Allium cepa

Allium cepa

Allium cepa monograph Allium cepa l. Definition Allium cepa Bulbus Allii Cepae is the fresh or dried bulbs of Allium cepa L. (Liliaceae) or its varieties and cultivars. Synonyms Allium esculentum Salisb., Allium porrum cepa Rehb. Description 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...