J. Planar Chromatogr. 35, 299-311 (2022).  HPTLC of powdered herbal drugs and finished products (leaves of Mentha piperita, Olea oleuropea, Ginkgo biloba and Camellia sinensis, fruits of Styphnolobium japonicum and Piper nigrum, roots of Angelica species (A. gigas, A. sinensis, A. dahurica, A. acutiloba, and A. pubescens, Curcuma longa and poly-herbal products containing powdered extracts of Curcuma longa root and Piper nigrum fruits) on silica gel with three complementary developing solvents (CDS): low polar developing solvent (toluene - ethyl acetate 9:1); medium polar developing solvent (cyclopentyl methyl ether - tetrahydrofuran - water - formic acid 40:24:1:1); and high polar developing solvent (ethanol - dichloromethane - water - tetrahydrofuran 16:16:4:1). Detection by heating at 100 °C for 3 min, followed by spraying with NP reagent (1.0 g of 2-aminoethyl diphenylborinate in 100 mL of methanol). For Olea oleuropea and Ginkgo biloba, the derivatization with NP was followed by spraying with anisaldehyde sulfuric acid reagent and heating at 100 °C for 3 min. Analysis was performed under UV light at 254 and 366 nm. Performance of the Universal HPTLC mix (UHM) was assessed in terms of precision. The hRF values for all substances were between 20 and 80. 

J Chromatogr A, 1608, 460415 (2019). Samples were acetonitrile extracts of Annona cherimola fruit peel, pulp and seeds (Annonaceae), as well as caffeic acid as standards. HPTLC on silica gel with chloroform – ethyl acetate – propanol 21:2:2 for peel extracts, with chloroform – methanol 9:1 for seed extracts. Derivatization by spraying Dragendorff’s reagent for alkaloids, secondary amines and non-nitrogenous oxygenated compounds.  Effect-directed assay was performed for inhibitors of α-glucosidase. Before sample application, plates were developed with enzyme substrate (2-naphthyl-α-D-glucopyranoside 0.1 % in methanol) and dried 20 min at 60 °C. Then, samples were applied and separated, and mobile phase was removed by heating 10 min at 60 °C. The chromatogram was sprayed with 4 mL enzyme solution (5 unit/mL in 100 mM phosphate buffer,  pH 7.4), liquid excess was removed under lukewarm air stream, the plate was incubated 10 min at 37 °C in a moisture box, followed by spraying chromogenic reagent Fast Blue salt B 0.1 % in water, giving after 2 min white inhibition bands visible on purple background under white light. Plate image was documented under illumination (reflectance mode) with white light. The bands of 3 inhibiting compounds were analyzed in a triple quadrupole mass spectrometer. 1) Full scan mass spectra (m/z 50−1000) in the positive ionization mode were recorded using electrospray ionization (ESI, spray voltage 3 kV, desolvation line temperature 250 °C, block temperature 400 °C) for compounds directly eluted with methanol – acetonitrile through the oval elution head of a TLC-MS interface pump. 2) Compounds were also isolated (either eluted directly from the plate into a vial through the same interface, or scraped from the plate and extracted with methanol – chloroform into a vial), dried, and submitted to HPLC-DAD-MS/MS; MS-MS spectra were recorded in the same conditions, using argon as collision gas and collision cell voltages from -20 and -40 V. Inhibitors were identified as phenolamides (phenylethyl cinnamides): moupinamide (hRF 66 in peels, 56 in seeds), N-trans-feruloyl phenethylamine (hRF 76 in peels), N-trans-p-coumaroyl tyramine (hRF 44 in seeds).

J. Planar Chromatogr. 35, 313-330 (2022).  HPTLC of orange peel extract on silica gel with gradient multiple development using seven different polarity ranges: cyclohexane, cyclohexane - n-heptane 3:7, cyclohexane - methyl tert-butyl ether 43:7, cyclohexane - methyl tert-butyl ether 7:3, cyclohexane - methyl tert-butyl ether 3:7, methyl tert-butyl ether, methyl acetate - ethanol 9:1, ethyl acetate - ethanol - formic acid 44:5:1. Detection by spraying with vanillin reagent (100 mg vanillin dissolved in 9.8 mL ethanol and 0.2 mL sulfuric acid), followed by heating at 100 °C for 2 min. DPPH staining was performed with 2 mL of a DPPH solution (15 mg dissolved in 10 mL of methanol). Bioautography was performed by dipping into Aliivibrio fischeri bacteria suspension for 6 s, followed by measurement of bioluminescence within 15 min. In this sample, more than 50 compounds could be separated.

