Efforts to reduce air pollution in developing countries may require increased use of biomass fuels. Even biomass fuels are a sustainable alternative to fossil fuels there is limited quantitative information concerning heavy metal content in their ashes. Therefore, this study focuses on the determination of the heavy metal concentrations in wood pellet ash obtained from the combustion of 10 pellet brans from Bosnia and Herzegovina and Italy, the effects of adding the ashes to soils, and the assessment of health risk assessment. Ash content was determined by gravimetric method. The amount and composition of ash remaining after combustion of wood pellets varies considerably according to the type of biomass and wood from which the pellet is made. Samples were prepared by wet digestion using HNO3, and heavy metals are determined by atomic absorption spectroscopy-flame and graphite furnace. The results showed that the lowest concentration in ashes was obtained for Co 0.01 mg kg−1 and the highest for Fe 571.63 mg kg−1. The Hazard Index (HI), calculated for non-cancerous substances for children was 2.23E−01, and the total Risk index was 4.54E−05. As for adults, HI was 1.51E−02, while the Risk index value was 3.21E−06. Human health risk calculated through HI and Risk index for children and adults associated with analyzed pellets is not of significant concern. The calculated enrichment factor and metal pollution index for wood pellet ashes indicate the risk of soil contamination with heavy metals. From this point of view, analyzed samples of ashes could be a serious contaminant of soil, so further monitoring is required.

Thymoquinone (TQ), a natural compound with antimicrobial and antitumor activity, was used as the starting molecule for the preparation of 3-aminothymoquinone (ATQ) from which ten novel benzoxazole derivatives were prepared and characterized by elemental analysis, IR spectroscopy, mass spectrometry and NMR (1H, 13C) spectroscopy in solution. The crystal structure of 4-methyl-2-phenyl-7-isopropyl-1,3-benzoxazole-5-ol (1a) has been determined by X-ray diffraction. All compounds were tested for their antibacterial, antifungal and antitumor activities. TQ and ATQ showed better antibacterial activity against tested Gram-positive and Gram-negative bacterial strains than benzoxazoles. ATQ had the most potent antifungal effect against Candida albicans, Saccharomyces cerevisiae and Aspergillus brasiliensis. Three benzoxazole derivatives and ATQ showed the highest antitumor activities. The most potent was 2-(4-fluorophenyl)-4-methyl-7-isopropyl-1,3-benzoxazole-5-ol (1f). Western blot analyses have shown that this compound inhibited phosphorylation of protein kinase B (Akt) and Insulin-like Growth Factor-1 Receptor (IGF1R β) in HeLa and HepG2 cells. The least toxic compound against normal fibroblast cells, which maintains similar antitumor activities as TQ, was 2-(4-chlorophenyl)-4-methyl-7-isopropyl-1,3-benzoxazole-5-ol (1e). Docking studies indicated that 1e and 1f have significant effects against selected receptors playing important roles in tumour survival.

In the present investigation, a series of coumarin-based compounds containing a chalcone moiety were studied for their in vitro and in silico properties. The DFT global chemical reactivity descriptors (chemical hardness, total energy, electronic chemical potential and electrophilicity) were calculated for four synthesized compounds and used to predict their relative stability and reactivity. The antibacterial activities of all compounds were screened against Bacillus subtilis (ATCC 6633) and Bacillus cereus (ATCC 11778). The quantum-chemical calculations indicated that the antibacterial activity correlates well with chemical reactivity descriptors of the molecules.

Twelve previously synthesized, biologically active 2,6,7-trihydroxyxanthen-3-one derivatives were evaluated in vitro for antiproliferative activity. Compounds were screened against HeLa, SW620, HepG2 and A549 tumor cell lines. Compound with the trifluormethyl group on C-4’ position of the phenyl ring showed the best inhibitory activity towards HeLa and A549 tumor cells with IC50 of 0.7 and 4.1 µmol L−1, resp. Compound with chlorine and fluorine substituents on aryl ring showed the best antiproliferative activity against SW620 with IC50 of 4.1 µmol L–1 and against HepG2 tumor cell line with IC50 of 4.2 µmol L–1. Analyses of cytotoxic and genotoxic potential of the trifluormethyl derivative were performed with cytokinesis-block micronucleus cytome assay in human lymphocyte culture and revealed no genotoxic and cytotoxic effects. The most potent compounds were subjected to molecular docking simulations in order to analyse bindings to molecular targets and, at the same time, further support the results of experimental cytotoxic tests. Docking studies showed sites of importance in forming hydrogen bonds of the most potent compounds with targets of interest.

For some synthesized coumarin derivatives, 1 H-and 13 C-NMR isotropic chemical shifts and some other molecular properties were calculated using the density functional theory. The calculations yielded reliable results that were in good correlation with experimental data. This is a good basis for collaboration between experimentalists and quantum chemists.