Synthesis, in vitro thymidine phosphorylase inhibitory activity and molecular docking study of novel pyridine-derived bis-oxadiazole bearing bis-schiff base derivatives

Abstract

The current study has afforded twelve analogs (4a-l) of pyridine-derived bis-oxadiazole containing bis-schiff base and subsequently evaluated for their potential to inhibit thymidine phosphorylase(in vitro). All the synthesized analogs were structurally elucidated using various spectroscopic tools including NMR and HREIMS. All synthesized scaffolds showed varied range of inhibitory potential with IC50values ranging from 5.19 ± 1.10 to 36.18 ± 4.60 μM in comparison to 7-deazaxanthine (IC50 = 30.28 ± 2.10 μM) as a standard drug. All analogs (except analog 4 l which displayed less potency than standard drug) showed improved potency having IC50 values of 19.73 ± 2.30, 16.14 ± 1.20, 18.93 ± 1.60, 22.78 ± 1.80, 30.47 ± 3.70, 5.19 ± 1.10, 23.13 ± 1.90, 21.56 ± 2.50, 4.88 ± 1.10, 26.63 ± 2.90 and 6.67 ± 1.10 respectively.Results obatined were compared to standard 7-deazxanthine drug with IC50 values of 30.28 ± 2.10 μM. Structure-activity relationship (SAR) studies revealed that analogs bearing –NO2, -CF3, –OH and –Cl moieties at various position of aryl part showed many folds more potency than standard 7-deazaxathine standard drug. In order to determine the potential mode of interactions with thymidine phosphorylase active sites, the most active analogs 4f (bearing 3-CF3& 5-NO2), 4i (bearing 3-OH & 5-NO2), and 4 k (bearing 2-OH &5-NO2) were further subjected to molecular docking study. The results confirmed that these active analogs adopted numerous important interactions including hyrognen bonding, pi-donor hydrogen bond, pi-pi T shaped, pi-pi stacking, pi-alkyl, pi-anion, pi-sigma, halogen (flourine) and numerous Vander Waals interactions with the amino acid of enzyme being targeted.