This document discusses the structure, properties, and constituents of various barks. It defines bark as all tissues outside the vascular cambium and describes bark shapes. Key points covered include the histology of bark tissues like cork, collection and drying methods. Specific barks discussed that contain alkaloids are Cinchona, which contains quinine, pomegranate bark, and Yohimbe bark, which contains the alkaloid yohimbine used to treat erectile dysfunction.

1. BARKS AND WOODS 1
DR. MOSTAFA MAHMOUD HEGAZY PH.D

2. ➢ content
➢ Barks
➢ Definition, Structure and Collection
➢ Shapes of barks (General shape, Outer and inner surface and
Fracture)
➢ Histology of bark (Transverse section and Secretory structure)
➢ Barks containing Alkaloids e.g., Cinchona, pomengranate and
Yohimbe
Barks and woods Dr. Mostafa Hegazy

3. Barks
Definition: All tissues outside vascular
cambium of stem or root
Barks and woods Dr. Mostafa Hegazy

4. Barks and woods Dr. Mostafa Hegazy
SHAPES OF BARKS
Flat Curved Chanelled Single quill Double quill Compound quill

5. Collection of Barks:
➢ When? Spring or early summer.
➢ Why? the cambium is active, more easily torn and
contains a high % active constituent.
Removal of Barks:
➢ How? Longitudinal incisions followed by horizontal
ones with a knife [wood may be present].
Method of Drying:
1.Sun heat [Natural drying]
2.Artificial heat.
Barks and woods Dr. Mostafa Hegazy

6. Barks and woods Dr. Mostafa Hegazy
DIFFERENCE BETWEEN OUTER & INNER
SURFACES OF BARK
 Outer surface:
1. Darker in Color***
2. Surface:
A. Smooth.
B. Furrows.
C. Wrinkles.
D. Fissures (cracks).
 Inner surface:
1. Lighter in color *****
2. Surface:
A. Smooth.
B. Striated.
C. Corrugated ‫مموج‬
.
D. Reticulate.

7. Barks and woods Dr. Mostafa Hegazy
Outer Surface features :
1- It may bear certain epiphytes
➢ any plant that grows upon another plant for physical
support but not parasitic
➢ air plant (no attachment to the ground)
such as:
➢ Lichens ‫األشنات‬ as in Cinchona.
➢ Liverwort ‫الكبد‬ ‫حشيشة‬ as in Cascara.
➢ Mosses

8. 2- Lenticles:
➢ Lenticels, 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.
Barks and woods Dr. Mostafa Hegazy

9. 3- Wrinkles and furrows:
➢ The greater shrinkage of the softer tissues result
in formation of wrinkles (because the shrinkage
of the barks during drying occur chiefly
transversely.
4- Cracks and fissures:
➢ arise owing to continued increase in growth and
to the lack elasticity.
Barks and woods Dr. Mostafa Hegazy

10. Fracture
Behavior of the barks when broken across transversely & the
appearance of the exposed surface.
➢ Short: breaks quickly & straight across the fractured surface.
➢ Fibrous: resists during breaking & shows fibrous projection.
➢ Splintery: breaks irregularly showing jagged projecting
points.
➢ Granular: broken surface shows grain.
➢ Laminated: breaks into tangentially arranged layers.
➢ Flexible: breaks only by tearing or twisting
Barks and woods Dr. Mostafa Hegazy

11. Bark
1- Rhytidoma (dead collapsed tissues)
2- Periderm: (Cork, Cork cambium and 2ry cortex).
3- Primary cortex.
4- Pericycle.
5- 1ry phloem.
6- 2ry phloem (Bast).
Vascular Cambium -------------------------------
Wood
2ry xylem
1ry xylem
Pith
Barks and woods Dr. Mostafa Hegazy

12. Decortication of Bark:
Removal of cork, secondary cortex
or whole tissues outside the 2ry
phloem.
Why?
➢ It contains low % of or
no active constituents.
➢ It contains higher % of
undesirable compounds e.g.,
tannins & coloring matter.
Barks and woods Dr. Mostafa Hegazy

13. 1- Rhytidoma:
➢ not frequently present in commercial barks.
➢ formed of dead cork and other collapsed dead
tissues.
2- Cork (Phellem):
➢ Function: protective tissue of secondary origin.
➢ Structure: rows of dead cells appearing polygonal
in surface view.
➢ Color: dark brown due to the presence of
amorphous brown or reddish content.
Barks and woods Dr. Mostafa Hegazy

14. 3- Phellogen (Cork cambium):
➢ secondary meristematic cells.
➢ produces cork to the outside and phelloderm to the
inside.
4- Phelloderm (Secondary cortex):
➢ devoid of coloring matter but may contain starch
granules.
➢ may be wholly parenchymatous, collenchymatous or
sclerenchymatous.
Barks and woods Dr. Mostafa Hegazy

