A Microplate-based Platform with Immobilized Human Glutathione Transferase A1-1 for High-throughput Screening of Plant-origin Inhibitors

Background: Glutathione transferases (GSTs) catalyze the conjugation of glutathione (GSH) to endogenous and xenobiotic electrophilic compounds and have been involved in the development of resistance toward cancer chemotherapeutic drugs and in the etiology, pathology and progression of several other diseases. In the present work, the human isoenzyme GSTA1-1 (hGSTA1-1) was used to assemble a microplate-based platform for high-throughput screening of natural productbased inhibitors from plant extracts. Methods: The enzyme was immobilized using sol-gel chemistry and deposited as a layer at the bottom surface of 96-well format ELISA microplate. The sensing signal was based on the inhibition of the colorimetric reaction between 1-chloro-dinitrobenzene (CDNB) and GSH, catalyzed by the sol-gel entrapped enzyme. Results: As a proof of concept, the system was used for screening aqueous extracts from medicinal and aromatic plants with excellent reproducibility (approximately 95%). Conclusion: The operational simplicity and accuracy of this system, suggest that it can be explored as a bioanalytical tool with potential use in drug design and development efforts for finding new sources of GST inhibitors useful in chemomodulation of cancer drugs.