Patent GB-816655-A (GB)
Title: Isolation of alkaloidal materials
IPC: C07G5/00
Filed: 1957-07-03
Abstract: Alkaloidal complexes "serpajmaline," "ajmalexine" and "resajmaline" are isolated from Rauwolfia species of plants, especially from the roots and root bark of Rauwolfia serpentina Benth., by percolating the plant material with ethanol or methanol, removing the solvent from the percolate, partitioning the semi-solid residue between water and a water-immiscible solvent selected from the acetates of alcohols of 2 to 5 carbon atoms per molecule and chlorinated paraffinic and olefinic hydrocarbons having substantially the same solvent action, extracting the aqueous layer with a hydroxylic, partially water-miscible solvent, preferably amyl alcohol, and extracting the combined organic solvent fractions thus obtained with water, whereby serpajmaline is isolated from the aqueous extract; removing the solvent from the water-immiscible solvent layer and digesting the residue with petroleum ether whereby ajmalexine is obtained as a petroleum ether-insoluble powder and resajmaline is obtained from the petroleum ether extract upon removal of the solvent.  The alkaloidal complexes may subsequently be resolved into their component alkaloids by known methods.  Modifications of the process include: (a) the direct partitioning of the residue, left after removal of solvent from the percolates of fresh undried roots, between water and amyl alcohol, repeatedly extracting the aqueous layer with more amyl alcohol, then repeatedly extracting the alcoholic extracts so obtained with water and concentrating the aqueous extracts in vacuo to give serpajmaline as a cream-coloured powder (further quantities of the complex are obtained from the extracted amyl alcohol solution by removal of the solvent, partition between water and ethyl acetate, extraction of the aqueous phase with ethyl acetate, then amyl alcohol, exhaustive extraction of the alcoholic extracts with water and concentration of the aqueous extracts so obtained); (b) evaporation of the amyl alcoholic extract obtained in (a); digestion of the residue with water and ethyl acetate, exhaustive extraction of the aqueous layer and insoluble matter with amyl alcohol, extraction of the alcoholic extracts with water and evaporation of the aqueous solution in vacuo to give serpajmaline; (c) evaporation of the ethyl acetate extracts remaining from (a) or (b), digestion of the residue with petroleum ether whereby ajmalexine remains undigested as a cream-coloured powder and resajmaline is obtained by concentration of the petroleum extract. "Serpajmaline" consists mainly of serpentine, serpentine, ajmaline and two unknown substances, it is readily soluble in water, alcohol and moist acetone, insoluble in benzene, ethyl acetate and ether, the pH of a 1 per cent solution is ca 6, the complex softens at 85 DEG  C., becomes sticky at about 100 DEG  C. and froths up at about 130 DEG  C.; "resajmaline" contains the fatty matter, serposterol, and unsaturated higher alcohols together with about 2.5 per cent reserpine, 0.5 per cent rescinnamine and other weaker bases in a lipoid soluble form, it forms a greenish viscous oil, soluble in ethyl acetate ether and petroleum ether and fairly so in methanol and ethanol; "ajmalexine" comprises the weaker bases with 5.5 per cent reserpine and 2.2 per cent rescinnamine, it is a cream-coloured powder, soluble in ethyl acetate, mostly so in benzene, fairly soluble in ethanol and methanol and insoluble in petroleum ether.  Treatment of serpajmaline and ajmalexine with dilute alkali, preferably 10 per cent ammonia, yields basic components of the complexes as acid-soluble cream powders.  Detailed examples illustrate the isolation of the alkaloidal complexes from R. serpentina Benth. Specification 734,108 is referred to.