Ultrasound-promoted Cu/ZnO-graphene oxide catalyzed synthesis of spirooxindole-fused quinazolines and evaluation of their antioxidant and antibacterial activities

This paper presents a proper and potent method for the direct preparation of a series of structurally intriguing and pharmacologically relevant spirooxindole-fused quinazoline derivatives via a rapid sonochemical treatment in water at room temperature. Consequently, several factors, including ultrasonication strength and time spent, diverse solvents, and catalysts, were examined to get the best process conditions. This procedure is characterized by the utilization of efficient treatment with ultrasound as an alternate source of energy, water as an eco-friendly solvent, and Cu/ZnO-graphene oxide nanocomposite (Cu/ZnO-GO) as a heterogeneous reusable catalyst (for at least 4 times cycles), alongside its straightforward operation, brief reaction time (20 min), and high product yields (92–97%). Several obtained products were also studied for their antioxidant and antibacterial properties. This study indicates that, amongst the four test compounds, 4 h showed highest antioxidant activity with IC50 at 64.5 µg/mL, in comparison to those of the standard butylated hydroxytoluene (BHT) and 2-tertbutylhydroquinone (TBHQ) at 57.1 and 61.4 µg/mL respectively for the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging. The antibacterial activity test of the selected products was showed moderate to high inhibitory effects against both Gram-positive and Gram-negative bacteria.