Transcript Collection of medicinal plants

Collection of medicinal plants
• Drugs may be collected from wild or
cultivated plants.
• It is known that the active constituents of
medicinal plants are affected by many
factors and may vary during the course of
plant growth.
• Proper time of collection is very important to
obtain a drug of a good quality.
Factors affecting collection
1. Time of the year:
The plant may contain a substance in winter that is not
present in summer, or its amount varies markedly e.g.
Rhubarb contains no anthraquinone in winter, instead
it contains anthranols, which in summer, are oxidized to
anthraquinones.
Colchicum corm is free from bitterness and is devoid of
the alkaloid colchicine in autumn, hence is used in
Austria as a food, instead of potatoes. Bitterness starts
to appear in spring and early summer when it is used
as a drug.
2- Time of the day:
Some drugs, like Digitalis, contain different
amounts of active constituents in different
times of the day. Being highest in the
afternoon.
3- Stage of maturity and age:
• The value and content of active
constituents of many drugs depends on
the stage of maturity and age.
• Conium fruits contain coniin when fruits
are mature and unripe.
• Santonica flowers are rich in santonin,
when unexpanded, when it starts to open,
the santonin content decreases.
Drying of crude drugs
Reasons for drying:
1. To help in their preservation.
2. To fix their constituents, by preventing
reactions that may occur in presence of water.
3. To prevent the growth of micro-organisms such
as bacteria and fungi.
4. To facilitate their grinding.
5. To reduce their size and weight.
6. Insufficient drying favors spoilage by microorganisms and makes it possible for enzymatic
destruction.
Methods of drying
Drying is carried out either by natural or artificial
methods.
1- Natural drying: this is accomplished by natural
air in sun or shade.
2- Artificial drying: this is a rapid method done at
well-controlled temperature and is accomplished
by:
• direct fire.
• Use of heated stones.
• Use of stoves.
Disadv. of natural drying:
Drying should be done carefully to prevent damage
or burning.
Excessive heat cause gelatinization of starch, as
well as, a smoky odour.
Drying chambers:
this method provides a controlled process. Drying
chambers consist of closed space with several
movable screen trays, arranged so as to allow
the circulation of heated air. Its temperature and
ventilation can be regulated to suit drying of
different organs.
• Lypholyzation (Freeze drying)
• Chemical drying using desiccators
• An absolutely dried drug is that
completely freed from water, when
exposed to air it absorbs 8-10% of
moisture and is called air-dry drug.
Several changes may occur on drying:
1. Size and weight: markedly decreases due to
loss of 80-90% of water.
2. Shape and appearance: some drugs shrivel
on drying, others have their surface wrinkled or
reticulated.
3. The method of drying also affects the
appearance of some unorganized drugs.
aloes, when rapidly heated and cooled,
produces homogenous glassy masses but
when slowly heated and cooled produces
heterogeneous opaque masses.
4- Texture: drugs on drying become harder
( roots),
brittle (leaves) while those containing starch become
horny.
5- Colour: generally on drying, drugs become darker in
colour and in certain cases a total change of colour
occurs, e.g. poppy, when fresh is scarlet-red, on drying
becomes dull-violet.
Tea leaves change from green to brown almost black.
Flowers may lose their colour especially when red or
blue due to destruction of anthocyanin pigment
responsible for the colour.
6- Odour: Hyoscyamus and Digitalis lose their bad odour
on drying.
Orris acquire a pleasant odour on drying.
7- Taste: this may be altered. Fresh Gentian is very bitter
becoming pleasant on drying.
8- Constituents: some drugs containing sensitive
constituents as cardiac glycosides may undergo certain
degrees of hydrolysis during drying. Fresh Vanilla pods
contain gluco-vanillin and gluco-vanillic alcohol. On
drying, hydrolysis of both glycosides and oxidation to
vanillin take place.
Some changes are favorable and hence conditions should be made
suitable to encourage such changes.
On the other hand certain changes are undesirable
and conditions should be controlled to guard against their occurrence.
Preservation and protection of crude drugs
Storage represents the last stage of preparing crude drugs. drugs
usually deteriorate along the time of storage,
except in few cases e.g. Cascara and Frangula should not be used
except after certain period of storage.
Certain drugs as Nux vomica are hardly affected by storage.
Generally, changes that take place during storage of crude drugs
are objectionable, e.g. drugs containing volatile oils gradually lose
their aroma.
Improper methods of storing and inadequate protection during storage
can cause a pronounced deterioration.
There are two principal reasons for deterioration:
Physiochemical: moisture, heat, air and light.
Biological: fungi, bacteria, insects and rodents.
Physicochemical factors
1. Moisture: moisture sometimes affects drugs adversely
through activating the enzymes (as in cardiac
glycosides).
2. Heat: rise of temperature up to 45 activates the
enzymes causing decomposition of active constituents.
Volatile oil containing drugs are also affected by higher
temperatures, their content decreases.
3. Air: oxygen of air oxidizes certain constituents of crude
drugs, e.g. linseed and lemon oil, it causes rancidity of
fixed oils and resinification of volatile oils.
4. Light: it affects drugs, especially those having marked
colours.e.g. yellow colour of Rhubarb changes to
reddish tint, white coloured corollas turn brown.
Biological factors
1. Bacteria: cotton fibres are rendered brittle by bacterial
attack which makes the cotton wool objectionable and
dusty.
2. Moulds: the mycelium of delicate hyphae produces an
unpleasant mass of clinging particles in powdered
drugs.
3. Insects: they seem to attack all drugs but have
preferences to certain drugs as ginger, belladonna, kola,
liquorice,.....
Insects which infest vegetable drugs include beetles, mites
and moths. They render drugs porous and powdery.
Methods for controlling insects
1. Heat treatment: it is the simplest method and
is done by exposing the drug to a temperature
of 60-65. it is effective especially for insect
eggs which are not affected by insecticides.
2. Fumigation: this is done by volatile
insecticidal agents in closed areas e.g. CCL4,
CS2, CN. Most fumigants do not kill eggs of
insects. It is advisable to repeat fumigation at
intervals to obtain better results.
3. Liming: liming of certain drugs as ginger,
nutmeg to protect against insect attack provides
only partial protection.
4. Low temperature storage: this method is
preferred to fumigants and liming. Adult insects,
pupae, larvae and eggs are sometimes killed by
very low temperatures.
5. Exposure to alternate periods of low and
high temperatures: frequently is more effective
for killing insects than a prolonged period of low
temperature exposure.
Rodents: they cause much spoilage of
crude drugs during storage, especially if
wrapped in paper, cloth or put in
cardboard or wooden containers. The
presence of rodent's filth, excreta, hairs
causes rejection of the drug.