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      Siamese Rough Bush Bark is the dried stem bark of Streblus asper Lour. (Diplothorax tonkinensis Gagnep., Streblus monoicus Gagnep., Trophis cochinchinensis Poir.) (Family Moraceae), Herbarium Specimen Number:  DMSC 5338, Crude Drug Number:  DMSc 1235.

Constituents  Siamese Rough Bush Bark contains triterpenoids, including lupeol and α-amyrin.  It also contains cardiac glycosides (e.g., asperoside, strebloside).

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 to 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, small, narrowly elliptic, at base of inflorescence; 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, elongating to 1.2 cm long, bifid.  Fruit a drupe, subglobose to ovoid, about 6 mm in diameter, indehiscent, enclosed by enlarged calyx lobes when young, yellow to orange when mature.  Seed 1, globose, 4 to 5 mm in diameter, greyish white.

Description  Odour, indistinct; taste, bitter and astringent.

      Macroscopical  (Fig. 1)  Stem bark, irregular-shaped and -sized, curved, simple or double quill.  Outer bark, smooth or longitudinally wrinkled, yellow to brownish.  Inner surface of inner bark, smooth to rough with fibre, yellow to brownish.            

      Microscopical  (Figs. 2a, 2b)  Transverse section of the bark shows periderm, cortex, and phloem tissue.  Periderm:  lenticels, several layers of rectangular cork cells with brown substance and layers of cork cambium.  Cortex:  several layers of sclereids underneath periderm, and parenchyma cells.  Phloem tissue:  parenchyma (cells some containing prismatic crystals or rosette aggregate crystals), laticifers, and phloem rays.

      Siamese Rough Bush Bark in powder possesses the diagnostic microscopical characters of the unground drug.  Broad phloem ray and articulated laticifer are characteristic.

Packaging and storage  Siamese Rough Bush Bark shall be kept in well-closed containers, protected from light, and stored in a dry place.

Identification 
A. Sonicate 500 mg of the sample, in powder, with 10 mL of ethanol for 30 minutes and filter (solution 1).  Evaporate 2 mL of solution 1 to dryness and dissolve the residue in 1 mL of acetic anhydride.  Slowly add 1 mL of sulfuric acid to form two layers:  a reddish brown to brown ring forms at the zone of contact.
B. To 2 mL of solution 1, add a few drops of a 1 per cent w/v solution of iron(III) chloride and shake well:  a blue-green colour develops.
C. Carry out the test as described in the “Thin-Layer Chromatography” (Appendix 3.1), using silica gel F254 as the coating substance and a mixture of 60 volumes of toluene, 40 volumes of ethyl acetate, and 10 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 6 mm, 2 μL of solution (A) and 1 μL of solution (B).  Prepare solution (A) by  sonicating 3 g of the sample, in No. 250 powder, with 60 mL of ethanol for 30 minutes and filtering.  Evaporate the filtrate to dryness under reduced pressure.  Dissolve the residue  in 2 mL of ethanol.  For solution (B), dissolve 1 mg of lupeol in 0.5 mL of methanol.  After  removal of the plate, allow it to dry in air, spray the plate with anisaldehyde TS, and heat at 105° for 10 minutes; the chromatogram obtained from solution (A) shows a violet band (hR_f value 72 to 75), corresponding to the lupeol band obtained from solution (B).  Eight violet bands are also observed (Fig. 3).

Loss on drying  Not more than 7.0 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 8.0 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 3.0 per cent w/w (Appendix 7.12).

Water-soluble extractive  Not less than 9.0 per cent w/w (Appendix 7.12).