ANTIPROLIFERATIVE ACTIVITY OF NEWLY SYNTHESIZED 3- AND 5- SUBSTITUTE RHODANINES ON TUMOR CELLS Introduction: Due to the increasing research of drugs and pharmaceutical products, rhodanines have been found as one of the most important compounds suitable for manipulation for the purpose of synthesizing derivatives with biological effects. Rhodanine derivatives show great effects primarily in antitumor activities, then in antidiabetic, antibacterial, antifungal, antimycobacterial and many other activities. Objectives: To determine the antiproliferative activity of rhodanine derivatives on three cell lines (HeLa, Caco-2, MRC-5). Materials and methods: The paper examined the effect of 3- ; of 5-substituted rhodanine derivatives that were synthesized at the Faculty of Food Technology in Osijek, and were prepared for analysis by dissolving in DMSO at a concentration of 0.01 mol/L. The final concentrations of the derivatives were 10-4 mol/L and 10-5 mol/L. After treating the cell lines with compounds and incubation for 72 hours in an incubator, antiproliferative effect was determined by the MTT test. Results: : 3- ; 5-substituted rhodanine derivatives showed an inhibitory effect on the growth of the tested cell lines. DR2 showed the greatest antiproliferative effect on cancer cells (HeLa and Caco-2 cell lines), with a partially smaller effect on normal fibroblast cells (MRC-5 cell line). At a lower concentration of 1x10-5 mol/L, the DR2 derivative did not show statistically significant inhibition. Conclusion: 3- ; 5-substituted rhodanine derivatives show an antiproliferative effect on cell lines. The antiproliferative effect depends on the applied concentration of the derivative and the type of cell line.