Macroscopic— Ginger occurs in horizontal, laterally flattened, sympodially branching pieces. Whole rhizomes are 5 to 15 cm long, 1.5 to 6 cm wide, and up to 2 cm thick, sometimes split longitudinally; pale yellowish buff or light brown externally, longitudinally striated, somewhat fibrous; branches flattish, obovate, short, about 2 cm long, each ending with a depressed stem scar; fracture, short with projecting fibers, or sometimes resinous; internally yellowish brown, showing a yellow endodermis separating the narrow cortex from the wide stele, and numerous yellowish points, secretion cells and numerous bigger greyish points, vascular bundles, scattered on the whole surface. The unscraped rhizome shows in addition an outer layer of dark brown cork. Morphological characteristics of different varieties and forms of Ginger from different geographical areas are listed in Table 1 of the general information chapter Supplemental Information for Articles of Botanical Origin 2030.

Histology— The scraped rhizome in transverse section shows a cortex composed of multiple layers of parenchyma cells rich in simple, large, flattened, ovoid or sack-shaped starch granules, 5 to 15 µm wide and 30 to 60 µm long having an eccentric hilum, some showing faint transverse striations. The cortex also shows numerous oleoresin cells with a yellow or yellowish-brown content and scattered collateral vascular bundles; a single layer of endodermal cells free from starch; a wide central stele composed of parenchyma cells rich in starch and oleoresin cells similar to those of the cortex, and containing scattered collateral vascular bundles, some enclosed in a sheath of septate nonlignified fibers with wide lumen. In addition to the above, the unscraped rhizome shows an outer zone of dark brown cork cells.

A: Pulverize about 5 g of Ginger. To about 1 g of the pulverized Ginger add 5 mL of dilute acetic acid, prepared by diluting 1 part of glacial acetic acid with 1 part of water, and shake for 15 minutes. Filter, and add a few drops of ammonium oxalate TS to the filtrate: not more than a slight turbidity is produced.

B: Dissolve about 50 mg of the residue obtained in the test for Alcohol-soluble extractives in 25 mL of water, and extract this solution with two 15-mL portions of ether. Combine the ether extracts, and evaporate in a porcelain dish. To the residue so obtained, add 5 mL of sulfuric acid solution (7.5 in 10.0) and about 5 mg of vanillin. Allow to stand for 15 minutes, and add an equal volume of water: the solution turns azure blue.

C: Thin-Layer Chromatographic Identification Test 201—

10(C / W)(rU / rS)

Solution A— Prepare a filtered and degassed mixture of acetonitrile, dilute phosphoric acid (1 in 1000), and methanol (55:44:1).

Solution B— Use filtered and degassed acetonitrile.

Mobile phase— Use variable mixtures of Solution A and Solution B as directed for Chromatographic system. Make adjustments if necessary (see System Suitability under Chromatography 621).

Standard preparation— Dissolve an accurately weighed quantity of USP Capsaicin RS in methanol to obtain a solution having a known concentration of about 0.1 mg per mL.

Test preparation— Use the filtrate retained from the test for Alcohol-soluble extractives.

System suitability solution— Reconstitute the content of 1 vial of USP Ginger Constituent Mixture RS in 1 mL of the Standard preparation.

Chromatographic system (see Chromatography 621)— The liquid chromatograph is equipped with a 282-nm detector and a 4.6-mm × 25-cm column that contains packing L1. The flow rate is about 1.0 mL per minute. The chromatograph is programmed as follows. Chromatograph the System suitability solution, and record the peak responses as directed for Procedure: the relative retention times are about 0.8 for 6-gingerol, 1.0 for capsaicin, and 1.9 for 6-shogaol; the resolution, R, between the 6-gingerol and the capsaicin peaks is not less than 3.0 and between the capsaicin and 6-shogaol peaks is not less than 10.0; and the tailing factors for the 6-gingerol, the capsaicin, and the 6-shogaol peaks are not more than 2.0. Chromatograph the Standard preparation, and record the peak responses as directed for Procedure: the relative standard deviation for replicate injections is not more than 2.5%.

Procedure— Separately inject equal volumes (about 25 µL) of the Standard preparation, the System suitability solution, and the Test preparation into the chromatograph, and proceed as directed for Chromatographic system. Record the chromatograms, and measure all of the peak responses. Calculate the sum of the peak responses due to gingerols and gingerdiones, occurring at about the following retention times, relative to 1.0 for capsaicin: 0.8 for 6-gingerol, 1.5 for 8-gingerol A, 2.2 for 8-gingerol B, 2.5 for 6-gingerdiol, 2.6 for 6-gingerdione, 3.4 for 10-gingerol, and 5.2 for 8-gingerdione. Calculate the percentage of gingerols and gingerdiones by the formula: in which C is the concentration, in mg per mL, of USP Capsaicin RS in the Standard preparation; W is the weight, in g, of Ginger used in the test for Alcohol-soluble extractives; rU is the sum of the peak responses due to gingerols and gingerdiones as calculated above; and rS is the capsaicin peak response obtained from the Standard preparation: not less than 0.8% is found.