Phloxine B

Phloxine B is a synthetic water-soluble red dye derived from fluorescein and characterized by the presence of four bromine atoms on the xanthene ring and four chlorine atoms in the carboxyphenyl ring[3][1]. It is primarily used as a color additive in drugs and cosmetics in the United States and as a food colorant in Japan[3][6]. In pharmaceuticals, it serves as an inactive ingredient to provide color to products such as tablets and capsules[1][5]. Phloxine B also functions widely as a biological stain for histology (notably in hematoxylin-phloxine-saffron staining) and microbiology to visualize cellular structures[1][5]. Additionally, it acts as an antimicrobial agent with photodynamic properties; upon exposure to light, it generates free radicals and singlet oxygen that cause oxidative damage leading to bacterial cell death—particularly effective against gram-positive bacteria such as MRSA strains[3][6][7]. Its mechanism involves binding negatively charged ions to positively charged cellular components; resistance among gram-negative bacteria is due to their outer membrane barrier but can be overcome with agents like EDTA[3].

Other names

phloxineCyanosinJapan Red 104CI Acid Red 92Acid Red 92Disodium 2′,4′,5′,7′-tetrabromo-4,5,6,7-tetrachlorofluoresceinEosin BlueEosine I BluishC.I. 45410