1. Bark is the outer protective layer of stems and roots of woody plants. It consists of inner bark and outer bark. 2. The outer bark protects the tree from weather, insects and fungi. The inner bark transports food made in the leaves throughout the tree. 3. Bark has important structural, protective and transport functions and can be used to identify tree species. Different barks have distinct characteristics and chemical compositions that determine their uses.

2. - It is the first part of a tree
that you see.
- It's the stuff that's on the
outside of the wood.
- It is a very important part of
the tree, and deserves to be
discussed in this section.

3. • Bark management is important not only for
securing 1 the supply of diverse raw materials
bark provides (e.g., fibers, dyes, and
medicines), but also for protecting the trees
supplying these resources.
• Bark does a number of important jobs for
trees, but its main job is to 2 protect the wood
underneath. It also 3 prevents the wood from
being scorched if there is a forest fire.

4. Formation of bark:
• meristematic zone
• located between the bark and the wood,
• the vascular cambium zone: "the cambium" .
• Its cells divide inward and outward, laying down
new wood cells on those already in place and
new inner bark cells inside those already
existing.
• Definition:
• Bark is all the tissues of the stem or the root of
woody plants that are exterior to the cambium.

5. Bark consists of:
a- Outer bark.
b- Inner bark.
A-Outer Bark
• Outer bark (= rhytidome)
• The surface of the outer bark of many species
is perforated by corky lenticels that allow
increased rates of gas exchange by living
tissues inside the stem.

6. - The outer surface of the bark usually exhibits
important features as:
1- Epiphytes:
a- Lichens:
- a type of fungus that grows on the surface of
barks.
- It exists as a grayish thalloid structure.
- grow on trees using the bark as a medium for
their nutrition and growth.

7. b-Liverworts:
- are foliaceous structure,
- consists of very small stems to which small
leaves are attached in one plane.

8. c-Mosses:
- are stem bearing spirally arranged leaves each
possesses a midrib and lamina of one cell
thick.

9. 2-Lenticles:
- Lenticles, are breathing pores for exchange of
gases, larger in size and smaller in number
than stomata.
- Placed transversely,
- the shape and abundance of which may help
in distinguishing the bark.

10. 3-Cracks and fissures: Arise due to continued
increase in growth and the lack elasticity.
4-Wrinkles and furrows: The greater shrinkage of
the softer tissues results in formation of wrinkles
because the shrinkage of the barks during drying
occurs chiefly transversely.
5-Smooth: When the cork is evenly developed.
6-Scaly: It may be rugged and scaly due to
exfoliation of the outer tissues.

11. N.B.: A tree can often be identified by its bark because bark looks different on different trees.

12. B- Inner Bark:
• Inner bark is produced by and adjacent to the
vascular cambium.
• It is composed of living secondary phloem.
• Progressing towards the outside of the stem,
inner bark is typically terminated by the
innermost and most recent periderm, which is
produced by the phellogen. The phellogen
develops from parenchyma in the older
phloem tissues or, in young stems, just
beneath the epidermis.

13. Collection of Bark
 Collection is usually in spring or early summer,
when the cambium is active, and after a rainy
season, the bark is most easily collected.
Drying of Bark
• Drying of barks is nearly always affected by the
sun's heat in open air, or sometimes, after a
preliminary drying in the open air, the
operation is completed by some kind of
artificial heat.

14. Different shapes of Bark (curvature)
the bark is described as:
1-Flat: When quite flat and very thick, i.e.
Quillaia.
2-Curved: When curved and slightly concave on
the inner side, i.e. Wild cherry.

15. 3-Recurved: When the concave side is the outer
one, i.e. Pomegranate.
4-Channelled: When deeply concave on the
inner side, i.e. Cassia.

16. 5-Single quill: When deeply concave on the
inner side that the edges of the bark nearly or
quite overlap, i.e. Cinchona.
6-Double quill: When both edges are separately
in rolled, i.e. Frangula.

