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         Dill is the dried ripe fruit of Anethum graveolens L. (Peucedanum graveolens Benth. & Hook. f.) (Family Umbelliferae), Herbarium Specimen Number:  DMSC 4535, QSBG 23272, Crude Drug Number:  DMSc 420.

Constituents  Dill contains volatile oil, of which (+)-carvone, (+)-limonene and  α-phellandrene are its major components.  It also contains coumarins, phenylpropanoids, xanthones, flavonoids, etc. 

Description of the plant  (Figs. 1a, 1b)  Annual or biennial glabrous aromatic herb up to  1.7 m tall, terete, striate, with subfusiform or fusiform taproot; main stem, hollow, glaucous, cylindrical, dichotomously branched with 5 to 8 branches.  Leaves bi- or tri-pinnately  compound with linear-filiform ultimate segments, 4 to 20 mm long; petiole 1 to 3.5 cm long; petiole sheathing, 5 to 6 cm long; upper cauline leaves greatly reduced.  Inflorescence   loose compound umbels; peduncle 7 to 20 cm long; rays 10 to 45, 3 to 15 cm in spread,  bearing 10 to 45 umbellules; pedicel 6 to 16 mm long.  Flower small, about 2 mm in  diameter; sepal minute or wanting; petals 5, yellow, suborbicular with a narrower, obtuse, inflexed apex; stamens 5, alternating with petals, inserted around an epigynous disc; ovary inferior, 2-celled, each cell 1-seeded; styles 2, short, reflexed, the stylopodium conic,  carpophore 2-cleft to the base.  Fruit ovoid, flattened dorsally, consisting of 2 dry, 1-seeded, indehiscent mericarps, up to about 5 mm long, 2 to 3 mm wide and about 1 mm thick. 

Description  Odour and taste, aromatic, pleasant and characteristic.

       Macroscopical  (Figs. 1a, 1b)  Mericarps normally separate and free of pedicels, brown  to yellow-brown, oval and glabrous, 3 to 4 mm long, 2 to 3 mm wide and 1 mm thick, compressed dorsally and almost flat.  Each mericarp exhibiting 3 pale brown dorsal ridges,  2 yellowish lateral ridges being extended to form membranous wings.  The commissural side, flat, attached with carpophore as a pale line. 

      Microscopical  (Figs. 2a, 2b)  Transverse section of the mericarp through the cotyledon shows epicarp covered with striated cuticle, a layer of slightly tangentially elongated  epidermal cells.  Mesocarp, several layers of more or less collapsed, tangentially elongated parenchyma cells; each of the ridge, a lignified fibrovascular bundle, surrounded by  reticulate and porous, thickened, lignified parenchyma cells in the lateral ridges, the  dorsal side, 4 large vittae located between the vascular bundles, the commissural side,  2 large vittae; each vitta, elliptical, brown, lined by small epithelial secretory cells.  Endocarp, a layer of broad tangentially elongated cells.  Spermoderm, a layer of brownish,  tangentially elongated cells united with the endocarp except in the region of the raphe  along the commissural side where separated by collapsed thin-walled cells.  Endosperm, thick-walled polygonal cells containing oil globules and aleurone grains with microcrystals.  Cotyledons, thin-walled cells containing aleurone grains and oil globules.  

          Dill in powder possesses the diagnostic microscopical characters of the unground drug.

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

Packaging and storage  Dill shall be kept in well-closed containers, preferably of metal or glass, protected from light and stored in a cool and dry place.

Identification

       A. Add 5 mL of chloroform to 1 g of the sample, in powder, shake well, set aside for 30 minutes, and filter.  Evaporate the filtrate to about 1 mL.  Evaporate 0.1 mL of this solution to dryness and add a few drops of a 5 per cent w/v solution of vanillin in sulfuric acid:  a reddish brown colour develops and changes to red and finally to purple.

       B. 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 95 volumes of toluene and  5 volumes of ethyl acetate as the mobile phase.  Apply separately to the plate, 4 μL each  of the following two solutions.  Prepare solution (A) by shaking 1 g of the sample, in coarse powder, with 2 mL of ethanol, for about 2 minutes and filtering.  For solution (B), dissolve 10 μL of carvone in 2 mL of ethanol.  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 a quenching spot (hR_f value 50 to 52) corresponding to the carvone spot from solution (B), and one spot of higher hR_f value.  Spray the plate with anisaldehyde TS and heat at 110° for 10 minutes; the spot due to carvone is salmon-pink.  Other several spots of different colours are observed (Table 1); see also Fig. 3. 

          Repeat the same procedure on another plate but spray with vanillin-sulfuric acid TS and heat at 120° for 20 minutes; the spot due to carvone is dark violet.  One greenish blue and one yellowish brown spots are observed (Table 1); see also Fig. 3.

Water  Not more than 9.0 per cent v/w (Azeotropic Distillation Method, Appendix 4.12).

Foreign matter  Not more than 4.0 per cent w/w (Appendix 7.2).

Acid-insoluble ash  Not more than 1.5 per cent w/w (Appendix 7.6).

Total ash  Not more than 10.0 per cent w/w (Appendix 7.7).

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

Volatile oil  Not less than 2.0 per cent v/w (Appendix 7.3H).  Use 20 g, in coarse powder, freshly prepared and accurately weighed.  Use 200 mL of water as the distillation liquid and a 500-mL round-bottomed flask.  Distil at a rate of 2 to 3 mL per minute for 4 hours.  Use 1.0 mL of xylene in the graduated tube.

Dose  1 to 4 g