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Updated: Jul 14, 2026

Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases
Published on: October 10, 2020
Studies on interactions between plant secondary metabolites and glutathione transferase using fluorescence quenching
Xian Zhang1, Xinsheng Cheng, Chuanqin Wang
1Department of Chemistry, University of Science & Technology of China, Hefei 230026, China.
Abstract:
The interactions between plant secondary metabolites (tannic acid, rutin, cinnamic acid and catechin) and glutathione transferase (GST) were investigated by fluorescence and UV-Vis absorption spectroscopy. Intrinsic fluorescence of GST was measured by selectively exciting their tryptophan (Trp) residues and quenching constants were determined using the Stern-Volmer equation. The binding affinity was found to be strongest for tannic acid and ranked in the order tannic acid>rutin>cinnamic acid>catechin. The pH values in the range of 6.7-7.9, except for tannic acid, did not affect significantly the affinity of rutin, cinnamic acid and catechin with GST. Results showed that the fluorescence quenching of GST was a static_quenching. Fluorescence quenching and UV-Vis absorption spectroscopy suggested that only the tannic acid changed the microenvironment of the Trp residues. Furthermore, the number of binding sites and binding constants at different pH values showed that tannic acid had strongest affinity towards GST and hydrogen bonding played an important role in the affinity between GST and the metabolites.
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