Background: The hybrid compounds hold promise for developing novel pharmaceuticals, potentially exhibiting greater activity, mainly against viruses and cancer diseases, than their components.

Objective: In this study, researchers explored the potential synergistic effects of hybrid molecules by designing and synthesizing a series of isatin-gallate hybrids, denoted as N’-(5-substituted-2-oxoindolin-3-ylidene)-3,4,5-trihydroxybenzohydrazide (3a–d).

Methods: Isatin-gallate hybrids (3a–d) were synthesized by reacting gallic hydrazide with each of the isatin analogs (2a–d). The structures of all produced compounds were described using spectrum methods such as fourier transform infrared (FTIR), ¹H-nuclear magnetic resonance spectroscopy (1H-NMR), and physicochemical attributes. The evaluation of the tested hybrids (3a–d) involved assessing their in vitro antioxidant activities using the α, α-diphenyl-β-picrylhydrazyl (DPPH) free radical scavenging method and cytotoxic activities through the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] colorimetric assay for measuring cellular growth. Furthermore, in silico analysis was applied to the final hybrids to evaluate their effects as anticancer and anti-coronavirus agents.

Conclusion: Among the examined hybrid compounds, 3b demonstrated substantial in vitro antioxidant and cytotoxic activities. In silico analysis revealed slight variations in the anticancer activity of compounds 3a–d, with differing affinities observed across various cancer cell lines. Additionally, these compounds exhibited moderate efficacy in inhibiting coronavirus activity.