Posted 30 July 2009 Essay on the Medical History of Methylene
Blue by Heiner Schirmer Biochemistry of MB MB is a tricyclic
phenothiazine drug (Wainwright and Amaral, 2005). Under
physiological conditions it is a blue cation that undergoes a
catalytic redox cycle: MB is reduced by NADPH or thioredoxin to
give leucoMB, an uncharged colorless compound. LeucoMB is then
spontaneously reoxidized by O2 (Figure 1). The typical redox-
cycling of MB in vivo can be illustrated in vitro using the
famous blue bottle experiment: MB is visibly reduced by glucose
to give leucoMB and then, by opening the lid of the bottle, one
can reoxidize it by atmospheric O2: the colour comes back.
Pathologists observe an analogous phenomenon at autopsies (Tan
and Rodriguez, 2008; Warth et al., 2009). After closing the lid,
one sees a lag phase and then MB is reduced again. Figure 1. MB
as a Redox-cycling Compound In vivo MB has prominent partners
such as NAD(P)H—which is the most important source of reducing
antioxidative equivalents in na