1. University of Jos
Faculty of Pharmaceutical Sciences
Department of Pharmacognosy & Traditional
Medicine
PCG 202 Lecture Notes
DR. PAUL N. OLOTU
September 2019
1
5/4/2024
2. PCG 202: Organised & Unorganised drugs of Natural
Origin.
Organised Plant Drugs: This comprise of whole
plants or herbs or any of their organs or any
morphological or anatomical part derived from them,
which are composed of definite organised cellular
structures.
Types: Organised drugs are grouped based on the plant
organs which they are derived from into:
1. Overground Structures: Leaves & herbs, flowers,
seeds, fruits, barks & woods.
2. Underground Structures: Roots, Rhizomes, Bulbs,
Corms & Tubers. 2
3. BARKS
A bark in botanical concept consists of the outer dead
tissues of stems and roots which occurs outside the
active cork-cambium and includes the cork,
epidermis and lenticels.
A Pharmacognostic bark consists of all tissues
outside the woody part of the stem or root separated
by the main cambium. Thus, it includes the
secondary phloem, primary phloem, cortex and
periderm.
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4. The botanical bark is thus referred to as the outer bark
in pharmacognostic terms which is often removed
from the medicinal bark when it lacks the medicinally
active constituents of the drug or contains undesirable
amount of tannin or coloring matter.
Anatomy of the bark
A bark consists of the following layers of tissues in
succession from inner surface to the outer.
One or two layers of cambial parenchymatous cells
A few layers of secondary phloem tissue, which
consists of sieve tubes, phloem parenchyma, phloem
fibres, and sometimes stone cells, and is traversed
radially by medullary rays. 4
5. Two or three layers of primary phloem
A layer or two of pericycle, which is composed of
parenchyma or fibres.
A layer of Endodermis, the inner layer of the cortex
which frequently contains starch.
A few layers of Primary cortex, a zone consisting of
chlorophyll- containing collenchyma and
parenchyma.
A few layers of Secondary cortex.
One or two layers of Cork-cambium or Phellogen
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6. A few layers of Cork cells.
One or two layers of dead tissues forming the outer
surface frequently showing lichens, lenticels, and
remains of primary tissues cut off by the cork.
In addition, group of Sclerenchyma occur in the
cortex.
Examples medicinal barks: Cinchona, Cinnamon,
Cascara Sagrada, Quillaia.
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7. Shape of Barks
Flat: Thick barks like Cinchona & Cascara are often dried
under pressure, thus the finished product does not undergo
any shrinkage or curvature and remain flat.
Curved: When the bark is slightly concave on the inside.
Recurved: When the bark is slightly concave on the
outside.
Chanelled: When the bark is deeply curved on the inside
to form a trough.
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8. Quill: When the bark is deeply curved on the inside such that
one edge of the bark overlaps the other.
Double Quill: When each edge of the bark is rolled
independently into a quill.
Compound Quill: When more than one single- or double
quilled pieces of the bark are packed inside one another.
Examples: Ceylon cinnamon.
Striation: When shrinkage due to drying resulted into the
production of parallel longitudinal ridges on the inside.
Corrugation: When shrinkage due to drying resulted into the
production of parallel transverse ridges on the inside.
Example, Cascara.
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9. Fractures of Barks
Short: When the bark breaks easily with a smooth fractured
surfaces.
Fibrous: When the bark breaks with resistance and the
broken surface shows fine projecting fibres.
Granular: When a bark breaks with less effort and exhibits
small rounded prominences.
Splintery: An irregular fracture, usually, into pieces with
larger and smaller projecting edges and splinters.
Brittle: When the bark easily breaks into many pieces when
drop unto a hard surface.
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10. Complete: Fracture of the bark may be complete when the
bark breaks clean across. Examples: short and brittle type.
Incomplete: Fracture of the bark may be incomplete when
the bark breaks apart across. Examples: fibrous, granular &
splintery.
Mealy: A bark is mealy when the constituents present in the
bark is abundant starch.
Resinous: A bark is resinous when the constituents present
in the bark is abundant resin.
Waxy: A bark is waxy when the constituents present in the
bark is abundant resins, waxes, gums & mucilages.
