Synthesis of new sulfa drugs containing FDA-approved sulfa pyridine: Evaluation of cholinesterase inhibition, antimicrobial, antibiofilm, anticancer, and antioxidant activities, along with theoretical calculation and molecular docking study

Abstract

In this study, three new compounds were synthesized using sulfa pyridine (SPD), an FDA-approved drug, and different aromatic aldehydes. The structure of SPD-1, SPD-2, SPD-3 compounds were elucidated by spectroscopic methods (FT-IR, ¹H-NMR, ¹³C-NMR, LC-MS). The inhibition activities of these compounds on the acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) enzymes were investigated by comparing IC₅₀ and Ki values. SPD-3 (IC₅₀ = 12.98±0.11 nM) showed the best inhibition of AChE, while SPD-1 had the best IC₅₀ value (IC₅₀ = 1.85±1.04 nM) for BChE. It was observed that the IC₅₀ and Ki values ​​on both enzymes of all compounds were as good as the standard substance donepezil. The synthesized compounds were tested in vitro against various standard strains of bacteria (Staphylococcus aureus, S. epidermidis, Escherichia coli, Pseudomonas aeruginosa) and yeast strains (Candida albicans, C. parapsilosis, C. auris). The compounds showed excellent inhibition against S. aureus ATCC 29,213, P. aeruginosa ATCC 27,853, and E. coli ATCC 25,922 (except SPD-1), outperforming sulfamethoxazole and sulfisoxazole by 1–4 fold. All compounds exhibited strong inhibition against C. auris CDC B11903 with a MIC of 0.312 mg/mL, twice as effective as fluconazole (Diflucan). The anticancer activities of these compounds on Caco-2 human colon cancer, MCF-7 human breast cancer, and SH-SY5Y human neuroblastoma cell line were investigated by comparing IC₅₀ values. Using the MTT method, the results showed that these three compounds have a dose-dependent toxic effect on Caco-2 human colon carcinoma, MCF-7 human breast carcinoma, and SH-SY5Y human neuroblastoma cells. Compared to doxorubicin, these compounds also inhibited the proliferation of these cells. The antioxidant activity of compounds containing SPD compounds was tested by the DPPH assay, using BHA and BHT as reference standarts. The results show that the compounds have antioxidant activity. In the DPPH assay, all three compounds performed better than the standards. BHA and BHT, especially SPD-1 giving the best results at all three concentrations.

In theoretical studies, optimized structures of new sulfa drug candidates were performed with the DFT/B3LYP/6–31+G (d,p) basis set using the Gaussian 09 package program. The frontier molecular orbitals (FMOs: HOMO and LUMO), chemical reactivity parameters, and molecular electrostatic potential (MEP) maps of the most stable conformations were obtained by this set. Additionally, molecular docking studies were carried out to investigate the activities of sulfa molecules against biological materials such as acetylcholinesterase (AChE) (PDB ID: 4EY7) and butyrylcholinesterase BChE (PDB ID: 4BDS)). As a result, the relationship between the biological activities and docking scores of the compounds was evaluated.