A new fluorescein isothiocyanate-based screening method for the rapid discovery of electrophilic compounds

In the present study, a simple fluorescein isothiocyanate (FITC)-based screening method was established for the rapid discovery of electrophilic compounds from natural products. The test sample is firstly allowed to alkylate a certain proportion of glutathione (GSH) under basic conditions (pH 8.0), then FITC is added to conjugate with the remaining GSH from the first step. By analyzing the fluorescence intensity of the reaction solution under acidic conditions (pH 3.0), it could be determined whether the test sample contained electrophilic compounds. A botanical sample, the ethyl acetate extract of Radix Salvia miltiorrhiza, was tested using this screening assay and we successfully discovered four electrophilic compounds from it, which were miltirone and its three derivatives (1-oxomiltirone, 4-methylenemiltirone, and 1,2-didehydromiltirone). The findings indicate that the screening method is effective and suitable for high-throughput screening (HTS) assays in the future.