Page 71 - phytochemistry general program

Local anaesthetic in small operations. Synthetic local anaesthetics are now
preferable than cocaine.

1- Preparation of crude total alkaloids from natural source

In case of Peruvian coca, the powdered leaves are moistened with sodium
carbonate and extraction is followed by petroleum ether (150-220oC). The organic
extract is then shaken with dil. hydrochloric acid. The aqueous layer is

concentrated where ecgonine esters crystallize out as hydrochlorides.

In case of Java leaves: it is extracted with benzene after alkalinzation with
sodium carbonate. The benzene extract is shaken with dil. sulphuric acid, the acid
extract is then rendered alkaline with sodium carbonate, and extracted with ether.
The ether extract, after dehydration over anhydrous sodium sulphate is distilled to

yield the total crude alkaloids.

2- Partial synthesis from crude natural alkaloids

Java leaves containing cocaine and cinnamyl cocaine are hydrolyzed
completely to ecgonine by boiling with dil. excess HCl. On pouring into water,
truxillic acid is precipitated. By filtration then concentration of the supernatant
layer, ecgonine HCl is crystallized out. The separated crystals are treated with
sodium carbonate to set free the base and extracted with dil. alcohol. After
evaporation of the alcohol, ecgonine is then benzoylated by digestion with benzoic
anhydride for one hour (excess benzoic anhydride and benzoic acid are removed
by extraction with ether). The residue (benzoyl ecgonine) is then washed with
water, methylated by treatment with methyl iodide and sodium in methanol to yield

cocaine.

Identification of cocaine

Cocaine causes numbness of tongue and lips. Cocaine is negative Vitali-
Morine’s. Most of the tests for identification of cocaine depends on the

crystallographic characters of cocaine derivatives.

1- When few mg of cocaine HCl are dissolved in few drops of water and treated
with 1 ml of N/10 potassium permanganate, a violet crystalline precipitate is
formed which shows characteristic crystalline aggregates under the
microscope. This test is used also for differentiation of cocaine from cinnamyl

cocaine.

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