Synthesis, Carbonic Anhydrase II/IX/XII Inhibition, DFT, and Molecular Docking Studies of Hydrazide-Sulfonamide Hybrids of 4-Methylsalicyl- and Acyl-Substituted Hydrazide

Abstract

Carbonic anhydrases (CAs and EC 4.2.1.1) are the Zn²⁺ containing enzymes which catalyze the reversible hydration of CO₂ to carbonate and proton. If they are not functioning properly, it would lead towards many diseases including tumor. Synthesis of hydrazide-sulfonamide hybrids (19-36) was carried out by the reaction of aryl (10-11) and acyl (12-13) hydrazides with substituted sulfonyl chloride (14-18). Final product formation was confirmed by FT-IR, NMR, and EI-MS. Density functional theory (DFT) calculations were performed on all the synthesized compounds to get the ground-state geometries and compute NMR properties. NMR computations were in excellent agreement with the experimental NMR data. All the synthesized hydrazide-sulfonamide hybrids were in vitro evaluated against CA II, CA IX, and CA XII isozymes for their carbonic anhydrase inhibition activities. Among the entire series, only compounds 22, 32, and 36 were highly selective inhibitors of hCA IX and did not inhibit hCA XII. To investigate the binding affinity of these compounds, molecular docking studies of compounds 32 and 36 were carried out against both hCA IX and hCA XII. By using BioSolveIT's SeeSAR software, further studies to provide visual clues to binding affinity indicate that the structural elements that are responsible for this were also studied. The binding of these compounds with hCA IX was highly favorable (as expected) and in agreement with the experimental data.

Figure 1

Scheme 1

Synthesis of hydrazide (10-13).

Scheme 2

Synthesis of hydrazide sulfonamide (19-36).

Figure 2

Optimized geometries of all the compounds under study (19-36) at PBE0-D3BJ/def2-TZVP/SMD_Solvent (Solvent = CDCl₃, DMSO experimental solvent for NMR spectroscopy) level of the theory. In 3D models, grey color represents carbon, white represents hydrogens, yellow is for sulfur, red color is for oxygen, brown represents bromine, and blue color shows nitrogen atoms.

Figure 3

Possible binding mode of inhibitor 24 inside CA II active pocket.

Figure 4

Possible binding mode of the inhibitor 23 inside the CA IX active pocket.

Figure 5

Possible binding mode of the inhibitor 30 inside the CA XII active pocket.

Figure 6

SeeSAR analysis (visual assessment of binding affinity) for compound 32 (a) and compound 36 (b) (selective hCA IX inhibitors over hCA XII) docked against hCA XII. The structural elements responsible for the favorable contribution to the overall binding affinity are shown in green coronas; the greater the sphere of the corona, the greater is the contribution. Similarly, the structural elements contributing unfavorably to the overall binding are shown in red coronas. The structural elements that are not contributing either favorably or unfavorably are not colored.

Figure 7

Sequence alignment of hCA II (4qiy), hCA IX (6g9u), and hCA XII (1jd0).