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                        Siamese Rough Bush Leaf is the dried leaf of Streblus asper Lour. (Diplothorax tonkinensis Gagnep., Streblus monoicus Gagnep., Trophis cochinchinensis Poir.) (Family Moraceae), Herbarium Specimen Number: DMSC 5338, Crude Drug Number: DMSc 1245.

Constituents  Siamese Rough Bush Leaf contains flavonoids such as rutin.  It also contains terpenoids, phenolic compounds, sterols, etc.

Description of the plant  (Fig. 1)  Tree or shrub, up to 15 m tall, monoecious or dioecious; stem much-branched, lenticel conspicuous when young; outer bark greyish, scabrous, inner bark whitish, thick, exuding white latex; branches usually drooping or straggling, branchlet with short stiff hairs. Leaves simple, spirally arranged or distichous, elliptic, oblong, obovate, or subobovate, 1 to 8(–13) cm long, 0.5 to 3.5(–6.5) cm wide, apex acute to acuminate, base rounded, subcordate or obtuse, margin crenate to dentate, coriaceous, hispidulous to puberulous and/or scabrous on both surfaces, lower part of midrib somewhat prominent in lower surface, lateral veins 4 to 8 pairs; petiole 1 to 5 mm long, puberulous; stipule small, puberulous, caducous. Male inflorescence axillary, capitate, in pairs or solitary; peduncle 0.2 to 1.5 cm long, sparsely puberulous; bracts few, at base of inflorescence, small, narrowly elliptic; bracteoles 2, at base of calyx, larger than bract. Female inflorescence axillary, uniflorous or biflorous; peduncle 0.4 to 2 cm long, puberulent; bracts few, 0.5 to 2 mm long, sparsely puberulous. Male flowers in a head of 4 to 15 flowers, 0.4 to 1 cm in diameter, subsessile; perianth 1.5 to 2 mm long, puberulent; stamens 4, 2 to 2.5 mm long, anther about 1 mm long. Female flowers 1 to 2; perianth 2 to 2.5 mm long, elongated to 5 to 8 mm long in fruit, reflexed, puberulent; ovary superior, about 1 mm long, style 1 to 3 mm long, stigma 2 to 4 mm long, elongated to 1.2 cm long, bifid. Fruit a drupe, subglobose to ovoid, about 6 mm in diameter, indehiscent, enclosed by enlarged perianth lobes when young, yellow to orange when mature. Seed 1, globose, 4 to 5 mm in diameter, greyish white.

Description  Odour, mild to green; taste, bland.

                        Macroscopical  (Fig. 1)  Whole or broken leaves, with or without petioles. Whole leaves brownish, elliptic, oblong, obovate, or subobovate, apex acute to acuminate, base rounded, subcordate or obtuse, margin crenate to dentate, coriaceous, hispidulous to puberulous, and/or scabrous on both surfaces, lower part of midrib somewhat prominent in lower surface; petiole, puberulous.

                        Microscopical  (Figs. 2a–2d)  Transverse section of the leaf through the midrib shows upper epidermis, mesophyll, vascular tissue, and lower epidermis. Upper epidermis: a layer of rectangular cells, some containing rosette aggregate crystals or brown substances; short and long unicellular trichomes with cystolith. Mesophyll: 2 to 3 layers of elongated palisade cells, some containing rosette aggregate crystals; spongy cells, some containing rosette aggregate crystals; angular collenchyma cells, some containing rosette aggregate crystals and parenchyma, some containing rosette aggregate crystals or brown substances, in the upper and lower parts of midrib. Vascular tissue: phloem and xylem. Lower epidermis: a layer of rectangular cells; stomata; and short and long unicellular trichomes with cystolith.

                In surface view, epidermises show irregularly-shaped epidermal cells, anomocytic stomata, and short unicellular cystolith trichomes.

                Transverse section of the petiole shows epidermis, cortex, and vascular tissue. Epidermis: a layer of small rectangular cells with unicellular trichomes, and rarely, multicellular glandular trichomes. Cortex: numerous annular collenchyma, some containing rosette aggregate crystals and thin-walled parenchyma, some containing rosette aggregate crystals. Vascular tissue: phloem and xylem.

                Siamese Rough Bush Leaf in powder possesses the diagnostic microscopical characters of the unground drug. The presence of both short and long unicellular trichomes with cystolith are characteristic. The shape of short unicellular trichomes with cystolith are unique. Annular collenchyma can also be found.

Packaging and storage  Siamese Rough Bush 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 fine powder, with 20 mL of methanol for 15 minutes and filter. To 2 mL of the filtrate, add 2 to 3 pieces of magnesium ribbon, shake well, mix with a few drops of hydrochloric acid, and warm in a water-bath for about 10 minutes: a reddish brown colour is produced.

B. Reflux 1 g of the sample, in fine powder, with 20 mL of water for 15 minutes and filter. To 2 mL of the filtrate, add a few drops of a 1 per cent w/v solution of iron (III) chloride and shake well: a bluish green colour is produced.

C. 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 100 volumes of ethyl acetate, 8 volumes of water, 4 volumes of glacial acetic acid, and 4 volumes of formic acid as the mobile phase and allowing the solvent front to ascend 8 cm above the line of application. Apply separately to the plate as bands of 7 mm, 15 µL of solution (A) and 2 µL of solution (B).  Prepare solution (A) by refluxing 500 mg of the sample, in fine powder, with 10 mL of methanol for 15 minutes and filtering. Evaporate the filtrate to dry and dissolve the residue in 3 mL of methanol. For solution (B), dissolve 1 mg of rutin in 1 mL of methanol. After removal of the plate, allow it to dry in air. Examine the plate under ultraviolet light (254 nm); marking the quenching bands, the chromatogram obtained from solution (A) shows a quenching band (hRfvalue 14 to 16) corresponding to the rutin band obtained from solution (B). Other four quenching bands are also observed. Subsequently examine the plate under ultraviolet light (366 nm); the band due to rutin is dark fluorescent; one blue fluorescent band is observed. Heat the plate at 80° for 10 minutes and then spray with natural products (NP) TS while the plate is still warm. Subsequently spray the plate with polyethyleneglycol (PEG) TS and observe the colours of the bands under ultraviolet light (366 nm) within 5 to 15 minutes; the band due to rutin is orange fluorescent. Four green and five blue fluorescent bands are also 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).

Acid-insoluble ash  Not more than 9.0 per cent w/w (Appendix 7.6).

Total ash  Not more than 17.0 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 15.0 per cent w/w (Appendix 7.12).