Pharm D Pharmacognosy 2 (PG 303)

Pharm D Program (2023/2024) Pharmacognosy 2 (PG 303) Lecture Notes (7)

• Herbs Introduction and Lobelia
• Various types of herbs are classified based on their lifespan.
• Annual herbs live for only one season.
• Biennial herbs live for two seasons but not more than two years.
• Perennial herbs live for more than two years.
• Parts of a plant: Leaves, flowers, fruits, stems, roots, rhizomes (underground organs).
• The Stem: The stem of a plant supports the leaves and other plant parts. It contains nodes and internodes.
• Shapes of stems: Cylindrical, ribbed, triangular, tetragonal/ quadrangular, flattened, winged.
• Kinds of stems: Herbaceous stems, succulent stems, woody stems, suffruticose stems, fruticose/shrubby stems, culm stems, creeping stems, sucker stems, climbing stems, and twining stems.
• Herbaceous stems are green, soft, easily broken, and lack or have very little cambium which dies at the end of a season.
• Succulent stems are thick and fleshy, storing water.
• Woody stems are strong and sturdy due to xylary elements and cork.
• Suffruticose stems are small and woody at the base, with herbaceous tops.
• Fruticose/Shrubby stems are woody, larger than suffruticose, branching near ground. They are shrub-like.
• Culm stems have large nodes and hollow internodes (e.g. Gramineae).
• Creeping stems spread along the ground and develop new plants.
• Sucker stems grow from below ground level.
• Climbing stems attach to supports using tendrils, hooks, or adventitious roots.
• Twining stems wrap around supports.
• Microscopical characters in Young herbaceous stems of Dicots: These stems have a vascular bundle, epidermis (outer layer), cortex (containing parenchyma, collenchyma, and endodermis), pericycle (parenchyma, collenchyma, fibers, and sclereids), and the vascular bundles with cambium which is responsible for secondary thickening and secondary phloem and xylem development. Xylem vessels show spiral, annular, or pitted structures. Pith is made of parenchyma cells.

Medicinal Herbs

• Lobelia, Peppermint, Thyme, Solanaceous Stramonium, Egyptian Henbane, Belladonna, Catharanthus (Vinca), Ephedra, Broom Tops, Cannabis, Indian Hemp, etc.
• Algae(Fucus, Laminaria, Carrageen), Fungi (Ergot, Yeast, Penicillium, Mushroom), Lichenes (Iceland Moss)
• Chemical taxonomy of herbs based on the types of chemicals within them: Alkaloids (Lobelia, Solanaceous Herbs, etc.), Volatile Oils (Peppermint, etc.), Resins (Cannabis).

Lobelia Herb

• Origin: The dried aerial parts of Lobelia inflata.
• Collected at the end of flowering stage
• Uses: Used as domestic medicine by North American Indians as a cigarette for asthma. Used to help quit smoking due to nicotine-like actions; used as an expectorant and in treatment of spasmodic asthma and dyspnea associated with chronic bronchitis.

Microscopical Characters of Lobelia Infata

• The stem of Lobelia Inflata shows characteristics like xylem, phloem, vascular bundles, cuticle, stomata, pith, and cortex. The leaf of Lobelia Infata has typical epidermal characteristics in addition to other cellular features.

Physical Characters of Powdered Lobelia

• Color: Green to dark green
• Odor: Slight irritant
• Taste: Slight at first, then burning, and acrid.

Active Constituents of Lobelia

• Alkaloids (lobeline, lobelanine, lobelanidine, isolobelanidine)
• Colorless crystalline neutral principles (inflatin)
• Lobelic acid
• Volatile oil and resin

Chemical Test for Lobelia

• Adding Mayer's reagent to an extract creates a whitish turbidity.

Contraindications

• Lobelia alkaloids are present in milk and should not be administered to pregnant or nursing mothers. Large doses can cause vomiting and collapse.