Can an N-donor motif make a difference? Synthesis, physicochemical characterization, and biological activity of selected derivatives of rhodanine-3-acetic acid.

The primary goal of this work was to check the effect of selected N-donor substituents on the physicochemical properties of rhodanine-3-acetic acid derivatives. Moreover, their application possibilities were assessed. All the studied rhodanine-3-acetic acid derivatives (B-1 - B-6) were obtained by Knoevenagel condensation, with high yields. Optical studies have shown that the presented compounds have one absorption band of the ICT transition nature between the N-donor substituent and rhodanine-3-acetic acid. The considered derivatives showed an emission maximum of 507-576 nm. Some of the tested compounds, B-1, B-3 and B-4, could stain all tested cell lines at relatively low levels of cytotoxicity. The B-3 compound was even able to achieve usable staining performance with concentrations as low as 1 μg/mL with no detectable cytotoxicity on any of the cell lines. Our results indicated also that some synthesized compounds B-1 to B-6 showed antimicrobial activity against reference bacteria and fungi belonging to Candida spp. Furthermore, all compounds were tested for their antitumor activity against MCF-7, MDA-MB-231, Caco-2, C32, SNB-19 and A549 cell lines. The best results were obtained for derivative B-3, particularly against MCF-7 breast adenocarcinoma cells.