Re: [Histonet] Orcein for copper-binding protein/Hep B
Orcein has always been a synthetic dye. The starting
material in manufacture is the phenolic compound
orcinol (3,5-dihydroxytoluene). Orcinol was
originally obtained by alkaline hydrolysis and
decarboxylation of a more complex compound that
occurs in certain lichens, including one called orchil.
Oxidaton of orcinol in the presence of ammonia yields
orcein, which is a mixture of 14 oxazine dyes. Related
dye mixtures are lacmoid and litmus, for which the
starting material is resorcinol (1,3-dihydroxybenzene).
The medieval method for making orcein involved boiling
the lichen in alkaline urine, a procedure that combined
hydrolysis of the precursor with oxidation in the
presence of a source of ammonia.
Although orcein is sometimes designated "synthetic" on
the label, this has never been a "natural" dye in
the sense of being responsible for the colour of an
animal or plant. The lichen (orchil) was simply a
source of a precursor of orcinol (which is not
coloured) in the years before coal tar became the
major source of aromatic compounds.
Orcein is one of the dyes regularly tested by the
Biological Stain Commission, and the tests include
methods for elastin and hepatitis A antigen. See
Penney, Powers, Frank & Churukian 2002 Biotech.
Histochem. 77:237-275 for the staining methods
used to do the testing. Any bottle of orcein with
a "Certified" label will therefore be suitable.
The December 2003 issue of Biotechnic & Histochemistry
(Vol 78 No. 6) was a special issue with six papers on
orcein and related dyes. One of these, by Tony Henwood
(pp. 303-308), addresses batch variation and staining
by aged solutions of orcein, with coloured photos
showing the varied results.
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London, Canada N6A 5C1
Malam Jacqueline wrote:
> Hello Histonetters.
> Has anyone got a really good orcein method for copper-binding protein/Hep B,
> and is there a recommended brand or vendor of the dye? Would you use
> synthetic or natural (if you can still get it)?
> Jacqui Malam
> Lancaster Infirmary
> N England
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