digitonin in nuclei isolation buffer - why?

Bernard Murray bernard at elsie.nci.nih.gov
Mon Jan 10 20:58:45 EST 1994

In article <brownbrd.758241656 at vincent1.iastate.edu>, brownbrd at iastate.edu (Grizzly Adams) writes:
> I am working on a project that involves isolating and examining nuclei, and of
> several references I have, they all have 0.1% digitonin (v/v) in the isolation
> buffer.  None of my professors, Biochemist friends, old textbooks, or the Merck
> index have been helpful.  So far most responses are along the lines of "thats
> in there. hmmm I've no idea why. All I know is that it is used for heart
> attacks." 
> So, If anyone knows what it is doing there I'd love to hear from you, since I
> really would like to understand what is going on.
> thanks
> eric anderson
> brownbrd at iastate.edu
> --- I certainly hope all my opinions are my own ---

Hello there,
	The reason such confusion arises is that Digitalis spp. have proved such
a rich source of biologically interesting products.  Digitonin and digitalis areboth glycosides and consist of an aglycone (which superficially resembles a
steroid) and a carbohydrate moiety.  The aglycone of digitonin is digitogenin
and I have no idea if this is pharmacologically active.  Merck lists the major
property of digitonin as precipitating cholesterol and I have always considered
it to be simply a non-ionic detergent (probably an oversimplification?).
	In contrast, the principal aglycones of the cardiac glycosides are
digoxigenin and digitoxigenin and the pharmacological activity (used in heart
failure) is dependent upon the aglycone (the carbohydrate part mainly affects 
the pharmacokinetics - how the body deals with it).  The doses of the cardiac
glycosides have to be carefully regulated as they are indeed poisonous in
overdose.  Since digitalis is the common name for the cardiac glycosides
(eg. digoxin, digitoxin) it could be easy to get this confused with digitonin.

NB: I am a toxicologist/pharmacologist and am pretty rusty when it comes to
    this topic.  I would appreciate corrections from botanists, chemists and
    cardiologists rather than have me passing dud/out of date information.
    (Still, it was good to get Goodman & Gilman and Bowman & Rand out again!)


Bernard Murray, Ph.D.
National Cancer Institute, NIH, Bethesda MD 20892, USA
bernard at elsie.nci.nih.gov  -  bmurray at helix.nih.gov  - (301) 496-0731/2

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