TLC-direct bioautography as a method for evaluation of antibacterial properties of Thymus vulgaris L. and Salvia officinalis L. essential oils of different origin.

The dot-blot bioautography was used to evaluate the antibacterial properties of Thymus vulgaris L. and Salvia officinalis L. essential oils (EOs)produced by three different manufacturers. The whole samples were applied at three concentrations on thin-layer chromatography (TLC)plates which were then subjected to bioautography against Bacillus subtilis. The samples of the highest activity were found. Then, they were separated using TLC and once again subjected to bioautography against B. subtilis. As was proved, only the essential oils of T. vulgaris L. possessed strong antibacterial properties for which mostly thymol and carvacrol were responsible. Their contents were calculated using TLC-UV densitometry. The highest contents were found in the essential oils of the highest antibacterial activity revealed in the dot-blot test. It means that a dot-blot test can be used for simple and fast evaluation of antibacterial properties of essential oils.