Untitled Quiz

Pharmacognosy-2

• This lecture is about Pharmacognosy-2.
• The lecturer is Ahmed Elbermawi, PhD, a Lecturer of Pharmacognosy.
• Herbs are plants whose stems don't become woody permanently, but die after fruiting.
• Pharmacognosy is a drug composed of tender parts of plant axis, leaves, flowers, and fruits from annual, biennial, or perennial plants.
• Herbs consist of flowering tops of flowering plants (e.g., Cannabis) and whole aerial parts of plants (e.g., Lobelia).

Types of Herb

• Annual: Live for one season before seed production and then die.
• Biennial: Live for two seasons before seed production and then die (e.g., Digitalis).
• Perennial: Live for more than two years, have perennial rootstocks, and throw up aerial shoots annually (e.g., Belladonna).

Definition of a Stem

• A stem is part of the plant axis that bears leaves or modifications of leaves.
• Aerial stems grow above ground.
• Subterranean stems grow below ground.

Functions of Aerial Stem

• Conducting water and mineral nutrients from the root to the leaves.
• Conducting food from the leaves to the root.
• When leaves are reduced, the stem serves for assimilation.

Morphological Characters

• Shape
• Color
• Type (Herbaceous, Succulent)
• Branching
• Surface
• Fracture
• Insertion of leaves
• Phyllotaxis
• Pith

Types

• Herbaceous: Soft stem, easily broken, with smooth or hairy surfaces.
• Succulent: Thick, fleshy stems.

Types of Stem Growth

• Creeper: Spread horizontally rather than vertically, producing new plants along the way.
• Runner: Long, slender, trailing shoots running on the surface, giving roots at nodes, with small brown scale leaves with buds in their axils.
• Sucker: Underground runner, later becoming aerial.
• Climber: Weak stems that attach themselves to support using tendrils or hooks.
• Twining: Grows in a spiral fashion around a suitable support.

Insertion of Leaves

• Cauline: Arise from the aerial stem.
• Radical: Arise from the crown of the root.

Phyllotaxis

• Alternate or spiral: Leaves occur singly at a node.
• Opposite: Occur in pairs at a node.
• Opposite decussate: Opposite, but each pair alternates at right angles to the other one.
• Whorled: Several leaves occur at a node.

Microscopical Characters - Dicot. Stem

• Cambium: Arranged in a single ring around the central region called pith.
• M.R.: A number of parenchymal strands between vascular bundles (V.B.) from the pith to the cortex.
• Ground tissues: Composed of cortex, pith, and medullary rays (M.R.).

Microscopical Characters - Monocot Stem

• Large number of closed collateral vascular bundles scattered irregularly throughout the ground tissues.
• Smaller and more crowded near the periphery of the stem than in the center.
• Pith, medullary rays (M.R.), limit of cortex, endodermis, and pericycle are indistinguishable.

Herbs of Medicinal Uses

• Various examples/types of medicinal herbs are mentioned.

Lobelia Herb (Asthma Weed, Indian, or American Lobelia)

• Dried aerial parts of Lobelia inflata L.

• Family: Companulaceae

• Macroscopical characters include stem (green to yellowish green color with large purple patches), leaves (alternate, stiff hairs), flowers (two-lipped tubular flower, shortly pedicellate, arranged in long raceme inflorescence), pale blue calyx, long with 5 linear teeth.

• Corolla: tubular, bilabiate (two-lipped).

• Stamens: 5 stamens united by their anthers (syngenesious) forming a tube enclosing the bifid stigma (two sections).

• Ovary: bilocular (two chambers) and bicarpellary.

• Fruit: Inflated capsule, dehiscing by 2 pores at top, ovoid, membranous pericarp

• Bilocular

• Numerous seeds arranged on an axial placenta

• Seeds: Minute, oblong, polygonal reticulation.

• Leaf: Dorsiventral with a single palisade layer, numerous small rod-shaped crystals of fat, midrib with central vascular bundle (V.B.), laticiferous vessels in phloem.

• Stem: Beaded, straight-walled cells with striated cuticle, few anomocytic stomata, numerous trichomes.

• Cortex: Chlorenchyma (collenchyma present), endodermis with distinct lignified Casparian strips.

• Stellar Tissues: Includes pericycle (parenchymatous with patches of pericyclic fibers), continuous ring of vascular bundles (V.B.), phloem, and pith (central large pith of lignified thin-walled parenchyma)

Powder

• Properties including Color, Odor, and Taste describe characteristics.
• Upper and Lower epidermis are included in the powder section, along with stomata and trichomes (including details of the structure of trichomes in the lower epidermis)

Active Constituents

• Lobeline (major alkaloid), lobelidine, lobelanine, lobelanidine, isolobelanine.
• Other constituents like inflatin, lobelic acid, wax, and resin.

Chemical Test

• Alkaloidal extract + few drops of H₂SO₄ + one drop of formalin produces a red color.

Uses

• Smoking deterrent (lozenges).
• Bronchial asthma (relaxes bronchial muscles).
• Respiratory stimulant (dyspnea of chronic bronchitis).
• Expectorant (for loosening mucus in lungs).