Fluoroquinolones are a relatively new group of synthetic antibiotics (chemotherapeutics) widely used both in human and animal treatment. Because veterinary enrofloxacin and its main metabolite ciprofloxacin, a widely used human antibiotic, can be present as residues in milk, there is a need for methods for their separation and determination. Matrix solid-phase dispersion (MSPD) on a siliceous sorbent was used for isolation and concentration of enrofloxacin and ciprofloxacin residues from cows’ milk. This preseparation method was combined with high-performance liquid chromatography and with thin-layer chromatography-direct bioautography. Mean recoveries were calculated for different levels of the antibiotics in milk. The results revealed that thin-layer chromatography-direct bioautography can be used for the screening of enrofloxacin and ciprofloxacin at the maximum residue level stipulated for milk by the European Union.
Thin-layer chromatography combined with bioautography (TLC-B) is a screening technique which combines TLC with microbiological detection and results in enhanced sensitivity. In the work discussed in this paper TLC-B was used to detect two veterinary antibiotics, doxycycline and flumequine, in milk. The sensitivity of bioautography was compared with that of UV detection. All procedures, i.e. clean-up, concentration, separation, and detection, were performed on the same TLC plate.
The main volatile compounds from three medicinal plants belonging to Lamiaceae family were screened for their biological properties. The plants were Salvia officinalis, Thymus vulgaris, and Mentha × piperita containing as the main volatile constituents thujone, thymol, and menthol, respectively. The applied chromatographic system was silica gel developed with toluene-ethyl acetate (93:7). Thin-layer chromatography — direct bioautography (TLC-DB) against Escherichia coli and Bacillus subtilis was used for detection of antibacterial activity of the plant extracts and essential oils. The bioautographic fingerprints were compared with the fingerprints obtained after derivatization with anisaldehyde.
Coffee, due to its common consumption, is one of the main sources of polyphenols in human diet. Coffee species and coffee-related products differ in composition and content of main components, such as chlorogenic acid and caffeine. Chemical and biological fingerprints of various Coffea arabica L. extracts were obtained in order to check and compare their antibacterial and antioxidant properties. The antibacterial activity of green and roasted coffee seeds and pomace was evaluated against Bacillus subtilis using thin-layer chromatography (TLC)-direct bioautography. TLC-2,2-diphenyl-1-picrylhydrazyl (DPPH) test was used to determine antioxidant properties of the afore-mentioned extracts. Furthermore, different solvents and several extraction methods such as simple maceration, maceration under stirring, and ultrasonic accelerated extraction were tested. The most efficient method of extraction of caffeine and chlorogenic acid was chosen based on quantitative TLC analysis. Additionally, these two main components of coffee were quantitatively determined in commercial products of green coffee.
In this study, thin-layer chromatography—direct bioautography (TLC—DB) was used for guiding the isolation and identification of antibacterial constituents of Thymus vulgaris L. ethanol extract. This TLC—bioassay method enables the separation and detection of active components directly on the surface of chromatographic plates. They can be identified by comparison with reference substances or using physicochemical methods, preferably spectroscopic ones (liquid chromatography—tandem mass spectrometry [LC—MS/MS], in the presented paper). The described method belongs to the effect-directed analyses (EDA). Seven bacterial strains were used as test organisms, both pathogenic and nonpathogenic, including methicillin-resistant Staphylococcus aureus as well as luminescent bacteria like Aliivibrio fischeri. Five fractions with the widest antimicrobial spectra were detected using TLC—DB, isolated by semi-preparative TLC and subjected to LC—MS/MS analyses. Finally, two bioactive components were tentatively identified, basing on their fragmentation pattern, as eriodictyol and 4,4′-dihydroxy-5,5′-diisopropyl-2,2′-dimethyl-3,6-bifenylodion.
Thin-layer chromatography—direct bioautography (TLC—DB) followed by liquid chromatography—tandem mass spectrometry (LC—MS/MS) was used for screening and tentative identification of the antibacterial constituents of Salvia officinalis L. ethanol extract. Seven bacterial strains were used as test organisms, both pathogenic and nonpathogenic, that is, Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Staphylococcus epidermidis, Micrococcus luteus, Bacillus subtilis, luminescence gene-tagged Pseudomonas syringae pv. maculicola, and naturally luminescent marine bacterium Aliivibrio fischeri. Eight fractions with the widest antimicrobial spectrum were detected using TLC—DB, isolated by semi-preparative TLC, and subjected to LC—MS/MS analyses. Finally, five bioactive components were tentatively identified, based on their fragmentation pattern, such as salvigenin, cirsimaritin, rosmanol, carnosic acid, and 12-O-methyl carnosic acid.