Allium cepa monograph
Allium cepa l.
Allium cepa Bulbus Allii Cepae is the fresh or dried bulbs of Allium cepa L. (Liliaceae) or its varieties and cultivars.
Allium esculentum Salisb., Allium porrum cepa Rehb.
A perennial herb, strong smelling when crushed; bulbs vary in size and shape from cultivar to cultivar, often depressed-globose and up to 20 cm in diameter; outer tunics membranous. Stem up to 100cm tall and 30 mm in diameter, tapering from inflated lower part.
Leaves up to 40 cm in height and 20mm in diameter, usually almost semicircular in section and slightly flattened on upper side; basal in first year, in second year their bases sheathing the lower sixth of the stem.
Spathe often 3-valved, persistent, shorter than the umbel. Umbel 4– 9cm in diameter, subglobose or hemispherical, dense, many-flowered; pedicels up to 40mm, almost equal. Perianth stellate; segments 3–4.5 × 2–2.5mm, white, with green stripe, slightly unequal, the outer ovate, the inner oblong, obtuse or acute.
Stamens exserted; filaments 4–5mm, the outer subulate, the inner with an expanded base up to 2 mm wide and bearing short teeth on each side. Ovary whitish. Capsule about 5mm, 2n = 16
Plant material of interest: fresh or dried bulbs
Major chemical constituents
Sulfur- and non-sulfur-containing chemical constituents have been isolated from Bulbus Allii Cepae; the sulfur compounds are the most characteristic.
The organic sulfur compounds of Bulbus Allii Cepae, including the thiosulfinates, thiosulfonates, cepaenes, S-oxides, S,S’-dioxides, monosulfides, disulfides, trisulfides, and zwiebelanes occur only as degradation products of the naturally occurring cysteine sulfoxides (e.g. (+)-S-propyl-L-cysteine sulfoxide).
When the onion bulb is crushed, minced, or otherwise processed, the cysteine sulfoxides are released from compartments and contact the enzyme alliinase in adjacent vacuoles. Hydrolysis and immediate condensation of the reactive intermediate (sulfenic acids) form the compounds as indicated below.
The odorous thiosulphonates occur (in low concentrations) only in freshly chopped onions, whereas the sulfides accumulate in stored extracts or steamdistilled oils. Approximately 90% of the soluble organic-bound sulfur is present as γ-glutamylcysteine peptides, which are not acted on by alliinase. They function as storage reserve and contribute to the germination of seeds.
However, on prolonged storage or during germination, these peptides are acted on by γ-glutamyl transpeptidase to form alk(en)yl-cysteine sulfoxides, which in turn give rise to other volatile sulfur compounds.
Fresh juice and 5% and 50% ethanol extracts have been used in clinical studies. A “soft” extract is marketed in France but is not recognized as a drug by French authorities. Dried Bulbus Allii Cepae products should be stored in well-closed containers, protected from light, moisture, and elevated temperature. Fresh bulbs and juice should be refrigerated (2–10°C).
Uses supported by clinical data
The principal use of Bulbus Allii Cepae today is to prevent age-dependent changes in the blood vessels, and loss of appetite
Uses described in pharmacopoeias and in traditional systems of medicine
Treatment of bacterial infections such as dysentery, and as a diuretic. The drug has also been used to treat ulcers, wounds, scars, keloids, and asthma. Bulbus Allii Cepae has also been used as an adjuvant therapy for diabetes.
Uses described in folk medicine, not supported by experimental or clinical data
As an anthelminthic, aphrodisiac, carminative, emmenagogue, expectorant, and tonic, and for the treatment of bruises, bronchitis, cholera, colic, earache, fevers, high blood pressure, jaundice, pimples, and sores.
more information at: http://apps.who.int/medicinedocs/es/d/Js2200e/3.html