17. 7-Compound quill: When single or double quills
are packed inside one another, i.e. Cinnamon.

18. Fracture
• It is the behavior of barks when broken across
transversely and the appearance of the exposed
surfaces. It is described as:
 Short: When the fractured surface is smooth.
 Granular: When the surfaces exhibit small
rounded prominences.
 Fibrous: When fibrous threads extend from the
broken surfaces.
 Laminated: When breaks into tangentially
arranged layers.

19. Histology of Bark
• The bark includes a number
of different tissues.
• From the outside to the
inside of a mature woody
stem,
The layers include:
(1) Cork (Phellem).
(2) Cork cambium (Phellogen).
(3) Phelloderm.
(4) Cortex.
(5) Phloem.
(6) Vascular cambium.
(7) Xylem.

20. BARK
Outer Bark Inner Bark
2ry Phloem
Transmits food made
in the leaves down to
the roots
The Periderm
2ry Cortex
Cork cambiumCork
Phelloderm

21. Cork cambium
(phellogen)
Vascular cambium
divides to the
outside
divides to the
inside
Cork
(phellem)
Phelloderm
Secondary Phloem
Secondary Xylem
divides to the
outside
divides to the
inside

22. Secretory Structures
• Secretory structures could be:
- External Secretory Structures
(found on the surface of the plant)
-Trichomes and Glands
-Nectaries
-Hydathodes
- Internal Secretory Structures
(embedded in various tissues)
-Secretory cells
-Secretory cavities and canals
-Laticifers

23. Internal Secretory Tissues
1- Secretory Cells (Idioblasts):
- are cells or groups of cells which produce a variety
of secretions.
- occur either isolated or rarely arranged in rows,
- frequently found in all the tissues,
- and differ from the other cells of the tissue
mainly by their contents and size.

24. - Secretory cells may be elongated so called
sacs or tubes and could be branched.
- The secretory cells secretions may be volatile
oil, resin, gum-resin, mucilage, enzyme or
tannins.

25. Schizogenous cells Lysigenous cells Schizolysigenous
sllec
2- Secretory Cavities or Sacs (Internal Glands)

26. 3- Secretory Ducts (Canals)
• These are tube-like structures containing and
producing secretion,
• may extend through the whole length of the organ
or even through the whole of the plant;
• usually produce volatile oil or oleo-resin.

27. 4- Laticiferous Structures
• These include cells and vessels which are, in
most cases, in the form of tubes, the contents
or secretion of these elements is called latex.
• Latex is a colorless, milky white, yellowish or
red slightly viscous emulsion or suspension of
variable composition.
• Laticiferous structures are most commonly
found in the phloem.

28. Simple vessels Branched vessels
Latex vessels

29. 1. The outer bark (cork).
protects the tree from extreme
temperatures, bad weather, insects and fungi.
2. The inner bark (2ry phloem)
conveys the food-bearing sap developed in the
leaves down to the various parts of the tree.
3. The cambium
is a thin layer of cells, which produce phloem on one side
and xylem (sapwood) on the other.
4. Sapwood is the living wood in the tree through
which the raw sap rises from the roots to the
leaves.
5. The heartwood consists of old cells. This is the
dead part of the tree that nevertheless provides
structural strength.
6. The pith is the central core of the tree (missing in
many species).
A transverse section in the trunk of an old stem

30. Cinchona Bark ‫الكـينــا‬ ‫قـشر‬
(Anti-malarial bark)
• Botanical Origin:
• It is the dried stem and root bark of
Cinchona succirubra (Red Cinchona),
C. ledgeriana, C. calisaya (Yellow
Cinchona) and C. officinalis L. (Pale
Cinchona), Family: Rubiaceae.

