Biological Activity and Structure–Activity Relationship of Mono- and Bis-Derivatives of 3-(Arylamino)propanehydrazides

A series of N’-(4-nitrobenzylidene)propanehydrazides and corresponding bishydrazones, as well as N-(1,3-dioxoisoindolin-2-yl)propanamides and corresponding bis(propanamides), were synthesised. Antioxidant properties were assessed using reducing power, FRAP, DPPH, ABTS radical scavenging, and NBT inhibition assays. Among the tested compounds, phenylaminopropanamide 17 demonstrated the highest activity, showing 1.70-fold higher reducing power and 6.71-fold higher DPPH radical scavenging activity compared to melatonin. Phenylaminopropanehydrazide 9 exhibited the highest activity in the FRAP assay (1.48 times higher than melatonin), while ethoxyphenyl-based bis(propanamide) 24 showed the greatest NBT inhibition (1.58-fold relative to melatonin). Four compounds exhibited moderate antibacterial activity against both Gram-positive and Gram-negative bacteria.