J. Planar Chromatogr. 35, 243-250 (2022). Micro TLC of three dyes (1-aminoanthraquinone, fat green and 2-nitroaniline) on silica gel with toluene at distances 1, 1.5, 2, 2.5, or 3 cm. Experiments were performed using a prototype device operated at a controlled velocity of the mobile phase, where the chromatographic plate was placed in the chamber with the adsorbent layer face-down and the mobile phase was delivered onto the adsorbent layer of the chromatographic plate by the pipette, which was driven into movement by a 3D machine controlled by a computer. Different solvents (acetone, methanol, toluene, or heptane) were used to wet and to narrow the starting zones. Detection under UV light at 286 nm. To take full advantage of the benefits of micro-planar chromatography, the size of the starting zone should be reduced as well as the processes
related to the dissolution kinetics of the starting zones of substances in the mobile phase should be optimized.
 

J. Planar Chromatogr. 35, 229-241 (2022). Review of the advances, limitations and challenges faced by the application of HPTLC for lipidomic analysis. The paper described methods for the separation of phospholipids (PL) and/or sphingolipids (SL) on silica gel HPTLC plates from different samples in lipidomic studies, including matrices and development conditions. HPTLC methods for separating lipid classes and subclasses, combined with semi-quantification by UV‒FL densitometry and mass spectrometry were also described. HPTLC and genetic knockouts was also discussed as an emerging field. 

J Chromatogr A, 1598, 209-215 (2019). Samples were methanolic extracts of honeys from Robinia pseudoacacia (Fabaceae) or from Tilia spp. (Tiliaceae / Malvaceae), as well as standards: abscisic acid (sesquiterpenoid), caffeic acid, chlorogenic acid, cinnamic acid, ferulic acid (phenolic acids), chrysin (flavone), myricetin, quercetin (flavonols), naringenin (flavanone). HPTLC on silica gel with chloroform – ethyl acetate – formic acid 5:4:1. Visualization under UV 254 nm and 366 nm, before and after derivatization by spraying with aluminium chloride (1 % in methanol), which rendered flavone bands bright yellow. Quantitative absorbance measuremet by densitometry at 366 nm. Linearity was in the range of 12,5–200 µg/mL for most standards (25–400 µg/mL for chrysin). Main differences observed in samples: 1) abscisic acid (hRF 56) and chrysin (hRF 82) were present only in Tilia honey samples, quercetin (hRF 55) only in Robinia honey; 2) ferulic acid (hRF 60) was the most prominent blue band in Tilia honey samples (1.35–18.73 g/kg of honey), and less intense in Robinia honey (0–1.24 g/kg of honey). Multivariate analysis was performed in two different ways with principal component analysis.

J. Planar Chromatogr. 35, 251-263 (2022). HPTLC of ten imidazoline and serotonin
receptor ligands on amino phase with acetonitrile modified with different volume fractions of methanol and water as mobile phases, acidified with 20 mM ammonium acetate and 0.1 % acetic acid. Detection under UV light at 254 nm. Correlation between retention descriptors and molecular properties was analyzed and different elution orders and separation performances were obtained for the compounds, depending on the chromatographic system employed. 
 

J. Planar Chromatogr. 35, 331-337 (2022). HPTLC of selected varieties of hop cultivars H. lupulus on silica gel with 8 % isopropanol in dichloromethane. Detection under UV light at 254 and 366 nm. Direct bioautography by dipping into Bacillus subtilis bacterial suspension for 10 s, followed by incubation at 37 °C for 17 h. TLC plates were covered with 0.2 % aqueous MTT tetrazolium dye solution (thiazolyl blue tetrazolium bromide, 98 %), followed by incubation at 37 °C for 30 min.