31. I- Stem Bark
- Shape: quills, double quills, chips or curved pieces.
- Size: up to 35 cm long, 1-4 cm wide and 2-9 mm thick.
- The outer surface: grey or greyish-brown to reddish brown,
bearing whitish or greyish lichens and mosses. It is rough
with-corky longitudinal ridges and transverse fissures,
exfoliation may occur.
- Inner surface: pale yellowish-brown, longitudinally striated;
fracture; short in the outer part, and shortly fibrous in the
inner part.
- Fracture: short in the outerpart and shortly fibrous in the
inner part.

32. II-Root Bark
- It is irregularly curved channeled, often twisted
pieces, 2-7 cm long.
- Lichens and other epiphytes are absent.
-The outer surface is somewhat scaly while the
inner surface is striated and is frequently
fissured while the rest of other characters are
similar to those of the stem bark.

33. Powder:
- Powdered Cinchona is yellowish-brown, brown or
reddish-brown in color.
- It is characterized by:
1- Fragments of yellowish bright bast fibres, either
entire or in broken pieces.
2- Fragments of brown parenchyma, occasionally
with idioblasts.
3- Fragments of reddish brown cork.
4- Few small starch granules usually simple, rarely
compound of 2 to 5 components and very minute
microsphenoidal crystals of calcium oxalate.

34. Powdered Cinchona Bark
starch granules
Cork Cells
Phloem fibres
crystals of
calcium oxalate

35. 1- Mainly alkaloids (Quinoline alkaloids): more than 30 alkaloids (6 -10
%). The four most important alkaloids are:
- Quinine (20 %),
- Cinchonidine (30 %),
- Cinchonine (45 %),
- Quindine (5 %)
- and their methoxy derivatives.
Active Constituents

36. 2- Tannins: Cinchotannic acid and Phlobatannin.
3- A glycoside Quinovin (up to 2%), which is yielding on
hydrolysis quinovic acid and the sugar quinovose.
4- Calcium oxalate and starch.
• The root bark is the richest in the alkaloidal contents
and the stem bark is richer than the branch bark.

37. 1- Quinine is used as antimalarial and suitable for treatment
of Plasmodium falciparum infection (falciparum malaria).
2- Quinine stimulates hair growth.
3- Quinidine is used for the prophylaxis from cardiac
arrhythmias and for treatment of arterial fibrillation.
4- Cinchonine and Cinchonidine are used as antirheumatic.
5- A decoction and acid infusion are sometimes used as
astringent gargles due to tannins.
6- Bitter tonic and stomachic.
7- Treatment of gastro-enteritis, gall-bladder problems and
flatulence.
Uses

38. 1- Test for Cinchona:
• 0.5 g powder in dry test tube  heat 
purplish red or carmine red fumes evolves 
condense as purplish-red drops, soluble in
alcohol (50 %)  a solution with blue
fluorescence.
Special Chemical Tests

39. 2- Test for alkaloids:
• Shake 0.1 g powdered cinchona with 2 ml dil. HCl  filter  add
to the filtrate a drop of potassium mercuric iodide (Mayer's
reagent)  precipitate is formed immediately.
3- Test for Quinine and Quinidine:
• + dil. oxygenated acids, i.e. dil. H2SO4  blue fluorescence.
4- Thalloquin test:
• 2-3 ml of weakly acidic solution of Quinine or Quinidine salt +
bromine water (few drops)  add 0.5-1 ml of strong ammonia
solution  emerald green color is produced.

40. Cinnamon Bark ‫صيني‬ ‫دار‬ ‫قـشر‬
• Botanical Origin:
• It is the dried shoot bark of
Cinnamomum zeylanicum
Nees., Family: Lauraceae,
deprived of most of its cortex
known as Ceylon Cinnamon.

41. Description:
- Cinnamon bark
- Odour a delicate, fragrant and
aromatic
- Taste it has sweet, agreeable
and warm taste.
Macroscopical Characters
- Shape: quills (single, double and
compound), compound quills
are formed of 10-40 pieces.
- Size: about 6-10 mm diameter
(in good qualities it is not more
than 0.5 mm).

