Orcein

Orcein (CAS 1400-62-0, EC 215-750-6) is a natural dye derived from the lichen Roccella tinctoria, classified under E182 and also known as Natural Red 28. It is available as a dark brown powder that yields red-to-purple hues depending on pH and substrate conditions.

In histology and microscopy, orcein selectively binds to elastic fibres and hepatitis B surface antigens, making it a standard staining reagent in tissue diagnostics. In textile and leather processing, it imparts reddish-purple tones to protein-based fibres such as wool and silk through direct ionic bonding with amino acid residues.

Orcein is supplied in powder form suitable for laboratory, food, and industrial applications. As an approved EU food colorant under E182, it falls within the scope of REACH regulation. Buyers should confirm grade specification and purity documentation prior to procurement, as quality standards vary between suppliers.