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11. CASCARA SAGRADA
Synonyms: Cascara bark, Sacred bark, Chittem bark.
Botanical Source: Cascara sagrada consists of the dried bark of
Rhamnus purshiana , D.C. collected at least one year before
being used. The plant is a shrub or small tree of the family-
Rhamnaceae.
Geographical Source: The plant is cultivated in British
Columbia, Oregon, California & Kenya.
Macroscopical Characters: The bark occurs in single quills or
chanelled or flat pieces, 5-20 cm in length, up to 2 cm in width &
1-4 mm in almost smooth cork with pale brown, transversely
elongated lenticels, occasional patches of silver-grey lichens and
mussel-scale insects. Inner surface has longitudinal striations &
faint transverse corrugations. Fracture is short & granular to the
outer side but somewhat fibrous to the inner side. Odour is faint
but characteristics, taste bitter & nauseous.
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12. Microscopical Characters:
The outer cells of cortex are Collenchymatous and the
inner cells contain minute starch grains. Numerous
idioblasts contain rosette of calcium oxalate. Stone cells
occur in oval or rounded, yellow-colored groups & are
thick-walled, striated & pitted. Slender phloem fibres
occur in narrow, elongated tangential groups and are
associated with sheaths of idioblasts containing prisms
of calcium oxalates. Sieve tubes occur in groups and are
not accompanied by companion cells.
Constituents:
It contains 1.5-2 % emodine & other similar
anthraquinone glycosides. It also contains dextrose and
an enzyme.
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13. Uses: It is a cathartic drug, usually used for the
correction of habitual constipation.
Substitutes/Adulterants: The dried bark of Rhamnus
frangula Linn. is a common substitute & barks of other
species of Rhamnus are used as adulterants.
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14. WOODS
The wood represents the central harder part of all shrubs
& plants inner to the pharmacognostic bark. That is, the
bark lies inner to the cambium ring.
Wood consists mainly of xylem tissues (vessels,
tracheids & fibres) & the associated parenchymatous
cells, the wood parenchyma.
Both the primary (original) & secondary xylem
constitute the wood of the plant.
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15. As the cambium continuously form the secondary
xylem, the primary xylem are gradually pushed toward
the Centre and become more compact.
As time goes on, the primary xylem dies due to over
congestion as well as the accumulation of tannins, oils,
gums, resins, etc & the formation of plugging xyloses (
a balloon-like ingrowths) in their cavities.
The dead xylem tissues then give rise to a hard, durable
& densely colored central wood called heartwood. Thus,
its function is no longer for the conduction of water but
simply for mechanical support for the plant.
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16. The outer region, consisting of the newly formed
secondary xylem; which are living, lighter in color and
comparatively softer in texture constitutes the sapwood.
This part of the wood is used by the plant for
conduction of water & salt solutions from the root to the
leaf.
Pharmacognostic wood are obtained from both sap- and
heartwoods but the great bulk comes from heartwood.
Examples of medicinal woods: Deal, Quassia, Sandal,
Guaiacum
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17. External Characters of the Wood
When a wood is cut transversely, the characters seen
include:
1. Annual rings: These are bands crossing a piece of
wood from one radial surface to the other. Each ring
represents the total growth of a plant in a year. They
are the spring wood & the summer wood; the latter
being much darker, forms a dark line on the outer
edge of each annual ring.
2. Medullary rays: They cross the annual rings at
right angles as parallel lines. In-between the rings
are small holes or pores which represents the
vessels.
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18. 3. Xylem parenchyma: These are associated with the
pores seen as small patches or bands which are lighter
in color than the remaining xylem.
4. Fibres: These form the remaining part of the wood
which are darker in color than the xylem parenchyma
and these give the wood its hardness & strength.
The type & arrangement of fibres in the wood
determine the splitting properties or grain type of the
wood, which may be straight-grained- that is, if the
fibres are straight & are arranged parallel to each
other. This type of wood split very easily.
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19. The wood is said to contain Interlocked grain, when
the wood contains wavy fibres which are arranged
crossing each other at angle of about 30 %. This types
of wood splits with great difficulty.
