Page 224 - Pharmacognosy 2 PG303

Pharmacognosy-2 (PG303) Level 2 Clinical Pharmacy-Pharm D

Pericycie is parenchymatous. Vascular bundles are collateral, present in a ring
and surrounding a very large parenchymatous pith, containing starch granules and
occasional scattered groups of sclereids with thick pitted walls and narrow lumen.
Xylem shows slender, annular, spiral, and pitted vessels, in small numbers.

Stolon is simlar to rhizome but with epidermis having striated cuticle and
with a prominent endodermis and a well-defined ring of vascular bundles showing
secondary thickening.

Root exhibits a piliferous layer, of papillosed cells, some being developed into
root hairs. Exodermis is of a single layer of quadrangular to polygonal cells, with
suberized walls and containing globules of volatile oil. Cortex is parenchymatous,
with numerous starch granules, the outermost cells containing globules of volatile
oil. Endodermis is of one, occasionally, in some places, of two layers of cells,
with cutinized walls and distinct casparian strips. The pericycle is of big
parenchyma. Primary xylem is of 4-19 arches, according to distance from rhizome:
surrounding a small central parenchymatous pith containing starch granules but
no sclereids. Older roots show a pith of starch-bearing parenchyma, vascular
bundles with secondary thickening and a periderm originating in the piliferous
layer.

Stem bases show a sclerenchymatous 1 or 2 layers of cortical cells
adjacent to the endodermis. This layer is composed of rectangular sclereids with
thick-pitted lignified walls. The area of the sclereids present in one gram of
2
powdered stem and leaf bases has been determined as 6.83 cm and a proposed
2
limit of 0.35 cm of these sclereids per gram of powdered valerian, corresponding
to 5% of stem bases is permitted in the drug. Pith is hollow.

Powder

Powdered European Valerian is light brown to grayish brown in color.
It is characterized by:

1- Numerous fragments of parenchyma cells containing globules of volatile oil
and starch granules.
2- Fragments of scalariform and reticulate thickened vessels and tracheids and
strongly lignified narrow fibers.
3- Fragments of peridermn and of piliferous layers with root hairs.
4- Numerous starch granules, rarely simple, mostly compound of 2- 6
components, spheroidal, plno-convex, 3-20 mostly 8-12µ in diameter with a
central hilum.
5- Occasional sclereids with lignified pitted walls, 3 -80µ in diameter.

181