Elm

(elm).

DEFINITION

Elm is the dried inner bark of Ulmus rubra Muhl. (Ulmus fulva Michx.) (Fam. Ulmaceae).

IDENTIFICATION

• A. Mucilaginous Substance

Sample: 1 g of finely powdered Elm

Analysis: Macerate the Sample with 40 mL of cold water for 1 h.

Acceptance criteria: The resulting mixture is of a thick mucilaginous consistency and yellowish brown in color.

• B. Thin-Layer Chromatographic Identification Test

Standard solution: 0.025% rutin in methanol

Sample solution: Extract 1 g of powdered Elm with 10 mL of 60% methanol on a water bath for 15 min. Cool, filter, and concentrate the filtrate to 2.5 mL.

Chromatographic system

(See Chromatography

621

, Thin-Layer Chromatography.)

Adsorbent: 0.25-mm layer of chromatographic silica gel mixture, typically 20 cm long (TLC plates)

Application volume: 20 µL

Developing solvent system: Ethyl acetate, anhydrous formic acid, glacial acetic acid, and water (100:11:11:27)

Spray reagent: 1% solution of 2-aminoethyl diphenylborinate ester in methanol, followed by a 5% solution of polyethylene glycol 4000 in alcohol

Analysis

Samples: Standard solution and Sample solution

Develop the chromatograms in the Developing solvent system until the solvent front has moved three-fourths of the length of the plate. Remove the plate from the chromatographic chamber, and allow to air-dry. Spray the plate with Spray reagent, and examine the plate under UV light at 366 nm.

Acceptance criteria: The RF values of the principal spots relative to rutin are 1.05 (blue) and 0.8 (orange).

SPECIFIC TESTS

• Botanic Characteristics

Macroscopic

Unground Elm: Unground Elm occurs as broad, flat, oblong pieces 1–4 mm in thickness. The outer surface is yellow-orange with some brown outer bark or cork layers attached; the inner surface, which is pale yellow, is marked faintly with striated phloem lines. The fracture is fibrous with projections of five bast bundles.

Powdered Elm:

Weak yellowish orange with a distinctive fenugreek-like odor

Microscopic

Powdered Elm: Bast fibers are numerous, very long, usually broken, up to 25 µm in diameter, thick-walled, unlignified, or with only a thin outer sheath of the wall lignified; have calcium oxalate prisms 10–35 µm in length; have starch grains that are spheroidal, or polygonal, usually 3–15 µm in diameter, occasionally up to 25 µm in length; and have numerous mucilage fragments, frequently lamellated. Cork cells are few or absent.

• Outer Bark: Contains NMT 2% of adhering outer bark

• Articles of Botanical Origin, Foreign Organic Matter

561

: NMT 2%

• Loss on Drying

731

: Dry 2 g at 105

to constant weight: it loses NMT 12% of its weight.