A new class of antimicrobial agents, 3-nitrocoumarins and related compounds, has been chosen as a subject of the present study. In order to explore their activity and molecular properties that determine their antimicrobial effects, QSAR models have been proposed. Most of the 64 descriptors used for the development were extracted from semiempirical and density functional theory (DFT) founded calculations. For this study literature data containing results of microbiological activity screening of 33 coumarin derivatives against selected clinical isolates of C. albicans (CA) and S. aureus (SA) have been selected. Multivariate predictive models based on random forests (RF) and two hybrid classification approaches, genetic algorithms (GA) associated with either support vector machines (SVM) or k nearest neighbor (kNN), have been used for establishment of QSARs. An applied feature selection approach enabled two-dimensional linear separation of active and inactive compounds, which was a necessary tool for rational candidate design and descriptor relevance interpretation. Candidate molecules were checked by cross-validated models, and selected derivatives have been synthesized. Their antimicrobial activities were compared to antimicrobial activities of the representative derivatives from the original set in terms of minimal inhibitory concentration (MIC) against chosen SA and CA ATCC strains. High ranking of descriptors consistent with the degree of hydrolytic instability of selected compounds is common to models of antimicrobial activity against both microorganisms. However, descriptor ranking indicates different antimicrobial mechanisms of action of chosen coumarin derivatives against selected microbial species.

This study encompassed 77 randomly assigned participants of both sexes and older than 65 of age. Every participant was questioned in his/her own house and completely familiarized with the methodology and the aims of the questionnaire. Out of 27 men, data on falls down were provided by 4 participants (14.81%): one of them lived alone while three of them lived in their families. Out of 50 women, data on falls down were provided by 17 (34%) participants: 9 of them lived in their families and 8 lived alone. Out of all living alone women 44% fell down twice or more during this study in comparison to 20% of living alone men. Regarding the values of the score of risk factors obtained throughout the questionnaire and the Berg balance scale, there are statistically significant differences between men and women (p < 0.005, i.e. p < 0.01), as well as participants that have never fallen down (p < 0.001, i.e. p < 0.01), while regarding the life style (living alone or in the family) there are no statistically significant differences (P > 0.05). Nowadays, the Berg balance scale is the most frequently used questionnaire that is, in total, significantly superior to other ever utilized tests. Average values of results obtained throughout the Berg balance scale in this study are statistically significantly higher in men and those participants who did not provide data on falls down, while regarding the life style there are no statistically significant differences.