Elm

This article is compiled based on the United States Pharmacopeia (USP) – 2025 Edition

Issued and maintained by the United States Pharmacopeial Convention (USP)

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1 DEFINITION

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

2 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 R values of the principal spots relative to rutin are 1.05 (blue) and 0.8 (orange).

3 SPECIFIC TESTS

Botanic Characteristics

Macroscopic

Unground Elm: Unground Elm occurs as broad, at, 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 brous 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.

Articles of Botanical Origin, Total Ash〈561〉: NMT 10% on the dried basis

Articles of Botanical Origin, Acid-Insoluble Ash〈561〉: NMT 0.65% on the dried basis

4 ADDITIONAL REQUIREMENTS

Packaging and Storage: Preserve in well-closed containers, and store in a cool, dry place.