Quinazolinones as Competitive Inhibitors of Carbonic Anhydrase-II (Human and Bovine): Synthesis, in-vitro, in-silico, Selectivity, and Kinetics Studies.

Ajmal Khan,Majid Khan,Ahmed Al-Harrasi,Zulfiqar Ali Khan,Sobia Ahsan Halim,Zahid Shafiq

doi:10.3389/fchem.2020.598095

Abstract

Carbonic anhydrase-II (CA-II) is associated with glaucoma, malignant brain tumors, and renal, gastric, and pancreatic carcinomas and is mainly involved in the regulation of the bicarbonate concentration in the eyes. CA-II inhibitors can be used to reduce the intraocular pressure usually associated with glaucoma. In search of potent CA-II inhibitors, a series of quinazolinones derivatives (4a-p) were synthesized and characterized by IR and NMR spectroscopy. The inhibitory potential of all the compounds was evaluated against bovine carbonic anhydrase-II (bCA-II) and human carbonic anhydrase-II (hCA-II), and compounds displayed moderate to significant inhibition with IC50 values of 8.9–67.3 and 14.0–59.6 μM, respectively. A preliminary structure-activity relationship suggested that the presence of a nitro group on the phenyl ring at R position contributes significantly to the overall activity. Kinetics studies of the most active inhibitor, 4d, against both bCA-II and hCA-II were performed to investigate the mode of inhibition and to determine the inhibition constants (Ki). According to the kinetics results, 4d is a competitive inhibitor of bCA-II and hCA-II with Ki values of 13.0 ± 0.013 and 14.25 ± 0.017 μM, respectively. However, the selectivity index reflects that the compounds 4g and 4o are more selective for hCA-II. The binding mode of these compounds within the active sites of bCA-II and hCA-II was investigated by structure-based molecular docking. The docking results are in complete agreement with the experimental findings.

Highlights

Carbonic anhydrases (CAs, EC 4.2.1.1) are zinc-containing metallo-enzymes, found in animals, plants, algae, archaea, and eubacteria
After completion of the reaction as checked by thin layer chromatography (TLC), the reaction mixture was cooled and separated solids were collected by filtration, washed with water/hexane, dried, and purified by column chromatography to afford the corresponding quinazolinones 4a-p
In-vitro bovine carbonic anhydrase-II (bCA-II) and human carbonic anhydraseII (hCA-II) activities were measured by following the spectrophotometric method described by Pocker and Meany with slight modifications (Pocker and Meany, 1967; Ur Rehman et al, 2020)

Summary

INTRODUCTION

Carbonic anhydrases (CAs, EC 4.2.1.1) are zinc-containing metallo-enzymes, found in animals, plants, algae, archaea, and eubacteria. Quinazolinones as Competitive Inhibitors of Carbonic Anhydrase-II processes (Hewett-Emmett, 2000). The inhibitors of CA-II have been considered as an adjunct in cancer chemotherapy (Zaraei et al, 2019) These highly abundant proteins are involved in crucial physiological processes related with respiration. These enzymes are mainly involved in pH/CO2 homeostasis, secretion of electrolytes in tissues/organs, and transportation of CO2 and bicarbonate between the lungs and metabolizing tissues. We report the synthesis and in-vitro bovine carbonic anhydrase-II (bCA-II) and human carbonic anhydraseII (hCA-II) inhibitory activities of a series of quinazolinone analogs.

General Procedure for Synthesis of

C14 H11 N3 O

C14 H10 FN3 O

RESULTS AND DISCUSSION