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         Khamin Oi is the dried rhizome of Curcuma sp. “Khamin Oi” (Family Zingiberaceae), Crude Drug Number: DMSc 0271.

Constituents Khamin Oi contains curcuminoids, of which curcumin, desmethoxycurcumin, and bisdesmethoxycurcumin are its major components. It also contains volatile oil, etc.

Description of the plant (Figs. 1a, 1b) Perennial herb; rhizome well-developed, mostly above ground, obconical to oblong-ovoid, branched, orange-yellow or pale yellow within, aromatic; leafy shoots up to 2 m tall, bearing 4 to 9 leaves. Leaves simple, oblong-lanceolate, up to 90 cm long, up to 25 cm wide, apex acuminate, glabrous or pubescent, base acute decurrent; petioles long, narrowly winged. Inflorescence scape from the rhizome, appearing before the leaves; peduncle 5 to 15 cm long; spike cylindric, usually gradually widened to the apex, 10 to 18 cm long, 6 to 8 cm in diameter; primary bracts numerous, lower ones halfway connate, free part obliquely erect, 3 to 8 cm long, bracts usually increasing in length to the apex of spike, those of the lower bracts pale green or whitish, coma bract free and spreading, usually red-purple or violet; bracteoles hairy. Flower pale yellow; calyx hairy, tubular, white or white with red teeth; corolla about 4 cm long, tube white or yellowish, lobes ovate or oblong, white with pink; labellum orbicular or obovate, bilobed, yellow or white with yellow median field; petaloid staminodes oblong-obovate, pale yellow; ovary inferior, trilocular. Fruit capsule, ovoid, trigonous. Seeds oblong, arillate.

Description Odour, characteristic and aromatic; taste, slightly bitter and pungent.

          Macroscopical (Fig. 1a) Dried slices of primary rhizomes and branched annulate tubers vary in size, shape and thickness; somewhat crooked, orange-yellowish brown to greyish brown; enclosed or nearly enclosed with outer cork layer, covered with coarse trichomes. Pseudoendodermal rings are seen in horizontal and oblique slices

          Microscopical (Figs. 2a, 2b, 2c) Transverse section of the fresh rhizome shows epidermis, composed of a layer of rectangular cells; covering trichomes, unicellular and uniseriate multicellular. Storied cork, several layers of rectangular cork cells. Cortex, composed of broad zone of thin-walled parenchyma cells, filled with numerous starch grains, some of which containing brownish yellow oleoresin or yellowish oil droplets. Pseudoendodermis, a circular layer of compressed rectangular cells, enclosing a broad zone of parenchyma cells similar to those in cortex. Vascular bundles, not yielding the reaction with phloroglucinol TS, scattering densely underneath endodermis; vessels, spiral, scalariform and reticulate.

          Khamin Oi in powder possesses the diagnostic microscopical characters of the unground drug.

Contra-indication It is contra-indicated in pregnant women

Packaging and storage Khamin Oi shall be kept in well-closed containers, preferably of metal or glass, protected from light and stored in a cool and dry place.

Identification

         A. Extract 10 mg of the sample, in powder, with 2 ml of acetic anhydride, add a few drops of sulfuric acid and observe under ultraviolet light (366 nm): the solution shows blood-red colour.

          B. Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1), using silica gel G as the coating substance and a mixture of 49 volumes of toluene, 49 volumes of chloroform and 2 volumes of absolute ethanol as the mobile phase and allowing the solvent front to ascend 17 cm above the line of application. Apply separately to the plate, 5 μL each of the following two solutions. Prepare solution (A) by placing 1 g of the sample, in powder, in a stoppered test-tube, adding 3 mL of methanol and shaking for a few minutes. Set aside for 1 hour and filter. For solution (B), dissolve 1 mg of curcumin in 1 mL of methanol. After removal of the plate, allow it to dry in air, and examine under ultraviolet light  (366 nm), locating the spots. The chromatogram obtained from solution (A) shows several spots of different colours. Two orange-brown spots (hR_f values 24 to 26 and 12 to 15) and one yellow spot (hR_f value 6 to 8) correspond to the spots of curcumin and its derivatives from solution (B). Spray the plate with a 10 per cent w/v solution of phosphomolybdic acid in ethanol and heat at 105° for about 10 minutes; the spots due to curcumin and its derivatives are brown. Other spots are blue (Table 1); see also Fig. 3.

         Repeat the same procedure on another plate but spray with vanillin-sulfuric acid TS and heat at 105° for about 10 minutes. The chromatogram obtained from solution (A) shows three orange-brown spots corresponding to the spots of curcumin and its derivatives from solution (B). Other spots are purple and violet (Table 1); see also Fig. 3.

Table 1 hRf Values of Component in Metanolic Extract of the Rhizomes of Curcuma sp. “Khamin Oi”

       *curcumin and its derivatives

Water Not more than 11.0 per cent v/w (Azeotropic Distillation Method, Appendix 4.12).

Acid-insoluble ash Not more than 6.0 per cent w/w (Appendix 7.6).

Sulfated ash Not more than 14.0 per cent w/w (Appendix 5.3).

Volatile oil Not less than 4.0 per cent v/w (Appendix 7.3H). Use 10 g, in fine powder, accurately weighed. Use 100 mL of water as the distillation liquid and a 500-mL round-bottomed flask. Distil at a rate of 2 to 3 mL per minute for 5 hours. Use 2.0 mL of xylene in the graduated tube. Calculate the content of volatile oil with reference to the anhydrous substance.

Dose 4.5 to 9 g.