*Article* **Anti-Cancer and Electrochemical Properties of Thiogenistein—New Biologically Active Compound**

**Elzbieta U. Stolarczyk ˙ 1,\* , Weronika Strzempek 2,3 , Marta Łaszcz <sup>1</sup> , Andrzej Le´s <sup>4</sup> , Elzbieta Menaszek ˙ 3 , Katarzyna Sidoryk <sup>5</sup> and Krzysztof Stolarczyk <sup>4</sup>**

	- weronika.strzempek@doctoral.uj.edu.pl

**Abstract:** Pharmacological and nutraceutical effects of isoflavones, which include genistein (GE), are attributed to their antioxidant activity protecting cells against carcinogenesis. The knowledge of the oxidation mechanisms of an active substance is crucial to determine its pharmacological properties. The aim of the present work was to explain complex oxidation processes that have been simulated during voltammetric experiments for our new thiolated genistein analog (TGE) that formed the self-assembled monolayer (SAM) on the gold electrode. The thiol linker assured a strong interaction of sulfur nucleophiles with the gold surface. The research comprised of the study of TGE oxidative properties, IR-ATR, and MALDI-TOF measurements of SAM before and after electrochemical oxidation. TGE has been shown to be electrochemically active. It undergoes one irreversible oxidation reaction and one quasi-reversible oxidation reaction in PBS buffer at pH 7.4. The oxidation of TGE results in electroactive products composed likely from TGE conjugates (e.g., trimers) as part of polymer. The electroactive centers of TGE and its oxidation mechanism were discussed using IR supported by quantum chemical and molecular mechanics calculations. Preliminary in-vitro studies indicate that TGE exhibits higher cytotoxic activity towards DU145 human prostate cancer cells and is safer for normal prostate epithelial cells (PNT2) than genistein itself.

**Keywords:** anticancer drugs; nanoparticles; molecular modeling; oxidation mechanisms; electrochemistry; MALDI; spectroscopic data; cytotoxic study; self-assembled monolayer; gold electrode
