Abstract
Thiourea derivatives display a broad spectrum of applications in chemistry, various industries, medicines and various other fields. Recently, different thiourea derivatives have been synthesized and explored for their anti-microbial properties. In this study, four carbonyl thiourea derivatives were synthesized and characterized, and then further tested for their anti-amoebic properties on two potential pathogenic species of Acanthamoeba, namely A. castellanii (CCAP 1501/2A) and A. polyphaga (CCAP 1501/3A). The results indicate that these newly-synthesized thiourea derivatives are active against both Acanthamoeba species. The IC50 values obtained were in the range of 2.39–8.77 µg·mL‑1 (9.47–30.46 µM) for A. castellanii and 3.74–9.30 µg·mL‑1 (14.84–31.91 µM) for A. polyphaga. Observations on the amoeba morphology indicated that the compounds caused the reduction of the amoeba size, shortening of their acanthopodia structures, and gave no distinct vacuolar and nuclear structures in the amoeba cells. Meanwhile, fluorescence microscopic observation using acridine orange and propidium iodide (AOPI) staining revealed that the synthesized compounds induced compromised-membrane in the amoeba cells. The results of this study proved that these new carbonyl thiourea derivatives, especially compounds M1 and M2 provide potent cytotoxic properties toward pathogenic Acanthamoeba to suggest that they can be developed as new anti-amoebic agents for the treatment of Acanthamoeba keratitis.
Highlights
IntroductionAcanthamoeba is one of the free-living amoebae that are widely distributed in the environment [1]
Acanthamoeba is one of the free-living amoebae that are widely distributed in the environment [1].This amoeba genus is among the most common protozoa to be found in soil and water samples [2].Acanthamoeba is known as the causative agent for a sight-threatening disease, Acanthamoeba keratitis
All compounds used in the present study have high anti-amoebic activity against Acanthamoeba with IC50 values in the range from 2.39 to 8.87 μg·mL−1 for A. castellanii, and 3.74 to 9.30 μg·mL−1 for A. polyphaga, which are equivalent to 9.47–30.46 μM and 14.84–31.91 μM respectively (Table 2)
Summary
Acanthamoeba is one of the free-living amoebae that are widely distributed in the environment [1]. Since synthetic organic compounds are being widely designed nowadays in parallel with the development of combinatorial chemistry and compound libraries, they could be exploited for the development of new drugs Some synthetic compounds such as quinoxaline derivatives and thiosemicarbazone analogs were investigated on the cells of Entamoeba histolytica and found to display beneficial properties which can be developed as anti-amoebic agents [11,12]. Thiourea, which is one of the earliest synthetic organic compounds, has been globally used directly and indirectly due to its ready availability This factor has attracted researchers to evaluate thiourea-based compounds from their safety point of view [13] and potential medical properties [14,15,16]. In the present study, four new carbonyl thiourea derivatives were synthesized and characterized, and could possibly be developed as new agent to treat Acanthamoeba keratitis after their anti-amoebic properties were examined. Microscopic observation was carried out to examine the morphological alterations in the amoeba cells caused by these newly-synthesized compounds
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