synthesis and characterization of novel indole-linked 1,3,4-oxadiazoles: evaluation of anticancer, antibacterial, and antioxidant activities

This research describes the synthesis of a new series of indole-linked 1,3,4-oxadiazoles (iloxs), created through a multi-step reaction involving indole-carbohydrazides and heterocyclic aromatic aldehydes. the resulting indole-containing hydrazide-hydrazones were heated in dmso at 100 °c, with molecular iodine and potassium carbonate serving as catalysts, which facilitated the formation of the corresponding iloxs. the structure of the synthesized iloxs was characterized using ftir, ¹h-nmr, and ¹³c-nmr spectroscopy. the cytotoxic effects of the iloxs 6a-f were tested in vitro against the mda mb-231 breast cancer cell line. notably, compound 6f, which contains 5-bromo-1h-indole, thiazole, and oxadiazole groups, showed the lowest ic50 value of 2.82±0.33 μm, outperforming the other derivatives (6a-e). furthermore, the antibacterial and antioxidant properties of all synthesized iloxs were evaluated against staphylococcus aureus (s. aureus) and escherichia coli (e. coli) using the mic method, along with the assessment of radical scavenging activity through the dpph assay. compound 6f exhibited the highest antioxidant capacity (92%, ic50= 10.97±0.47 μm), surpassing ascorbic acid (85%, ic50= 13.65±0.39 μm). while compound 6c showed the most notable activity against s. aureus (mic=0.312 mm), compound 6f was the most effective against e. coli (mic=0.625 mm). this study provides a foundation for future research into the synthesis of more complex structures with enhanced biological activities within the field of heterocyclic chemistry.