AIM: To study the Macroscopical and Microscopical and powder characteristic and 

Extraction of  Senna


Synonym: Indian senna, Alexandrian senna

B. S.: It is obtained from the dried leaf lets of Cassia senna, Cassia acutifolia known in commerce as Alexandrin senna & Cassia angustifolia known in commerce as Tinnevelly senna.

Family: Leguminosae

G.S.: Cassia is indigenous to tropical Africa and it is cultivated in the Sudan. Cassia angustifolia is indigenous to Somaliland, Arabia, Sind, and Punjab and is cultivated in South India.

Plant Habitat: Senna is a small shrub of about 1m high, with pari pinnate compound leaves.

Method of Cultivation: Seed propagation.

Harvesting: Hand picking method.

 

Macroscopy:



Features : Alexandria senna,  Tinnevelley senna

Colour : Pale greyish green Yellowish green

Odour : Slight Slight

Taste : Mucilagenous slightly bitter Mucilagenous, bitter and 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


4)  Microscopy: 

The  transverse  section  of  a  senna  leaflet  exhibits  isobilateral  structure  under  the microscope. 

The following tissues are observed in the lamina and midrib region: 

a)  Lamina: 

i)  Upper Epidermis: 

It  is  composed  of  polygonal  cells  arranged  in  a  single layer,  covered  on  the  outer side with 

prominently thick, warty cuticle. Few epidermal cells contain mucilage and straight  anticlinal  walls.  

The  epidermis  bears  only  nonglandular  covering  trichomes which  are  unicellular,  short,  thick  

walled,  conical,  non-lignified,  warty  and  often  curved  at  the  bulbous  base  or  with  papillose  

walls.  Paracytic  stomata  are  seen  at regular intervals. 

ii)  Mesophyll: 

It  is  differentiated  into  palisade  and  spongy  parenchyma.  Isobilateral  structure exhibits  presence  

of  upper  palisade below  the  upper  epidermis  and  lower  palisade placed above the lower 

epidermis:
 
1)  Upper Palisade: 

It  is  a  single  layer  of  elongated,  narrow,  columnar  cells  with  chloroplastids.  The upper epidermis

also continues over the midrib region. 

2)  Spongy Parenchyma: 

It  is  made  up  of  loosely  arranged  parenchymatous  cells  and  contains  rosette  or prismatic crystals

of calcium oxalate. 

3)  Lower Palisade: 

It  extends  to  somewhat  limited  area,  i.e.  to  the  lamina  region  only.  Cells  are  small and loosely 

arranged and have wavy walls.
 
4)  Lower Epidermis: 

Cells  possessing  prominent  cuticle  and  sunken  stomata  are  seen.  These  cells  are somewhat  

shorter  than  those  of  the  upper  epidermis  and  have  slightly  wavy  walls. Non-glandular richomes 

are also found on the lower epidermis. 

b)  Midrib: 

The transverse section through the midrib region exhibits a flat ventral surface and convex dorsal surface. The epidermal layers are in continuation over the midrib also. The lower epidermis possesses small cells with thick cuticle. The upper palisade is also made up of smaller cells particularly in the midrib region. The lower palisade is absent in the midrib portion, and a group of collenchymatous cells is seen. 

5)  Powder Character: 

The senna leaflet powder is greyish green or yellowish green in colour with a faint, characteristic odour and a mucilaginous, slightly bitter taste. The powder shows the following features microscopically: 

1)  Fragments of Lamina: 

Upper  and  lower  epidermises  of  the  lamina  are  similar,  cells  with  thin,  straight  or slightly  sinuous  walls  and  polygonal.  Plenty  of  unicellular  trichomes  and  paracytic stomata  are  seen.  Both  epidermises  also  show  cicatrices  where  trichomes  were attached; these consist of small circular scars from which the epidermal cells radiate outwards in a characteristic arrangement. 

