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          Black Cumin is the dried ripe seed of Nigella sativa L. (Family Ranunculaceae), Herbarium Specimen Number:  DMSC 4536, QSBG 22815, Crude Drug Number:  DMSc 418.

Constituents  Black Cumin contains volatile oil, of which p-cymene and thymoquinone are its major components.  It also contains fixed oil, alkaloids, flavonoids, sterols, etc.

Description of the plant  (Fig. 1)  Annual herb 30 to 60 cm tall, branched at the top; stem green, round, hairy, 2 to 5 mm in diameter, internodes 2 to 5 cm long.  Leaves alternate, 1- to 3-pinnately dissected into linear, linear-lanceolate, capillary or irregularly lobed, lower leaves small, petiolated, upper leaves sessile, 6 to 10 cm long, glabrous on the upper surface, hairy beneath and on the rachis.  Flower regular, bisexual, terminal or axillary on branches, white, greenish white or pale blue, about 3 cm in diameter, long-stalked, pedicel 1.5 to  5.5 cm long, becoming longer as the fruit matures.  Sepals 5, free, greenish white to pale purple, petaloid, caducous, lanceolate or ovate, 1.2 to 1.5 cm long, 0.4 to 0.5 cm wide,  longer than petals.  Petals 8, about 5 mm long, about 2.5 mm wide, 3-lobed, anterior lobe small ovate, acuminate, blue, flapped over the fused concave hairy base of the pair of  posterior lobes, posterior lobes ovate, greenish white, apex blue with a blue line across the body, each carrying a shining green mass, scantily ciliated.  Stamens numerous, outer  one longer than the inner ones, basifixed; filament 2.5 to 5.2 mm long, slender; anther 1.5 to  2 mm long; ovary superior, about 5 mm long, smooth, carpels 2 to 4, style and stigma about  7 mm long.  Fruit united follicles forming a capsule, ultimately inflated with persistent horn-like styles.  Seeds numerous, ovate to lanceolate, trigonal, black. 

Description  Odourless; taste, bitter, spicy and aromatic.

      Macroscopical  (Fig. 1)  Trigonal to nearly pentagonal, 2.0 to 3.2 mm long, 1.3 to 1.8 mm wide; surface black, rough, glabrous; apex narrow and sharp; base obtuse. 

       Microscopical  (Figs. 2a, 2b)  Transverse section of the seed through the cotyledon shows seed coat composed of the three layers; the outer, dark brown, thick-walled cells with  irregular papillae; the middle rectangular, brown, thin-walled cells, more or less collapsed; and the inner, dark brown, thick-walled, tangentially rectangular cells.  Endosperm,  thick-walled polygonal cells containing aleurone grains and oil globules.  Cotyledons, thin-walled cells containing aleurone grains and oil globules. 

         Black Cumin in powder possesses the diagnostic microscopical characters of the  unground drug; in surface view, the inner epidermis shows striated wall.

Additional information  It is commonly used with other herbal drugs in Thai traditional herbal preparations.

Packaging and storage  Black Cumin 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. Shake 1 g of the sample, in powder, with 20 mL of ethanol for 10 minutes and filter.  To 1 mL of the filtrate, add 2 mL of ethanol, 2 drops of ninhydrin TS and place in a water-bath for a few minutes:  a violet-blue colour appears. 

       B. Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1), using silica gel GF254 as the coating substance and a mixture of 90 volumes of toluene and 10 volumes of ethyl acetate as the mobile phase and allowing the solvent front to ascend 12 cm above the line of application.  Apply separately to the plate, 2 μL each of solutions (A), (B) and (C).  Prepare solution (A) by shaking 3 g of the sample, in powder, with 10 mL of methanol for 2 minutes and filtering.  For solution (B), dissolve 2 mg of thymoquinone in 1 mL of methanol.  For solution (C), add 10 μL of olive oil to 1 mL of ethyl acetate and mix.  After removal of the plate, allow it to dry in air and examine under ultraviolet light (254 nm), marking the quenching spots.  The chromatogram obtained from solution (A) shows  a quenching spot (hR_f value 74 to 76) corresponding to the thymoquinone spot from solution (B), and three spots of lower hR_f values.  Spray the plate with anisaldehyde TS and heat at 105° for 15 minutes; the spot due to thymoquinone is yellowish brown.  One violet spot (hR_f value 94 to 96) corresponds to a spot of triglycerides of olive oil from solution (C).  Other two pale violet and five violet spots are also observed (Table 1); see also Fig. 3.

       Water  Not more than 7.0 per cent v/w (Azeotropic Distillation Method, Appendix 4.12).

       Foreign matter  Not more than 4.0 per cent w/w (Appendix 7.2). 

       Total ash  Not more than 7.0 per cent w/w (Appendix 7.7).

       Ethanol-soluble extractive  Not less than 24.0 per cent w/w (Appendix 7.12).

       Volatile oil  Not less than 0.15 per cent v/w (Appendix 7.3H).  Use 20 g, in coarse powder, freshly prepared and accurately weighed.  Use 200 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.