetative
Propagation
They are two types:
1. Methods of Natural Vegetative
Propagation
2. Methods of Artificial Vegetative
Propagation.
1. Methods of Natural Vegetative
Propagation
Vegetative Propagation
by Stem
Examples
Runner :
peppermint.
Bulb
: Allium, Squill.
Corms :
Colchicum.
Tuber : Potato,
aconite.
Offset :
Valerian.
Rhizome :
Ginger and haldi.
2. Methods of Artificial Vegetative
Propagation
These are the parts of
the plant (stem, root or leaf) which, if grown under suitable' conditions,
develop new plants.
Stem cutting are
generally used to obtained new plants.
Examples: Sugar cane and rose,
etc.
2. Layering
Roots are induced on
the stem while it is still attached to the parent plant. This part of stem is
later detached from the parent plant and grown into a new plant.
3. Grafting
New variety is
produced by joining parts of two different plants. The rooted shoot of one
plant, call.
stock, is joined with
a piece of shoot of another plant known as scion.
Examples: Rose,
citrus, rubber, etc.
4. Micro propagation
Importance of Asexual
Propagation
2. Plants like roses
and chrysanthemum, etc do not form viable seeds. Thus, vegetative propagation
is the only method of propagation is the only method of reproduction and
continuation of species in such plants.
3. All the plants
developed by these methods will be generally similar to the parent plant.
4. Micro propagation
is useful in raising disease free plants, homozygous diploids, and those
without viable seeds.
B. Seed Propagation
(Sexual Propagation)
Microspores are formed
from microspore mother cells inside the anther.
(ii) Pollination
This is the transfer
of pollen grains from the anther to the stigma.
This involves the
formation of male gametes from microspore.
This process leads to
the formation of megaspores from megaspore mother cell, inside the ovule .
(v) Mega-gametogenesis
The events involving
the formation of embryo sac from megaspore are included in this process.
(vi) Fertilization
Fusion of male and
female gametes takes place, resulting in the formation of zygote.
(vii) Embryogeny
The process involves
development of embryo from zygote.
Collection of crude drugs
For the collection of
medicinal plants, a proper time should be selected. Herbs are selected for
collection at a stage when they yield maximum amount of chemical constituents
Skilled labour should be employed as they are trained to identify and
select the herbs at a proper stage.
The age of the plant
also plays a vital factor for their selection. Diseased plants should be
rejected, Season of collection should also be given due consideration while
selecting the plants for collection.
Harvesting
The time of harvest
depends on the plant part to be used.
Detailed information
concerning the appropriate timing of harvest is often available in national
pharmacopoeias, published standards, official monographs and major reference
books.
As Per WHO Guidelines
possible quality for
the proposed use.
2.Damaged plants or
parts plants need to be excluded.
3.Medicinal plants
should be harvested under the best possible conditions avoiding
wet soil, dew, rain or
exceptionally high air humidity. If harvesting occurs in wet
conditions possible
adverse effects on the herbal drug due to increased moisture
levels should be
counteracted.
4.Cutting devices or
harvesters must be adjusted such that contamination from soil
particles is reduced
to a minimum.
5.The harvested
medicinal plant/herbal drug should not come into direct contact
with the soil. It must
be promptly collected and transported in dry, clean
conditions.
6. During harvesting,
care should be taken to ensure that no toxic weeds mix with
harvested medicinal
plants/herbal drugs.
7. All containers used
during harvesting must be clean and free of contamination from previous
harvests. When containers are not in use, they must be kept in dry conditions
free of pests and inaccessible to mice/rodents, livestock and domestic animals.
8. Mechanical damage
and compacting of the harvested medicinal plant/herbal drug that would result
in undesirable quality changes must be avoided.
In this respect,
attention must be paid to (a)
overfilling of the sacks, (b) Stacking up of sacks.
9. Freshly harvested
medicinal plants/herbal drugs must be delivered as quickly as possible to the
processing facility in order to prevent thermal degradation.
Processing of herbal
raw materials involves various stages from which the crude drugs undergo after
harvesting. It can be classified into primary and secondary processing which
are further sub categorized as follows.
Garbling (Sorting)
This process helps in
ensuring the purity and cleanliness of the harvested material. Dirt like soil,
dust, impurities like insects, dead tissues and residual non medicinal plants
are Separated from the raw material.
The process depends on
the part of the plant to be prepared. The process may involve procedures such
as removing dirt and foreign Substances, discarding damaged parts, peeling of
barks, sieving, trimming, removal of hairs from roots, removal of seeds from fruits,
stripping of leaves from stems.
This may be done by mechanical means
but in some cases it is usually performed manually by hands.
Drying
In some cases, the
plant material should be thoroughly dried after washing in order to prevent the
deterioration and degradation of active constituents. They must be dried as
soon as possible to remove moisture and reduce the damage due to microbial or
mould infestation.
Drying also prevents
the activation of certain enzymes which may otherwise degrade the active
ingredients and also facilitate grinding and milling of the raw material.
Depending on the drug
& nature of ingredients, different drying methods can be used which are as
follows.
I) Natural drying
a) Sun drying:
Most herbal raw
material can be dried in open air under direct sunshine provided the climate is
suitable. The duration of drying process depends on the physical structure of
the plant material and weather conditions. The plant material should be spread
out in thin layers, care should be taken to prevent contamination by diet.
impurities. While drying the plant material should also be protected from insects,
Birds, rodents, pests and other domestic animals.
b) Shade drying:
Some medicinal plants
cannot be directly exposed to sunlight, hence need to be dried under
shade. This drying process is slow but helps in minimizing
loss of colour, volatile oils and aromatic components from
being evaporated.
II) Artificial
drying
Drying by artificial
heat is more rapid than open air drying and is necessary in rainy season and
regions where there is high humidity. The temperature and equipment used for
drying depends on the physical and chemical nature of the drug and its
constituents. Various equipment's such as tray dryers, spray dryers, vacuum
dryers are used.
Over heating may lead
to excessive loss of volatile components as well as decomposition of chemical
constituents. The temperature should be kept below 60 0C
wherever possible.
a. Tray dryers (Oven)
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
Few 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.
Example: papaya latex,
pectin, tannins, etc.
Secondary processing
The secondary
processing differs from one herb to another depending on the nature of active
ingredients as well as therapeutic properties.
Secondary processing includes
techniques such as removal of foreign substances, prevention of microbial /
infestation, enhancing the efficacy of drugs, reducing the toxicity, extraction
using suitable solvents, conc. & drying of extracts.
These are further
standardized by different methods.
Cutting, Sectioning
and Communition :
After thoroughly
drying, the herbal materials are processed by cutting and sectioning into
smaller sizes which are convenient for storage as well as extraction.
Various sizes can be
obtained depending on the part of herb and extraction methods used. It may be
small particles, coarse powder or fine powder.
Aging /Sweating :
Aging refers to
storing the raw material for a specified time after harvesting.
It is generally done
under sun or in shade for up to a year.
During the process of
aging excessive water is evaporated & enzymatic reactions may occur to
alter the chemical composition of herbal material.
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