Senna Tablets

Definition

Senna Tablets contain the powdered pericarp of Senna Fruit, Alexandrian or Tinnevelly.

Content of total sennosides, calculated as sennoside B

85.0 to 115.0% of the stated amount.

Identification

The powdered tablets exhibit diagnostic structures of senna pericarp. External epidermis of isodiametric cells with very thick outer walls. Occasional stomata. Trichomes few, unicellular, conical and warty. Parenchymatous cells from inner part of a two-to five-layered zone subjacent to the epidermis, each containing a single prism of calcium oxalate. Thick-walled fibres in two to four layers, the fibres of the outer and inner zones respectively with their long axes at right angles to each other. Sutural vascular strands sheathed by cells containing prisms of calcium oxalate; elements of seed tissue may also be present.

Tests

Disintegration

Maximum time, 60 minutes, Appendix XII A.

Assay

Weigh and powder 20 tablets. Carry out the following procedure protected from light. To a quantity of the powder containing the equivalent of 7.5 mg of total sennosides add 30 mL of water, weigh, heat under a reflux condenser on a water bath for 15 minutes, allow to cool, weigh and restore the original weight with water. Centrifuge, transfer 20 mL of the supernatant liquid to a separating funnel, add 0.1 mL of 2m hydrochloric acid, shake with two 15 mL quantities of chloroform, allow to separate and discard the chloroform layers. Add 0.10 g of sodium hydrogen carbonate and shake for 3 minutes; centrifuge and transfer 10 mL of the liquid to a round-bottomed flask fitted with a ground-glass neck. Add a mixture of 8 mL of iron(iii) chloride solution and 12 mL of water and mix. Heat under a reflux condenser on a water bath for 20 minutes, add 1 mL of hydrochloric acid and continue heating for a further 20 minutes, shaking frequently, until the precipitate is dissolved. Allow to cool, transfer the mixture to a separating funnel and extract with three 25-mL quantities of ether previously used to rinse the flask. Wash the combined ether extracts with two 15-mL quantities of water and add sufficient ether to produce 100 mL. Evaporate 10 mL just to dryness on a water-bath and dissolve the residue in 10 mL of 1m potassium hydroxide, filtering if necessary through a sintered-glass filter (ISO 4793, porosity grade 3, is suitable). Measure the absorbance of the resulting solution without delay at the maximum at 500 nm, Appendix II B. Calculate the content of total sennosides, as sennoside B, taking 200 as the value of A(1%, 1 cm) at the maximum at 500 nm.

Labelling

The quantity of active ingredient is stated in terms of total sennosides expressed as the equivalent content of sennoside B.