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         Garden Cress Seed is the dried mature seed of Lepidium sativum L. (Family Cruciferae), Herbarium Specimen Number:  DMSC 4533, QSBG 22819, Crude Drug Number:  DMSc 431.

Constituents  Garden Cress Seed contains sinapic acid, sinapine and imidazole alkaloids.  It also contains volatile oil, fatty acids, amino acids, isothiocyanate glycosides, mucilage, etc. 

Description of the plant  (Figs. 1a, 1b)  Annual herb 20 to 80 cm tall; stem erect, branched, nearly glabrous, glaucous.  Basal leaves, pinnatisect or lyrate-pinnate, 2 to 10 cm long, 1 to  5 cm wide, segments toothed or finely divided, crispate, stalked to subsessile; stem leaves becoming successively simple, linear and entire in the upper part.  Inflorescence raceme, terminal or axillary.  Flower small, 2 to 3 mm in diameter, bisexual, regular; sepals 4,  oblong, 1 to 1.3 mm long, 0.5 to 0.8 mm wide; petals 4, white or lavender, spatulate or obovate, 2.5 to 4 mm long, 0.7 to 1.4 mm wide; stamens typically 6, tetradynamous; ovary superior,  2-carpeled, 1 ovule each, ripening into a thin partitioned pod.  Fruit silique,  elliptic or oblong-ovate, 4 to 6 mm long, 3 to 5 mm wide, retuse, narrowly winged, with deep apical notch, style not projecting beyond notch; dehiscent by 2 valves; stalk more than half as long as fruit.  Seed obliquely ovate to elliptic or oblong, 2 to 3 mm long, 1 to 1.5 mm wide, red to reddish brown. 

Description  Odourless; taste, aromatic, slightly bitter

        Macroscopical  (Figs. 1a, 1b)  Obliquely ovate to elliptic or oblong, 2 to 3 mm long,  1 to 1.5 mm wide, externally reddish brown, glabrous, smooth, with a short longitudinal groove on one side at the narrow end.  Seed coat swollen when moistened.

        Microscopical  (Figs. 2a, 2b)  Transverse section of the seed shows seed coat composed of outer integument and inner integument.  Outer integument, a mucilaginous layer and a layer of reddish thick-walled cells; inner integument, colourless rectangular cells with aleurone grains and oil globules. Embryo, cotyledons, thin-walled cells, oil globules,  small aleurone grains and vascular tissue.

         Garden Cress Seed in powder possesses the diagnostic microscopical characters of the unground drug. 

Contra-indication  It is contra-indicated in pregnant women. 

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

Packaging and storage  Garden Cress Seed shall be kept in well-closed containers, protected from light, and stored in a dry place.

Identification

      A. Transfer 1 g of the sample, in powder, to a 25-mL ground-glass stoppered cylinder. Moisten the sample with 1 mL of ethanol, add water to 25 mL, stopper and shake vigorously for 5 minutes.  Allow to stand for 1 hour and shake intermittently.  Add 0.5 mL of ruthenium red TS and mix well:  a pinkish swollen mucilage is observed.

       B. To 1 g of the sample in a stoppered centrifuge tube, add 3 mL of ethanol, stopper, shake for 3 minutes, and filter.  To the filtrate, add 2 or 3 drops of acetic potassium  iodobismuthate TS:  an orange precipitate is produced.

       C. To 100 mg of the sample, in fine powder, add 2 mL of sodium hydroxide TS and shake well:  a yellow colour is produced immediately.

       D. Prepare iron(II) sulfate strip by impregnating a 2 to 3 mm wide paper strip in iron(II) sulfate TS.  Allow it to dry in a current of air and impregnate it in a 10 per cent w/v solution of sodium hydroxide and dry in the same manner.  Place the strip in a glass tube passing through a rubber bung of a suitable vessel.  Place 5 g of the sample, in fine powder, in the vessel, add 3 g of zinc powder and 30 mL of dilute sulfuric acid.  Quickly place the bung in position and heat on a water-bath for about 45 minutes:  a black stain on the strip is  produced.  When the strip is treated with a mixture of 1 mL of 6 M hydrochloric acid and a few drops of iron(III) chloride TS:  the black stain is decolorized with the evolution of hydrogen sulfide and a blue stain is produced.

       E. 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 chloroform and 10 volume of methanol as the mobile phase and allowing the solvent front to ascend 10 cm above the line of application.  Apply separately to the plate, 2 μL of solution (A) and 5 μL of solution (B).  Prepare solution (A), by macerating 5 g of the sample, in fine powder, with 30 mL of petroleum ether (boiling range, 40° to 60°) for 15 minutes and filtering.  Macerate the marc with two successive 25-mL portions of methanol, filter, and combine the filtrates.  Evaporate the filtrate on a water-bath to dryness and dissolve the residue in 30 mL of dilute hydrochloric acid.  Transfer to a separator, extract with two successive 30-mL portions of ethyl acetate, combine the ethyl acetate extracts, evaporate to dryness on a water-bath, and dissolve the residue in 0.5 mL of methanol.  For solution (B) dissolve 10 mg of sinapic acid in 0.5 mL of water, add 1 mL of methanol and mix well.  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 one quenching spot (hR_f value 27 to 29) corresponding  to the sinapic acid spot from solution (B), and several spots of different hR_f values.  Expose  the plate to iodine vapour; the spot due to sinapic acid is pinkish brown.  Other spots of different colours are observed (Table 1); see also Fig. 3.

Table 1 hR_f Value of Components in the Extract of the Seeds of Lepidium sativum L.

Loss on drying  Not more than 10.0 per cent w/w after drying at 105° to constant weight (Appendix 4.15). 

Foreign matter  Not more than 2.0 per cent w/w (Appendix 7.2). 

Acid-insoluble ash  Not more than 0.4 per cent w/w (Appendix 7.6). 

Total ash  Not more than 6.0 per cent w/w (Appendix 7.7).

Ethanol-soluble extractive  Not less than 15.0 per cent w/w (Appendix 7.12).

Swelling index  Not less than 20, when determined by the following method.

           In a 25-mL ground-glass stoppered cylinder graduated over a height of 125±5 mm in 0.5-mL divisions, place 1 g of Garden Cress Seed, accurately weighed, moisten it with 1.0 mL of ethanol, add 25 mL of water and close the cylinder.  Shake vigorously every 10 minutes for 1 hour.  Allow to stand for 3 hours.  At 90 minutes after the beginning of the test, release any large volume of liquid retained in the layer of the Seed and any particles of the Seed floating at the surface of the liquid by rotating the cylinder about a vertical axis.  Measure the volume occupied by the Seed, including any adhering mucilage.  Carry out three tests at the same time.  The swelling index is given by the mean of the three tests.

Dose  3 g.