A. Coniine
Synonyms Cicutine; Conicine.
Biological Source It is the toxic principle of poison Hemlock, Conium maculatum L. (Umbelliferae). It is found in the seeds of Cicuta maculata L. (Apiaceae) (Water Hemlock).
Chemical Structure
(S)-2-Propylpiperidine (C8H17N)
It occurs naturally as the (S)–(+) isomer.
Isolation It is isolated by standard procedures described earlier from the pitcher plant Sarracenia flava*.
The various steps involved in the isolation of coniine are as follows:
1. The powdered Hemlock fruits are mixed with KOH solution and then subjected to steam distillation. The distillate thus obtained is neutralized and evaporated to dryness.
2. The resulting residue is extracted with ethanol successively, filtered and the solvent evaporated under vacuo. The ethanol extracts the alkaloidal salts that are dissolved in water, which is subsequently rendered alkaline with KOH solution and finally extracted with ether at least 3-4 times.
3. Ether is evaporated under vacuo, when an oily liquid comprising of the free bases remains as the residue.
4. The fractional distillation of the oily liquid under vacuo or in a current of hydrogen gas, separates them into coniine and γ-coniceine at approximately 171-172°C. These two alkaloids are converted to their corresponding hydrochlorides, evaporated to dryness and extracted with acetone. Thus, coniine hydrochloride will be obtained as the insoluble substance, while the coniceine hydrochloride shall remain in acetone and recovered separately.
Note: Coniine enjoys the distinction of being the first ever alkaloid prepared synthetically.
Characteristic Features
1. It is a colourless alkaline liquid, which darkens and polymerizes on exposure to light and air.
2. It has a typical mousy odour.
3. It has mp ~ – 2°C, and bp 166-166.5°C; bp20 65-66°C.
4. It is a steam-volatile substance.
5. Its physical parameters are: d420 0.8440-0.848; nD23 1.4505; [α]D25 +84o (C = 4.0 in chloroform); [α]D23 +14 6o (neat) and pKa 3.1.
6. Solubility: 1 ml dissolves in 90 ml of water, and less soluble in hot water. The base dissolves about 25% of water of ambient temperature. It is freely soluble in ethanol, ether, benzene, acetone and amyl alcohol; and slightly soluble in chloroform.
Identification Tests
1. Coniine Hydrobromide Derivative (C8H17N . HBr): Its prisms have mp 21°C ; 1 g dissolves in 2 ml water, 3 ml ethanol, and freely soluble in ether and chloroform.
2. Coniine Hydrochloride Derivative (C8H17N. HCl): It occurs as rhomboids having mp 221°C, freely soluble in water, chloroform and ethanol. (R)-(–) Form: It is a liquid, bp756 165°C; [α]D25 -81o (C = 4.0 in chloroform); [α]D23 -14 2 o(neat). (±)-Form: It has bp 200-210°C.
Uses
1. It has been used in convulsive and spasmodic diseases, such as: asthma, chorea, epilepsy, pertussis and tetanus.
2. Coniine has also been recommended is carditis, delirium, glandular swellings, jaundis, mania, nervous diseases, neuralgia, rheumatism, spasms and ulcers.
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* N.V. Mody et al. Experientra, 32, 829 (1976)
