Microwave-Assisted Synthesis and Characterization of Flavone–Thiazole–Aryl Hybrids with Potential Anticancer and Antiparasitic Activity

Flavone–thiazole–aryl hybrid molecules based on 6-aminoflavone and 5-arylidene-4-aminothiazol-2(5H)-ones were synthesized and subjected to physicochemical and biological studies. Microwave-assisted synthesis was performed in two steps. First, an aminolysis reaction of isorhodanine with 6-aminoflavone was carried out to achieve the corresponding hybrid flavone-thiazole 3, which was later subjected to a Knoevenagel condensation with selected aromatic aldehydes, yielding 5-arylidene derivatives 5a–5i. The resulting hybrids were purified and characterized by UV–Vis, NMR, and HR-MS (ESI). In the UV–Vis spectra of all compounds, two characteristic bands were noted. The UV–Vis spectra in DMF of the studied flavone–thiazole–aryl hybrids consist of two major bands with maxima appearing at 280–288 nm, corresponding to band II and 383–399 nm, corresponding to band I, which clearly distinguish them from the large group of modified flavonoids. Among the compounds tested on human bladder cancer 5637 cells, (5Z)-5-[(4-hydroxyphenyl)methylene]-4-[(4-oxo-2-phenyl-chromen-6-yl)amino]thiazol-2-one (5b) exhibited interesting micromolar activity (IC50 2.37 µM). In addition, four of the tested compounds (3, 5f, 5d, and 5b) presented noteworthy antiplasmodial activity against P. falciparum in the low micromolar range (IC50 1.90–4.90 µM). The obtained group of flavone–thiazole–aryl hybrid molecules constitutes valuable starting points for further structural optimisation, which could usher in future novel active pharmaceutical ingredients and pave the way for novel therapeutic strategies.