J Chromatogr A, 1629, 461511 (2020). HPTLC of methanolic extracts of female inflorescences from ten hemp varieties (Cannabis sativa, Cannabaceae) on silica gel with toluene – ethyl acetate 1:1 or (for yeast assays) on RP-18W with toluene – ethyl acetate 7:3. When intended for MS experiments, layers were previously washed twice with methanol – formic acid 10:1, once with acetonitrile – methanol 2:1 and air-dried. Chromatograms were documented under white light, UV 254 nm and for fluorescence detection (FLD) at 366 nm. Afterwards, 6 derivatization assays were performed with the following reagents, either without heating: primuline; or requiring heating 5 min at 120 °C: p-aminobenzoic acid; anisaldehyde sulfuric acid; diphenylamine aniline phosphoric acid; ninhydrin; vanillin sulfuric acid. Besides, 8 effect-directed assays (EDA) were performed for free radical (DPPH•) scavengers, for antimicrobial compounds (Gram-positive Bacillus subtilis assay, Gram-negative Aliivibrio fischeri bioluminescence assay), for phytoestrogens (planar yeast estrogen assay), for inhibitors of the following enzymes: acetyl-cholinesterase (AChE), α- and β-glucosidase, tyrosinase. AChE assay was performed by immersion (speed 3.5 cm/s, time 5 s) into AChE solution (666 units in TRIS buffer 0.05 M, with bovine serum albumin 0.1 %, pH 7.8), incubation 25 min at 37 °C, spraying with substrate solution, and heating 2 min at 50 °C. Two AChE substrate solutions were used: A) α-naphthyl acetate 0.1 % and chromogenic reagent Fast Blue salt B 0.18 % in ethanol – water 1:2, giving white inhibition bands visible on purple background under white light; B) with 3-indoxyl-3-acetate, giving black inhibition bands on blue background under UV 254 nm, which was useful to prevent false negatives when Fast Blue Salt B formed colored bands with analytes. Two bands of multipotent compounds were eluted from normal-phase layer with methanol through the oval elution head of a TLC-MS interface pump, into a quadrupole-Orbitrap mass spectrometer. Full scan mass spectra (m/z 50−750) in the positive and negative ionization modes were recorded using heated electrospray ionization (HESI, spray voltage 3.5 kV, capillary temperature 270 °C). By comparison to literature and standards, they were identified as cannabidivarinic acid (hRF 55) and cannabidiolic acid (hRF 60-70).

J Chromatogr A, 1616, 461434 (2020). Samples were acetonic extracts of Malus domestica fruit peels (Rosaceae) and of Salvia officinalis, Thymus vulgaris and Origanum vulgare spice powders (Lamiaceae), as well as standards of maleic acid (dicarboxylic acid), carvacrol, thymol (phenolic monoterpenes), rosmanol (phenolic diterpene), betulinic acid, corosolic acid (CA), maslinic acid (MA), oleanolic acid (OA) and its isomer ursolic acid (UA) (triterpenes). HPTLC on silica gel, when intended for MS and NMR experiments, layers were prewashed twice with methanol – water 3:1, followed by 30 min drying at 120 °C. When intended for quantitative densitometry, start zones were submitted to prechromatographic derivatization with iodine solution (10 g/L in chloroform) allowed to migrate up to 12 mm, incubated 10 min at 27 °C and dried under cold air stream; this allowed separation of isomeric triterpenes. Separation with toluene – methanol – ethyl acetate 17:2:1 after 5 min chamber saturation at 50 % relative humidity. CA coeluted with MA, and OA with UA. Four hyphenations: A) Quantitative HPTLC densitometry for active analytes was performed by measuring absorption at 665 nm with a tungsten lamp after immersion of the chromatograms in anisaldehyde sulfuric acid reagent and heating 5 min at 110 °C. Linear range was obtained at 25 - 200 ng/band for OA and 100 - 400 ng/band for UA. B) Effect-directed analysis by immersing the chromatograms into Gram-positive Bacillus subtilis suspension for antibacterial activity and into acetyl-cholinesterase and tyrosinase solutions for enzymatic inhibition. C) Active bands were eluted with methanol through the oval elution head and in-line filter frit of a TLC-MS interface pump, into a quadrupole-Orbitrap mass spectrometer. Full scan mass spectra (m/z 100−1000) in the positive and negative ionization modes were recorded using heated electrospray ionization (HESI, spray voltage 3.5 kV, capillary temperature 270 °C, probe heater temperature 200 °C). D) With higher amounts applied, preparative HPTLC, by scraping the multipotent band corresponding to OA and UA, and dissolving these analytes in methanol, for NMR analyses (1H raw or deconvoluted, and 2D 1H–13C Heteronuclear Single Quantum Coherence). Both isomers were distinguished by their allylic H-18 protons and separately quantified by applying PULCON method (PUlse Length-based CONcentration). LOQ was 267 μM for OA and 173 μM for UA; optimal range was 300 – 4600 mM, corresponding to 126 - 2090 μg of triterpenes.

