NIS - libdoc.who.int - World Health Organization

WHO monographs on medicinal plants commonly used in the Newly Independent States (NIS)
Description
Urtica dioica L.
A herbaceous perennial with erect, green to purplish square stems, 30–150 cm
high, with creeping roots; whole plant covered with stinging hairs. Leaves
opposite, cordate at the base, oblong or ovate, finely toothed; upper surface
dark green and underside paler. Flowers incomplete, small, green, dioecious
(plant has either male or female flowers in separate inflorescences) and occur
as racemes in axils of upper leaves; male or barren flowers have a perianth of
4 segments and 4 stamens, which are bent inwards at bud stage; female or
fertile flowers have similar perianth surrounding a single 1-seeded carpel,
bearing 1 style with a brush-like stigma. Fruit an achene (3, 8).
Urtica urens L.
A herbaceous annual resembling Urtica dioica, but is smaller (usually up
to 30 cm high), has smaller leaves and flowers are in short, mostly unbranched
clusters; male and female flowers appear together in the same
raceme. Glabrous except for the stinging hairs (8, 11).
Plant material of interest: dried roots and rhizomes
General appearance
Rhizome cylindrical and tapering, occasionally branched, up to about
6 mm thick at upper end; outer surface yellowish-brown; internodes with
deep longitudinal furrows, numerous smooth, very thin and wiry roots
arising from the nodes; in the outer part, inner surface creamy-white with
a central hollow; fracture fibrous and tough.
Root greyish-brown, irregularly twisted, about 5 mm thick, distinct
longitudinal furrows; hollow in cross-section, cut surface white; fracture
fibrous and tough (1, 7).
Organoleptic properties
Odourless; taste: faintly aromatic, characteristically bitter (1).
Microscopic characteristics
Rhizome: thin cork composed of brown, thin-walled cells, a few rows of
tangentially elongated cortical parenchyma and a pericyclic region with
fairly numerous fibres; fibres usually in small groups, sometimes single;
individual fibres greatly elongated with very thick, lignified walls; some
cells of pericycle and outer part of the secondary phloem contain fairly
large cluster crystals of calcium oxalate. Cambial region distinct and continuous,
with narrow radial groups of vascular tissues separated by wide
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