2.1.5 Senna
Senna was first used in the European medicine as early as the 9th or 10th century by the Arabs. An Egyptian native Issae Judaeus (850 to 900 A.D.) was reported to be the pioneer in bringing and introducing the drug to Egypt from Mecca,
Synonyms Senna leaf; Sennae folium; Tinnevelley Senna; Indian Senna;
Biological Sources Senna is the dried leaflets of Cassia senna L. (Cassia acutifolia Delile, (Alexandria senna), or of Cassia angustifolia Vahl (Indian or Tinnevelley Senna) belonging to the family Leguminoseae. However, the modern taxonomists recommend to club together both the commonly available species of senna, namely: Alexandria senna and Thinnevelley senna—under one name as Senna alexandria Mill.
Geographical Source C. acutifolia grows wild in the vicinity of Nile River (Egypt) extending from Aswan to Kordofan; whereas, C. angustifolia grows wild in the Arabian Peninsula, Somalia, India, and Northwest Pakistan. In India the drug is cultivated in Southern part- Tinnevelly, Mysore and Madurai; Northern part- Jammu, Western part Pune and Kutch region of Gujrat.
Preparation After a duration of 2-3 months of sowing the Alexandra senna is harvested both in April and in September by cutting off the tops of the plants approximately 15 cm from the ground level and subsequently allowing them to dry in the sun. Later on, the unwanted stems and pods are segregated from the leaflets with the help of sieves using mechanical vibrators. The portion that passes through the sieves, is now ‘tossed’ carefully, whereby the leaves are colleted on the surface and the relatively heavier stalk fragments at the bottom. The dried leaves are now graded, packed in bags and stored in dry place. The commercial drug at present is distributed through Port Sudan located on the Red Sea, and from the Port of Tuticorin, in India.
Description
Features Alexandria senna Tinnevelley senna
Colour : Pale greyish green Yellowish green
Odour : Slight Slight
Taste : Mucilagenous slightly bitter Mucilagenous, bitter and
and characteristic characteristic
Size : Length = 2-4 cm, Length = 2.5-5cm
Width = 7-12 mm; Width = 3-8 mm
Shape : Ovate -lanceolate; Lanceolate
Texture : Thin and brittle Thin and flexible
Chemical Constituents The principle active constituents of senna are four sennosides A, B, C and D, which are the dimeric glycosides having their aglycones composed of either rhein and/or aloe-emodin moieties i.e.; 10, 10’-bis (9, 10-dihydro-1, 8-dihydroxy-9-oxoanthracene-3-carboxylic acid). The structure of the above four glycosides are as given below:
Besides, relatively small quantities of monomeric glycosides and free anthraquinones are also present in senna pods, such as: rhein–8-glucosides, rhein-8-diglucoside, aloe emodin-8-glucoside, aloe-emodin anthrone diglycoside, rhein, aloe-emodin and isorhamnetin.
It also contains kaempterol (a phytosterol), mucilage, resins, myricyl alcohol, chrysophanic acid, calcium oxalate and salicylic acid.
Specific method of extraction for the sennosides: Exclusively for commercial purposes, the sennosides are extracted as their corresponding calcium sennosides in varying strengths because of its enhanced stability.
Methodology: The drug powder (about 80-100 mesh size) is duly macerated with either 80% acetone or 90% methanol for a period of 6 hours, followed by 2 hours with cold water. This process helps to achieve an extract that contains between 17-18% sennosides and enables to extract about 65% of sennosides from the crude drug.
The sennosides and other anthracene derivatives may be extracted by the help of a mixture of polyethylene glycols (in 70% v/v ethanol) and solutions of non-ionic surfectants.
However, the isolation of individual sennosides may be achieved by employing non-polar synthetic resins having porous structural features. Alternatively, the drug powder is macerated with citric acid in methanol which is followed by a repeated extraction with a mixture of methanol, toluene and ammonia. The resulting extract is treated with a concerntrated solution of calcium chloride to salt out the sennosides as their respective calcium salts.
Chemical Tests
1. Modified Borntrager’s Test: It gives a pink to red colouration for the presence of anthraquinone glycosides (see under section 4.2.1.1).
2. The mucilage of senna gives a distinct red colouration with Ruthenium Red solution.
Substituents and Adulterants Tinnevelley senna is invariably found to be adulterated with the
following three cheaper varities of senna namely:
(a) Dog senna ie; Cassia abovata,
(b) Palthe senna ie; Cassia auriculatad, and
(c) Arabian Senna or Mecea senna or Bombay senna i.e.; wild variety of Cassia angustifolia Vahl. from Southern Arabia.
Dog senna : It contains approximately 1% of anthraquinone derivatives.
Palthe senna : It contains no anthraquinone glycosides
Arabian senna : It is brownish-green in appearance.
Uses
1. Senna and its branded preparations, for instance: GlaxennaR (Glaxo); Pursennid(R) (Sandoz); Helmacid with senna(R) (Allenburrys); are usually employed as purgative in habitual constipation. The glycosides are first absorbed in the small intestinal canal after which the aglycone portion gets separated and ultimately excreted in the large intentine (colon). The released anthraquinones irritate and stimulate the colon thereby enhancing its peristaltic movements causing bulky and soft excretion of faces.
2. The inherent action of senna is associated with appreciable griping , and therefore, it is generally dispensed along with carminatives so as to counteract the undesired effect.
