GB668413A - Improvement in the preparation of a cardio-active glycoside - Google Patents

Abstract

Crystalline digitoxin is obtained from Digitalis purpurea leaves by extracting them with an aqueous alcoholic solvent (50-95 per cent of C1-4 alcohols), washing the extract with a water-immiscible solvent which dissolves fats and other vegetative materials but not digitoxin principles (e.g. carbon tetrachloride, turpentine, amyl ether, kerosene or cyclohexane), separating the two solvents, extracting the digitoxin principles with a water-immiscible organic solvent (e.g. ethyl or isopropyl ether, dimethyl carbonate, n-propyl chloride, methylchloroform or mixtures such as chloroform+amyl ether) and isolating the digitoxin from the extract. The term "digitoxin principles" includes digitoxin and its addition products. The initial alcoholic extraction may be combined with or preceded by treatment with a tannin- and extractive-precipitant which precipitates unwanted material such as tannins and resins or renders them less soluble in the alcoholic solvent. Such a precipitant comprises an acetate, chloride, carbonate or basic salt of a bivalent metal such as lead, iron, copper, tin or chromium, in solid form or as an aqueous solution or suspension. The preferred alcoholic solvent is denatured ethanol (10 : 1 ethyl and methyl)+water, containing, e.g., 60-70 per cent alcohols and 40-30 per cent water. After extraction with this, the alcohol is preferably removed in vacuo before the next step. The isolation of digitoxin from the final extract is carried out by washing with water and alkalis (to remove gitalin), drying, and concentrating to precipitate crude digitoxin. This is recrystallized from aqueous alcohol until sufficiently pure. Examples are given of the process.