NIS - libdoc.who.int - World Health Organization

Herba Origani
rolla-like, glabrous or lightly hairy, inconspicuous. Corolla of labiate
type, white or violet (1, 2).
Organoleptic properties
Odour: aromatic; taste: slightly bitter, spicy and astringent (1).
Microscopic characteristics
The stem is quadrangular in transverse section, with rectangular epidermal
cells; 1-layered collenchyma underlying epidermis and 3-layered one in each
corner of the stem. A broken ring of fibres and few stone cells in cortex;
cortex cells with brown content in about 3 layers of cells adjoining phloem
tissue. Leaf: the cells of leaf epidermis are sinuous (much more so on the
underside), with regularly or sometimes irregularly thickened walls. The
epidermis is covered by a thin cuticle. Diacytic stomata more frequent on
the lower epidermis. Simple and glandular trichomes on both epidermises,
preponderant on the lower one. The simple trichomes are curved, pointed,
1–5 celled, rugous. Glandular trichomes with 1–3-cellular stalk and unicellular
head. The secretory glands are 8–12-celled, mainly on the lower side of
leaves. Petiole with isodiametric or rectangular epidermal cells; simple and
glandular trichomes; collenchyma tissue in corners and partly underlying
upper and lower epidermis; central vascular bundle. Flower bracts and calyx
have similar structure to the leaf but in the calyx there are no hairs on the
inner epidermis. The corolla tube has irregular cells in the inner lobe and is
regular and papillose towards and at lobes (1, 30–32).
Powdered plant material
The powder is green. When examined under a microscope, the covering
trichomes are of lamiaceous type or short, unicellular and rarely conical;
conical trichomes are shaped like pointed teeth; covering trichomes are
thick-walled and contain minute needles. Cuticle of covering trichomes is
warty. The epidermises of the leaves have cells with sinuous walls; diacytic
stomata; cells of the upper epidermis are beaded; secretory trichomes
with 8–12 cells; glandular trichomes are rare, they have a unicellular head
and bicellular or tricellular stalk; pollen grains are smooth, spherical and
abundant (2).
General identity tests
Macroscopic and microscopic examinations (1, 2), and thin-layer chromatography
tests for the characteristic volatile oil constituents, thymol
and carvacrol (2).
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