HPTLC Bioautography-Guided Isolation of Isogeranic Acid as the Main Antibacterial Constituent of Artemisia santonicum Essential Oil

This study was performed to determine the main antibacterial com­po­unds of the essential oil of saltmarsh plant Artemisia santonicum (Asteraceae). The combination of HPTLC and direct bioautography was used for the activity guided isolation of isogeranic acid as the main antibacterial constituent with remarkable antimicrobial activity, although it was the minor component of the EO present only in 0.2 %, as calculated from GC/FID. Its structure was determined by 1D, 2D NMR and GC-MS techniques. Antibacterial activity of isogeranic acid against all tested bacteria was significantly higher than EO and even than both controls streptomycin and ampicillin. In further investigation of antibiofilm and antiquorum sensing activity EO exhibited the best inhibition of the biofilm formation at 1/8 MIC and isogeranic acid at 1/2 MIC. Both EO and isogeranic acid possessed pyocyanin inhibitory activity showing the reduction of pigment at 60.6 and 62.8 %, respectively, at 1/2 MIC concentrations.