The case of determination of rosmarinic acid in different matrices. J. Chromatogr. A 1220, 156-161 (2012). Description of a new method for determination of rosmarinic acid in different matrices by HPTLC on silica gel with toluene – ethyl formate – formic acid 6:4:1. Quantification by densitometry in absorbance mode at 330 nm. The influence of the main HPTLC operative parameters was figured out in view of a more stringent validation process. Together with the fundamental HPTLC instrumentation an automatic developing chamber is mandatory as it allows for control of the relative humidity and the saturation conditions and thus assures reproducibility. Several commercial preparations containing rosmarinic acid in different amounts were tested and rosmarinic acid in the range of 132-660 ng/band was found. The %RSD of repeatability and intermediate precision did not exceed 2.

extracts. J. Planar Chromatogr. 28, 178-183 (2015). TLC of (1) chlorogenic acid and (2) caffeine in coffee samples on silica gel with ethyl acetate - methanol - water 77:13:10 to a distance of 8 cm using a horizontal sandwich chamber. The plates were dried at room temperature for 1 h. Detection of polyphenols with NP-PEG reagent, of terpenoids with anisaldehyde-sulfuric acid reagent followed by heating at 110 °C for 5 min, of purine derivatives with iodine-hydrochloric acid reagent. Quantitative determination of (1) and (2) at UV 254 nm using VideoScan software. The hRF value of (1) was 14, and of (2) 51. The antibacterial activity of green and roasted coffee seeds and pomace was evaluated against Bacillus subtilis using TLC-direct bioautography. TLC-2,2-diphenyl-1-picrylhydrazyl (DPPH) test was used to determine the antioxidant properties. For bioautography with Bacillus subtilis, the plates were immersed for 8 s in the bacterial suspension, placed in a moistened plastic box, and incubated at 37 °C for 17 h. Detection after spraying with 0.2 % MTT aqueous solution. For the DPPH test, plates were sprayed with 0.2 % methanolic DPPH solution. Detection of antioxidant activities as yellow zones against a purple background.

J. Planar Chromatogr. 29, 318-322 (2016). HPTLC of trans-resveratrol, aromatic acids (benzoic, cinnamic, ferulic, salicylic and caffeic acid) and flavones (flavone, daidzein, chrysin, kaempferol, quercetin and morin) in coffee, tea and wine on LiChrospher® plates with ethyl acetate – cyclohexane – 1-butanol 9:9:2 for trans-resveratrol and ethyl acetate – methanol – water 77:13:10 for aromatic acids and flavones. Chemiluminescence was induced by dipping the plate into a bis(2,4,6-trichlorophenyl)oxalate (250 mg in 36 mL 1-butyl acetate followed by shaking with 0.4 mL hydrogen peroxyde 35 % for 20 min) solution for 1 s. Fluorescence evaluation under UV 366 nm.

J. Chromatogr. A 1468, 228-235 (2016). Development and validation of a rapid and simple screening method by HPTLC for antioxidant activity in samples of 16 algal species collected from local Victorian beaches. Quantification of fucoxanthin, one of the most abundant marine carotenoids directly from the HPTLC plates before derivatization either with 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical or ferric trichloride to analyze antioxidants in marine algae, based on their ability to chelate iron ions or to scavenge non-biological stable free radical, respectively. Classification of algae species into 5 groups according to the chemical/antioxidant profiles by principal component analysis of obtained HPTLC fingerprints. The investigated brown algae samples were rich in non-polar and moderate-polar and phenolic compounds with antioxidant activity, while most of the phenolic iron chelators showed free radical scavenging activity. Strong positive and significant correlations between total phenolic content and DPPH radical scavenging activity showed that phenolic compounds, including flavonoids are the main contributors of antioxidant activity in these species, which could be considered for future applications in medicine, dietary supplements, cosmetics or food industries. Discussion of the advantages of the proposed methods in terms of screening for antioxidants and quantification of antioxidant constituents in complex mixtures using the flexible and versatile standard HPTLC system in the drug discovery, and the possibility of using the method for the bioassay-guided isolation of unknown natural antioxidants and subsequent identification if combined with spectroscopic identification.

J. Planar Chromatogr. 30, 392-400 (2017). HPTLC of 13 Achillea species on silica gel with toluene – ethyl acetate – formic acid 50:49:1. Detection by spraying with anisaldehyde reagent, followed by heating at 126 °C for 10 min. TLC chromatograms were photographed and processed with ImageJ program. Also TLC on cyano phase with 2-propanol – n-heptane 1:1 and ethanol – water 3:2 for dichloromethane extracts and methanol – water 2:3 for methanolic extracts. Detection by spraying with 1 % solution of diphenylborinic acid 2-aminoethylester in methanol, followed by drying and spraying with 5 % solution of polyethylene glycol in methanol. Detection under UV 366 nm. Principal component analysis, similarity and distance measures were used to confirm the similarity between the studied samples.

Food Chem. 260, 344-353 (2018). HPTLC profiling of phenolic compounds in 50 commercially available beers on silica gel with methyl ethyl ketone – toluene – formic acid 25:15:2. Detection by dipping into a 0.5 % methanolic 2-aminoethyl diphenylborinate solution, followed by drying in the air for 5 min and immersion for 3 s in a 5 % methanolic PEG 400 solution. Image acquisition at UV 366 nm. The HPTLC method was hyphenated to four different assays to demonstrate the fast discovery of single DPPH scavengers, Gram negative (A. fischeri) and Gram positive (B. subtilis) antimicrobials as well as AChE inhibitors in beers. For the DPPH assay, the plate was immersed into a 0.02 % methanolic DPPH_x000D_ solution, followed by drying at ambient temperature (25 °C) in the dark for 30 s and then heated for 30 s in a stream of warm air. Images were acquired every 30 s for a period of 10 min. For the B. subtilis bioassay, the plate was immersed_x000D_ in the prepared bacterial suspension, incubated at 37 °C for 2 h, immersed in a 0.2 % PBS-buffered MTT solution and incubated again at 37 °C for 0.5 h. For the luminescent A. fischeri bioassay, the plate was immersed in the bacterial suspension for 2 s and instant bioluminescence was captured. For the AChE assay, the plate was immersed in the enzyme solution (AChE 666 units plus 100 mg BSA ad 100 mL 0.05M TRIS buffer, pH 7.8), incubated at 37 °C for 25 min, and immersed in a substrate solution (25 mg α-naphthyl acetate and 50 mg Fast Blue salt B ad 90 mL with ethanol – water 1:2). Phenolic compounds in active zones were also characterized by HPTLC-HRMS. Effect-directed fingerprints were investigated for image processing and multivariate data analysis. Isoxanthohumol was found to be the main phenolic beer component that showed the widest spectrum of activities.

Anal. Letters 18, (A6) 719-728 (1985). Study of the effect of commonly occurring salts in soil, organic matter and pH levels of the soil leachates on the movement of some water soluble phenols by TLC.

I. Polyphenol substances in beer.) (Hungarian). Söripar, 37, 18-21 (1989). TLC on silica, cellulose, polyamide, polyamide-cellulose 80:20 with chloroform - methanol - 15N NH3 65:25:4 or butanol - acetic acid - water 63:10:27. Visualization under UV.