Screening and Characterization of Antimicrobial Components of Natural Products Using Planar Chromatography Coupled with Direct Bioautography, Spectroscopy and Mass Spectrometry: A Review

Objective & Background: In this review, we summarize the principle and applicability of hyphenations of planar chromatography in natural product research. Direct bioautography, the combination of planar chromatography with antimicrobial assay, is suitable for rapid, high-throughput screening of plant extracts, and can be used as a bio-monitoring system in effect-directed processes. It permits testing of separated, individual matrix components against various bacterial or fungal species. Discussion: The bioautogram (developed adsorbent layer immersed into a cell suspension) can be visualized using vital dyes or by detecting the emitted light of luminescent cells. Further characterization of active compounds, selected according to the bioautogram, can be carried out in or ex situ by spectroscopic (e.g., FTIR, FT-Raman, SERS, NMR) and/or spectrometric (MS with various ionization techniques) techniques. In the last decade, intense innovation work on planar chromatography-mass spectrometry implemented a rapid characterization of separated components by the use of a manually operated, pneumatically driven TLC-MS interface comprising an elution head or by techniques with one-step desorption and ionization that can be carried out with spray, laser or excited gas beam. The advantages of overpressured layer chromatography (OPLC) in these approaches are also demonstrated.