In this article we will discuss about the microscopic examination of some drug materials.
1. Swertia Chirayita (Family: Gentianaceae):
Fragments of epidermal cells with cruciferous type of stomata, acicular crystals of calcium oxalate present in the cortical cells and in the mesophyll cells; some cortical cells contain resins, vessels having bordered pits on the walls.
Morphology:
Stem:
About 6 mm in thickness, yellow to purple brown in colour, glabrous, branched.
Leaf:
Ovate to lanceolate, acuminate, entire, opposite sessile.
Root:
About 5-10 cm long, somewhat twisted.
Flower:
Paniculate cyme; two sac-like nectaries on each petal; fruits bicarpellary, superior ovoid.
Anatomy:
The young stem in T.S. show a single-layered epidermis with striated cuticle, parenchymatous cortex, single-layered endodermis surrounding an emphiphloicsiphonostele. In older stems, secondary growth prominent, both external and internal phloem present pith parenchymatous, cortical cells contain calcium-oxalate crystals.
The leaf consists of a single-layered epidermis with a thick cuticle. Mesophyll cells and little differentiated cruciferous type of stomata present in the lower epidermis, spongy tissue predominant, large fan-shaped collateral vascular bundle in the mid-rib region.
Powder Features:
(a) Colour:
Dark-brownish
(b) Taste:
(c) Microscopic Features:
The powder shows the presence of acicular crystals of calcium oxalate in cortical cells of stem and mesophyll cells of leaf, resinous cells in cortex, cruciferous type of stomata, vessels with bordered pittings.
2. Zingiber Officinale (Family: Zingiberaceae):
Fragments of epidermal cells with caryophyllaceous stomata, glandular and non-glandular hairs, cystolith, acicular fibers, palisade and spongy parenchyma cells, spiral and reticulate vessels, crystals of calcium oxalate; starch grains, parenchymatous oil containing cells.
Morphology:
Rhizome:
Pale-yellowish buff-coloured, surface is covered with scale leaves, with distinct nodes and internodes, presence of buds.
Anatomy:
In T.S. rhizome shows a well-marked endodermis which separates the cortex from vascular tissue zone; cortex is cellulosic, thin-walled parenchymatous, containing starch grains and oleoresin bearing cells, vascular bundles are smaller, collateral and surrounded by a group of arch-shaped fibres; vessels may be associated with some pigmented cells.
Powder Features:
(a) Colour:
Yellowish
(b) Taste:
Aromatic and pungent
(c) Microscopic features:
Abundant starch grains, mostly simple, up to 50 × 30 × 7 × µm non-lignified fibres, vessels with pigmented cells; thin-walled cork cells, abundant parenchymatous cortical cells filled with starch; and some oleoresin-bearing cortical cells.
3. Rauvolfia Serpentina (Family: Apocynaceae):
Cork thin-walled; presence of latex tube in the bark; fibers present in isolated patches; presence of prismatic calcium oxalate crystals; starch grains present in the medullary rays, rounded grains 7 to 15 µm, stone cells present — looks like group of thin-walled cells having rectangular shape, yellow in colour.
Morphology:
Rhizome:
About 1-2 mm in diameter, dull greyish-brown in colour with faint longitudinal ridges.
Root:
About 0.5-1.0 cm in thickness, sub-cylindrical or slightly tapering, rootlets usually attached to the root axis.
Anatomy:
In T.S., root shows the external stratified cork layer, followed by thick xylem layer, pith absent. In T.S., rhizome also shows thick cork layers followed by cortex and massive secondary tissues surrounding the centrally located pith zone; presence of distinct growth ring in the secondary xylem tissue layers; some cortical cell filled with granular secretions which stain yellow with iodine, presence of starch granules in cortical cells.
Powder Features:
(a) Colour:
Greyish.
(b) Microscopic features:
Presence of abundant starch grains, grains simple to compound; prism shaped calcium-oxalate crystals present, fibres non-lignified, cork cells polygonal; vessels elongated, pitted, with oblique end walls.
4. Alstonia Scholaris (Family: Apocynaceae):
Cork thin-walled or sometimes absent; secretion cells parenchymatous, containing oleoresin and having thin suberised walls; parenchymatous cells abundant, polygonal, elongated, filled with starch granules, sack-shaped, mostly simple, up to 50 x 30 x 7 µm no calcium oxalate crystals, no stone cells; nonlignified fibers present in the vascular- bundles; vessels non-lignified, reticulate, accompanied by narrow pigmented cells, vessels 50 to 75 µm wide.
Morphology:
Bark:
Bark is pale-yellowish in colour with latex bearing tissues, bitter and astringent.
Anatomy:
In T.S., presence of multiple layers of cork cells, latex-bearing tissues and fibres in isolated patches, starch grains and calcium-oxalate crystals bearing parenchymatous cells also present, starch grains rounded, 7-15 fim in diameter; stone cells present, rectangular.
