Atropine is an alkaloid obtained from Atropa belladonna, Datura stramonium, and Hyoscyamus muticus, all members of the Solanaceae family. Each of the plants has a different concentration of the crude drug. The isolation of atropine from these plants differs. Here we will see all about the crude drug atropine- its properties, uses, and isolation methods.
Properties of Atropine
- Atropine (C17H23O3N) is seen as colourless crystals.
- This has a bitter taste and no odour.
- It is soluble in both chloroform and alcohol.
- This is a racemic form of hyoscyamine.
- In leaves, more amount of hyoscyamine is present than atropine.
- During the extraction process, the hyoscyamine is converted into atropine.
- Atropine has a melting point of 115–116°C.
- Atropine is optically inactive.
- It is a laevorotatory isomer of hyoscyamine.
- Its Rf value is 0.18
Identification of Atropine
Identification of atropine is done with the help of the Vitali-Marin test.
- A dilute solution of atropine is treated with nitric acid.
- The mixture is allowed to evaporate.
- It becomes dry in a steam bath.
- Steam baths cause the formation of yellow precipitation.
- When a drop of freshly prepared potassium hydroxide is added to this yellow precipitate, it turns violet.
Uses of Atropine
- Atropine has several therapeutic uses.
- It is mainly used as a parasympatholytic drug.
- It can stimulate action in nerve centres.
- Atropine is used as an antidote to certain chemicals.
- It suppresses gastric secretions and is useful for peptic ulcers.
- It is also used to reduce tremors and rigidity due to Parkinson’s disease.
- Atropine can relieve pain in cystitis.
Isolation of Atropine
Hyoscyamus muticus is the major source of commercial production of atropine due to its high alkaloidal content. The chemical is also isolated from Datura stramonium and Atropa belladonna. The drug is isolated from the herbal juice or powdered herb.
Isolation of Atropine from Hyoscyamus
The procedure of isolation of atropine from Hyoscymus is as follows.
- The powdered drug is moistened with an aqueous solution of sodium carbonate.
- This mixture is used for the extraction using ether or benzene.
- From this extract, non-alkaloidal compounds are filtered out using water with acetic acid.
- When this mixture is shaken with ether, the alkaloids are precipitated with sodium carbonate.
- The precipitate is filtered and dissolved in ether or acetone and dehydrated with sodium sulfate.
- The filtrate is concentrated and cooled to get the crude drug hyocyamine.
- This crystalline mass is dissolved in alcohol and sodium hydroxide solution and this mixture is allowed to stand for a while.
- During this time, the hyocyamine is racemized into atropine.
- The crude atropine is purified from acetone.
Isolation of Atropine from Belladonna
- The powdered belladonna leaves are treated with ethanol.
- The solvent is allowed to evaporate to get a syrupy residue.
- This residue is treated with 1% hydrochloric acid to form alkaloid salts and resinous matter.
- The acidic solution is filtered and the precipitate of the resinous matter is removed.
- The acidic solution is treated with petroleum ether and chloroform to remove the acidic layer.
- Ammonia solution is added to the acidic layer and extracted with chloroform.
- A crude alkaloid mixture is obtained from the distillation of the solvent.
- The crude mixture is treated with oxalic acid to form oxalates of atropine and hyoscyamine.
- The oxalates are separated by fractional crystallization using acetone and ether to obtain atropine oxalate crystals.
Isolation of Atropine from Datura
- The dried powdered plant is extracted in a solvent mix of chloroform, methanol and 25% ammonia
- In the ratio 15:15:1.
- The extraction process is carried out at room temperature and it takes about one hour.
- Later, it is filtered and washed with water.
- The mixture is transferred to a separatory funnel and treated with chloroform. The organic fraction is collected and the solvent is allowed to evaporate until it is dry.
- This residue is dissolved in chloroform and sulfuric acid mix and is again separated using a separatory funnel.
- The organic layer is removed and treated with 25% ammonium hydroxide ice.
- It is again treated with chloroform for further extraction.
- Once again the solvent is evaporated to get the dry drug. This is conducted at room temperature and disallowed to dry for two days.
References
- Shah, Biren N, Avinash Seth. (2010). Textbook of Pharmacognosy and Phytochemistry. Elsevier.
- https://faculty.uobasrah.edu.iq/uploads/teaching/1702930256.pdf
- https://www.iftmuniversity.ac.in/iftmuniversity/profile/download/econtent/93.pdf
