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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.

A simple environmentally friendly solid-phase microwave-assisted method was used to synthesis of the 1,3 0 -diazaflavanone (2) and 1,3 0 -diazaflavone (3) from the cyclization of 2 0 -amino (E)-3 00 -azachalcone (1). Ten new N-alkyl (C 5-12,14,15 )-substituted 1,3 0 -diazaflavanonium bromides (2a-j) were prepared from compound 2 with corresponding alkyl halides in acetonitrile under reflux. In addition, nine new N,N 0 -dialkyl (C 5-12,14 )-substituted 1,3 0 -diazaflavonium bromides (3a-i) were also synthesized from compound 3 with corresponding alkyl halides using basic silica in acetonitrile. The antimicrobial activities of compounds 1-3, 2a-j, and 3a-i were tested against Gram-positive (Gþ) (Bacillus subtilis, Staphylococcus epidermidis, Staphylococcus aureus, and Enterococcus faecalis) and Gram-negative (GÀ) (Escherichia coli, Klebsiella pneumonia, Pseudomonas aeruginosa, Proteus vulgaris, Salmonella typhimirium, Yersinia pseudotuberculosis, and Enterobacter cloaceae) microorganisms. They showed good antimicrobial activity against the Gram-positive bacteria tested with the minimal inhibitory concentration values less than 7.8 lg/mL in most cases. The optimum length of the alkyl chain for better and broader activity is situated in the range of 9-12 carbon atoms in the series of compounds 2a-j and five to six carbon atoms in the series of compounds 3a-i. The nonalkylated compounds 1-3 were not effective, as were the ones alkylated with five or six C alkyl groups (2a and 2b) and 8-13 C alkyl groups for N,N 0 -dialkyl compounds (3c-3i). The antimicrobial activity increased as the length of the alkyl substitution increased from 8 to 12 carbons in compounds 2a-j. However, antimicrobial activity decreased as the length of the alkyl substitution increased from 7 to 13 carbons in compounds 3c-i.

The volatile constituents of the essential oils from the flower, leaf, and stem of Verbascum wiedemannianum were analysed by GC and GC-MS. A total of forty-three compounds were identified, constituting over 99.1%, 94.3%, and 98.7% of oil composition of the flower, leaf, and stem of V. wiedemannianum, respectively. Hydrocarbons were shown to be the main group of constituents of the flower and stem part in the ratio of 83.3% and 32.1%, respectively. But, the major group in the leaf oil was found to be aldehydes (46.8%). The main components of the flower, leaf and stem oils of V. wiedemannianum were pentadecane (58.2%), (2E)-hexenal (33.2%), and hexadecanoic acid (24.6%), respectively.

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