Antibacterial compounds of Cymbopogon nardus essential oil exposed by high-performance thin-layer chromatography–direct bioautography

Essential oil of citronella grass (Cymbopogon nardus) was screened for antibacterial compounds by high-performance thin-layer chromatography (HPTLC) combined with direct bioautography using soil bacterium Bacillus subtilis, marine bacterium Aliivibrio fischeri, and plant pathogens Pseudomonas syringae pv. maculicola and Xanthomonas euvesicatoria. The parallel derivatization using HPTLC–anisaldehyde reagent also revealed the bioactive compounds separated with n-hexane–isopropyl acetate (9:1, v/v), which were analyzed by offline solid-phase microextraction–gas chromatography–electron ionization-MS (SPME–GC–EI-MS) after scraping off and elution. The compounds responsible for the antibacterial effect were identified as citronellal, geranial, neral, geraniol, α-cadinol, and elemol. These compounds inhibited all studied bacterial strains except elemol that demonstrated activity only against B. subtilis and X. euvesicatoria.