Spectrofluorimetric Determination of Thiols in Biological Samples with a New Fluorescent Probe 3‐Maleimidylbenzanthrone

Abstract A new thiol weak‐fluorescence probe, 3‐maleimidylbenzanthrone (3‐MB), has been developed for the spectrofluorimetric determination of thiols in biological samples. The maximal fluorescence for the reagent and the adduct were both at excitation and emission wavelengths of 401 and 496 nm, respectively. When 3‐MB conjugated to a thiol, a strong fluorescent derivative formed at 35°C. The relative fluorescence intensity (RF) was linear in the range of 1.0×10−8 mol·l−1–6.0×10−7 mol·l−1 for cysteine (Cys) and 6.0×10−9 mol·l−1–4.0×10−7 mol·l−1 for glutathione (GSH). The detection limit was 5.71×10−9 mol·l−1 (S/N=3) for Cys and 5.64×10−9 mol·l−1 (S/N=3) for GSH. The proposed method has been applied to the determination of GSHs in human serum, plasma, and Cys in urine with recoveries of 96.2–103.0%.