Alexandrian Senna leaf

Tinnevelly Senna leaf

Description. Odour, slight; taste, first mucilaginous and sweet, then slightly bitter.

Category. Cathartic drug.

Storage. Senna leaf should be kept protected from light and moisture.

Additional information. Even in the absence of light, Senna leaf is gradually degraded on exposure to a humid atmosphere, the decomposition being faster at higher temperatures.

Requirements

Definition. Senna leaf consists of the dried leaflets of Cassia senna L., known as Alexandrian or Khartoum Senna (C. acutifolia Delile) or Tinnevelly Senna (C. angustifolia Vahl), or a mixture of both species.

Senna leaf contains not less than 2.5% of hydroxyanthracene derivatives, calculated as sennoside B.

Identity test

To about 0.5 g of the powdered leaf add 10 mL of sodium hydroxide/ethanol TS and boil on a water-bath, dilute with 10 mL of water, and filter. Acidify the filtrate with hydrochloric acid (~70 g/l) TS and extract with 10 mL of ether R. Separate the ether layer and shake it with 5 mL of ammonia (~100 g/l) TS; a yellowish red colour is produced in the ammonia layer.

Macroscopic examination

Alexandrian Senna leaf. Pale greyish green, thin, fragile leaflets; lanceolate, mucronate; length, 20-40 mm; width, 5-15 mm, the maximum width being at a point slightly below the centre; lamina, slightly undulant; both surfaces covered with fine, short trichomes; pinnate venation, slightly prominent midrib with lateral veins leaving the midrib at an angle of about 60° and anastomosing to form a ridge parallel to the margin.

Tinnevelly Senna leaf. Yellowish green leaflets; elongated and lanceolate; length, 25-50 mm; width at the centre, 7-20 mm; lamina, flat; both surfaces are smooth with a very small number of trichomes, and marked with impressed transverse or oblique lines.

Microscopic examination. Epidermis with polygonal cells containing mucilage; unicellular thick-walled trichomes, length, up to 260 μm, slightly curved at the base, warty; paracytic stomata on both surfaces; under the epidermal cells a single row of palisade layer; cluster crystals of calcium oxalate distributed throughout the lacunose tissue; on the adaxial surface of the leaf, sclerenchymatous fibres and a gutter-shaped group of similar fibres on the abaxial side containing prismatic crystals of calcium oxalate.

Water-soluble extractive. Shake 5 g with a mixture of 0.5 mL of chloroform R and 200 mL of water, filter, evaporate 20 mL of the filtrate and weigh; the residue is not less than 300 mg/g.

Acid-insoluble ash. Carry out the procedure as described under 4.1 Determination of ash and acid-insoluble ash; not more than 20 mg/g.

Stems and foreign matter. Weigh about 200 g and spread it in a thin layer. Detect the stems and the foreign matter by eye or with the use of a 6× lens; separate and weigh individually the stems and the foreign matter; not more than 20 mg/g of stems and not more than 10 mg/g of foreign matter.

Assay. Place 0.15 g of the powdered leaf in a 100-mL flask. Add 30.0 mL of water, mix, weigh and place in a water-bath at 80-90°C. Heat under a reflux condenser for 15 minutes. Allow to cool, weigh, and adjust to the original mass with water. Centrifuge and transfer 20.0 mL of the supernatant liquid to a 150-mL separating funnel. Add 0.1 mL of hydrochloric acid (~70 g/l) TS and shake with 3 quantities, each of 15 mL, of chloroform R. Allow to separate and discard the chloroform layer. Add 0.10 g of sodium hydrogen carbonate R and shake for 3 minutes. Centrifuge and transfer 10.0 mL of the supernatant liquid to a 100-mL round-bottomed flask with a ground-glass neck. Add 20 mL of ferric chloride (65 g/l) TS and mix. Heat for 20 minutes under a reflux condenser in a water-bath with the water level above that of the liquid in the flask; add 1 mL of hydrochloric acid (~420 g/l) TS and heat for a further 20 minutes, with frequent shaking, to dissolve the precipitate. Cool, transfer the mixture to a separating funnel and shake with 3 quantities, each of 25 mL, of ether R previously used to rinse the flask. Combine the ether layers and wash with 2 quantities, each of 15 mL, of water. Transfer the ether layers to a volumetric flask and dilute to 100 mL with ether R. Evaporate 10.0 mL carefully to dryness and dissolve the residue in 10.0 mL of a solution containing 5 mg of magnesium acetate R per mL of methanol R. Measure the absorbance of this solution in a 1-cm layer at the maximum at about 515 nm against a solvent cell containing methanol R. Calculate in % the amount of hydroxyanthracene derivatives as sennoside B with an absorptivity value of 24.0 ( = 240) as follows: 1.25 A/W, where A is the absorbance at 515 nm and W is the mass of the material examined in g.