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Interactions Between Indomethacin and Quercetin in Binding to Human Serum Albumin

Indomethacin, as well as a large number of drugs, binds in the IIA subdomain of human serum albumin (HSA). The binding site located in the IIA subdomain of HSA is very spacious and able to bind two or more ligands at the same time. Certain flavonoids, such as quercetin, exhibit significant increase in fluorescence when they are bound to HSA, so their fluorescence can be used as a proof of their binding. In this study we measured quercetin fluorescence by steady-state fluorescence spectroscopy when a certain percentage of HSA binding sites in the IIA subdomain were occupied by indomethacin, which was coupled with docking studies of quercetin to indomethacin-bound HSA. Fluorescence results show that with the increasing occupation of the subdomain IIA by indomethacin, the intensity of quercetin fluorescence also increases. This is also confirmed by docking results, which show that indomethacin and quercetin bind in close vicinity of each other, suggesting additional steric constraints of quercetin molecule or even an energy transfer between indomethacin and quercetin, resulting in increased fluorescence intensity of the quercetin molecule.

Indomethacin, quercetin, binding, interactions, human serum albumin

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