The essential oils of Centaurea pulcherrima Willd. var. pulcherrima (Asteraceae) were isolated by hydrodistillation (HD) and a microwave distillation (MD), than characterised by GC-FID and GC-MS. A total of 58 and 57 compounds were identified, constituting over 93.7%, and 91.6% of volatile oil composition of C. pulcherrima var. pulcherrima, respectively. Sesquiterpene hydrocarbons were shown to be the main group of constituents (HD: 42.4% versus MD: 51.5%). The major component of the oils of C. pulcherrima var. pulcherrima was germacrene D (HD, 17.8% versus MD, 23.2%). The antimicrobial activity of the isolated essential oils of the plant was also investigated, and they showed good antibacterial activity against to tested gram-positive bacteria, especially to M. smegmatis and a yeast-like fungus C. albicans.

Twenty-five new hydroxy-and methoxy-substituted 4,6-diarylpyrimidin-2(1H)-ol (20-34) and 4,6-diarylpyrimidine-2(1H)-thiol derivatives (35-44) were synthesized from the reaction of the corresponding 1,3-diaryl-2-propene-1one compounds (1-19) with urea or thiourea using the solid-phase microwave method. All the new synthetic compounds (20-44) were evaluated with regard to their α-glucosidase activity. However, only compounds 22-25, 27, 31, 34, 35, 37, and 40 exhibited a greater inhibitory effect than standard acarbose. The IC 50 values of the active compounds ranged between 2.36 and 13.34 µ M. The 25 new compounds were also screened for their in vitro pancreatic lipase activity and compounds 20-27 and 35-39 were found to be active. Of these compounds 26, 27, and 39 exhibited the best antilipase activities at concentrations of 0.40 ± 0.06, 0.26 ± 0.07, and 0.29 ± 0.026 µ M. All the new compounds (20-44) were evaluated for their in vitro antimicrobial activity for nine test microorganisms. Compounds 20-24 and 35-39 were determined to possess a significant broad spectrum against the gram-positive bacteria Escherichia faecalis, Staphylococcus aureus, and Bacillus cereus among the tested bacterial agents. Compounds 20-24 and 35-39 exhibit the best activity against Mycobacterium smegmatis, with minimum inhibitory concentrations of 62.5-500 µ g/mL, indicating their potential use as antituberculous agents.

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