The Assay of Tincture of Digitalis and the Determination of the Constituents of Digitalis Species

Increase in the concentration of ethanol or the inclusion of methanol, ethylene glycol or glycerol in the alkaline 3:5‐dinitrobenzoic acid assay for digitalis glycosides, progressively reduces the maximum optical density of the reaction mixture. The constituents of mixtures of two digitalis glycosides have been separated by paper partition chromatography and recovered. The percentage recoveries obtained lay between 90 and 110 per cent of the quantity taken. The concentrations of four named glycosides in samples of powdered D. purpurea have been estimated by chromatographic separation followed by chemical assay. Estimates of the biological activity represented by the concentrations of these four constituents in each of the leaf samples have been made; the total biological activity of each leaf sample estimated in this way was found to be approximately half of the total biological activity of the whole leaf sample, as estimated by direct biological assay.

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The Actions of Digitalis Leaf Preparations and of Cardiac Glycosides on the Isolated Right Ventricle of the Guinea Pig

Ga¹

1958

Journal of Pharmacy and Pharmacology

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A method is described for recording kymographically the systolic contraction and the resting length of the electrically stimulated, isolated right ventricle of the guinea pig. Two samples of Digitalis purpurea leaf and a sample of Digitalis lanata have been assayed in terms of the Third International Standard of D. purpurea using metameters dependent on changes in the systolic contractions and resting length of the muscle and the time elapsing before the changes occur. In a similar manner digitoxin and ouabain have been assayed in terms of digoxin. The results are compared with those obtained by slow intravenous infusion of the preparations into guinea pigs. The potencies derived from the two methods are in close agreement in the case of the digitalis leaf preparations. Digitoxin, however, is more active than digoxin on the ventricle preparation irrespective of the metameter used and less active by the slow infusion method, while ouabain has the same activity as digoxin on the ventricle and twice the activity by the infusion method. The results for ouabain on the ventricle using the different metameters, are homogenous, those for digitoxin are not. There is little difference between the general actions of the three glycosides on the ventricle but each glycoside is capable of producing different effects on systolic contraction and resting length depending on the dose employed. The possible mechanisms responsible for these effects are discussed.

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The Assay of Tincture of Digitalis and the Determination of the Constituents of Digitalis Species

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Digoxin

Digoxin

AN INVESTIGATION OF THE CONSTITUENTS OF DIGITALIS PURPUREA

The Actions of Digitalis Leaf Preparations and of Cardiac Glycosides on the Isolated Right Ventricle of the Guinea Pig

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