Morphology, histology and powder characteristics & extraction & detection of
Cinchona
AIM: To study the macroscopical and microscopical and powder characteristic
extraction & detection of Cinchona Bark.
Cinchona Bark
Synonym:
Jesuit’s bark, Peruvian bark.
B. S.:
Quinine is quinoline alkaloid obtained from the dried bark of Chinchona
officinalis, Cinchona calisaya, Cinchona ledgeriana and Cinchona succirubra.
Family:
Rubiaceae.
Macroscopy:
Colour : Stem bark :
Outer surface is dull brown to brown, while inner surface
is yellowish brown to
deep reddish brown.
Odour : Slight
and characteristic
Taste : Bitter
and somewhat astringent.
Size and Shape : 10
to 25 mm in diameter and 1.5 to 2.5 mm in thickness, quills or curved pieces.
Extra Features :
The fracture is short in external layers and fibrous in inner portions.
Microscopy
:
Transverse section of the cinchona bark shows the following tissues microscopically:
Periderm: It is made up of cork, phellogen and phelloderm:
Cork: It consists of many layers of thin-walled cells arranged in regular radial rows.
Cells appear as flat and polygonal with reddish-brown cell contents. The cell walls are suberised.
Phellogen: It is made up of two to three layers of thin-walled rectangular cells.
iii) Phelloderm: It is placed within the cork cambium. It is made up of several (up to
eight) layers of regular, thin-walled rectangular cells with dark walls and without any cell contents. Cork cambium is not distinctly seen in commercial samples.
b) Cortex:
This portion of the bark is wide and consists of many layers of tangentially elongated, thin-walled cells. These are made up of cellular parenchyma and walls are reddish brown. Some of the cells of the cortex are filled with microsphenoidal crystals of calcium oxalate. Sometimes idioblasts, containing microcrystals (mostly prisms) of calcium oxalate and secretary cells (cavities or secretion canals or latex ducts), are also found as scattered in the layers of the cortex. A few cells show presence of minute starch granules contained within them.
c) Secondary Phloem: This region is made up of sieve tubes, phloem parenchyma,
phloem fibres and medullary rays:
i) Sieve Tubes: The end walls of the sieve tubes are seen at the right angles to the axis as the component cells are long and wide. The companion cells are narrow. Sieve tubes are collapsed and compressed most of the time in commercial samples of the bark.
ii) Phloem Parenchyma: It resembles the cortical parenchyma in many respects. It consists of dark reddish-brown thin walls. A few of these cells show presence of microprisms of calcium oxalate within them.
iii) Phloem Fibres: These are many, large, fusiform, thick walled and lignified. These phloem fibres occur as single or in irregular radial rows, as groups of two to five fibres. These are seen as intermingled with phloem parenchyma and in between the medullary rays.
Many times these groups of fibres occur as rounded, oval or spindle shaped. The thick walls of fibres are striated and show conspicuous tubular or funnel-shaped pits. These fibres appear yellowish in colour and have a small lumen.
iv) Medullary Rays: These rays run radially transversing the phloem parenchyma. These are one, two or three seriate. These are narrow, thin walled and almost straight and run up to the cortex. The cells are thin walled and somewhat radially elongated. Some of these cells of the medullary rays contain starch grains.
Powder Character of Cinchona Bark:
The powder of cinchona bark is reddish brown with a slight, characteristic odour and bitter, astringent taste. The powder microscopically shows the following characters:
a) Fibres: These phloem fibres are many, yellowish, fusiform, large, lignified and fragmented. These occur as isolated or in groups of two or three. Individual fibres have bluntly pointed ends. The walls are thick and show striations. Walls are strongly lignified and possess simple or branched pores. The lumen is small, uneven and short.
b) Cork: Cork cells are seen as thin walled, flat, polygonal and suberised. These cells contain reddish-brown matter within them. Generally numerous fragments of cork cells are observed.
c) Parenchyma: These parenchymatous cells are abundant and arise from phloem parenchyma and medullary rays. These cells appear yellowish to reddish brown in colour. Phloem parenchyma cells are thin walled and fragmented. Few of these cells show presence of some colouring matter along with small starch granules, and some contain microprisms of calcium oxalate.
d) Calcium Oxalate Crystals: These are mainly observed in some of the parenchymatous cells. Isolated or scattered crystals are very small and irregular in shape.
e) Starch Grains: These are within some of parenchymatous cells and some as scattered.
components.
Chemical Constituents:
More than 30 alkaloids have been reported in cinchona. The chiefly identified alkaloids are quinidine, quinine, cinchonine and cinchonidine. These constituents are the stereoisomers of each other like quinine is stereoisomer of quinidine and cinchonine is stereoisomer of cinchonidine. The other constituents available are quiniarnine, cinchotine, hydroquinine, hydrocinchonidine, cinchotannic acid, etc.
Quinine and quinidine has a methoxy group in it but cinchonine and cinchonidine do not have a methoxy group. Other than these it also consist of bitter glycoside, starch grains, calcium oxalate crystals and crystalline acid like quinic acid.
Chemical Tests :
- Heat powdered bark in dry test tube
with glacial acetic acid purple coloured vapours are produced in upper
part of the test tube.
- If treated with diluted sulphuric
acid, it gives blue fluorescence.
- Thalleoquin test :
The powdered drug gives emerald green colour with bromine water and dilute
ammonia solution.
Estimation
TLC Method-I
Stationary phase : silica gel plates
Mobile phase : Diethylamine:
ether: toluene (10:24:40)
Spraying reagent: lodoplatinate
reagent.
Estimation
HPLC Isocratic Method
Stationary phase : C18
Mobile phase : Methanol 1- acetonitrile-0.1 mol/L: ammonia: acetone
(45:15:40)
Detection: Fluorescence
at excitation 325 nm.
Emission: 375
nm.
Uses
It is
mainly employed as
antimalarial drug, but
it is also
used as analgesic,
antipyretic, protoplasmic, bitter stomachic
& tonic.
Quinidine is cardiac
depressant and Cinchonidine is used in rheumatism & neuralgia.
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