Pale Catechu

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Chapter: Pharmacognosy and Phytochemistry : Drugs Containing Tannins

Gambier or pale catechu is a dried aqueous extract produced from the leaves and young twigs of Uncaria gambier Roxburgh., belonging to family Rubiaceae.


PALE CATECHU

 

Synonyms

 

Gambier, pale catechu, catechu.

 

Biological Source

 

Gambier or pale catechu is a dried aqueous extract produced from the leaves and young twigs of Uncaria gambier Roxburgh., belonging to family Rubiaceae.

 

Geographical Source

 

U. gambier is a native of erstwhile Malaya. It is cultivated in Indonesia, Malaysia, Sumatra, Bornea, and Singapore at eleva-tion up to 150 m. The plant is used mostly for the production of the drug, which is marketed through Singapore.

 

Cultivation, Collection, and Preparation

 

Propagation of U. gambier is done by seeds. Seeds are sown in the nursery to raise the seedlings, which after about 9 months are planted out in the clearing about 3 meters apart. Leaves and young shoots are collected as a first crop during second year’s growth. Later the crop is taken every year. The plant continues to give sufficient leaves and twigs up to 20 years, but the maximum yield is obtained during eighth year of growth.

 

The collected leaves and twigs are transported to the factory as loose material. The material is put into large drums with about three quarters of boiling water. It is boiled for about three hours with intermittent stirring. The marc is subsequently removed by large wooden forks and lodged on surface to drain the liquor back to the vessels. It is pressed and washed. The washing is added to the extract. The combined total aqueous extract is then concentrated for one and half-hour till it becomes thick, yellowish-green paste. It is transferred from the vessels to wooden tubs, stirred while it is hot, and cooling in a stream of water to crystallize tannins. Semicrystallized paste is again transferred to wooden trays in which it sets. They are cut into cubes by wooden knife and dried in sum. The drug is also made into large blocks in kerosene tins.

 

Morphology

 


 

Microscopy

 

The powdered drug, if mounted in the solution of lactophenol or water, shows the small circular crystals of catechu under microscope. The water insoluble part of the pale catechu under the microscope exhibits epidermal pieces, unicellular hairs, cork tissues, lignified fibres, etc. Alcohol insoluble part shows the absence of starch. The pale catechu from Indonesia is reported to have minute starch grains.

 

Chemical Constituents

 

Pale catechu contain from about 7 to 30% of pseudotannin catechin and 22 to 55% of a phlobatannin catechutannic acid. Both of the about component constitute over 60% of the drug. It also contains catechu red, gambier fluorescin and quercetin. It contains indole alkaloid up to 0.05%, which includes gambirtannin and its derivatives. Gambirtannin gives a strong fluorescence under UV light. Catechin forms white, needle like crystals, which dissolves in alcohol and hot water. Catechutannic acid gives green colour with ferric chloride.

 


 

Chemical Tests


1.       Gambier fluorescin test: Gambier fluorescin present in pale catechu gives the fluorescence. If to its alcohol extract, a little sodium hydroxide is added and shaken with petroleum ether. The petroleum ether layer shows green fluorescence. Black catechu gives negative test.

 

2.       Vanillin-hydrochloric acid test: Drug shows pink or red colour with a mixture of vanillin:alcohol:dilute HCl in the ratio 1:10:10. The reaction produces phloroglucinol which along with vanillin gives pink or red colour.

 

3.     A matchstick dipped in decoction of Pale catechu is air dried and again dipped into concentrated HCl and warmed near the burner. Pink or purple colour is produced.

 

4.     Small quantity of powder is heated on water bath with 5 ml chloroform and filtered. The filtrate is evaporated in white porcelain dish on a water bath. A greenish-yellow residue is produced due to the presence of chlorophyll in the drug. Black catechu gives this test negative due to the absence of chlorophyll.


Uses

 

Pale catechu is medicinally used as local astringent. In diarrhoea, it is used as general astringent. It is largely used in various countries of east for chewing with betel leaf. Large proportion of gambier is used in dyeing and tanning industries. It is used for tanning of animal hides to convert it to leather.

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