In vitro enzymatic evaluation of some pyrazolo[1,5‐ a]pyrimidine derivatives: Design, synthesis, antioxidant, anti‐diabetic, anti‐Alzheimer, and anti‐arthritic activities with molecular modeling simulation

Abstract

The strategy of utilizing nitrogen compounds in various biological applications has recently emerged as a powerful approach to exploring novel classes of therapeutics to face the challenge of diseases. A series of pyrazolo[1,5‐ a]pyrimidine‐based compounds 3a–l and 5a–f were prepared by the direct cyclo‐condensation reaction of 5‐amino‐1 H‐pyrazoles 1a, b with 2‐(arylidene)malononitriles and 3‐(dimethylamino)‐1‐aryl‐prop‐2‐en‐1‐ones, respectively. The structures of the new pyrazolo[1,5‐ a]pyrimidine compounds were confirmed via spectroscopic techniques. The in vitro biological activities of all pyrazolo[1,5‐ a]pyrimidines 3a–l and 5a–f were evaluated by assaying total antioxidant capacity, iron‐reducing power, the scavenging activity against 1‐diphenyl‐2‐picryl‐hydrazyl (DPPH) and 2, 2'‐azinobis‐(3‐ethylbenzothiazoline‐6‐sulfonic acid) (ABTS) radicals, anti‐diabetic, anti‐Alzheimer, and anti‐arthritic biological activities. All compounds displayed good to potent bioactivity, and three compounds 3g, 3h, and 3l displayed the most active derivatives. Among these derivatives, compound 3l exhibited the highest antioxidant (total antioxidant capacity [TAC] = 83.09 mg gallic acid/g; iron‐reducing power [IRP] = 47.93 µg/ml) and free radicals scavenging activities with (DPPH = 18.77 µg/ml; ABTS = 40.44%) compared with ascorbic acid (DPPH = 4.28 µg/ml; ABTS = 38.84%). Furthermore, compound 3l demonstrated the strongest inhibition of α‐amylase with a percent inhibition of 72.91 ± 0.14 compared to acarbose = 67.92 ± 0.09%. Similarly, it displayed acetylcholinesterase inhibition of 62.80 ± 0.06%. However, compound 3i showed a significantly higher inhibition percentage for protein denaturation and proteinase at 20.66 ± 0.00 and 26.42 ± 0.06%, respectively. Additionally, some in silico ADMET properties were predicted and studied. Finally, molecular docking simulation was performed inside the active site of α‐amylase and acetylcholinesterase to study their interactions.