Synthesis, Characterization and Evaluation of Novel Isatin–Apigenin Derivatives as Anticancer Drugs

Abstract

The present research focuses on the design, synthesis, structural characterization, and preliminary biological evaluation of a novel series of Isatin–Apigenin hybrid derivatives (4a–4f) developed as potential anticancer agents. The synthetic pathway involved a two-step methodology. In the first step, Apigenin was activated through chloroacetylation using chloroacetyl chloride under basic conditions to introduce a reactive chloroacetyl linker. In the second step, nucleophilic substitution between the activated Apigenin intermediate and a series of substituted isatin derivatives (5-chloro, 5-fluoro, 5-bromo, 7-nitro, etc.) yielded the final hybrid molecules. Reaction progress was monitored by TLC, and products were purified using recrystallization or silica gel column chromatography.

Comprehensive structural confirmation was achieved through FTIR, 1H NMR, 13C NMR, Mass Spectrometry, and Elemental Analysis. FTIR spectra verified the presence of phenolic O–H, flavone C=O, and isatin C=O functional groups. NMR spectra confirmed the incorporation of the –CH₂CO– linker and appropriate aromatic proton arrangements, while mass spectrometry validated the expected molecular ion peaks.

Cytotoxicity evaluation using the MTT assay against MCF-7, A549, and HeLa cell lines revealed encouraging biological activity. Among the synthesized analogues, compound 4c exhibited the highest anticancer potency with significantly lower IC₅₀ values, outperforming parent Apigenin and approaching the activity of the standard drug Doxorubicin. The key findings indicate that conjugating Apigenin with electron-withdrawing-substituted isatin derivatives greatly enhances anticancer efficacy, establishing compound 4c as a promising lead for further mechanistic, ADMET, and in vivo studies.