Introduction 2

PHARMACOGNOSY
Lecture-2
(Introduction)
Dr. Ahmed Metwaly

Objectives
■ Collection
■ Preparation

Collection Of Drugs
■ Factors affecting collection of
drugs:
■ Time of the year:
The constituents vary in amount
and nature throughout the year.
e.g. Rhubarb, in winter, it contains
no anthraquinone, but contains
anthranols, which oxidized to
anthraquinones in warmer
weather
Hyoscyamus, contains less
alkaloids in winter than in
summer.
Rhubarb anthraquinones
winter
Anthranols
warmer
weather

Colchicum corm is collected at
the end of autumn and used
as food instead of potatoes
because it is free of bitterness
and devoid of its active
constituents (no colchicine)
and is full of starch.
And it is collected for
medicinal use on spring and
early summer when it is better
and contains colchicine.
Colchicum corm
colchicine

■ Time of the day:
Digitalis leaves contain a higher
glycosides when collected in
the afternoon than in the
morning, due to the glycosides
may be hydrolyzed during the
night and recombine with sugar
during day- time carbon
assimilation.
Solanaceous leaves contain a
higher alkaloidal content in the
morning than in the afternoon,
may be due to the constituents
are hydrolyzed by sun.
Digoxin
Atropine

■ Stage of maturity and age:
Clove contains a highest concentration of
oils at the bud stage.
Chamomile and pyrethrum are collected
before full expansion, because the
constituents are present in the ovary, so
that we leave the chance for the ovary to
grow to its full size.
Santonica flowers are collected before
expansion, because the constituents
(santonin) oxidized by sun to inactive
photosantonin.
Clove
Chamomile
Santonin

■ Solanaceous leaves contain the maximum
amount of alkaloids when the plant is in the
flowering stage.
■ Lobelia herb must be collected towards the
end of the flowering stage.
hyoscyamus leaves

General rules for the collection of drugs
■ Leaves are collected before maturation of flowers (just beginning to
expand) i.e. at a time when they may be expected to be very active
(contain an optimum of the products of the plant metabolism) and before
their biosynthesized products have been translocated to other parts of the
plant
It is collected in dry weather.
■ Flowers are collected before the full expansion. It must be collected in dry
weather because petals which are damp when gathered may infected with
fungi or become badly discolored during drying.

■ Fruits are collected when fully mature but not ripe; fruits usually undergo
chemical changes during ripening.
■ Seeds being storage organs, are collected when mature.
■ Roots and rhizomes are collected in autumn or winter, usually after the
withering of aerial parts and before the vegetative process starts and when
their tissues are fully stored with reserve food and medicinal constituents.
■ Stem barks are collected in spring when the bark can be stripped from the
trunk and branches more easily.

Preparation Of Drugs
■ The preparation of crude drugs from the collected plants involves cleaning
or garbling and drying. Certain plants are subjected to a process of
bleaching.

1- Cleaning and Garbling
2- Decortication
3- Bleaching
4- Drying
5- Curing of drugs

■ Cleaning and Garbling:
Removal of extraneous matter from the drug such as soil particles; sand,
dirt or parts of plants which are not officially indicated.
Rhubarb and Liquorice are peeled.
Large roots as Calumba and Inula are sliced to facilitate drying.
Some plants like cinnamon are decorticated to acquire a good appearance, or
to remove tissues containing undesirable matters.
■ Bleaching:
Which alters the appearance of certain drugs when they are being prepared
for the market, and protect against insect attack. e.g. Ginger and Nutmeg
are coated with a layer of calcium carbonate.
Ginger

Drying
■ The object of drying of drugs:
■ To aid in their preservation.
■ To fix their constituents i.e. to stop the enzymatic or hydrolytic reactions
that might alter the chemical composition of the drug.
■ To prevent the growth of microorganisms such as bacteria and fungi.
■ To facilitate grinding of the drugs into a powder).
■ To reduce weight and bulk (size), to facilitate packing, storage and
transport (lowering transportation cost).

Methods of Drying
■ Natural Drying:
the drug dried by exposure to direct sun, or spreading in the shade by putting
on the floor or mats or trays in a single layer and by time, drugs are turned over.
■ Shade drying is employed
when it is desirable to retain the natural
color of the drug and preserve its
sensitive active constituents.
■ Sun drying is employed for drugs
not affected by direct action of sunlight.

