Journal of Chromatography B, 1184, 122956 (2021). Test for acetyl- and butyrylcholinesterase (AChE and BChE) inhibition without development of piperin (standard inhibitor of AChE and BChE) and ethanol – water (3:2) extracts of Iranian plants, on HPTLC silica gel prewashed twice with methanol – water 3:2 and dried 60 min at 120°C. After sample application the plate was immersed (speed 3.5 cm/s, time 2 s) into enzyme solution (6.6 units/mL AChE or 3.3 units/mL BChE in TRIS buffer 0.05 M, with bovine serum albumin 0.1 %, pH 7.8), incubation 25 min at 37°C and immersion (speed 3.5 cm/s, time 1 s) into chromogenic substrate solution (α-naphthyl acetate 0.1 % and Fast Blue salt B 0.2 % in ethanol – water, 1:2). Seven mobile phases were tested for the active samples. Best separation was obtained with toluene – ethyl acetate – formic acid – water 4:16:3:2 and with toluene – ethyl acetate – methanol 6:3:1. Before enzymatic assay, plates developed with acidic mobile phases were neutralized by spraying 3 mL citrate phosphate buffer (Na2HPO4 8 %, citric acid q.s. ad pH 7.5) followed by 10 min of automatic drying. Enzymatic assay was performed using a piezoelectric spraying device: a) pre-wetting by spraying 1 mL TRIS buffer (0.05 M, pH 7.8); b) spraying 3 mL of the enzyme solution; c) incubation 25 min in a humid box at 37°C; d) spraying 0.5 mL substrate solution; e) 5 min drying at room temperature, and then 10 min of automatic drying. By spraying, zone shift and zone diffusion, which occurred with plate immersion, were avoided. For development control, derivatization was done by piezoelectrically spraying 4 mL of sulfuric anisaldehyde reagent (anisaldehyde – sulfuric acid – acetic acid – methanol, 1:10:20:170), followed by heating 3 min at 110°C. For identification of zones of interest, direct elution with methanol from underivatized HPTLC plates through a TLC-MS interface directly to a MS. Identified zones were 3-O-acetyl-β-boswellic acid (triterpenoid) from Boswellia carteri gum-resin (Burseraceae), pimpinellin and psoralen (furocoumarins) from Heracleum persicum flowers (Apiaceae), oleuropein (seco-iridoid) from Olea europaea leaves (Oleaceae), harmine, harmaline, vasicine, deoxyvasine (alkaloids) from Peganum harmala seeds (Zygophyllaceae), costic acid (sesquiterpene) from Nardostachys jatamansi hypocotyl (Valerianaceae), elaidic, linoleic, palmitic, palmitoleic acids (fatty acids) from Pistacia atlantica fruits (Anacardiaceae).

J Chromatogr. A, 1652, 462377 (2021). Samples were vanilla tinctures, water − ethanol − ethyl acetate 1:1:1 extracts of vanilla-flavored food products and of natural Vanilla sp. (Orchidaceae) pods, oleoresin, paste and powders, as well as calibration standards of vanillin (1) and ethylvanillin (2). HPTLC on silica gel with n-hexane – ethyl acetate 1:1 for profiling, 3:2 for quantification. Other mobile phases were also tested and given in the supplement. Compounds (1) and (2) (hRF 68 and 82, respectively) were quantified by absorbance densitometry (at maximal wavelength 310 nm, deuterium lamp, scanning speed 10mm/s). Contents were found to be between 1 μg/g and 36 mg/g for (1) and null for (2) except in one tincture (62 µg/mL). Derivatizations performed for five assays: A) to detect radical scavengers, immersion (speed 3 cm/s, time 5 s) into DPPH• (0.5 mM in methanol), followed by drying for 90 s at room temperature and 30 s at 60 °C; B) to detect activity against Gram-negative bacteria, immersion (speed 2 cm/s, time 3 s) into Aliivibrio fischeri suspension, followed by recording the bioluminescence; C) to detect activity against Gram-positive bacteria, immersion (speed 3.5 cm/s, time 6 s) into Bacillus subtilis, followed by incubation 2 h at 37 °C, immersion in MTT solution, incubation for 30 min at 37 °C and heating for 5 min at 50 °C; D) to detect acetylcholinesterase (AChE) inhibitors, immersion (speed 2.5 cm/s, time 2 s) into AChE solution (666 units in TRIS buffer 0.05M, with bovine serum albumin 0.1 %, pH 7.8), incubation for 25 min at 37 °C and immersion into substrate solution (α-naphthyl acetate 0.1 % and Fast Blue salt B 0.18 % in ethanol – water, 1:2; E) to detect tyrosinase inhibitors, spraying with enzyme solution (400 unit/mL, in phosphate buffer 0.02 M, pH 6.8), followed by 2 min drying, immersion into substrate levodopa (18 mM in phosphate buffer, pH 6.8), 10 min incubation at room temperature and drying. For identification, zones of interest were transferred with methanol from underivatized HPTLC layer through a TLC-MS interface and a filter frit directly to a Quadrupole-Orbitrap MS (heated electrospray ionization, probe heater at 270°C, spray voltage 3.5kV, lock masses acetic acid for negative, dibutyl phthalate for positive ionization, mode full HR-MS scan in m/z range 50–750). Afterwards, the following substances assigned by MS were confirmed by using HPTLC comparison with standards: (1) and (2), vanillyl alcohol, vanillic acid, ethyl vanillyl ether, coumarin, 4-hydroxybenzoic acid, 4-methoxybenzoic acid, 4-hydroxybenzaldehyde, 4-allyl benzoic acid, oleamide, triacetin.

