Lecture 6 (Ahmed-Herbs-1) PDF

Pharmacognosy-2 Lecture‫السادسة‬ 6 ‫المحاضرة‬ Ahmed Elbermawi, PhD Lecturer of Pharmacognosy Botanical A plant whose stem does not become woody and Permanent but dies after Fruiting. Pharmacognosy A drug composed of tender parts of plant axis, leaves, flowers and fruits taken fro...

Pharmacognosy-2 Lecture‫السادسة‬ 6 ‫المحاضرة‬ Ahmed Elbermawi, PhD Lecturer of Pharmacognosy Botanical A plant whose stem does not become woody and Permanent but dies after Fruiting. Pharmacognosy A drug composed of tender parts of plant axis, leaves, flowers and fruits taken from annual, biennial or perennial plants.  Herbs consists of Flowering tops of flowering plants e.g., Cannabis Whole aerial parts of plant e.g., Lobelia  Types of Herb  Annual: Live for one season before seed production then dies.  Biennial: Live for two seasons before seed production then dies e.g. Digitalis.  Perennial: Live for more than two years and have perennial rootstock, which throw up aerial shoots annually e.g. Belladonna. Definition of a Stem is a part of the plant axis which bears leaves or modification of leaves at certain points usually swollen, called nodes. ♣ Aerial stem: Usually grows above the ground. ♣ Subterranean stem: Stem grows below the surface of the ground. Functions of Aerial Stem 1- Conducting water and mineral nutrients from the root to the leaves. 2- Conduction of food from the leaves to the root. 3- When leaves is reduced, it serves for assimilation. Morphological Characters 1- Shape 2- Color 3- Type 4- Branching 5- Surface 6- Fracture 7- Insertion of leaves 8- Phyllotaxis 9- Pith  3- Type 1- Herbaceous: stem is soft easily broken has smooth or hairy surface. 2- Succulent: thick fleshy. 3- Creeper: spread horizontally rather than growing vertically. They produce new plants along the way and can quickly cover large areas. Others send out runners that develop a new plant at the end. 4- Runner: Long, slender and trailing shoots run on the surface of the ground and give roots at the nodes. It bears at intervals small brown scale leaves with buds in their axils. 5- Sucker: it is an underground runner but later becoming aerial. 6- Climber: stem is so week that it attaches itself to some support by means of tendrils or by hooks. 7- Twining stem: grows in a spiral fashion around a suitable support. 7- Insertion of leaves  Cauline: arise from the aerial stem.  Radical: arise from the crown of the root.  Mode of arrangement of cauline leaves 8- Phyllotaxis on the stem.  Alternate or spiral: leaves occur singly at a node (Lobelia)  Opposite: leaves occur as pair at a node  Opposite decussate: opposite but each pair alternate at right angles to one another e.g., Mentha  Whorled: when several leaves occur at a node Microscopical Characters 1- Dicot. Stem ♣ Cambium arranged in a single ring around central region called pith. ♣ M.R. are a number of parenchymatous strands between V.B. from pith to the cortex. ♣ Ground tissues: composed of cortex, pith and M.Rs  2- Monocot. Stem  Large number of closed collateral V.B. scattered irregularly through the ground tissues. They are smaller and more crowded near the periphery of the stem than in the center, where they are larger and less in number.  Pith, M.R., limit of cortex, endodermis and pericycle are indistinguishable. Herbs of medicinal uses  Lobelia Herb (Asthma weed, Indian tobacco, American Lobelia) Dried aerial parts of Lobelia inflata L., family: Companulaceae I- Macroscopical Characters: 1- Stem Green to yellowish green usually with large purple patches Upper part has 2-5 wings and is hairy. Lower part is channeled and nearly glabrous. 2- Leaves Green in color. Alternate. Have stiff hairs especially along the margin and veins on the lower surface. Oblong to lanceolate. Irregularly crenate-dentate margin. Each tooth ends in a yellowish-brown swollen apex (water pores). 3- Flowers Two-lipped tubular flower Shortly pedicellate. Arranged in long raceme inflorescence. Pale blue. Calyx: long with 5 long linear teeth. Corolla: tubular, bilabiate, - Posterior lip with 2 erect lobes. - Anterior lip with 3 spreading lobes. Stamens: 5 stamens united by their anthers (syngenesious) forming a tube enclosing the bifid stigma. Ovary: bilocular – bicarpellary. Flower of Indian Tobacco 4- Fruit Inflated capsule. Dehiscing by 2 pores at the top. ovoid. The pericarp is membranous. Internally Bilocular. Containing numerous seeds arranged on an axial placenta. 5- Seeds Minute. Oblong. With polygonal reticulation. II- Microscopical Characters: 1- Leaf Dorsiventral with a single palisade layer. Numerous small rod-shaped crystals of fat are present in many of the cells of the mesophyll. Midrib: has a central large V.B. which shows the presence of laticiferous vessels in the phloem and two layers of subepidermal collenchyma. 2- Stem a- Epidermis: Consists of axially elongated cells, beaded straight–walled cells with striated cuticle, few anomocytic stomata and numerous trichomes. b- Cortex: Is formed of chlorenchyma (collenchyma is present in wing region) followed by well- marked endodermis with distinct lignified Casparian strips. c- Stellar tissues: 1- Pericycle: parenchymatous with patches of pericyclic fibers. 2- Continuous ring of V.B. 3- Phloem: enclosed a net-work of laticiferous vessels. 4- Pith: central wide pith of lignified thin-walled pitted parenchyma. Powder Color: green Odor: slight irritant Taste: burning and acrid Upper epidermis: consists of papillosed cells with nearly straight beaded anticlinal walls, striated cuticle and trichomes. Stomata is absent on upper epidermis Lower epidermis: Consists of wavy walled cells, numerous anomocytic stomata and trichomes. Trichomes: are non-glandular, unicellular, uniseriate, conical, wide at the base with lignified walls and longitudinally striated cuticle. More numerous on the lower surface.  Active constituents:  Lobeline (major alkaloid), lobelidine, lobelanine, lobelanidine and Isolobelanine.  Other: inflatin, lobelic acid, wax, resin. Chemical test  Alkaloidal extract + few drops H2SO4 + one drop formalin, a red color is produced.  Others ??  Uses 1- Used as smoking-deterrent in the form of lozenges. 2- Used in bronchial asthma as it relaxes the bronchial muscles. 3- Respiratory stimulant, used in dyspnea of chronic bronchitis. 4- Expectorant.