Aconine-obtained from the dried roots of Aconitum napellus Linn

A. Aconine

Biological Source Aconine is the hydrolyzed product of aconitine which is obtained from the dried roots of Aconitum napellus Linn. (Ranunculaceae) and other aconites. A. napellus in also known as aconite, blue rocket and monkshood. Usually it contains upto 0.6% of the total alkaloids of aconite, of which approximately one third is the alkaloid aconitine.

Chemical Structure (1α, 3α, 6α, 14α, 15α, 16α)-20-Ethyl-1, 6-16-trimethoxy-4-(methoxymethyl) aconitane-3, 8, 13, 14, 15-pentol.

Isolation The alkaloid aconitine is subjected to hydrolysis which yields benzoyl aconine and acetic acid. The resulting benzoyl aconine is further hydrolyzed to yield aconine and benzoic acid.

Aconine being very soluble in water may be separated easily from the less water-soluble by product, i.e., benzoic acid.

Characteristic Features

(i) It is an amorphous powder with a bitter taste.

(ii) It has mp 132°C, [α]_D + 23° and pKa 9.52.

(iii) It is extremely soluble in water, alcohol; moderately soluble in chloroform and slightly soluble in benzene. It is practically insoluble in ether and petroleum ether.

Identification Tests It forms two distinct derivatives as given below:

(a) Aconine Hydrochloride Dihydrate (C₂₅H₄₂ClNO₉.2H₂O): It is obtained as crystals having mp 175-176°C and [α]_D–8°.

(b) Aconine Hydrobromide Sesquihydrate (C₂₅H₄₂BrNO₉ .1½ H2O]: It is obtained as crystals from water with mp 225°C.

Uses

1. It is used in the treatment of neuralgia, sciatica, rheumatism and inflammation.

2. It is employed occasionally as analgesic and cardiac depressant.
Source:Pharmacognosy And Pharmacobiotechnology By Ashutosh Kar