J. Planar Chromatogr. 34, 217-228 (2021). HPTLC of cordifolioside A (1), 20‑β‑hydroxyecdysone (2) and columbin (3) in stems of Tinospora cordifolia on silica gel with hexane - chloroform - methanol - formic acid 40:40:20:1. Detection by spraying with anisaldehyde‒sulfuric acid reagent. Quantitative determination by absorbance measurement at 254 nm for (1) and (2) and 600 nm for (3). The hRF values for (1) to (3) were 12, 43 and 85, respectively. Linearity was between 750 and 2250 ng/zone for (1) and (2) and 675 and 1875 ng/zone for (3). Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 107 and 324 ng/zone for (1), 41 and 123 ng/zone for (2) and 54 and 163 ng/zone for (3). Recovery was between 99.0 and 101.4 % for (1), 98.1 and 101.6 % for (2) and 98.1 and 98.8 % for (3). Further analysis was performed by electrospray ionization‒tandem mass spectrometry.

Pharmacogn. Mag. 17, 233-239 (2021). HPTLC of esculin in the leaves of Launaea pinnatifida on silica gel with chloroform - methanol - formic acid 13:6:1. Quantitative determination by absorbance measurement at 343 nm. The hRF value of esculin was 70. Linearity was between 8 and 250 µg/mL. The LOD and LOQ were 8 and 25 µg/zone. Average recovery rate was 99.8 %.

J. Ethnopharmacol. 276, 114144 (2021). Review of analytical methods for the analysis of the main secondary metabolites detected and isolated from Ammi majus. The paper described TLC and HPTLC methods for the determination of coumarins in fruits.

J. Liq. Chromatogr. Relat. Technol. https://doi.org/10.1080/10826076.2021.1939046 (2021). HPTLC of picroside-I (1), andrographolide (2) and silybin (3) in Picrorhiza kurroa (roots), Andrographis paniculata (aerial parts) and Silybum marianum (seeds), respectively, on silica gel with n-butanol - glacial acetic acid - water 6:1:3. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) to (3) were 49, 68 and 89, respectively. Linearity was between 60 and 600 ng/zone for (1) to (3). The intermediate precision was below 2 %. The LOD and LOQ were 15 and 45 ng/zone for (1), 22 and 67 ng/zone for (2) and 26 and 78 ng/zone for (3), respectively. Recovery was between 99.7 and 103.7 % for (1), 99.7 and 101.1 % for (2) and 99.0 and 101.7 % for (3).

J. Food. Sci. 81, 1378-1384 (2016). HPTLC of Lycium barbarum samples on silica gel with n-butanol - acetic acid - water 15:8:6. DPPH bioautography assay by spraying with 0.04 % 2,2-diphenyl-1-picrylhydrazyl in methanol under dark conditions. Detection under UV light at 535 nm. 

Anal. Bioanal. Chem. 412, 2633-2644 (2020). HPTLC of  cannabinol in sediment samples on silica gel with n-heptane - diethyl ether 9:1. Detection by spraying with cerium- molybdenum reagent (400 mg cerium IV sulfate and 20 g ammonium molybdate in 400 mL 10 % sulfuric acid). HPTLC plates were further analyzed by electrospray ionization mass spectrometry. The hRF value for cannabinol was 20. Linearity was between 25 and 155 ng/zone. Intermediate precision was below 5 % (n=3). The LOD and LOQ were 6 and 21 ng/zone. Average recovery was 73 %.