42. - Outer surface: Yellowish-brown colored shows longitudinal shining
wavy lines (pericyclic fibers) and shows scars and holes indicating the
positions of leaves and twigs.
- Inner surface: Dark brownish color shows fine longitudinal
striations.
-Fracture: short and splintery fracture, the drug is brittle.
Powder
- Powdered cinnamon colour: slight brown or yellowish-brown.
- It is characterized by:
1- Fragments of bast fibres mostly isolated with thick walls.
2- Sclereids, numerous, unequally thickened and containing starch
granules.
3- Fragments of parenchyma, containing either starch granules or
minute acicular crystals of calcium oxalate and accompanied with
occasional isolated oil cells.

43. 1- Volatile oil (0.5-1.0%): containing mainly
Cinnammaldehyde (65%)
Eugenol (4-10 %).
2- Tannins (1%).
3- Mucilage.
4- Traces of alkaloids.
5- Calcium oxalate and starch.
Active Constituents

44. 1- Warming stimulant in cold conditions.
2- Antispasmodic in mild cramp-like GIT disorders,
carminative in flatulence or distension and in
mild digestive problem, i.e., nausea, vomiting
and diarrhea.
3- Cinnammaldehyde is used as sedative and
analgesic.
4- Flavoring agent.
5- It has also, aromatic antiseptic and mild
astringent properties.
Uses

45. 1- Powder + KOH (50%)  needle crystals of
potassium eugenate (due to the presence of
eugenol one of the volatile oil constituents).
2- Powder + Sudan III  examine under the
microscope  orange red oil globules are seen
indicating the presence of volatile oil.
Special Chemical Tests

46. Cassia bark ‫صيني‬ ‫قرفة‬ ‫قـشر‬
Chinese Cinnamon
• Botanical Origin
• Dried stem bark of Cinnamomum cassia
(Nees.& T.Nees.) J.Presl., Family: Lauraceae.

47. 1- Volatile oil containing about 85 %
Cinnamaldehyde but Eugenol is absent.
2- Mucilage.
3- Tannins.
4- Flavonoid glycoside.
5- Series of diterpenes.
Active Constituents

48. Differences between Cinnamon and Cassia Bark
Cassia BarkCinnamon Bark
Point of
Comparison
Dried stem bark of Cinnamomum
cassia (Nees.& T.Nees.) J.Presl.,
Family: Lauraceae.
It is the dried shoot bark of Cinnamomum
zeylanicum Nees., Family: Lauraceae,
deprived of most of its cortex known as
Ceylon Cinnamon.
Botanical Origin
South of ChinaCeylonGeographical Origin
Channeled piecesSingle, double, compound quillShape
Dark brownYellowish brownColor
Astringent & mucilaginousWarm, sweet, aromaticTaste
PresentAbsentCork and cortex
Up to 1.5%0.5-1.2 %Volatile oil
Higher percent (80 %)Lower percent (65%)Cinnammaldehyde
Absent (no eugenol)PresentEugenol
Powder + KOH  No needle
crystals formed.
Powder + KOH  needle crystals of
potassium eugenate.
Chemical test

49. Cascara Bark ‫الكسكرة‬ ‫مقدس‬ ‫قـشر‬
(Laxative Bark)
Botanical Origin:
It is the dried stem bark of Rhamnus purshiana,
Family: Rhamnaceae.
Geographical Source: North America and Canada.
• Cascara should be collected at least one year
before being used medicinally and not to be
after four years of collection.

50. Description:
Cascara bark has a slight characteristic odor and
bitter reseating taste.
Macroscopical Characters:
- Shape: single quills, curved, channeled or flatten
pieces.
- Outer Surface: smooth, dark purplish-brown in
color, showing few lenticels. The bark more or
less completely covered with silvery grey patches
of lichens, bryophytes or mosses are often
attached to the outer surface.
- Inner Surface is yellowish to reddish-brown in
color, showing longitudinal striations and faint
transverse corrugations in some pieces.
- Fracture: has short fracture in cork, cortex and
shortly fibrous in the phloem.