 


i)  Epidermis in surface view with paracytic stomata and an attached trichome 

ii)  Xylem elements from one of the larger veins 

iii)  Part of a pitted vessel from one of the larger veins 

iv)  Part of a group of fibres with calcium oxalate prism sheath 

v)  Part  of  the  lamina  In  sectional  view  showing  the  upper  epidermis  containing mucilage,  the  upper and  lower  palisade,  spongy  mesophyll  cells  containing  cluster crystals of calcium oxalate and the lower epidermis 

vi)  Groups  of  fibres  with  calcium  oxalate  prism  sheaths  at  the  junction  of  two  small veins 

vii)  Part of the lamina In sectional view with a trlchome attached to the lower epidermis 

viii)  Cluster crystals of calcium oxalate 

ix)  Covering trichomes 

x)  Epidermis in surface view showing paracytic stomata, a cicatrix underlying pailsade cells  and  the  elongated  cells  over  a  vein  with  striated  cuticle  and  an  attached trichome. 

2)  Covering Trichomes: 

These  are  unicellular  and  conical  with  thick  and  warty  walls,  found  attached  to pieces of epidermises of the lamina. Straight or curved fragments with thick papillose walls can be seen. 

3)  Calcium Oxalate Crystals: 

These are abundant and seen as scattered in the powder. Prisms of calcium oxalate are  seen  inside  the  cells  of  the  parenchymatous  sheath  surrounding  the  group  of sclerenchymatous  fi  bres,  and  rosettes  are  seen  in  the  cells  of  spongy  mesophyll. Rosettes (cluster crystals) are of moderate size. 

4)  Groups of Fibres: 

These are thick walled, lignified with few pits and encircled with a sheath of prisms of calcium oxalate. 

5)  Fragments of spiral, annular and pitted vessels are also seen. 

Extraction and Isolation 

Methods-I

Method II

250gms of powdered senna leaves are taken and extract with benzene (600ml) for 2 hours in an electric shaker,  filtered in vacuum and distil off the solvent. Dry the residue at room temperature and extract again with 70% methanol on a shaker for 2-3hrs. Concentrate the methanolic extract to 1/8th of the volume. Acidify to pH 3.2 by the addition of HCl with constant stirring. Add anhydrous CaCl2 in 25ml of denatured spirit with vigorous stirring to the extract. Adjust the pH of the solution to 8 by ammonia solution and set aside for 2 hours. Filter the solution under vacuum and dry the precipitate over P2O5 in a desicator.

 Method – III

The drug powder (about 80-100 b mesh size) is duly macerated with either 80% acetone or 90% methanol for a period of 6 hrs, followed by    2hrs 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 surfactants.

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 concentrated solution of CaCl2 to salt out the sennosides as their respective calcium salts.


Chemistry (Chemical constituents)

Senna is an anthraquinone glycoside (O-linkage glycoside).

Senna consists of two active Dimeric glycosides, sennoside A and Sennoside B. Both on hydrolyses to give two molecules of glucose and the aglycone sennidin A & B.

Sennidin A is dextrorotatory and Sennidin B is Mesoform.

Senna also contains Sennoside C and D (Hetero dianthrone).

The other glycosides are palmidin A, Aloe-emodin dianthrone-diglycoside, rhein-anthrone-8-glycoside, rhein-8-diglucoside, aloe-emodin-8-glucoside-emodin-anthrone-diglucoside.


 Identification Test (Detection of Sennoside)

TLC Method

Stationary Phase         : Absorbent – Pre-coated Silica gel

Mobile Phase               : n-Propanol : Ethyl acetate: H₂O (50:30:20)

Sample                         : Leaf extract

Rf values                      : A=0.4, B=0.2, C=0.7 & D=0.55

Detecting Agents           : Nitric acid & KOH reagent

Observation                    : Red to brown spots in visible light lemon yellow or light blue at UV 365nm 















Chemical Tests: 

a)  Modified Borntrager’s Test:




Uses: 

a)  Senna is 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. 

b)  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. 


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