Historically, woods are composed of 5 types of
elements: vessels, fibres, medullary ray parenchyma,
tracheids & wood parenchyma.
Vessels are characteristics of the angiospermous
woods and are absent from the coniferous woods.
Tracheids form the great bulk of the wood of the
conifers. Examples: pinus, ephedra, alnus.
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20. Fibres constitute the major bulk of the wood &
determine the texture of the wood.
Wood parenchyma occurs in association with vessels
of most woods.
Medullary ray parenchyma transverse the wood
tissue forming the medullary rays in a radiating
pattern.
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21. Deal wood
Synonyms: Red deal, yellow deal, white deal
Botanical source: Red or yellow deal consists of the
wood of Pinus sylvestris Linn. & that of Picea excelsa
constitute the white Deal. Other species of Pinus &
Abies also yield similar wood. This plant belong to the
family, Pinaceae.
Geographical Source: Deal plants are grown in many
European countries, North America & Canada.
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22. Macroscopical Characters: Deal wood is straight-
gained and split readily longitudinally with smooth
surface. It is soft in texture & buff in color, has a
density of about 0.35-0.8 & possesses a resinous odor.
Annual rings are well-marked, pores absent but resin
ducts occur in the central & outer part of each annual
ring. The medullary rays appear as fine whitish lines.
Microscopical Characters: The wood consists almost
entirely of narrow, long tracheids having pits on the
radial walls. The pits are large, circular and bordered.
Schizogenous resin ducts are abundant in the middle
region of each annual ring.
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23. Thin-walled parenchymatous cells occur surrounding
the resin ducts. Both uniseriate & multiseriate
medullary rays are present, which are composed of
elongated rectangular or rhomboid parenchymatous
cells.
Constituents: Deal contains about 75 % cellulose, 25 %
lignin, about 1 % resin (colophony) & a small quantity
of volatile oil (turpentine).
Uses: Deal is used as the chief source of wood cellulose
& for making mechanical wood pulp.
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24. Roots
Root drugs are usually the strongly developed primary
(tap) roots, although many secondary roots & root
system sometimes produce some important root drugs.
Roots bear no leaf or bud. The only appendage present
on the root is the lateral branch-roots which are similar
in construction to the main root.
Examples of medicinal roots: Aconite, Belladonna,
Gentian, Ipecacuanha, Jalap, Rauwolfia, African
Rauwolfia,
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25. Internal Structure of the Root
The transversely cut surface of the root reveals
characteristic features by which a monocotyledonous
root can be distinguished from a dicotyledons, to which
most root drugs belong.
There is a central woody core surrounded by the
cambium, a cylinder of secondary phloem & an
external layer of the cork.
In monocotyledons, a central pith is usually present &
often composed of thick-walled lignified cells. The
xylem is porous & a cortex is present.
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26. However, all roots are externally covered by a
piliferous layer. The major part of the root is made up
of parenchymatous cortex.
Internal to the cortex is a well-developed endodermis.
The stele is surrounded by a single layer of pericycle &
has alternating bundles of xylem & phloem on different
radii arranged in a circle.
The xylem bundles frequently develop until they meet at
the centre of the root, forming a rod-shaped mass of
xylem.
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27. Ipecacuanha Root
Synonyms: Ipecac, Ipecacuanha Root, Ipecacuanhae
Radix.
Botanical Source: Ipecacuanha consists of the dried ,
enlarged advantageous roots & slender rhizomes of
Cephaelis ipecacuanha (Brot.) A. Rich. Of the family
Rubiaceae.
Geographical Source: The drug is obtained from plants
growing both wild & cultivated in the forest of Brazil. It
has been successfully produced by cultivation in west
Bengal, Burma, Singapore & Malaysia.
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28. Macroscopical Characters: The root is tortious &
roughly cylindrical in shape. It occurs in pieces, 5-15
cm long & 4-6 mm thick. It is covered with an
annulated bark which is often separated completely
from the wood.
The bark is reddish-brown to dark brown in color & the
wood is yellow. The drug has a short fracture usually
with a characteristic fractured surface which is horny or
starchy in the bark & splintery in the wood.
