Role of a metabolite in allergenicity of Sudan I

A metabolite of Sudan I (l-phenylazo-2—naphthol) was isolated alter in vitro incubation with the supernatant of guinea pig liver homogenate (S·9). The metabolite was found to be 4′-hydroxy-l-phenylazo-2—naplithol by gas chromatography-mass spectrormetry (GC-MS), and proton and carbon-13 nuclear magnetic resonance (NMR) analyses. It elicited positive reactions in guinea pigs sensitized ot Sudan I. It was also shown to be allergenic. The results suggest that para-hydroxylation of the phenyl group of Sudan I may play an important role in its allergenicity.