NIS - libdoc.who.int - World Health Organization

Radix Urticae
medullary rays; secondary phloem mainly parenchymatous, whereas secondary
xylem dense and completely lignified; medullary rays in secondary
xylem show alternating areas of lignified and unlignified cells; lignified
cells have moderately thickened walls and numerous simple pits. Pith
composed of rounded, unlignified parenchyma.
Root: very thin cork, narrow phelloderm and secondary phloem and
xylem with alternating areas of lignified and unlignified parenchyma in
the wide medullary rays, as in the rhizome; a strand of primary xylem in
the centre with a few small vessels (1).
Powdered plant material
Fibrous and pale beige. Fragments of greatly elongated pericyclic fibres,
occurring singly or in groups, with thick and lignified walls, xylem vessels
with bordered pits, associated with thick-walled fibres with slit-shaped
pits; lignified, moderately thick-walled and pitted parenchyma from the
medullary rays of xylem; abundant thin-walled parenchymatous cells,
some containing large cluster crystals or scattered crystals of calcium oxalate;
fragments of brownish cork (1).
General identity tests
Macroscopic and microscopic examinations (1, 2), and thin-layer chromatography
for scopoletin and phytosterols (2).
Purity tests
Microbiological
Tests for specific microorganisms and microbial contamination limits are
as described in the WHO guidelines on quality control methods for medicinal
plants (12).
Foreign matter
Not more than 2% (1).
Total ash
Not more than 8% (2).
Acid-insoluble ash
Not more than 3.5% (1).
Water-soluble extractive
Not less than 15% (1).
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