Design and synthesis of novel 3,7-dihydro-1H-purine-2,6-diones as DPP-4 inhibitors: An in silico, in vitro and in vivo approach

The inhibition of enzyme DPP-4 is pivotal for targeting type 2 diabetes mellitus (DM). The study introduces two series of novel 1,3-dimethyl-3,7-dihydro-1H-purine-2,6-diones derivatives (PB01-PB10) and 3,7-dihydro-1H- purine-2,6-diones compounds (PB11-PB16) were developed using linagliptin scaffold. Sixteen derivatives were synthesized and screened in vitro against DPP-4, revealing IC50 ranging from 15.66 f 2.546 to 28.45 f 4.441 nM. Compounds PB01 and PB11 demonstrated high potency comparable to reference standard linagliptin (IC50 = 15.66 f 2.546, 16.16 f 1.214, 15.37 f 2.481 nM, respectively). Further studies showed that the compound possesses negligible cytotoxicity up to 100 mu M concentration. A high glucose-induced DPP-4 upregulation model was further utilized to assess the protective effect of PB01 and PB11, and their efficacy was compared with linagliptin. PB01 and PB11 showed comparable protective effects against high glucose-induced ROS generation and mitochondrial superoxide production, and the compounds also effectively reduced the DPP-4 cellular expression. The in vivo anti-diabetic efficacy, effect on change in body weight, and OGTT due to PB01 and PB11 treatments were evaluated using the STZ-Nicotinamide-induced experimental model of diabetes in mice. Post induction of diabetes, the periodic estimation of blood serum glucose levels reveals that treatment with PB01 and PB11 decreased the high blood serum glucose levels in both acute and chronic studies. The expressions of DPP-4 were observed by IHC, Flowcytometry, and RT-qPCR. The docked complexes of both compounds, along with the standard drug linagliptin, were subjected to molecular dynamics simulation for 140ns to evaluate the complexes' stability and binding affinity.