Synthesis, crystal structures, Hirshfeld surface analysis and spectroscopic studies of two Schiff bases of anisaldehyde and their urease and acetylcholinesterase inhibitory and antioxidant properties.

The growing demand of pharmaceutical industry for more effective drugs requires new molecules with promising medicinal activities. In the present work, a natural product anisaldehyde was treated with hydrazine and 3,5-dichloroaniline to synthesize their Schiff bases, ASB1 and ASB2, which were assessed for various bioactivities. ASB1 was synthesized by conventional reflux method while ASB2 was synthesized by reflux as well as by mechanochemical grinding method which gave higher yield. The bases were recrystalised, and their structures were elucidated based on XRD and spectroscopic studies. Hirshfeld surface analysis was also carried out. They showed considerable urease inhibitory activity, almost comparable with the standard thiourea. The activity of ASB1 was much higher than ASB2. Acetylcholinesterase inhibitory activity of ASB1 was also higher than that of ASB2. The antioxidant activities were determined using DPPH, ABTS radical scavenging and total antioxidant capacity (TAC) assays. The bases were very poor scavengers of DPPH radical. However, they showed considerable anti-radical activity against ABTS radical, ASB2 being more active than ASB1, while ASB1 showed higher TAC than ASB2. In conclusion, the bases appeared to have good drugability as inhibitors of urease and acetylcholinesterase enzymes. They can be easily synthesized for possible large-scale applications. The grinding method proved to be more efficient than the reflux method.