An examination of Digitalis purpurea and its glycosides in relation to the loss of activity on storage

Fish, Francis (1955) An examination of Digitalis purpurea and its glycosides in relation to the loss of activity on storage. PhD thesis, University of Glasgow.

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1. Tinctures prepared from either dried or stabilised digitalis leaf sure unstable on storage, losing up to 60 per cent, of initial potency as determined by the 18-hour method of assay on frogs. 2. The loss of potency is not due to breakdown of solubilising agents with resultant loss of absorption from the frog lymph sac, since aged tinctures are well absorbed within twelve hours and the addition of saponin does not increase the potency of these tinctures. 3. Intravenous assays of aged tinctures of digitalis reveal a 20 to 30 per cent, loss of potency to frog during nine to twelve months storage. 4. The loss of potency to frog is not due to hydrolysis of the secondary glycosides because digitoxin, in ethanolic (70 per cent.) solution has been shown to be stable and no free digitoxose, which would result from hydrolysis of the secondary glycosides, could be found in aged tinctures. 5. Spectrophotometric assays based on the Keller-Kiliani reaction show a slight increase in strength of digitalis tinctures during storage. This indicates conversion of primary glycosides to secondary glycosides, a change which would account for the loss of potency to frog, but would result in no potency loss to oat. 6. Samples of digitoxin found equipotent by chemical assay, using the Keller-Kilismi reagent, were of widely different bio1ogical potency measured on frog. 7. No satisfactory method exists for the accurate assay of all digitalis preparations and work is proceeding in an effort to establish a method based on cardiotonic effects as shown by changes in the electrocardiogram of frog.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J P Todd
Keywords: Pharmacology
Date of Award: 1955
Depositing User: Enlighten Team
Unique ID: glathesis:1955-73657
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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