Vitamin B3 as a high acid-alkali tolerant peroxidase mimic for colorimetric detection of hydrogen peroxide and glutathione

Small-molecule enzyme mimics as biocatalysts have been extensively applied in diverse colorimetric sensors fabrication. However, excavating potential organic enzyme mimics with high catalytic activity still remains challenging. In this study, the peroxidase mimicking activity of nicotinic acid (VB3) was demonstrated for the first time through chromogenic substrate 3, 3′, 5, 5′-tetramethylbenzidine (TMB) at the existence of hydrogen peroxide (H 2 O 2 ). The catalytic activity of VB3 kept more than 80% of its optimum activity in a broad pH range of 3.0–9.0. In addition, the kinetic parameter (Michaelis constant, K m  = 0.037 mM) of VB3 catalysis to H 2 O 2 is smaller than natural horseradish peroxidase (HRP) and previously reported peroxidase mimics. The catalytic mechanism of VB3 is mainly attributed to the active species of hydroxyl radical ( OH) and partially attributed to the superoxide free radicals ( O 2 − ). A convenient and sensitive colorimetric method based on VB3-H 2 O 2 -TMB chromogenic system for H 2 O 2 and glutathione detection was fabricated with the linear ranges of 5.0–100.0 μM and 5.0–50.0 μM, respectively. In short, this work will not only bring new enlightenment on the physiological functions and practical applications in the analytical field of VB3, but also provide a new type of structural reference for small-molecule enzyme mimics.