A. Atropine
Synonyms Tropine tropate; dl-Hyoscyamine; dl-Tropyl Tropate; Tropic acid ester with Tropine.
Biological Sources It is obtained from the roots and leaves of Atropa belladona Linn. (Solanaceae) (Belladona); and the seeds and leaves of Datura stramonium Linn. (Syn.: Datura tatula Linn.) (Solanaceae) (Jimson Weed, Thorn Apple, Stramonium), besides other species of Solanaceae, such as: D. metel Linn.; D. innoxia Mill., D. alba Nees.; and D. fastuosa Linn.
Chemical Structure
1α H, 5α H-Tropan-3α-ol (±)-tropate (ester); (C17H23NO3).
Characteristic Features
1. Atropine is obtained as long orthorhombic prisms from acetone having mp 114-116°C.
2. It usually sublimes in high vacuum at 93-110°C.
3. It has a dissociation constant pK 4.35; and the pH of a 0.0015 molar solution is 10.0.
4. Solubility: 1 g dissolves in 455 ml water; 90 ml water at 80°C; 2 ml ethanol; 1.2 ml ethanol at 60°C; 27 ml glycerol; 25 ml ether, 1 ml chloroform; and in benzene.
Identification Tests It forms various types of salts, namely:
1. Atropine Hydrochloride (C17H23NO3.CH3NO3): The granular crystals have mp 165°C. It is soluble in water and ethanol. The pH of 0.05 molar solution is 5.8.
2. Atropine Methyl Bromide (C17H23NO3.CH3Br) (Tropin): Its crystals have mp 222-223°C. It is soluble in 1 part of water, slightly soluble in ethanol, and practically insoluble in ether and chloroform.
3. Atropine Methylnitrate (C17H23NO3.CH3NO3) (Methylatropine nitrate, Eumydrin, Metropine, Harvatrate, Metanite, Ekomine): Its crystals have mp 163°C. It is found to be freely soluble in water or ethanol; and very slightly soluble in chloroform and ether.
4. Atropine Sulphate Monohydrate [(C17H23NO3)2.H2SO4.H2O] (Atropisol): It is obtained as either crystals or powder with mp 190-194°C. It is inactive optically. It has a very bitter taste. It shows pH ~ 5.4. Its bitterness is threshold 1:10,000. It is found to be incompatible with a host of substances, such as, tannin, alkalies, salts of gold and mercury, borax, bromides, iodides, benzoates and vegetable decoctions or infusions.
Its solubility profile is: 1 g dissolves in 0.4 ml water; in 5 ml cold and 2.5 ml boiling ethanol; in 2.5 ml glycerol; 420 ml chloroform and 3000 ml ether.
Uses
1. It is used in preanaesthetic medication.
2. It is employed as an anticholinergic agent.
3. It is also used as a mydriatic.
4. It is employed as an antidote in opium and chloral hydrate poisoning.
5. It is frequently employed to minimize spasm in cases of intestinal gripping caused due to strong purgatives.
6. It also find its applications to reduce such secretions as: saliva, sweat, and gastric juice.
