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                        Snake Jasmine Leaf is the dried leaf of Rhinacanthus nasutus (L.) Kurz (Justicia nasuta L., Rhinacanthus communis Nees) (Family Acanthaceae), Herbarium Specimen Number: DMSC 5372, Crude Drug Number: DMSc 1274.

Constituents  Snake Jasmine Leaf contains naphthoquinones (e.g., rhinacanthins and rhinacanthone). It also contains polyphenols, 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 with 2 ovules, 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, aromatic, characteristic; taste, slightly bitter.

                Macroscopical  (Fig. 1)  Dried whole or broken leaves, with or without petioles; whole leaves apex acute or shortly acuminate, base cuneate or attenuate, margin entire or slightly undulate, blade thin, wrinkled, slightly curled, brownish green to brown.
                Microscopical  (Figs. 2a‒2d)  Transverse section of the leaf through the midrib shows upper epidermis, mesophyll, vascular bundle, and lower epidermis. Upper epidermis: a layer of epidermal cells, stomata, glandular and multicellular uniseriate trichomes, and lithocysts. Mesophyll: palisade cell, a layer of columnar cells; spongy cell, loosely parenchyma; several layers of angular collenchyma in midrib. Vascular bundle: phloem and xylem. Lower
epidermis: a layer of epidermal cells, stomata, glandular and multicellular uniseriate trichomes, and lithocysts.

                Transverse section of the petiole shows epidermis, cortex, and vascular tissue. Epidermis: a layer of subrounded cells, stomata, glandular and multicellular uniseriate trichomes, and lithocysts. Cortex: several layers of angular collenchyma, chlorenchyma, numerous round-shaped parenchyma. Vascular tissue: U-shaped collateral vascular bundles; phloem and xylem.

                Snake Jasmine Leaf in powder possesses the diagnostic microscopical of the unground drug. The combination of lithocyst, glandular and multicellular uniseriate trichomes, are characteristic and can be seen in abundance.

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

Identification

A. Reflux 500 mg of the sample, in powder, with 10 mL of chloroform for 15 minutes and filter. To 2 mL of the filtrate, add 1 mL of strong ammonia solution: a pink colour develops.

B. Reflux 500 mg of the sample, in powder, with 10 mL of ethanol for 15 minutes and filter. Add 200 mg of activated charcoal to the filtrate, swirl, allow to stand for 5 minutes, and filter. To the filtrate obtained, add a few drops of a 10 per cent w/v solution of potassium hydroxide in ethanol and mix. Apply a few drops of this solution to a filter paper and examine under ultraviolet light (366 nm): a greenish blue colour appears.

C. Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1), using a high-performance plate with silica gel GF254 as the coating substance and a mixture of 65 volumes of hexane and 35 volumes of ethyl acetate as the mobile phase and allow the solvent front to ascend 8 cm above the line of application. Apply to the plate as a band of 8 mm, 10 µL of the test solution prepared by refluxing 500 mg of the sample, in powder, with 10 mL of ethanol for 15 minutes and filtering. Add 100 mg of activated charcoal to the filtrate, swirl, allow to stand for 5 minutes, and filter. After removal of the plate, allow it to dry in air. Spray the plate with a 10 per cent w/v solution of potassium hydroxide in ethanol and examine the plate under ultraviolet light (366 nm); one blue and two bluish green fluorescent bands are observed (Fig. 3).

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).

Total ash  Not more than 18.0 per cent w/w (Appendix 7.7).

Ethanol-soluble extractive  Not less than 4.0 per cent w/w (Appendix 7.12).

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