J Chromatogr A, 1647, 462154 (2021). Hydromethanolic extracts of Cinnamomum verum and C. cassia (Lauraceae) were separated on MS-grade HPTLC silica gel (prewashed twice with methanol – water 4:1 and dried at 110 °C for 20 min) with toluene – ethyl acetate – methanol 6:3:1. Residual organic solvent was removed by drying under automated cold stream air for 20 min. Chromatograms were documented under white light, UV 254 nm and for fluorescence detection at 366 nm, and afterwards submitted to Aliivibrio fischeri bioassay: 2 mL of bacterial suspension were piezoelectrically sprayed on the plate and bioluminescence was measured every 3 min for 30 min (120 s exposure time). For the first time, analytes from a bioactive zone, isolated by the oval elution head of a TLC-MS interface pump, were trapped from the highly salted layer by a heart-cut elution (45 s, flow rate 0.1 mL/min) through a biocompatible in-line filter to different on-line desalting devices. Using a two-position switching valve, the desalted analytes were guided to a reverse-phase UPLC column and separated at 40 °C using a fast gradient (ca. 13 min, 0.6 mL/min) with methanol (from 2 - 90 %) and an ammonium acetate solution (2.5 mM, pH 4.5 adjusted with acetic acid). After HPLC separation, analytes were detected by photodiode array (PDA) and then ESI-MS in polarity switching mode (cone voltage of 10 V, ESI probe at 600 °C, ESI source at 120 °C). Identified active compounds were cinnamic acid, coumarin, as well as the in HPTLC coeluting cinnamaldehyde and 2-methoxycinnamaldehyde. Separately, proof-of-concept tests were also made for more polar phenolic acids (gallic, chlorogenic, caffeic, cinnamic, ferulic and coumaric acids) but without HPTLC separation.

CBS 127, 13-15 (2021). HPTLC of rutin and quercetin in Ginkgo biloba (1), rosmarinic acid in rosemary (2) and oleuropein in olive oil (3) on silica gel with ethyl acetate - formic acid - acetic acid - water 100:11:11:26. Detection by spraying with NP reagent (1 g 2-aminoethyl diphenylborinate in 100 mL methanol) for (1) and (2) or with anisaldehyde reagent (0.5 mL p-anisaldehyde in 85 mL methanol, 10 mL acetic acid and 5 mL sulfuric acid), followed by heating at 100 °C for 3 min. Absorbance measurement at 254 nm and 238 nm for oleuropein and in fluorescence mode at 366>/400 nm for rosmarinic acid. The method showed the application of Quantified Reference Extracts for the identification of plant materials and quantification of markers by HPTLC.

J. Planar Chromatogr. 35, 181-187 (2022). HPTLC of gallic acid (1) and gallic acid ester (2) in Turkish gall on silica gel with dichloromethane - ethyl acetate - formic acid 5:3:1. Detection by spraying with 2 % ferric chloride ethanol solution. Quantitative determination by absorbance measurement at 280 nm. The hRF values for (1) and (2) were 67 and 81, respectively. Linearity was between 507 and 3045 ng/zone for (1) and 499 and 2994 ng/zone for (2). Interday and intra-day precisions were below 2 % (n=6). Average recovery was 100.6 % for (1) and 97.8 % for (2). The method was used to analyze the changes in the content of components which was treated by static simulated gastrointestinal digestion.

J. Planar Chromatogr. 35, 23-33 (2022). HPTLC of 6‑gingerol (1), guggulsterone (2) E and guggulsterone Z (3) on silica gel with toluene - acetone 9:1. Quantitative determination by absorbance measurement at 280 nm. The hRF values for (1) and (2) were 15, 19 and 25, respectively. Linearity was between 100 and 1200 ng/zone for (1) to (3). Interday and intra-day precisions were below 3 % (n=5). The LOD and LOQ were 100 and 400 ng/zone for (1) to (3), respectively. Recovery was between 95.4 and 101.05 %. 

J. Planar Chromatogr. 35, 43-50 (2022). HPTLC of curcumin (1) and cineole (2) on silica gel with n-hexane - ethyl acetate 12:7. Quantitative determination by absorbance measurement at 242 nm. The hRF values for (1) and (2) were 31 and 71, respectively. Linearity was between 1 and 6 µg/zone for (1) and 10 and 60 µg/zone for (2). Interday and intra-day precisions were below 2 % (n=3). The LOD and LOQ were 45 and 135 ng/zone for (1) and 34 and 102 ng/zone for (2), respectively. Recovery was between 93.3 and 98.8 % for (1) and 94.6 and 99.4 % for (2).

J. Planar Chromatogr. 34, 481-492 (2021). HPTLC of cynaroside (1), apiin (2), diosmin (3) and linarin (4) in Ziziphora clinopodioides on silica gel with ethyl acetate - dichloromethane - ethanol - formic acid - water 10:13:6:2:4. Quantitative determination by absorbance measurement at 350 nm. The hRF values for (1) to (4) were 30, 36, 45 and 60, respectively. Linearity was between 0.05 and 0.35 μg/zone for (1), 0.02 and 0.14 μg/zone for (2), 0.15 and 0.60 μg/zone for (3) and 0.05 and 0.70 μg/zone for (4). Interday and intra-day precisions were below 5 % (n=6). The LOD and LOQ were 5 and 16 ng/zone for (1) and (2), 150 and 500 ng/zone for (3) and 10 and 33 ng/zone for (4), respectively. Average recovery was 98.9 % for (1), 100.7 % for (2), 98.8 % for (3) and 100.2 % for (4).

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, 447-453 (2021). HPTLC of gallic acid (1) and ellagic acid (2) in Triphala on silica gel with toluene - ethyl acetate - formic acid - methanol 15:15:5:1. Quantitative determination by absorbance measurement at 254 nm. The hRF values for (1) and (2) were 35 and 28, respectively. Linearity was between 200 and 2000 ng/zone for (1) and 50 and 400 ng/zone for (2). LOD and LOQ were 200 and 606 ng/zone for (1) and 50 and 151 ng/zone for (2), respectively. Intermediate precisions were below 2 % (n=3). Average recovery was 98.6 % for (1) and 99.1 % for (2).