In silico and in vitro studies of a number PILs as new antibacterials against MDR clinical isolate Acinetobacter baumannii

QSAR analysis of a set of previously synthesized phosphonium ionic liquids (PILs) tested against Gram‐negative multidrug‐resistant clinical isolate Acinetobacter baumannii was done using the Online Chemical Modeling Environment (OCHEM). To overcome the problem of overfitting due to descriptor selection, fivefold cross‐validation with variable selection in each step of the model development was applied. The predictive ability of the classification models was tested by cross‐validation, giving balanced accuracies (BA) of 76%–82%. The validation of the models using an external test set proved that the models can be used to predict the activity of newly designed compounds with a reasonable accuracy within the applicability domain (BA = 83%–89%). The models were applied to screen a virtual chemical library with expected activity of compounds against MDR Acinetobacter baumannii. The eighteen most promising compounds were identified, synthesized, and tested. Biological testing of compounds was performed using the disk diffusion method in Mueller‐Hinton agar. All tested molecules demonstrated high anti‐A. baumannii activity and different toxicity levels. The developed classification SAR models are freely available online at http://ochem.eu/article/113921 and could be used by scientists for design of new more effective antibiotics. Predictive classification QSAR models for antibacterials against A. baumannii were developed using the On‐line Chemical Database and Modeling Environment (http://ochem.eu) platform. The most promising 1,3‐oxazolylphosphonium derivatives with predicted activities were synthesized. All synthesized PILs were tested for antibacterial activity against MDR clinical isolate A. baumannii. The acute toxic effects of the investigated compounds on Daphnia magna were evaluated. All PILs showed high activity against MDR A. baumannii.