The transversely cut surface shows a distinct cambium,
a wide bark & a narrow, compact central wood. It has a
slight odor & a bitter taste.
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29. Microscopical Characters: The cork of the bark
consists of tangentially elongated polygonal cells
containing a granular brown content. The cortical cells
are parenchymatous with numerous small intercellular
spaces. They contain much starch grains & occasional
acicular raphides of calcium oxalate.
The phloem occurs as wedge-shaped groups around the
wood. The xylem tissue consists of lignified pitted
tracheids; long, narrow obliquely pitted & thick-walled
fibrous cells (not typical fibres), & elongated, lignified
cells of medullary rays.
Simple or compound starch grains with well-marked
hila occur in the xylem tissue.
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30. Constituents: Ipecac contains 2-5 % total alkaloids,
which include emetine (about 70 %), cephaeline (about
30 %), psychotrine, methyl psychotrine & emetamine.
It also contains a glycoside, ipecacuanhic acid, starch
& calcium oxalate.
Uses: The drug is mainly used as an expectorant and
emetic, & as a remedy for amoebic dysentery. It also
possesses diaphoretic & cholagogue properties.
Substitutes/Adulterants: These include the dried roots
& rhizomes of Psychotria acuminata (Cartagena
Ipecac), Psychotria emetica, Richardsonia scabra
(undulated Ipecac), Menettia ignita & Ionidium
ipecacuanha (White Ipecacuanha).
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31. Rhizomes
Rhizomes, bulbs & corms are modified underground stems.
Rhizomes are thickened stems growing horizontally,
vertically or obliquely under the surface of the soil.
They posses distinct nodes & internodes, & bear scale
leaves at the nodes. Occasionally, buds occur in the axils of
the scale leaves.
They bear slender adventitious roots on their under surface.
Rhizomes may be unbranched bearing a bud at the
growing end, or branched; each branch ending in a terminal
bud.
Examples of rhizome drugs: Arnica, Ginger, Hydrastis,
Liquorice, Male fern, Podophyllum, Rhubarb, Turmeric, &
Valerian.
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32. Internal Characters of Rhizomes
They have a general internal structures similar to that of
aerial stems but do not have any well-developed
column of xylem tissue in the form of a central wood, a
useful character which help to distinguish rhizome from
root.
Drugs of cryptogamic rhizomes from a transverse
section shows a number of separate steles; the
dicotyledonous rhizomes have a circle of vascular
bundles & a central pith, whereas, in
monocotyledonous rhizome, the vascular bundles are
scattered throughout the stele & cortex & an
endodermis is evident.
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33. In the unpeeled rhizomes & corms, either an epidermis
or a few layer of thin-walled cork cells constitute the
outer part.
The cortex usually consists of thin-walled
parenchymatous cells containing food reserves like
starch, inulin & hesperidin.
the vascular bundles in the stele are collateral &
consists of both xylem & phloem. They are variously
distributed in the ground tissue depending in the group
of plants the rhizome belongs to, as mentioned before.
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34. Liquorice
Synonyms: Liquorice root, Glycyrrhiza, Glycyrrhizae
Radix.
Botanical Source: Liquorice is derived from the stolon
& roots of Glycyrrhiza glabra Linn. & other species of
the genus Glycyrrhiza, family Leguminosae.
Macroscopical Characters: The stolons are cylindrical
in shape & occur in pieces of 15 cm or more in length
& 1-2 cm in breadth. They are unbranched & may be
peeled or unpeeled.
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35. The unpeeled drug is longitudinally wrinkled with
occasional buds and the peeled drug is coarsely fibrous
on the surface.
The color varies from yellowish-brown to dark brown
(unpeeled drug) & pale yellow (peeled drug). The
fracture is fibrous, the fracture surface being starchy
with projecting fibres.
The transversely cut surface shows a radiate wood & a
distinct cambium ring. A pith is visible in the stolon but
is absent from the root. It has a faintly characteristic
odor & a sweet taste.
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36. Microscopical Characters: The peeled drug contains no
cork but the unpeeled drug contains a typical cork, the
outer cells of which have thick walls & contain a
reddish brown substance & the inner cells have thinner
walls.
