A. Ajmalicine
Synonyms Raubasine; Circolene; Hydrosarpan; Lamuran; Isoarteril;
Biological Sources It is obtained from the plants of Catharanthus lanceus Pichon (Boj.) (Apocynaceae) (Lanceleaf Periwinkle); Catharanthus roseus (L.) G. Don (Apocynaceae) (Periwinkle, Madagascar or Cape Periwinkle, Old Maid]; leaves of Mitragyna speciosa Korth. (Rubiaceae) (Katum, Kutum, Krantum); Rauvolfia scrpentina (L.) Benth. (Apocynaceae) (Rauvolfia, Chandra, Sarpaganda); and bark of Corynanthe johimbe K. Schum., (Rubiaceae).
Chemical Structure
(19α)-16, 17-Didehydro-19-methyl-oxayohimban-16-carboxylic acid methyl ester; (C21H24N2O3).
Isolation Ajmalicine may be isolated either from the bark of Corynanthe johimbe by the method suggested by Heinemann*, or from the roots of Rauwolfia serpentina by the procedure adopted by Hofmann.**
Characteristic Features
1. It is obtained as prisms from methanol which decompose at 257°C.
2. It has specific optical rotation [α]20D – 60° (C = 0.5 in chloroform); [α]20D – 45° (C = 0.5 in pyridine); and [α]20D – 39° (C = 0.25 in methanol).
3. It exhibits uvmax (methanol): 227, 292 nm (log e 4.61, 3.79).
Identification Tests
1. Ajmalicine Hydrochloride (C21H24N2O3.HCl): It is obtained as leaflets from ethanol having mp 290°C (decomposed); [α]20D – 17° (C = 0.5 in methanol); and is sparingly soluble in water or dilute HCl.
2. Ajmalicine Hydrobromide (C21H24N2O3.HBr): It is obtained as diamond-shaped plates from methanol having mp 295-296°C.
Uses
1. It is mostly used as antihypertensive and anti-ischemic agent (both ceretral and peripheral).
2. It has a broad application in the relief of obstruction of normal cerebral blood flow.
-------------------------------------------
* Heinemann, H., Ber. 67, 15 (1934).
** Hofmann, A, Helv. Chim. Acta. 37, 849, (1954).
