Elm is the dried inner bark of Ulmus rubra Muhl. (Ulmus fulva Michx.) (Fam. Ulmaceae).
• 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.
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
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).
• Botanic Characteristics
Unground Elm: Unground Elm occurs as broad, flat, oblong pieces 14 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
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 1035 µm in length; have starch grains that are spheroidal, or polygonal, usually 315 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
• 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
• Packaging and Storage: Preserve in well-closed containers, and store in a cool, dry place.