U okviru ove disertacije opisani su sinteza, strukturna karakterizacija i rezultati ispitivanja antioksidativne i citotoksične aktivnosti novih derivata 1,3,4-tiadiazola koji u svojoj strukturi sadrže fenolne hidroksilne grupe. U cilju određivanja mehanizma antitumorskog delovanja, za odabrana jedinjenja izvršena su dodatna ispitivanja poput analize raspodele faza ćelijskog ciklusa, ispitivanja uticaja na stvaranje ROS-a u malignim ćelijama usled dejstva vodonik-peroksida, morfološke analize tipa ćelijske smrti, određivanja ciljnih kaspaza, analize ekspresije gena, kao i ispitivanja interakcija sa DNK. Sintetizovane su tri serije jedinjenja koje ukupno sadrže 44 amidna derivata 1,3,4-tiadiazola, polazeći od fenolnih kiselina. Prve dve serije amida sintetizovane su kuplovanjem 5-supstituisanih-2-amino-1,3,4-tiadiazola izvedenih iz fenolnih kiselina sa različitim hloridima kiselina, koji su u slučaju serije B u svojoj strukturi sadržali i halkonsku jedinicu. Treća serija amidnih derivata dobijena je reakcijom hlorida fenolne kiseline sa supstituisanim 2-amino-1,3,4- tiadiazolima. Sva novosintetizovana jedinjenja strukturno su okarakterisana primenom NMR i IR spektroskopskih metoda. Antioksidativna aktivnost svih sintetizovanih 1,3,4-tiadiazolskih derivata ispitana je primenom DPPH metode, a dobijeni rezultati upoređeni su sa poznatim antioksidantima, askorbinskom i/ili nordihidrogvajaretinskom kiselinom. Jedinjenja sve tri serije pokazala su umerenu do dobru aktivnost neutralisanja DPPH radikala. Antioksidativni kapacitet sintetizovanih jedinjenja može se objasniti mogućnošću stabilizacije radikala, formiranog nakon apstrakcije vodonikovog atoma DPPH radikalom, delokalizacijom nesparenog elektrona preko 1,3,4- tiadiazolskog prstena. Ispitana je i aktivnost neutralisanja ABTS radikal-katjona amidnih derivata serije V, a dobijeni rezultati su pokazali da sintetizovana jedinjenja, pored kapaciteta za neutralizaciju DPPH radikala, imaju bolju sposobnost neutralisanja ABTS radikal-katjona u odnosu na askorbinsku kiselinu, NDGA i polaznu 3,4-dihidroksibenzojevu kiselinu. Within this study, the synthesis, structural characterization, and evaluation of the antioxidant and cytotoxic activities of novel 1,3,4-thiadiazole derivatives containing phenolic hydroxyl groups in their structure were described. In order to elucidate the mechanism of the antitumor activity, additional tests were performed for the selected compounds, such as cell cycle phase distribution analysis, investigation of their influence on ROS generation in malignant cells due to the action of hydrogen peroxide, cell death type morphology analysis, target caspase determination, gene expression analysis, and DNA interaction assays. Three series containing a total of 44 1,3,4-thiadiazole amide derivatives were synthesized starting from phenolic acids. The first two series of amides were synthesized by coupling 5-substituted-2-amino-1,3,4-thiadiazoles derived from phenolic acids with different acid chlorides, which in the case of series Б contained a chalcone unit in their structure. The third series of amide derivatives was obtained by the reaction of the phenolic acid chloride with substituted 2-amino-1,3,4-thiadiazoles. All newly synthesized compounds were structurally characterized using NMR and IR spectroscopic methods. The antioxidant activity of all synthesized 1,3,4-thiadiazole derivatives was examined using the DPPH method, and the obtained results were compared with well-known antioxidants, ascorbic and/or nordihydroguaiaretic acid. Compounds of all three series showed moderate to good DPPH radical scavenging activity. The antioxidant capacity of the synthesized compounds can be explained by the possibility of stabilizing the radical formed after abstraction of the hydrogen atom by the DPPH radical, via delocalization of the unpaired electron across the 1,3,4-thiadiazole ring. ABTS radical cation scavenging activity of amide derivatives of series В was also investigated and the obtained results showed that the synthesized compounds, in addition to the DPPH radical scavenging capacity, have a better ABTS radical cation scavenging ability compared to ascorbic acid, NDGA and starting 3,4-dihydroxybenzoic acid.