Eosin B

Eosin B is a xanthene-class acidic dye broadly used in histology, cytology and parasitology research for its staining properties and emerging pharmacological activity. In histology, Eosin B is used primarily as a counterstain for hematoxylin in methods like the H&E stain, differentiating between cell cytoplasm and nuclei by binding to positively charged components like proteins. Unlike the more common Eosin Y, Eosin B provides a distinctly bluish or bluish-purple hue to tissues rather than a yellowish one. It is used to stain cytoplasmic structures, connective tissues, and microorganisms, and is an integral part of the Romanowsky staining method. Beyond staining, more recent studies have revealed Eosin B’s potent antiparasitic/antimalarial effects, via a multifaceted mode of action involving enzyme inhibition (DHFR-TS, glutathione reductase, thioredoxin reductase), damage to parasite membranes and organelles, and possible redox cycling. Its differential toxicity, potent against parasites, much less against mammalian cells, makes it a promising lead for development of new antiparasitic agents. Spectral Data: λmax = 514nm (water, green fluorescence).