Macroscopic— The outer surface of the rhizome is pale to yellowish-brown, crowned with the remains of the aerial stem, and sometimes shows surface annulations up to 15 mm in diameter. The roots are pale to yellowish-brown, cylindrical or slightly tapering, sometimes spirally twisted, longitudinally wrinkled and deeply furrowed, up to 4 to 10 mm in diameter, and pass imperceptibly into rhizome. The short fracture, when dry, becomes tough and pliable on exposure to air.

Microscopic— The rhizomes and roots in transverse section show a thin outer bark separated from a wide xylem by a distinct cambial line. The cork is composed of several rows of thin-walled cells containing yellowish-brown pigment. The rhizome has a small circular pith, occasional small groups of thick-walled, lignified fibers in the pericycle, and a parenchymatous cortex. The phloem and xylem are composed of narrow strands of vascular tissue separated by wide, nonlignified medullary rays. Xylem vessels are lignified, 25 to 75 µm in diameter, usually with reticulate thickening but occasionally with spiral or annular thickening. Sclereids occur singly or in small groups, varying considerably in size and shape from rounded to rectangular to elongated and fiber-like, are up to 300 µm long and 20 to 40 µm wide, with intercellular spaces forming schizogenous oleoresin canals that are 80 to 150 µm in diameter and contain a dense black deposit present both inside and outside of the central cylinder (unlike Echinacea angustifolia, where the canals are present only outside of the central cylinder). Spherocrystalline masses of inulin occur throughout the parenchymatous tissues. Lignified fibers, present in the periphery of the cortex, are 100 to 300 µm long and occur singly with phytomelanin often absent (unlike Echinacea angustifolia, where the fibers occur scattered in groups, are 300 to 800 µm long, and are usually surrounded by phytomelanin).

A: Thin-Layer Chromatographic Identification Test 201—

B: Thin-Layer Chromatographic Identification Test 201—

C: The retention time of the major peak in the chromatogram of the Test solution corresponds to that of the echinacoside peak in the chromatogram of Standard solution 1, as obtained in the test for Content of total phenols. The peak area of any peak detected at the locus of 1,3-dicaffeoylquinic acid is not more than 1% of the peak area for the echinacoside peak.

Solvent, Solution A, Solution B, Mobile phase, and Standard solution 2— Prepare as directed for Content of total phenols under Echinacea angustifolia.

Standard solution 1— Proceed as directed for Content of total phenols under Echinacea angustifolia, except to use USP Powdered Echinacea pallida Extract RS instead of USP Powdered Echinacea angustifolia Extract RS.

Test solution— Proceed as directed for Content of total phenols under Echinacea angustifolia, except to use finely powdered Echinacea pallida instead of Echinacea angustifolia.

Chromatographic system (see Chromatography 621)— Prepare as directed for Content of total phenols under Echinacea angustifolia. Chromatograph Standard solution 1, and record the peak responses as directed for Procedure: the chromatogram obtained is similar to the Reference Chromatogram for total phenols provided with USP Powdered Echinacea pallida Extract RS. Chromatograph Standard solution 2, and record the peak responses as directed for Procedure: the capacity factor, k¢, is not less than 3.0; the tailing factor is not more than 2.0; and the relative standard deviation for replicate injections is not more than 2.5%.

Procedure— Proceed as directed for Content of total phenols under Echinacea angustifolia. Separately calculate the percentages of caftaric acid (C13H12O9), chicoric acid (C22H18O12), chlorogenic acid (C16H18O9), and echinacoside (C35H46O20) in the portion of Echinacea pallida taken by the formula: in which F is the response factor and is equal to 0.695 for chicoric acid, 0.881 for caftaric acid, 1.000 for chlorogenic acid, and 2.220 for echinacoside; C is the concentration, in mg per mL, of USP Chlorogenic Acid RS in Standard solution 2; W is the weight, in mg, of Echinacea pallida taken; and ri and rS are the peak responses for the relevant analyte obtained from the Test solution and Standard solution 2, respectively. Calculate the percentage of total phenols in the portion of Echinacea pallida taken by adding the individual percentages calculated.