Research paper
Novel hydrazido benzenesulfonamides-isatin conjugates: Synthesis, carbonic anhydrase inhibitory activity and molecular modeling studies

https://doi.org/10.1016/j.ejmech.2018.07.054Get rights and content

Highlights

  • Three novel series of isatin-based sulfonamides (5a-h, 10a-g and 11a-c) were synthesized.

  • Inhibitory activity of these sulfonamides was evaluated toward hCA I, II, IX and XII isoforms.

  • 10b emerged as a single-digit nanomolar hCA IX and XII inhibitor (8.9 and 9.2 nM).

  • Molecular docking studies were carried out for 10b within the hCA II, IX and XII active sites.

Abstract

As a part of our ongoing efforts towards developing novel carbonic anhydrase inhibitors based on the isatin moiety, herein we report the synthesis and biological evaluation of novel sulfonamides (5a-h, 10a-g and 11a-c) incorporating substituted 2-indolinone moiety (as tail) linked to benzenesulfonamide (as zinc anchoring moiety) through a hydrazide linker. The synthesized sulfonamides were evaluated in vitro for their inhibitory activity against the following human (h) carbonic anhydrase (hCA, EC 4.2.1.1) isoforms, hCA I, II, IX and XII. All these isoforms were inhibited by the sulfonamides reported here in variable degrees. hCA I was inhibited with KIs in the range of 671.8: 3549.5 nM, hCA II in the range of 36.8: 892.4 nM; hCA IX in the range of 8.9: 264.5 nM, whereas hCA XII in the range of 9.0: 78.1 nM. In particular, compound 10b emerged as a single-digit nanomolar hCA IX and XII inhibitor (8.9 and 9.2 nM, respectively). Molecular docking studies carried out for compound 10b within the hCA II, IX and XII active sites allowed us to rationalize the obtained inhibition results.

Graphical abstract

Three series of novel sulfonamides incorporating substituted isatin moieties linked to benzenesulfonamide through hydrazide linkers were synthesized and evaluated for their inhibitory activity against a panel of carbonic anhydrase isoforms hCA I, II, IX and XII. 10b emerged as a single-digit nanomolar hCA IX and XII inhibitor (8.9 and 9.2 nM, respectively). Molecular docking studies were carried out for 10b within the hCA II, IX and XII active sites.

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Introduction

Carbonic anhydrases (CAs, EC 4.2.1.1) are ubiquitous metalloenzymes, present throughout most living organisms and encoded by seven evolutionarily unrelated gene families: the α-, β-, γ-, δ-, ζ-, η and θ-CAs. Conversion of CO2 to the bicarbonate ions and protons is a plain physiological reaction that is effectively sped up by CAs [[1], [2], [3], [4]]. This simple reaction is required in many physiological processes, including pH and CO2 homeostasis, biosynthetic reactions, respiration and transport of CO2 and bicarbonate between lungs and metabolizing tissues [1,2].

Many of the CA isozymes involved in these processes are significant therapeutic targets with the potential to be inhibited to treat a wide range of disorders. Indeed CA isoforms are involved in diverse physio/pathological conditions such as glaucoma (hCA II, IV and XII), edema (hCA II, IV, XIV), central nervous system (CNS)-related pathologies (hCA VII and XIV) and tumors (hCA IX and hCA XII) [1,2]. In detail, human CA isozymes IX and XII are two tumor-associated proteins, being overexpressed in many tumors and involved in serious processes related to cancer progression and response to therapy. These two CA isozymes have been the recent targets for anticancer drugs during last years [[5], [6], [7], [8], [9], [10]].

Literature surveying revealed that isatin is a promising tail scaffold to design compounds with interesting carbonic anhydrase inhibitory activity profiles towards different CA isoforms. Several studies have developed diverse isatin-based derivatives as potent CA inhibitors, compounds I-VI (Fig. 1) [[11], [12], [13], [14], [15], [16], [17], [18]].

Based on the aforementioned findings and as a part of our ongoing effort to develop potent isatin-based CAIs [[11], [12], [13], [14]], herein we report the synthesis and biological evaluation of three novel series of sulfonamides (5a-h, 10a-g and 11a-c, Fig. 1) featuring benzenesulfonamide, a zinc anchoring moiety, conjugated with an isatin tail through hydrazide linker (=NNHCdouble bondO). Two strategies were adopted to design the target sulfonamides. The first one focused on grafting various substituents (compounds 5a-h) at 5-position of the isatin tail to ensure different electronic and lipophilic environments which could manipulate the activity of the target sulfonamides, and to evaluate their influence on activity. In the second strategy, different N-alkyl (compounds 10a-g) and N-benzyl (compounds 11a-c) substituents were incorporated into the isatin tail. The N-substitution pattern on the isatin moieties was varied in a systemic fashion to define the optimal length (methyl, ethyl, n-propyl, n-butyl), bulkiness (isopropyl) and unsaturation (allyl, benzyl) which confer the best CA inhibitory effect.

All the newly synthesized sulfonamides were in vitro evaluated for their inhibitory activity against a panel of hCA I, II, IX and XII isoforms, using stopped-flow CO2 hydrase assay. Molecular docking studies were carried out for compound 10b to justify its activity through investigating its key interactions within the active site of hCA II (PDB 5LJT), hCA IX (PDB 5FL4) and hCA XII (PDB 1JD0) isoforms.

Section snippets

Chemistry

The synthesis of the new sulfonamides in this study is outlined in Scheme 1, Scheme 2. In Scheme 1, esterification of 4-sulfamoylbenzoic acid using methanol with catalytic amount of H2SO4 under reflux afforded methyl 4-sulfamoylbenzoate 2 which converted to 4-(hydrazinecarbonyl)benzenesulfonamide 3 by refluxing with hydrazine hydrate in methanol. Hydrazide 3 condensed with different isatin derivatives 4a-h to afford the target compounds 5a-h.

In Scheme 2, N-substituted isatins 8a-g and 9a-c were

Molecular docking studies

Compound 10b was selected for molecular docking simulations to justify its activity by investigating its key interactions within the active site of hCA II (PDB 5LJT [20]), hCA IX (PDB 5FL4 [21]) and hCA XII (PDB 1JD0 [22]) isoforms. The top poses for 10b docked within the active site of hCA II, hCA IX and hCAXII were illustrated in Fig. 2, 3 and 4, respectively. As a result, the sulfonamide group played the usual role as zinc-binding group (ZBG) for compound 10b with the three different hCA

Conclusion

In summary, we report here the synthesis of three novel series of sulfonamides (5a-h, 10a-g and 11a-c), incorporating different isatin moieties linked to benzenesulfonamide (as zinc anchoring moiety) through hydrazide linker. The structure of the novel sulfonamides was confirmed by the different spectral and elemental analyses methods. Biological evaluation of the newly prepared sulfonamides was performed against hCA I, II, IX and XII. All the tested isoforms were inhibited by the synthesized

General

Melting points were measured with a Stuart melting point apparatus and were uncorrected. Infrared (IR) Spectra were recorded as KBr disks using Schimadzu FT-IR 8400S spectrophotometer. Mass spectral data are given by GCMS-QP1000 EX spectrometer at 70 e.V. NMR Spectra were recorded on Bruker AVF-400 spectrometer. 1H spectrum was run at 400 MHz and 13C spectrum was run at 100 MHz in deuterated dimethylsulfoxide (DMSO‑d6). Chemical shifts are expressed in values (ppm) using the solvent peak as

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