botany & medicinal plants

Pharmacognosy

Sherif S. Ebada, Ph.D.

Contact information:

Assoc. Prof. Dr. Sherif S. Ebada

Pharmaceutical Chemistry Dept.

Office hours:

Tuesdays and Thuresdays: 10:00 am–12:00 pm

E-mail: [email protected]

Lecture 2AB

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Lecture Outline

Introduction to Medicinal Leaves.

Senna.

Digitalis.

Solanaceous Leaves.

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What is a Leaf?

An aerial lateral outgrowth on the stem.

Function of the Leaf:

Photosynthesis.

Food exchange.

Protection of the floral parts & buds.

Leaf composed of three Parts:

Leaf Base.

Leaf Stalk “Petiole”.

Leaf Blade “Lamina”.

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Leaf Insertion on Stem:

Radical, e.g. carrot.

Cauline.

Phyllotaxis:

a. Alternate.

b. Opposite:

I. Decussate.

II. Superposed.

c. Whorled.

a b.I. b.II. c

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Leaf Base.

Stipulate or Ex-stipulate.

Leaf Stalk “Petiole”.

Petiolate or Sessile.


According to the continuity divided into Three types:

Simple.

Lobed: either pinnate (midrib) or palmate (base).

Compound: divided into leaflets arranged on both sides

of leaf stalk named “Rachis”, i.e. continuation of midrib.

It can be either compound pinnate or palmate.

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Simple Leaf Pinnate Leaf Palmate Leaf

Compound paripinnate Leaf Compound imparipinnate Leaf

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According to its margin divided into:

Serrate Crenate Incised Dentate

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According to its surface divided into:

Glabrous “Smooth”.

Pubescent “Hairy”.


According to its texture divided into:

Brittle: when very thin easy to break (dry).

Fleshy or “Succulent”: thick, juicy and fleshy.

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Histology of Leaf.

I. Epidermis:

Shape of cells: single layer, tubular with no intercellular

spaces except for the stomata. Anticlinal wall is either:

Straight e.g. Senna.

Wavy e.g. Belladonna.

Beaded e.g. Digitalis.

Straight e.g. Senna Wavy e.g. Belladonna Beaded e.g. Digitalis

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Histology of Leaf.

I. Epidermis:

Cuticle: a protective film covering the epidermis, it

might be:

Smooth e.g. Senna.

Striated e.g. Jaborandi.

Smooth e.g. Senna Striated e.g. Jaborandi

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Histology of Leaf.

I. Epidermis:

Stomata: consists of two similar cells, “Guard cells”,

enclosing a small lenticular (oval) space “Osteole”.

Guard cells are smaller & containing chloroplast

and starch granules.

Epidermal cells surrounding the stomata are

Subsidiary cells which differ in size & shape from

the remaining epidermal cells.

Guard cells

Osteole

Subsidiary cells

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Histology of Leaf.

I. Epidermis:

Types of Stomata:

In Monocotyledons: In Dicotyledons:

Dumbbell-shaped A. Anomocytic e.g. Digitalis.

“Graminaceous type” B. Anisocytic e.g. Solanaceous leaves.

C. Paracytic e.g. Senna.

D. Diacytic e.g. Mentha.

A B C D

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Histology of Leaf.

I. Epidermis:

Types of Stomata:

Stomatal number: it is the average number of

stomata per 1mm2

Stomatal index: it is the percentage of number of

stomata (S) to sum of total number of epidermal cells

(E) and Stomata together in the same unit area i.e.

= S x 100 / E + S N.B.: It is a constant value for a given

species.

Trichomes “Hairs”:

Extensions of the epidermdal cells divided into:

Non-glandular.

Glandular.

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Histology of Leaf.

I. Epidermis:


Extensions of the epidermdal cells divided into: Non-glandular: might be either:

A. Unicellular: covered with warty cuticle e.g. Senna.

B. Multicellular: can be further divided into:

Unbranched: Branched:

Uniseriate e.g. Digitalis, Pyrethrum Simple e.g. Hyoscyamus

Biseriate e.g. Calendula flower Stellate e.g. Boldo leaf

Pluriseriate e.g. Cumin

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Histology of Leaf.

