Page 156 - Pharmacognosy 2 PG303 (1)

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

SUBTERRANEAN ORGANS

Subterranean organs include the following:
1- Subterranean stems including rhizomes and others which are related to
rhizomes such as corms, stem tubers and bulbs.
2- Subterranean roots including roots and root tubers.

There is no clear division between rhizomes and roots in a commercial
sense. When the presence of a rhizome is clearly obvious as in filix mas, the drug
is usually termed a rhizome. When the rhizome superficially resembles the root
in size and appearance as in Liquorice, the drug is usually described as root,
even when it consists mainly of rhizome. Hence commercial rhizomes almost
always contain a considerable proportion of root and similarly comer-cial roots
often consist of rhizome in the upper part.

Subterranean organs used in medicine are usually collected from perennial
plants where they serve as storage organs and thus generally, they are full of
reserved food materials.

Usually, they are rich in carbohydrate compounds such as starch as in Filix
mas, Rhubarb, Ipecacuanha; as sugars as in Gentian, squil, as inulin as in those
derived from the Compositae, as Triticum as in couch grass. They are devoid of
chlorophyll.

The general characters and the histological features of subterranean stems
(Rhizomes and other related underground organs) and Roots are discussed as
follows.

Subterranean Stems
The members of this group are characterized externally by bearing scale
leaves, axillary buds, adventitious roots and by having a growing point protected
by scale leaves forming a bud (not by a cap as in roots); and internally they never
show a central solid mass of xylem and in the Dicotyledons they have a
parenchymatous pith. The drugs obtained from this group occur on the market in
the following condition:
a. Entire form as in some veratrum.
b In broken pieces as in ginger, Iris, podophyllum etc.
c. In longitudinal slices as in some filix mas or in transverse slices as in squill,
colchicum etc
d. Partially or wholly decorticated as in ginger, Rhubarb, Iris etc.

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