J. Sep. Sci. 43, 2477-2486 (2020). HPTLC of urea produced by arginase as a bioautographic method for the detection of arginase inhibitors in Myrtus communis on silica gel with ethyl acetate - methanol - water - formic acid 800:100:100:1. Detection by spraying with arginase solution (50 U in 3 mL of a buffer containing Tris–HCl 50 mM, pH 7.5 and 0.1 % of BSA), followed by spraying with 3 mL of L-arginine solution (200 mM, pH 9.7) and incubation at 37 ºC for 60 min. Visualization by spraying with 3 mL of sulfuric acid - phosphoric acid - water 2:7:91 and 2 mL of alpha-isonitrosopropiophenone solution (5% in absolute ethanol) followed by heating at 100 ºC for 1h. The hRF value for the inhibitor N-trans-caffeoyltyramine was 27. Sensitiviy was estimated for the arginase inhibitor Nω-hydroxy-nor-Arginine (nor-NOHA), resulting in a LOD of 0.1 µg/zone.

Phytochem. Anal. 31, 57-67 (2019). HPTLC profiling of the leaves of Fraxinus excelsior on silica gel with ethyl acetate - water - formic acid 8:1:1. Qualitative identification under UV light at 254 and 366 nm. The hR_F value of chlorogenic acid was 90.

J. Liq. Chromatogr. Relat. Technol. 43, 361-366 (2020). HPTLC of the dried root and rhizome of Rhodiola rosea on silica gel with ethyl acetate - methanol - water 77:13:10. Detection by spraying with 1) a solution of p-anisaldehyde (0.5 mL in 85 mL methanol, 10 mL acetic acid and 5 mL sulfuric acid), followed by heating at 105 ºC for 5-7 min, 2) a solution of 2-isopropyl-5-methylphenol (0.5 g in 95 mL ethanol and 5 mL sulfuric acid), followed by heating at 120 ºC and 3) NP solution (1 g diphenylboryloxyethylamine in 100 mL methanol) and PEG solution (5 g PEG-4000 in 100 mL ethanol). Detection under UV 254 and 366 nm. Effect directed detection was performed using 1) DPPH* radical reagent assay: spraying with 0.2 % 2,2-diphenyl-1-picrylhydrazyl solution in methanol, 2) AChE assay: spraying with the enzyme solution (20 units of AChE and 150 mg BSA in 150 mL 0.05 M TRIS buffer, pH 7.8), follwed by incubation at 37 ºC for 20 min and spraying with 50 mg Fast Blue B salt diluted in 100 mL of water and 3) Bacillus subtilis bioassay: dipping into bacterial suspension for 8 s, followed by incubation at 37 ºC for 17 h and spraying with 0.2 % MTT aqueous solution. The bioautographic tests showed presence of both antioxidants (DPPH assay) and antibacterials (Bacillus subtilis assay) in the methanolic plant extract, however no acetylcholinesterase inhibitors were found. As marker compound, rosavin was detected.

J. Liq. Chromatogr. Relat. Technol. 43, 344-350 (2020). HPTLC of hydrodistilled Plectranthus amboinicus essential oil on silica gel with n-hexane - ethyl acetate - ethanol 95:3:2. Detection by dipping into anisaldehyde sulfuric acid reagent, followed by heating at 100 ºC for 5 min. HPTLC-bioprofiling was performed using the following assays by dipping the chromatogram into the respective solution, followed by drying, incubation and documentation at white light or measuring bioluminescence: DPPH* radical reagent assay (using a 0.2 mg/mL 2,2-diphenyl-1-picrylhydrazyl solution in methanol), AChE inhibitory assay, tyrosinase inhibitory assay, alpha- and beta-glucosidase inhibitory assays, alpha-amylase inhibitory assay, Gram-negative antimicrobial bioassay (chromatogram immersion into a A. fischeri suspension), and Gram-positive antimicrobial bioassay (chromatogram immersion into a B. subtilis bacterial suspension). Direct analysis in real time mass spectrometry allowed the detection of five bioactive compounds: caryophyllene oxide (hR_F 20), a-humulene (hR_F 26), carvacrol (hR_F 40), methyl carvacrol ether (hR_F 76) and caryophyllene (hR_F 84).

J. Liq. Chromatogr. Relat. Technol. 43, 233-246 (2020). HPTLC of lutein (1) and lactucaxanthin (2) in three varieties of lettuce (Iceberg, Romania, and green lettuce) on silica gel with heptane - acetone 7:3. The hRF values for (1) and (2) were 44 and 41, respectively.

J. Liq. Chromatogr. Relat. Technol. 43, 300-304 (2020). HPTLC of thymol, carvacrol and linalool in Solidago canadensis on silica gel with n-hexane - acetone 4:1. The method was compared with bilateral band compression (BBC) of the 10 mm wide lanes of HPTLC separation, resulting in more than 6 times increase in peak height and peak area. In BBC a solvent flow perpendicular to the direction of chromatogram development squeezes the chromatographic bands into a smaller area The method improved detection sensitivity of sample components with low abundance.

J. Liq. Chromatogr. Relat. Technol. 43, 328-335 (2020). HPTLC of verapamil, diltiazem, ivabradine, and its related analogs on silica gel with acetonitrile - methanol (acidified with 25 % formic acid) with the following volume fraction of methanol: 0.25, 0.20, 0.15, 0.13 and 0.10. Detection under UV 254 nm. Retention behavior was investigated and quantitative structure retention relationship (QSRR) modeling was performed with the use of the stepwise multiple linear regression.

J. Planar Chromatogr. 33, 203-206 (2020). HPTLC of profenofos in visceral samples on silica gel with hexane - acetone 7:3. Detection by spraying with cupric acetate reagent (4 g of cupric acetate in 100 mL distilled water), followed by heating at 120 ºC for 10 min. The hR_F value for profenofos was 44.