15. 5- Cortex (Primary Cortex):
➢ absent in many barks either due to decortication e.g., Cinnamon or
due to exfoliation as in case of all root- barks.
➢ formed of parenchyma and may contain sclereids e.g. Cascara, oil
cells e.g., Cascarilla, laticiferous structures e.g., Cinchona. Also
contains starch granules, and crystals of calcium oxalate.
6- Pericycle:
➢ parenchymatous ( indistinguishable from cortex) or
sclerenchymatous.
7- Primary phloem:
➢ usually collapsed becoming indistinguishable or totally absorbed. It is
called Ceratenchyma.
Barks and woods Dr. Mostafa Hegazy

16. 8- Secondary phloem:
➢ characterized by the presence of sieve tubes, accompanied
by companion cells and phloem parenchyma traversed by
medullary rays.
➢ commonly contain fibers (phloem fibers) and sometimes
sclereides, oil cells.
* The phloem parenchyma usually contains starch granules
and sometimes calcium oxalate crystals.
Barks and woods Dr. Mostafa Hegazy

17. Secretory Structures
These are either: (contain mainly volatile oil
and sometimes resin, tannin, mucilage or
enzyme)
1. Internal including: secretory cells,
secretory cavities or sacs (glands), secretory
ducts or canals and laticiferous structures.
2. External including: glandular hairs.
Barks and woods Dr. Mostafa Hegazy

18. How to Differentiate between stem & root bark ?
Item Stem bark Root bark
Position of
cork cambium
Any where In the pericycle
Outer
surface
Color Darker than inner
surface.
Both inner and outer surfaces
have the same color; Lighter.
Epiphytes
Present Absent
Lenticels Present Absent
Texture Smooth. Scaly (exfoliated).
Shape
Thicker
Flat, curved, quill
Thinner
Irregularly quill or Twisted.
Barks and woods Dr. Mostafa Hegazy

19. Barks containing
1.Alkaloids e.g., Cinchona, pomengranate and Yohimbe
2.Volatile oils e.g., Cinnamon & Cassia.
3.Anthraquinone glycosides e.g., Cascara & Frangula.
4.Saponin glycosides e.g., Quillaia.
Remember in each case:
• Nature of A.C.
• General test for detection.
• Presence of these A.C. in other organs (nature & name)????
Barks and woods Dr. Mostafa Hegazy

21. Barks containing
Alkaloids
Barks and woods Dr. Mostafa Hegazy

22. CINCHONA ‫الكينا‬ ‫قشر‬
• Origin: Dried stem and root barks of
Cinchona succirubra ( red Cinchona), C.
Ledgeriana, C. calisaya ( yellow cinchona),
and C. officinalis ( pale cinchona)
Family Rubiaceae.
Barks and woods Dr. Mostafa Hegazy

23. Description:
Shape: double quills, or curved pieces,
Outer surface:
color: grayish-brown to reddish-brown,
bearing whitish or grayish lichens and mosses.
touch: rough with longitudinal and transverse
fissures, exfoliated cork may be present.
Inner surface; paler in color, longitudinally
striated.
odorless and bitter astringent taste.
Barks and woods Dr. Mostafa Hegazy

24. Cinchona powder
reddish- brown has characteristic odor
and bitter astringent taste.
Microscopically shows:
1- lignified phloem fibers, having
funnel-shaped pits
2- parenchyma cells with idioblasts
containing Microcrystals of Ca-ox .
3- Brown cork.

25. Constituents:
Quinoline Alkaloids:
l-Quinine and d-quinidine (stereoisomers)
d-Cinchonine and l-Cinchonidine (stereoisomers)
The alkaloids are combined with quinic acid and cinchotannic acid.
Higher percentage of alkaloids in root bark
Condensed tannins which decomposed to give cinchona red
Barks and woods Dr. Mostafa Hegazy

26. ➢ General Tests for identity
➢ Dry heat Violet fumes
➢ dil H2SO4 blue fluorescence
➢ powder + dil HCl filtrate + Mayer’s reagent immediate
creamy white precipitate
➢ extract + FeCl3 greenish black color
Barks and woods Dr. Mostafa Hegazy

27. •Uses:
• quinine:
• anti-malarial, stimulate hair
growth, antiseptic and Tonic.
• Quinidine:
• Prophylactic in early arrhythmia
and atrial fibrillation,
• cinchonine and cinchonidine as
antirheumatic
Barks and woods Dr. Mostafa Hegazy

29. Pomegranate Bark ‫الرمان‬ ‫قشر‬
Origin: Dried stem & root barks of Punica granatum,
Family : Punicaceae = Lythraceae
Constituents:
1. Alkaloids: 0.5 %, pelletierine, isopelletierine.
2. Tannins (hydrolysable) up to 22%.
Uses:
1. Anthelmintic against tape worm.
2. Astringent for the treatment of diarrhea
3. Antimicrobial

30. Yohimbe bark
Origin: Pausinystalia yohimbe Fam. Rubiaceae
constituents: Indole alkaloid yohimbine
Uses:
- Aphrodisiac for sexual disorders (erectile desfunction)
improve the quality and staying power of erections,
usually without increasing sexual excitement
- Increasing athletic performance
Dose: 15-20 mg/day
Barks and woods Dr. Mostafa Hegazy

31. Barks and woods Dr. Mostafa Hegazy