I. Epidermis:


Extensions of the epidermdal cells divided into: Glandular: might be either:

A. Uniseriate stalk: can be either:

Unicellular head unicellular stalk e.g. Digitalis.

Unicellular head multicellular stalk e.g. Belladonna & Lavander.

Multicellular head unicellular stalk “Clavate” e.g. Solanaceous leaves.

Multicellular head unicellular stalk “Labiaceous” e.g. Mentha.

B. Biserate stalk:

Biseriate head biseriate stalk “Compositae” e.g. Compositae.

Multicellular head pluriseriate stalk e.g. Cannabis.

Labiaceous hairCompositae hair

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Histology of Leaf.

I. Epidermis:

Cell content: Mucilage: with methylene blue gives Blue.

Volatile oils: with sudan III gives Red.

Calcium Oxalate Crystals:

a) Prisms e.g. Senna; Styliod e.g. Quillaia.

b) Clusters e.g. Rhubarb.

c) Rosette e.g. Argel.

d) Raphides e.g. Squill.

e) Microsphenoidal crystals e.g. Stramonium & Belladonna.

Prism Styloid Cluster Rosette Raphides Microsphen-

oidal crystal

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Histology of Leaf.

II. Mesophyll:

Vascular system “ Stellar System”:

It consists of network structure.

It appears in transverse section (T.S.) as an arc opens above with the

phloem towards the lower surface of the leaf and the xylem towards the

upper surface.

Phloem: formed of small thin-walled elements.

Xylem: consists of radial rows of vessels with the protoxylem

towards the upper surface and separated by rows of wood

parenchyma.

Medullary rays may be visible, traversing the xylem and

phloem in the form of radiating lines.

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Histology of Leaf.

II. Mesophyll:

Vascular system “ Stelar System”:Types of Vascular Bundles:

A. Radial: when xylem & phloem form separate bundles which lie on different

alternating radii with each other, as in roots.

B. Conjoint: when xylem & phloem combine in one bundle there are three types:

1. Collateral: when xylem & phloem lie together on the same radius

When it has cambium it is an Opened V.B.

When it has no cambium it is a Closed V.B.

N.B. cambium is difficult to be differentiated

2. Bicollateral: both cambium & phloem occur twice; (above & below the xylem).

3. Concentric:

i. Vasocentric:

When xylem lies in the center & is surrounded by phloem as in ferns.

ii. Amphivasal:

When phloem lies in the center & is surrounded by xylem as in sweet flag. N.B.:

concentric bundle is always closed bundle.

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Diagnostic Elements of Powder

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Uses:

It is a cardio tonic drug. It increases the

contractibility and improves the tone of the

cardiac muscle, both reactions resulting in a

slower but much stronger heart beat, thus it is

used in most forms of cardiac failure, as

auricular fibrillation & ascitis.

N.B.: Digitoxin is cumulative drug, thus thedose

used must be monitored.

SOLANACEOUS LEAVES

General Characters of Solanaceous Leaves:

1. The leaves show adnation phenomenon; the leaves grow fused for a certain distance with the petiole thus, the leaves appear arise to from the stem “i.e. as if it is sessile”.

2. All solanaceous leaves contain alkaloids; atropine, hyoscine & hyoscyamine, which are mydriatics “dilate eye pupil”, thus used for eye examination.

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3. All Solanaceous leaves contain:

anisocytic type of stomata.

non glandular hairs (uniseriate from 3-5 cells).

glandular hairs; Clavate hairs (ovoid multi-cellular bi-serriate head & uni-

cellular stalk).

Uni-cellular head with uni-serriate or branched stalk.

Ca Ox crystals (clusters, prisms or sandy).

starch sheath.

pre-medullary or intra-xyllary phloem (batches of phloem cells above the xylem vessels).

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“Egyptian & European Henbane”

Origin: It is the dried leaves with or without the flowering fruiting tops of Hyoscyamus muticus &

Hyoscyamus nigra, Family Solanaceae

Hyoscyamus Leaves وراق السكرانأ

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Leaf insertion: cauline; alternate.

