Synthesis and characterization of a isothiouronium-calix[4]arene derivative: self-assembly and anticancer activity

Calix[<i>n</i>]arenes are polyphenolic macrocycles known for their remarkable synthetic versatility, which supports their broad application in various areas, including drug discovery. Their unique conformational features, functionality, and low toxicity make calixarene derivatives valuable drug candidates against cancer. The aim of the present study was the synthesis and characterization of a calix[4]arene derivative in which known anticancer isothiouronium groups were clustered on a calix[4]arene scaffold bearing long C12 alkyl chains at the lower rim. The resulting amphiphilic calix[4]arene derivative <b>3</b> spontaneously self-assembled into nanoscale aggregates in aqueous medium, as demonstrated by dynamic light scattering analysis. The cytotoxicity of compound <b>3</b> towards cancer cells was assessed using human renal carcinoma cells (786-O cells) and compared with that in non-malignant fibroblast cells (SW1 cells). Compound <b>3</b> showed a significantly greater antiproliferative effect on cancer cells (IC₅₀ 37.4 µM) than on normal fibroblasts (517 µM). The importance of the isothiouronium moieties in the observed cytoxic effect was confirmed by comparison with the calix[4]arene precursor (<b>1</b>) lacking these functional units. The selective antiproliferative profile of compound <b>3</b> highlights its potential as a lead anticancer agent. Moreover, compound <b>3</b> holds promise for further development in combination multidrug therapy due to the potential to load drug molecules in the bioactive nanoassembled structure.