The cortex contains idioblasts with prisms of calcium
oxalates.
The phloem tissue is made up of parenchyma traversed
by numerous groups of sieve tubes & is characterised by
the presence of numerous bundles of thick-walled
fibres surrounded by a sheath of idioblasts with calcium
oxalate prisms.
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37. The xylem tissue is divided into sections by 3-4 cells
wide with large medullary rays & is composed of
numerous yellow pitted vessels, lignified wood
parenchyma & wood fibres. Large number of rounded
starch grains are present in the parenchymatous cells.
Constituents: It contains 5-7 % glycyrrhizin, a sweet
principle made up of potassium & calcium salts of
glycyrrhizic acid. it also contains glucose, sucrose, a
bitter principle, starch, fat, & oxalate.
Uses: It is used as a demulcent & expectorant. It is also
used in the treatment of gastric & duodenal ulcers.
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38. Substitutes/Adulterants: The Russian & Iranian
varieties of liquorice (G. glabra) var. glandulifera & G.
glabra var. violacea respectively & Manchurian
Liquorice are common substitutes & adulterants of
liquorice.
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39. Bulbs
They consist of a shortened convex or slightly conical
stem, a terminal bud & numerous scale leaves. The
scale leaves grow from the upper surface of stem or
from around it, while a cluster of advantageous roots
arise from its base.
Drugs which are represented by the fleshy scale leaves
of bulbs include garlic, onion & squill.
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40. Squill
Synonyms: Scilla, Scillae Bulbus, Scillae Radix.
Botanical source: Squill consists of the sliced & dried
fleshy scale leaves of the bulb of Urginea maritima
(Linn.) Baker (= Urginea scilla Stein) of the
monocotyledonous family Liliaceae.
Geographical source: Squill is largely obtained from
Malta & the countries of the Mediterranean coast.
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41. Macroscopical characters: The dried slices of the bulb
scales occur in concavo-convex curved strips,
frequently tapering at both ends, 1-5 cm long. They are
slightly translucent & pale yellow in color with
longitudinal furrows.
The dried pieces are brittle & have a short fracture but
they are tough but flexible when moist. The fractured
surface is mucilaginous. The transversely cut surface
shows a number of scattered vascular bundles
The drug has a slight odor & possesses a bitter,
mucilaginous & acrid taste.
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42. the entire bulb is ovoid in shape, 18-20 cm high & 12-
15 cm in diameter. It is often crowned with the bases of
the aerial leaves at the upper end & bases of the
adventitious roots at the lower end. The dry thin scale
leaves of the bulb are removed during cleaning of the
drug.
Microscopical characters: The epidermal cells are
axially elongated & quadrangular or polygonal is shape.
Nearly circular stomata are present on the lower (outer)
surface of the scale leaves in very small number. They
also occur very rarely on the upper (inner) surface.
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43. The bulk of the mesophyll tissue is made up of
parenchymatous cells, some of which are occasionally
filled with raphides of calcium oxalates embedded in
mucilage.
Vascular bundles are also present in the mesophyll and
are composed of spiral vessels & phloem with
parenchyma in-between. Rarely rounded starch grains
& prisms of calcium oxalate occur in the mesophyll
tissue.
The powdered drug is yellowish-white in color &
contained abundant, large, thin-walled cells of the
mesophyll parenchyma.
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44. Idioblasts containing raphides of calcium oxalate &
mucilages are present in the powder drug. Free single
acicular crystals & very occasional prisms of calcium
oxalate are also present in the powdered drug.
Constituents: It contains a number of cardiac glycosides
which include scillaren A, a pure crystalline substance
& scillaren B, an amorphous mixture of glycosides. It
also contains xanthoscillide, sinistrin, mucilage (4-11
%) & calcium oxalate.
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45. Uses: It is a heart muscle stimulant & a powerful
expectorant. It is used to improve the tone of the heart
muscle of weak hearts & in the treatment of chronic
bronchitis & coughs.
Substitutes: The fleshy scale leaves of Urginea indica,
the Indian squill is a good substitute of the European
squill.
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