Isolation of Atropine

Isolation of Atropine: It is a tropane alkaloid obtained from plants like Atropa belladonna, Datura strawmonium, and Hyoscyamus niger belongs to the family Solanaceae. The other important alkaloids are Hyoscine, hyoscyamine, belladonine, apoatropine, and norhyoscyamine. Atropine is an optically inactive laevorotatory isomer of hyoscyamine.

Chemical structure of Atropine
Fig.1: Chemical structure of Atropine

Hyoscyamus muticus contains high alkaloidal content than other sources like Datura strawmonium. The powdered drug is moist with an aqueous solution of sodium carbonate and extracted with ether or benzene. The free alkaloidal bases are extracted from the dilute solvent and acidified with acetic acid. The acidic solution is shaken with ether solvent which separates colouring matter. The alkaloids get precipitated with sodium carbonate which is filtered, washed, and dried. The dried residue is dissolved in ether/acetone and dehydrated with anhydrous sodium sulfate. This all treatment should be done before filtration. The filtrate is concentrated and cooled. This process will yield crystals of hyoscyamine and atropine. The crystalline mass is separated and dissolved in alcohol. Then sodium hydroxide solution is added and the mixture is kept for some time. The hyoscyamine will completely be racemized into atropine. The purification of crude atropine should be done by crystallization with acetone.

Atropine sulphate is the most important salt of atropine which occurs in colourless crystalline powdered form. It has a solubility in water and alcohol and insolubility in ether and chloroform.

Melting point: 115 to 116°C

Thin-layer chromatography of Atropine

Atropine solution (1%) is dissolved in 2N acetic acid and it is spotted over silica gel-G plate and eluted into solvent system strong ammonia solution: methanol (1.5:100). The TLC plates are spreaded with acidified iodoplatinate solution. It gives an Rf value of 0.18. Atropine sulphate gives Rf value 0.70 in solvent system acetone: sodium chloride with Dragendorff reagent as spraying agent.

Identification Test of Atropine

Vitali-Morin reaction: Dilute solution of atropine is treated with concentrated nitric acid. The mixture is evaporated to dryness which produces pale yellow residue. A violet colour appears when a drop of potassium hydroxide solution is added to the residue.

Make sure you also check our other amazing Article on : Isolation of Citral
Sharing Is Caring:

Leave a Comment