Determination of activities of human carbonic anhydrase II inhibitors from curcumin analogs

Purpose: To evaluate the activities of new curcumin analogs as carbonic anhydrase II (CA-II) inhibitor.
Methods: Carbonic anhydrase II (CA-II) inhibition was determined by each ligand capability to inhibit the esterase activity of CA-II using 4-NPA as a substrate in 96-well plates. Dimethyl sulfoxide was used to dissolve each curcumin analog compound, and then diluted with biological buffer. They were then mixed with CA-II solution and to start the reaction, 4-NPA was added. Hydrolysis of the substrate was evaluated at 405 nm after incubation for 2 h at 25 °C. The IC₅₀ value of compounds with inhibitory activity higher than 40 % was then evaluated. Molecular docking was also used to predict enzymeinhibitor interaction.
Results: Eight new curcumin analogs were potent to inhibit CA-II activity with IC₅₀ values ranging from 7.92 ± 0.54 to 72.31 ± 2.21 μmol; the lowest value was exhibited by (3E,5E)-3,5-bis[(2-hydroxyphenyl)methylidene]piperidin-4-one (a1). Molecular docking analysis revealed that this molecule formed hydrogen bonds with Thr199, Thr200 and Gln92 at the active site of CA-II.
Conclusion: These curcumin analogs have inhibitory potential against CA-II; (3E, 5E)-3,5-bis[(2-hydroxyphenyl)methylidene]piperidin-4-one (a1) has the highest inhibitory activity and may be useful in the development of CA-II inhibitors for glaucoma treatment.