Sennosides are isolated from the dried leaves of Cassia angustifolia through a process involving extraction with benzene and methanol, acidification, precipitation with calcium chloride, and drying. They are characterized through IR, 1H NMR, 13C NMR and mass spectroscopy. Sennosides consist of an anthraquinone ring structure derived from the condensation of eight acetyl CoA molecules and are used as a laxative.

1. Sennoside Isolation
Sennosides are isolated from Tinnevelly senna, consists of dried compound leaflets of
Cassia angustifolia (Leguminosae).

2. Method of Isolation
• The leaves are dried and powdered. The powdered drug is shaken with
benzene for 2 h on an electronic shaker. Filter and distill off the
solvent and marc is dried at room temperature and extracted with 70%
methanol for 4–6 hours. The extract is filtered under vacuum and it is
reextracted with 70% of methanol for 2 h, and filtered. The methanolic
extract is combined and concentrated to l/8th portion of its original
volume. The concentrated solution is acidified with hydrochloric acid
to a pH of 3.2. The acidified solution is kept aside for 2 h at a
temperature of 5°C.
• The solution is filtered and to the filtrate add anhydrous calcium
chloride dissolved in 25 ml of denatured spirit with constant and
vigorous stirring. The pH is again adjusted to 8 by ammonia and it is
set aside for 2 h. The solution is filtered; the precipitate obtained is
dried over P2O5 in a dessicator.

3. Biosynthesis of Sennoside
• Eight molecules Acetyl CoA undergoes condensation to give Octa keto
acyl chain. This further undergoes condensation to give anthraquinone.

4. Spectral characterization of Sennosides
IR Spectra
IR(KBr): 3400 cm-1(br, OH)
1742 cm-1 (C = 0 str.)
2900 cm-1 (aromatic C=C str.)

5. 1HNMR Spectra (DMSO)
δ6–δ 8.00(C2-H, C4-H, C5-H, C6-H, C7-H, C2ˡ - H, C4ˡ -H, C5ˡ - H, C6ˡ- H, C7ˡ- H)
δ12 (C1 –OH, C1ˡ – OH)

6. 13 CNMR (DMSO)
δ 160 (C-1, C-1ˡ)
δ 125 (C-2, C-4, C-5, C-6, C-7, C-2ˡ, C-4ˡ, C-5ˡ, C-6ˡ, C-7ˡ)
δ 200 ( C-9, C-9ˡ)

7. Mass Spectra (EIMS)
Molecular formula : C42H38O20
Molecular weight: 862
EIMS (M/Z): 862 (M+ , C42H38O20)
Uses of Sennosides
• As Laxative