Oxidative stress is directly related to several diseases and symptoms, where antioxidant compounds, such as xanthenes, may become important in prevention and/or treatmant. Ten biologically active 9-aryl substituted 2, 6, 7-trihydroxyxanthen-3-one derivatives were synthesized using reliable one-pot synthesis and their structures were confirmed by IR, 1H and 13C NMR spectroscopy and mass spectrometry. Some of the synthesized compounds were scanned for their antioxidant potency using electrochemical method cyclic voltammetry of immobilized microparticles. Substitution of hydrogen at the phenyl ring of 2, 6, 7-trihydroxy-9-phenylxanthen-3-one with an electron-donating group affected the reducing power of the compounds by lowering the biological oxidation potential. These results signify the importance of xanthen-3-one derivatives as antioxidant agents and their further biological evaluation.

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

In the present investigation, a series of coumarin-based compounds containing a chalcone moiety were studied for their in vitro and in silico pro- perties. 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.

Coumarin-based compounds containing a chalcone moiety exhibit antimicrobial activity. These substances are potential drugs and it is important to determine their pKa values. However, they are almost insoluble in water. The dissociation constant was experimentally determined by potentiometric titration for 3-[3-(2-nitrophenyl)prop-2-enoyl]-2H-1-benzopyran-2-one because this compound shows good activity and solubility. A number of different computer programs for the calculation of the dissociation constant of chemical compounds have been developed. The pKa value of the target compound was calculated using three different computer programs, i.e., the ACD/pKa, CSpKaPredictor and ADME/ToxWEB programs, which are based on different theoretical approaches. The analysis demonstrated good agreement between the experimentally observed pKa value of 3-[3-(2-nitrophenyl)prop-2-enoyl]-2H-1-benzopyran- 2-one and the value calculated using the computer program CSpKa.