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          Shallot is the air-dried bulb of Allium ascalonicum L. (Allium cepa var. ascalonicum  Backer) (Family Amaryllidaceae), Herbarium Specimen Number: DMSC 5172, BKF 156785, Crude Drug Number: DMSc 1143.

(Note The samples used are air-dried in the well-ventilated shade until the outermost bulb scales become dried.)

Constituents Shallot contains volatile oil comprising sulfur-containing organic compounds (e.g., diallyl disulfide, dipropyl disulfide, dipropyl trisulfide, methyl propyl trisulfide), flavonoids and their glycosides, saponins, etc.

Description of the plant (Figs. 1a, 1b) Biennial herb 20 to 50 cm tall; subterranean bulbs ovoid, 1.5 to 5 cm long, 1 to 4 cm wide, often consisting of 1 to 3 bulblet(s), usually reddish purple. Leaves simple, alternate, basally clustered, blade terete or cylindrical, 10 to 40 cm long, 0.3 to 1 cm wide, apex acuminate, sheathing at base, shiny green. Inflorescence terminal, scapose, umbel-like, globose, subtended by a few membranous spathe-like bracts; peduncle 30 to 45 cm long; pedicel 1.5 to 2 cm long. Flower bisexual, small; tepals 6, white to greenish white, pink or purple, ovate-lanceolate or oblong-lanceolate, 4 to 9 mm long; stamens 6, biseriate, inner filaments dilated at base; ovary superior, consisting of 3 connated carpels, 3-loculed, ovules numerous in each locule, style 1, filiform. Fruit locucidal capsule, 3-lobed. Seed flat, black

Description Odour, acrid and characteristic; taste, acrid.

          Macroscopical (Fig. 1a) Ovoid bulbs, 1.5 to 5 cm long, 1 to 4 cm wide, often consisting of 1 to 3 bulblet(s), reddish purple.

          Microscopical (Figs. 2a, 2b, 2c) Transverse section of the bulb shows upper and lower epidermis layers, mesophyll and vascular bundles. Upper and lower epidermises, small rectangular cells, some of which containing purple pigment. Mesophyll composed of parenchyma cells, some of which containing rod-shaped crystals and oil globules. Vascular bundles, in mesophyll layers, circularly arranged; vessels, annular, spiral and reticulate.

          Shallot in powder possesses the diagnostic microscopical characters of the unground drug. Typical rod-shaped crystals in some parenchyma cells and small unbranched vessels are characteristic.

Additional information

         1. It is usually harvested after one crop of cultivation (70 to 110 days) to obtain its bulbs although it is a biennial herb.

          2. Traditionally, inhaling the vapour or soaking the head with warm water containing the freshly crushed bulbs could alleviate nasal congestion from common cold.

Packaging and storage Shallot shall be stored in a well-ventilated, dry place, protected from light; under these conditions it may be stored for 6 months after harvesting.

Identification

          A. Shake 2 g of the crushed, peeled sample with 25 mL of methanol for 5 minutes and filter. Dilute 0.5 mL of the filtrate to 2 mL with methanol, add 2 drops of ninhydrin TS and immerse in a water-bath for a few minutes: a violet-blue colour appears.

          B. Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1), using silica gel G as the coating substance and a mixture of 45 volumes of 1-butanol, 15 volumes of water, 15 volumes of 1-propanol, and 15 volumes of glacial acetic acid as the mobile phase and allowing the solvent front to ascend 10 cm above the line of application. Apply to the plate, 4 μL of the test solution prepared by refluxing 30 g of the crushed, peeled sample, with 50 mL of ethanol on a water-bath for 30 minutes. Cool, filter, evaporate the filtrate to dryness, and dissolve the residue in 1.0 mL of ethanol. After removal of the plate, allow it to dry in air. Spray the plate with ethanolic ninhydrin TS and heat at 110° for 10 minutes. Several spots of different colours are observed (Table 1); see also Fig. 3.

Table 1 hR_f Values of Components in Ethanolic Extract of the Bulbs of Allium ascalonicum L.

Water Not more than 87.0 per cent v/w (Azeotropic Distillation Method, Appendix 4.12).

Foreign matter Not more than 2.0 per cent w/w (Appendix 7.2).

Total ash Not more than 1.0 per cent w/w (Appendix 7.7).

Dose 15 to 30 g as a decoction.