Leaf base: exstipulate.

Leaf petiole: very short cylindrical petiole “adnate” .

Lamina type: simple.

Shape: oval lanceolate.

Apex: acuminate.

Margin: repand “sinuate”.

Base: assymetric, decurrent “adnate with the petiole”.

Surface: pubescent; Clothed with hairs.

Texture: thick fleshy leaf.

Venation: reticulate pinnate.

Morphology:

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Egyptian

Henbane leafEuropean

Henbane leaf

Egyptian Henbane

“surface preparation”

European Henbane

“surface preparation”

Clavate Hair

with long stalkCrystal of CaOx

Clusters

Twin

prismsSandy

prisms

with short stalk

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Therapeutic Uses:

It has parasympatholytic “Sympathomimetic” action thus;

• It inhibits the contraction of iris eye muscle causes mydriasis

“dilatation of eye pupil” ; thus it is used in eye examination.

• It relaxes the intestinal smooth muscles “antispasmodic action”;

thus it is used with strong laxatives to prevent the gripping.

• It has sedative effect, on central nervous system; thus it is used

in insomnia as hypnotic.

It is also used as a source of hyoscyamine alkaloid.

Active constituents:

Alkaloids of tropane group; Hyoscyamine & Atropine

N.B.: 1.7% present in the Egyptian leaves, while 0.14%

present in the European leaves.

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Identifying Chemical Tests:

“tests for tropane - group alkaloids”:

Powdered plant + 10ml dil HCl., boil for 2 min., filter,

Vitali - Morin Color Reaction:

evaporate the filtrate (in a porcelain dish) till dryness then add drops of conc.

HNO3 yellow solution, evaporate to dryness, add drops of alc. KOH

purple colorless

Mayer’s Reagent:

Filtrate + drops of K2HgI creamy white ppt.

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• Parts of branched glandular hair.

• Parts of leaf epidermis showing anisocytic stomata, striated cuticle & hair cicatrix.

• Clusters of CaOx crystals.

• Sclerides of the testa & of the pericarp “in surface view”.

• Parenchyma of the stem showing Idioblast containing CaOx microsphenoidal crystals.

• Pollen grains.

Diagnostic Elements of Hyoscyamus

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Origin:

It is the dried leaves with or without the flowering tops of Atropa belladonna ,

Family Solanaceae

Belladonna Leaves وراق ست الحسنأ

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Hyoscyamine, Hyoscine & Belladonine

alkaloids

Therapeutic Uses:

1. as anodyne i.e. analgesic for tooth ach (it has

local anesthetic effect).

2. as sedative.

3. as antispasmodic.

Identifying Chemical Tests: as for all Solanaceous1. Vitali - Morin Color Reaction

2. Mayer’s Reagent

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• Parts of leaf epidermis showing anisocytic stomata & striated cuticle; 1, 2 & 4

• Parts of the lamina in sectional view showing Idioblast in the spongy mesophyll & idioblast of CaOxmicrosphenoidal crystals; 5 & 9

• Parts of glandular & non- glandular hairs; 6, 10 &11

• Fragments of the inner tissues of the stem in S.V. showing reticulate thickened vessels & xylem parenchyma; 8

• Pollen grains; 3

Diagnostic Elements of Atropa belladonna

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Origin:

It is the dried leaves with or without the flowering tops of Datura stramonium ,

Family Solanaceae

Datura Leaves وراق داتورة أ

سترامونيوم

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Therapeutic Uses:

Sedative

Spasmodic cough

Identifying Chemical Tests:as for all Solanaceous Leaves:1. Vitali - Morin Color Reaction

2. Mayer’s Reagent


Hyoscyamine & Atropine

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• Parts of leaf epidermis showing strong wavy walled-cells, anisocytic stomata, smooth cuticle; 1 & 2

• Fragments of the crystal layer in surface view showing cluster of CaOx crystals; 4 & 9

• Parts of glandular & non- glandular hairs; 7 & 8

• Parenchyma of the midrib in longitudinal view showing prisms & sandy CaOx crystals; 5

• Pollen grains; 10

Diagnostic Elements of Datura stramonium

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