51. Crystal sheath
Cork cells (S.V)
Prisms and cluster crystals of
calcium oxalate
Groups of sclerides
Cork & cortex cells
bearing clusters of ca.ox.

52. Anthraquinone derivatives (6-9%), which consists of the
following:
1- Cascarosides A, B, C and D, they are O & C glycosides of aloin
and chrysophanol.
2- Barbaloin and isobarbaloin are C-glycosides of aloin and
chrysophanol.
3- O-glycosides of emodin, oxanthrone, aloe-emodin and
chrysophanol.
4- Free aloe-emodin, emodin and chrysophanol.
5- Various dianthrones of emodin, aloe-emodin, chrysophanol.
Active Constituents

53. 1- Purgative
2- Tonic and stomachic.
3- Emetic action.
• The fresh bark is unsuitable for drug use, causing
griping and nausea, and thus the bark is stored for at
least a year before being processed. During this time,
enzymatic hydrolysis and oxidation modify the
anthraquinone-based constituents and thus the
cathartic activity.
Uses

54. 1- On microsublimation, powder Cascara gives a
yellow crystalline sublimate, which produces a
reddish-brown color with alkalie solutions.
2- Mount a section of corallin soda solution, wash
with alcohol by irrigation. The callus plates
acquire  red stain due to callose mucilage.
Special Chemical Tests

55. 3- Borntrager’s test (test for anthraquinones):
- In this test boil Cascara powder + 1ml of sluphuric
acid in a test tube for 5min  filter while hot.
- Cool the filterate and shake with equal volume of
chloroform then separate the lower layer of
chloroform and shake it with half volume of
dilute ammonia  A ROSE PINK to RED colour is
produced in the ammonical layer.

56. Frangula Bark ‫األسود‬ ‫العوسج‬ ‫قشر‬
Botanical Origin
It is the dried stem bark of Rhamnus frangula L.,
Family: Rhamnaceae.
- Frangula barks should be collected one year
before being used medicinally.
- The bark is obtained from the stem and
branches.
- It has an emetic effect and unpleasant odour
when fresh, these properties disappears when
the bark is dried and stored.

57. Frangula bark contains anthraquinone
glycosides:
1- Glucofrangulins A and B which changes during
drying process to glucose and frangulins A & B.
Frangulin: crystallizes in lemon-yellow needles,
slowly volatile at ordinary temperature
and stains the paper in which it is kept.
Active Constituents

58. 2- The fresh bark contains anthranols and
anthrones which are unstable and readily
oxidized to the corresponding
anthraquinones.
3- Emodin-dianthrone, palmidin C, palmidin C
monorhamnoside, emodin-dianthrone
monorhamnoside and emodin -8-O-b-
gentioside.

59. - It has been used as an agreeable laxative,
preferable to Cascara on account of its less
disagreeable taste.
- Microsublimation (as Cascara).
- Borntrager’s test as Cascara but gives cherry red
colour.
Uses
Special Chemical Tests

60. Quillaia Bark ‫الكوياليا‬ ‫قشــر‬
Botanical Origin
It is the dried inner part of the bark of Quillaia
saponaria Molina, Family: Rosaceae.
Active Constitutents
1- Two colorless amorphous, triterpenoid saponin
glycosides named:
• Quillajic acid.
• Quillaia sapotoxin.
2- Sugars and uronic acids.
3- Starch and calcium oxalate.

