» Elm is the dried inner bark of Ulmus rubra Muhlenberg (Ulmus fulva Michaux) (Fam. Ulmaceae).
Unground Elm Unground Elm occurs as broad, flat, oblong pieces from 1 to 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 Powdered Elm is weak yellowish orange and has a distinctive fenugreek-like odor. 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; calcium oxalate prisms from 10 to 35 µm in length; starch grains spheroidal or polygonal, usually from 3 to 15 µm in diameter, occasionally up to 25 µm in length; and numerous mucilage fragments, frequently lamellated. Cork cells are few or absent.
A: Macerate 1 g of finely powdered Elm with 40 mL of cold water for 1 hour: the mixture is of a thick mucilaginous consistency and yellowish brown in color.
B: Extract 1 g of Powdered Elm with 10 mL of 60% methanol on a water bath for about 15 minutes, cool, filter, and concentrate the filtrate to about 2.5 mL. Separately apply 20 µL of this solution and 20 µL of a standard solution containing 0.025% rutin in methanol to a thin-layer chromatographic plate coated with a 0.25-mm layer of chromatographic silica gel. Develop the chromatogram in a solvent system consisting of a mixture of ethyl acetate, water, anhydrous formic acid, and glacial acetic acid (100:27:11:11) until the solvent front has moved about three-fourths of the length of the plate. Remove the plate from the chromatographic chamber, and allow to air-dry. Spray the plate with a 1% solution of 2-aminoethyl diphenylborinate ester in methanol followed by a 5% solution of polyethylene glycol 4000 in alcohol, and examine the plate under UV light at 366 nm: the RF values of the principal spots relative to rutin are about 1.05 (blue) and 0.8 (orange).
Outer bark It contains not more than 2% of adhering outer bark.
Foreign organic matter 561 : not more than 2%.
Loss on drying 731  Dry about 2 g of Elm, accurately weighed, in an oven at 105 to constant weight: it loses not more than 12% of its weight.
Total ash 561 : not more than 10%, calculated on the dried basis.
Acid-insoluble ash 561 : not more than 0.65%, calculated on the dried basis.
USP32NF27 Page 2245