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       Snake Jasmine Root is the dried root of Rhinacanthus nasutus (L.) Kurz (Justicia nasuta L., Rhinacanthus communis Nees) (Family Acanthaceae), Herbarium Specimen Number: DMSC 5263, Crude Drug Number: DMSc 1173.

Constituents Snake Jasmine Root contains naphthoquinones (e.g., rhinacanthin A, rhinacanthin B, and rhinacanthin C). It also contains triterpenoids, flavonoids, etc.

Description of the plant (Fig. 1) Subshrub, up to 2 m tall; stem erect, stout, quadrangular, much branched, finely striated, densely pubescent when young, becoming glabrescent with age; young branch hairy. Leaves simple, opposite decussate, ovate-elliptic, elliptic to lanceolate, 6 to 12 cm long, 2 to 5 cm wide, apex acute to shortly acuminate, base cuneate or attenuate, margin entire or slightly undulate, abaxially densely pubescent, adaxially sparsely pubescent to subglabrous, secondary veins 5 or 6 pairs; petiole 1 to 1.5 cm long. Inflorescence paniculate, terminal or axillary, up to 50 cm long; rachis densely pubescent; bract lanceolate, about 2 mm long, about 0.5 mm wide; bracteole minute. Flower white to greenish white, bilabiate, sessile to subsessile; calyx 5 to 6 mm long, deeply 5-lobed, lobe lanceolate, up to 4 mm long, about 0.7 mm wide, both surfaces pubescent, outer surface with glandular trichome; corolla tube 1.5 to 2.5 cm long, upper lip upright, oblong, 8 to 9 mm long, 2 to 3 mm wide, revolute, lower lip obovate, 3-lobed, with red marking at base, 1 to 1.5 mm long, 1 to 1.3 mm wide; stamens 2, attached to apex of corolla tube, filament short, glabrous; ovary superior, elliptic, 2-loculed, each locule 2-ovuled, style slender, sparsely pubescent, stigma 2-lobed. Fruit a capsule, oblong-elliptic, 1.5 to 2 cm long, about 2 mm wide. Seeds 4, subglobose, about 2.5 mm in diameter, papillose.

Description Odour, characteristic; taste, bland to slightly bitter.

       Macroscopical (Fig. 1) Cylindrical, up to 4 mm in diameter, with small lateral roots, greyish brown; surface with longitudinal wrinkles.

       Microscopical (Figs. 2a, 2b, 2c) Transverse section of primary growth of the root shows epidermis, cortex, vascular tissue, and pith. Epidermis: 1 to 2 layers of polygonal cells with greenish brown cell wall. Cortex: numerous round parenchyma, some containing cystoliths or microcrystals; red liquid substance in intercellular space of parenchyma; and 1 to 2 layers of endodermis. Vascular tissue: 1 to 2 pericycle layers; vascular bundle, alternate; and 5 arches of xylem tissues and phloem tissues. Pith: thin-walled round parenchyma.
       Transverse section of secondary growth of the root illustrates periderm, cortex, and vascular tissue. Periderm: numerous layers of rectangular cork cells. Cortex: numerous round parenchyma; lithocyst, oblong parenchyma, some containing microcrystals; red liquid substance in intercellular space; and crushed brown layers of endodermis cells. Vascular tissue: secondary phloem comprising parenchyma and groups of sclereids; secondary xylem consisting of vessels, xylem ray and xylem fibres; and primary vascular tissue in the centre.
       Snake Jasmine Root in powder possesses the diagnostic microscopical characters of the unground drug. Lithocysts, cystoliths, and reddish substance are characteristic.

Packaging and storage Snake Jasmine Root shall be kept in well-closed containers, protected from light, and stored in a dry place.

Identification

       A. To 1 g of the sample, in powder, add 20 mL of chloroform, heat in a water-bath for 5 minutes, and filter immediately, and allow to cool (solution 1): a reddish solution is obtained.

       B. To 10 mL of solution 1, add 10 mL of ammonia TS and shake: the aqueous layer becomes pale orange-brown.

       C. Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1), using silica gel G F254 as the coating substance and a mixture of 70 volumes of hexane and 30 volumes of ethyl acetate as the mobile phase and allowing the solvent front to ascend 8 cm above the line of application. Apply to the plate as a band of 8 mm, 20 µL of the test solution, prepared by sonicating 100 mg of the sample, in fine powder, with 2 mL of methanol for 10 minutes and filtering. After removal of the plate, allow it to dry in air and examine the plate under ultraviolet light (254 nm), marking the quenching bands. Examine the plate under ultraviolet light (366 nm) through the cut-off filter; one brown and three blue fluorescent bands are observed. Subsequently spray the plate with the solution prepared by dissolving 500 mg of vanillin in 40 mL of sulfuric acid, adding 10 mL of ethanol, and mixing. Then heat at 105° for 10 minutes. Two brown and three purple bands are observed (Fig. 3).

Loss on drying Not more than 9.0 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 2.0 per cent w/w (Appendix 7.6).

Total ash Not more than 16.0 per cent w/w (Appendix 7.7).

Ethanol-soluble extractive Not less than 7.0 per cent w/w (Appendix 7.12).

Water-soluble extractive Not less than 35.0 per cent w/w (Appendix 7.12).