■ Artificial Drying:
– Physical methods, that is involve the use of
elevated temperature and / or decreased
pressure (vacuum) or the use of radiation of
infra-red or radio-frequency wave length.
– Chemical method, by using of desiccants.

■ Artificial drying has the advantage over air-drying in that it immediately
stops enzymatic action.
e.g. If the Digitalis leaves are allowed to dry naturally, a very rapid enzymatic
hydrolysis of the cardiac glycosides will occur.

■ Artificial heat may be applied by:
■ Uncontrolled heat;
by using direct fire, heated stones or using of stoves, this must be done
carefully to prevent the damage produced to drugs when dried e.g.
scorching or burning. Excessive heat produces gelatinization of starch, as
will as, smoke will impart to the drug a smoky odor.

■ Controlled heat by using,
– Drying sheds or chambers:
Care is taken that drugs,
becoming dry are moved
downwards on the lower shelves
and fresh drugs are placed
upon the uppermost shelves, so
that moisture given off from the
fresh drugs may not dampen
the already partially dried ones.

• Pneumatic high-speed
dryer:
High temperature for few
second. Some firms use
vacuum ovens for drying
leaves as Digitalis, which are
rapidly and efficiently dried
by this means.
Fairly rapid drying helps flowers and leaves to retain their
coloring and aromatic drugs to keep their aroma, but the
temperature must be governed by the constituents and
physical nature of the drug.

• Freeze drying (lyophilization):
Which is used for thermo labile
drugs such as biological fluids e.g.
blood plasma, enzymes, hormones,
royal jelly, vitamins, antibiotics. This
method depends on drying of the
plant in the frozen state at low
pressure (vaccum).

Advantage of lyophilization
■ Prevents chemical and enzymatic hydrolysis in the chemical constituents
■ Prevents oxidative changes of substances that are usually
oxidized if dried by other means.

Drying using chemical method
■ The drug is placed in a dissicator at the
bottom of which a desiccating agent
(H2SO4, silica gel, anhydrous calcium
chloride or sodium sulphate) is placed. In
this closed atmosphere, water vapor is
absorbed by the dissicating agent leaving
a dry atmosphere in which evaporated
water from the drug is carriage.
■ As a general rule, leaves, herbs and
flowers must be dried between 40 and
60, while barks and roots are dried
between 40 and 80 c.

Effects of drying on the drugs involves
Size and weight:
The drugs lose 80-90 % of their original weight due to loss of water where they
get smaller in size.

■ Shape and appearance:
Some drugs shrivel and shrink when dried
and the surface gets wrinkled or reticulated
e.g. Black pepper on drying shows polygonal
reticulations, duo to the presence of stone
cells in the hypodermis.
The petiole of Datura stramonium leaves
becomes hooked and bent on drying as it
contains more collenchyma on the lower than
the upper side.
The inner surface of most barks shows depressed
dark appearance, gets curved, channeled,
quill, double quill as the inner tissues are soft
and outer ones are hard (more scelrides).

Vanilla changes from yellow to dark
brown.
The green color of certain drugs change
to brown on drying due to
decomposition of chlorophyll,
Flowers may lose their color especially
when red or blue due to the
destruction of the anthocyanin
pigments producing these colors.
Certain barks are changed in color due to
oxidation of tannins to certain
phlobaphenes e.g. Cinchona and
Cinnamon.

Odor:Drying may changes the natural odor of certain drugs
e.g. Digitalis and Hyoscyamus lose their bad odors, when dried
Taste: May be altered e.g. Gentian and Tea is very bitter when fresh, and
becoming pleasant or slightly bitter

■ Constituents (curing of drugs):
Constituents of some drugs may change due to drying e.g. the purine bases
present in some fresh drugs in a combined glycoside form are hydrolyzed on
drying and the dried drugs contain the free bases.
Gentiopicroside present in Gentian are hydrolyzed during drying into
gentiamarin and glucose which reduce the bitter taste of Gentian.
Fresh vanilla pods contain the glycosides gluco-vanillin and gluco-vanillyl
alcohol. On drying, hydrolysis of both glycosides and oxidation of the latter to
vanillin occurs.

■ If these changes are required, drying should be done slowly (curing of
drugs). If the changes are objectionable, drying must be carried out as
rapidly as possible.
■ Rapid drying, not only prevents the decomposition of active constituents,
but also retains the color of the drug.

Summary
■ Collection
■ Preparation

Introduction 2

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Introduction 2