61. 1- Treatment for various chest problems mainly as
an expectorant.
2-As a substitute for soap, since it forms a lather
with water.
3- In some skin creams to treat skin ulcers and
eruptions.
4- In hair preparations and shampoos as anti-
dandruff.
5- Also as foaming agent in fire extinguishers.
Uses

62. 1- When powdered Quillaia is shaken with water
 a copious persistent froth is produced.
2- Saponins are characterized by their
haemolytic effect on RBCs.
Special Chemical Tests

63. Pomegranate Bark ‫الـرمان‬ ‫قشـر‬
Botanical origin
It is the dried stem and root bark of Punica
granatum L., Family: Punicaceae.
Active Constituents
1- Four liquid alkaloids; pelletierine (punicine),
iso-pelletierine, methyl-pelletierine and
methyl-isopelletierine.
2- One crystalline, alkaloid pseudo-pelletierine.
3- Tannins.

64. 1- Anthelmintic, expel tapeworms (not actually killed) due to
irritant action.
2- Astringent.
Macerate 0.5 g of powdered pomegranate bark with 25 ml of
water and filter  the light yellow filtrate responds to the
following tests;
1- 10 ml of the filtrate + a drop of ferric chloride  a BLUISH
BLACK precipitate is formed.
2- 10 ml of the filtrate + a drop of calcium hydroxide  an
ORANGE BROWN flocculent precipitate is formed.
Uses
Special Chemical Tests

65. Wild Cherry Bark ‫بـري‬ ‫كـرز‬ ‫قشــر‬
Botanical Origin
Wild cherry bark is the dried stem bark of
Prunus serotina, Family: Rosaceae.
1- The cyanogenic glycoside Prunasin and
Prunase enzyme in bark.
2- Organic acids; benzoic acid, trimethyl-gallic
acid and p-coumaric acid.
3- Tannins and traces of volatile oils.
Active Constituents

66. 1- Antitussive; in cough preparations, for
chronic, dry and whooping coughs, bronchitis,
increases perspiration rate and mild sedative.
2- Nervous dyspepsia, poor digestion, gastritis
and diarrhea.
3- Antibacterial and antiviral.
Uses

67. - Test for hydrocyanic acid (Guignard's test):
One gram of small pieces of the bark are put
into a test tube + 1.0 ml of water and the tube
is closed with a cork holding a strip of
moistened sodium picrate paper (Guignard
paper) between it and the tube  the HCN
evolved over a period of 30 minutes 
change to the yellow color of the picrate
paper to BRICK RED colour.
Special Chemical Test

68. Cascarilla Bark ‫العـنبــر‬ ‫قشــر‬
Botanical origin
It is the dried stem bark of the trees of Corton
elutaria L., Family: Euphorubiaceae.
1- Volatile oil (1-3 %), containing eugenol,
limonene, an oxygenated principle, vanillin.
2- A crystalline bitter principle, cascarillin.
3- The alkaloid Cascarilline.
4- Tannins, lignins and resins.
Active Constituents

69. 1- An aromatic, bitter stomachic, often mixed with
rhubarb.
2- Fragrant component in soaps, creams and lotion.
3- On account of the aromatic odour which is emits on
burning, it is used in fumigating mixtures.
4- It is largely used in flavouring liquors and in
scenting tobacco.
5- Fumigant.
Uses

70. Witch-hazel Bark ‫الهـمـاميـلـس‬ ‫قشــر‬
Botanical Origin
It is the dried bark of Hamamelis virginiana L.,
Family: Hamamelidaceae.
1- Hamamelitannin (gallotannin 7%) and smaller
amounts of condensed tannins.
2- Saponins, fixed oil (0.6%) and wax.
3- Volatile oil (0.5%) and resin.
Active Constituents

71. 1- Treatment of diarrhea, in mucous colitis.
2- Treatment of varicose veins.
3- Treatment of prostate congestion and
inflammation.
Uses

72. • Boil 1 g powder in 10 ml of water for 2
minutes, filter, add to the filtrate few drops of
ferric chloride (T.S.)  a BLACK BLUE ppt. is
produced.
Special Chemical Test