Inhibition of free radical generation by biotin

Abstract To assess the inhibitory effect of biotin on free radical generation, we used a spectrophotometric assay of cytochrome c reduction and determined the 2-methyl-6-phenyl-3,7-dihydroimidazo[1,3- a ]-pyrazin-3-one (CLA)-dependent chemiluminescence response of human neutrophils or a hypoxanthinexanthine oxidase (XOD) system. In the spectrophotometric assay of cytochrome c reduction, Superoxide (O 2 − ) generation by neutrophils stimulated with N -formyl-methionyl-leucyl-phenylalanine (f-MLP) was reduced significantly when biotin was added. In the CLA-dependent chemiluminescence test of neutrophils stimulated by f-MLP, biotin significantly reduced the gneration of free radical species, including O 2 − , in a concentration-dependent manner, the concentration corresponding to 50% inhibition ( ic 50 ) of biotin for free radical generation was 1.12 × 10 −7 mol. However, biotin did not exert an inhibitory effect on oxidative metabolism by directly scavening Superoxide anion, as shown by the study using the hypoxanthine-XOD system.