Powder Features:
(a) Colour:
Yellowish-white
(b) Microscopic features:
The powder is light-yellowish and shows the presence of thin- walled cork cells, latex-bearing cells, stone cells, starch grains and calcium oxalate crystals.
5. Adhatoda Vasica (Family: Acanthaceae):
Cork cells polygonal, tubular, of two kinds — broad lignified and narrow nonlignified; presence of occasional rounded secretion cells with granular contents; presence of mostly lignified parenchyma; presence of simple starch grains in parenchymatous cells — 4 to 20 to 50 µm, presence of calcium oxalate crystals like prisms in the phloem and medullary ray cells; presence of non-lignified, pericycle fibers; stone cells absent; presence of vessels — 36 to 54 µm in diameter, about 235 µm long joined by lateral openings.
Morphology:
Leaf:
Simple, ex-stipulate, petiolate, entire, glabrous, lanceolate, acute, reticulate-unicostate. Anatomy
In T.S., the leaf shows dorsiventral structure — presence of both upper and lower epidermis of which lower epidermis contain caryophyllaceous stomata, presence of multicellular trichomes, and glandular hairs on upper epidermis, presence of palisade and spongy mesophyll cells, palisade layers containing cystolith, vascular bundles surrounded by pericycle, xylem and phloem present side by side, presence of oil globules and calcium-oxalate crystals in the mesophyll cells.
Powered Features:
(a) Colour:
Greenish or greyish green
(b) Microscopic features:
Presence of epidermal fragments with caryophyllaceous stomata, glandular and multicellular hairs, cystolith in palisade layers, oil-containing parenchymatous cells.
Special Anatomical Studies (after clearing of leaf by chloral hydrate or lactic acid):
Material: Leaf of Adhatodavasica:
(a) Palisade ratio:
Average 1: 6 (approx.)
(b) Stomatal index:
Average 16
(c) Vein islet number:
6. Strychnos Nux Vomica (Family: Loganiaceae):
Morphology:
Seed:
Flat, hard, heavy, endosperm, thin, cotyledon somewhat oval, 1.3 to 1.5 cm diameter, dark grey colour.
Anatomy:
In section through seed, there is distinct seed coat, endosperm, central canal, cotyledons radical; seed coat cell wall thick and coloured epidermal cells having long lignin hair arises out of epidermal cells, hypodermal cells are thick-walled dead type, endosperm cells are thick-walled square type, there are distinct plasmadesmata connections among the endosperm cells; each cell contain aleurone grain and oil droplets.
Taste:
Bitter taste, due to presence of strychnine alkaloid (indole type).
7. Digitalis Purpurea (Family: Scrophulariaceae):
Morphology:
Leaf:
Simple oval leaf with serrated margin, leaf hairy, veination simple reticulate type.
Anatomy:
In T.S. the leaf shows the features of dorsiventral structure, presence of both upper and lower epidermis; lower epidermis possesses anemolisic stomata, both surface bears multicellular glandular hairs; both pallisade and spongy mesophylls present; at the midvein region hypodermal collenchyma tissue present; vascular bundle collateral, conjoint close type; oxalate crystals absent.
Powder Features:
(a) Colour:
Greenish or greyish-green
(b) Odour:
Slight, like that of tea
(c) Taste:
Bitter, due to presence of cardiac glycosides
(d) Microscopic features:
Presence of epidermal fragment with stoma and glandular hair
8. Cinchona Officinalis (Family: Rubiaceae):
Bark:
Slight yellowish to gray coloured, outer surface rough, fissured, odour slight, taste bitter, thickness 1 to 1.5 mm.
Anatomy:
In T.S. of bark prominent cork cells noticed, cortex cells bear characteristic secretory canals, starch grains and oxalate crystals prominent in cortical cells; phloem fibre — long, spindle-like; xylem vessels smaller and simple; pith tissue arranged in two to three rows.
Powder Features:
(a) Colour:
Greyish to yellowish
(b) Odour:
Slightly stringent
(c) Taste:
Bitter due to presence of quinine alkaloid
(d) Microscopic features:
Presence of ruptured cork cells, cortical parenchyma possess batches of secretory canals, Starch grains and oxalate-containing crystals, pith tissues predominate with fibres.
9. Caphaelis Ipecacuanha (Family: Rubiaceae):
Morphology:
Root:
Tubular, slightly coiled or nodular type, 3-5 mm diameter, dark brown in colour, strongly odorous, bitter taste.
Anatomy:
In T.S. through root, cork layer prominent, phelloderm cell parenchymatous and possess oxylate crystals, cortex layer merged with phelloderm, vascular tissues show secondary wood formation; starch grain and sclerides present in cortical layers.
Powder Features:
(a) Colour:
Greyish black
(b) Odour:
Strongly present
(c) Taste:
Bitter, due to presence of ascoquinoline alkaloid
(d) Microscopic features:
Presence of cork tissues, complex starch grain, idioblasticsclerides, calcium oxalate crystals in the cuticle or phelloderm cells.