Research Article DFT Study and Antiparasitic Activity of Some Azo Dyes Containing Uracil NevinS¨ uleymano˘ glu , 1 Pınar Kubas ¸ık , 2 andS ¸ahin Direkel 3 1 Vocational School of Technical Sciences, Gazi University, 06374 Ostim, Ankara, Turkey 2 Graduate School of Natural and Applied Sciences, Advanced Technologies, Gazi University, 06500 Ankara, Turkey 3 Department of Medical Microbiology, Faculty of Medicine, Giresun University, 28100 Giresun, Turkey Correspondence should be addressed to Nevin S¨ uleymano˘ glu; nevinseylan@gmail.com Received 12 April 2021; Accepted 27 July 2021; Published 4 August 2021 Academic Editor: Takayuki Ebata Copyright © 2021 Nevin S¨ uleymano˘ glu et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this study, for the first time, molecular modeling and antiparasitic activity studies were carried out on some azo dyes containing uracil, 6-amino-5-[(4-nitrophenyl) diazenyl] pyrimidine-2,4 (1H, 3H)-dione (dye I) and 6-amino-5-[(4-bromophenyl) diazenyl] pyrimidin-2,4 (1H, 3H)-dione (dye II), which were resynthesized using the same method in the literature and whose molecular structures were confirmed using FTIR and 1 H-NMR methods. In molecular modeling study, all calculations were performed using DFT/B3LYP/6-311++G(d,p) method. e molecular structures of the possible tautomeric forms of dyes I and II were optimized, and their molecular total energies were calculated in the gas phase and DMSO solvent. IR and 1 H-NMR spectral data of the possible tautomeric forms of dyes were obtained, and theoretical spectral data were compared with experimental ones. e evaluations show that, for both dyes, the spectral data of the imine-diketo-hydrazone form, which has the lowest energy and is hence determined to be the most stable form, are in agreement with the experimental ones. In antiparasitic activity study, dyes I and II were tested for the first time against parasites Leishmania infantum, Leishmania major, Leishmania tropica promastigotes, and Trichomonas vaginalis trophozoites. In vitro antileishmanial activities against Leishmania promastigotes were tested by microdilution broth assay with Alamar Blue in RPMI 1640 medium, and in vitro trichomonacidal activities against Trichomonas vaginalis parasite were tested using TYM medium. In tests, antileishmanial and trichomonacidal effects were determined by comparing the obtained minimum inhibitory concentration (MIC) and minimum lethal concentration (MLC) values with those obtained for standard drugs (amphotericin B and metronidazole, respectively). 1.Introduction Azo dyes are important colorants with chromosome azo group (-N�N-). Due to their special chemical and biological properties, they have potential applications in medicine and pharmacology, such as antibacterial, antifungal, antitumor, and antioxidant activities [1–3]. In addition, they are easy to use and offer strong colors in textile applications as well as being relatively inexpensive. With these aspects, azo dyes attracted considerable attention in scientific studies [4, 5]. Uracil derivatives belonging to the pyrimidines group, which have an important role in the binding of ribosomes and phosphate in the synthesis of enzymes required in basic biological processes, show important pharmacological activities [6, 7]. Studies on synthetic pyrimidines reveal the presence of remarkable biological and pharmacological properties [8]. erefore, uracil derivatives are used in drugs with antitumor, antibacterial, and antiviral properties [7]. Leishmaniasis is a disease caused by Leishmania para- sites and transmitted by the bites of some sandflies, which differs clinically and epidemiologically, and is an important health problem worldwide [9, 10]. Visceral leishmaniasis (VL, Kala-Azar), cutaneous leishmaniasis (CL, Oriental Boil), and mucocutaneous leishmaniasis (MCL) are three different clinical forms of leishmaniasis [11]. In the Medi- terranean basin, types of Leishmania causing leishmaniasis are as follows: generally Leishmania infantum (L. infantum) for VL and Leishmania major (L. major) and Leishmania Hindawi Journal of Chemistry Volume 2021, Article ID 6714151, 11 pages https://doi.org/10.1155/2021/6714151