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                        Persicaria Odorata Herb is the dried aerial part of Persicaria odorata (Lour.) Soják  (Polygonum odoratum Lour.) (Family Polygonaceae), Herbarium Specimen Number: DMSC 5343, Crude Drug Number: DMSc 1221.

Constituents  Persicaria Odorata Herb contains flavonoids and tannins. It also contains a volatile oil consisting of aliphatic aldehydes, amino acids, phenolics, terpenoids, sterols, etc.

Description of the plant  (Fig. 1)  Perennial herb 15 to 50 cm tall; stem erect, terete, grooved, glabrous, reddish green, branched; ocrea cylindrical, about 1 cm long, membranous, pellucid-dotted, loosely enveloping stem, apex truncate with bristles. Leaves simple, alternate, lanceolate, elliptic, or ovate, 3 to 10 cm long, 1 to 3 cm wide, apex acute or acuminate, base cuneate or attenuate, margin entire with hispid hairs, thin, green with red markings along margin and veinlets, glabrous, pellucid-dotted; petiole 2 to 5 mm long, reddish, glabrous, attached to the base of ocrea. Inflorescence spicate or spicate-paniculate, terminal or axillary, erect, 4.5 to 15 cm long, branched; inflorescence branch glabrous with glandular dots; side branches 2.5 to 8.5 cm long, lax flowers; rachis conspicuous, bract ovate, 1.5 to 5.5 mm long, 0.4 to 1 cm wide, apex acute margin with hispid hairs. Flowers 4 to 8 each enclosed  by ocreola; perianth 5-merous, whitish, pinkish, or purplish pink; lobe ovate-orbicular, 1.5 to 3.5  mm long, 1.5  to 2.5 mm wide, apex obtuse, pellucid-dotted, tube 0.8 to 1 mm long; glandular nectaries; ocreola completely enclosing rachis, 3.5 to 6 mm long, pellucid-dotted, apex obtuse or acute, margin entire with hispid hairs; stamens 8, arranged in two whorls, outer ones 1.5 to 2 mm long, inner ones 1.8 to 2.6 mm long, anther elliptic, white; ovary superior, styles 3, 2.5 to 3.2 mm long, stigma capitate, white. Fruit an achene, triangular, about 1.5 mm long, shiny black; with scarious perianth.

Description  Odour, aromatic, characteristic; taste, slightly tingling.

                Macroscopical  (Fig. 1)  Whole or broken aerial parts; whole leaves, with or without petioles, brownish green, lanceolate, elliptic, or ovate, apex acute or acuminate, base cuneate or attenuate, margin entire, with hispid hairs, brittle; stem erect, slightly twisted, longitudinally grooved, with ocrea.

                Microscopical  (Figs. 2a‒2f)  Transverse section of the leaf through the midrib shows upper epidermis, mesophyll, vascular tissue, and lower epidermis. Upper epidermis: a layer of thin-walled oblong epidermal cells, glandular trichomes, lignified trichomes, stomata, and epithelial cells with secretory cavities. Mesophyll: 1 to 2 layers of palisade cells, spongy cells some containing rosette aggregate crystals, and several layers of angular collenchyma in midrib. Vascular tissue: phloem and xylem. Lower epidermis: small epidermal cells, glandular trichomes, lignified trichomes, epithelial cells with secretory cavities, and stomata.

                Transverse section of the petiole shows epidermis, cortex, vascular tissue, and pith. Epidermis: a layer of polygonal epidermal cells, epithelial cells with secretory cavities, glandular trichomes, lignified trichomes, and stomata. Cortex: angular collenchyma and parenchyma, some containing rosette aggregate crystals or starch grains. Vascular tissue: collateral bundles, containing phloem and xylem. Pith: large round parenchyma, some containing rosette aggregate crystals.

                Transverse section of the stem shows epidermis, cortex, vascular tissue, and pith. Epidermis: a layer of oblong cells, epithelial cells with secretory cavities, glandular trichomes, lignified trichomes, and stomata. Cortex: several layers of angular collenchyma and polygonal parenchyma, some containing starch grains or brown substances. Vascular tissue: slightly secondary growth, collateral bundles, containing pericyclic fibres, phloem, vascular cambium, and xylem. Pith: large round parenchyma, some containing starch grains or rosette aggregate crystals and degenerated cells in the centre.

                Persicaria Odorata Herb in powder possesses the diagnostic microscopical characters of the unground drug. Epithelial cells with secretory cavities, lignified trichomes, and sclerenchymatous bundles of ocrea are characteristic.

Packaging and storage  Persicaria Odorata Herb shall be kept in well-closed containers, protected from light, and stored in a dry place.

Identification

A. Reflux 1 g of the sample, in powder, with 25 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: a bluish black precipitate appears.

B. Heat 500 mg of the sample, in powder, with 10 mL of water on a water-bath for 10 minutes and filter. To 2 mL of the filtrate, add two pieces of magnesium ribbon, shake well, mix with a few drops of hydrochloric acid, and warm on a water-bath for 5 minutes: a red colour develops.

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 64 volumes of ethyl acetate, 10 volumes of water, 4 volumes of formic acid, and 4 volumes of glacial acetic acid 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 6 mm, 2 mL of the test solution prepared by warming 500 mg of the sample, in powder, with 10 mL of methanol in a water-bath at 65°for 15 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. Subsequently examine the plate under ultraviolet light (366 nm); one blue fluorescent band is observed. Heat the plate at 80° for 5 minutes and then spray the plate with natural products (NP) TS while the plate is still warm. Subsequently spray the plate with polyethyleneglycol (PEG) TS and observe the plate under ultraviolet light (366 nm); one blue, three green, and four yellow 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 17.0 per cent w/w (Appendix 7.7).

Ethanol-soluble extractive  Not less than 8.0 per cent w/w (Appendix 7.12).

Water-soluble extractive  Not less than 13.0 per cent w/w (Appendix 7.12).