Food Chem. 374, 131714 (2022). HPTLC of authentic samples (7 apricot and 5 pumpkin samples) and simulated adulterated products on silica gel with methanol - ethyl acetate - n-hexane 170:40:3. Fluorescence detection (FLD) at 366 nm. Carotenoids (hRF=18) were identified as chemical markers, being responsible for their differentiation in apricot and most pumpkins extracts. Partial least squares discriminant analysis (PLS-DA) proved to be a promising tool for predicting the amount of added pumpkin down to 2.5 %, with prediction errors as low as 20 %.

Journal Chromatogr A, 1641, 461727 (2021). HPTLc of an ethanolic maceration of Solidago gigantea roots (Asteraceae) on silica gel with n-hexane – isopropyl acetate – acetone 16:3:1, or n-hexane – isopropyl acetate – acetic acid 40:9:1. With the second mobile phase, acid residues had to be eliminated by 20 min automated drying or by 2 h incubation with potassium hydroxide in the opposite twin trough (followed by 15 min cold air streaming); this latter mobile phase allowed to obtain higher hRF values, but some butyrylcholinesterase (BChE) inhibiting activities were lost. The chromatograms were documented at UV 254 nm and 365 nm and white light before and after A) derivatization with vanillin – sulfuric acid reagent; B) enzymatic reaction by immersion into acetylcholinesterase, BChE, glucosidase and amylase solutions; C) Aliivibrio fischeri and Xanthomonas euvesicatoria bioassays, to detect activity against Gram-negative bacteria; D) Bacillus subtilis bioassay to detect activity against Gram-positive bacteria; E) a new antifungal assay with Fusarium avenaceum. For this assay, the chromatograms were immersed 6 s into the isolated mycelium suspension (diluted to OD600 0.4-0.8) and incubated in a vapor chamber at 21 °C for 48-72 h. Inhibition zones were indicated by the lack of visible white fungal hyphae. An aqueous solution of iodonitrotetrazolium (INT, 1 mg/ml) was sprayed on the plate to enhance the contrast (bright zones on a purple background). Benomyl (a benzimidazole fungicide) was used as positive control. Eight clerodane diterpenes (including kingidiol, hautriwaic lactone, and solidagoic acids A and B) were identified from six multipotent zones by bioassay-guided purification through preparative flash chromatography and HPLC, followed by HRMS and NMR, as well as by HPTLC hyphenated to quadrupole-orbitrap HRMS: A) by eluting with methanol (flow 100 µL/min) the compounds from the plate through the oval elution head of an interface of heated electro-spray ionization (spray voltage 3.5 kV, capillary temperature 270 °C, nitrogen as sheath and auxiliary gas, full scan in negative and positive ionization modes in m/z range 50-750); B) without eluent with a DART interface (Direct Analysis in Real-Time, needle voltage 4 kV, grid voltage 50 V, helium as gas, temperature 500 °C, full scan in positive ionization mode in m/z range 100-750).

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).

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).

Chromatography Research International 2014, 626801 (2014). HPTLC of extracts of Gymnema sylvestre (Apocynaceae) in tablets, as well as standards for calibration, on silica gel (prewashed with methanol and activated at 120°C for 15 min) with toluene – ethyl acetate – methanol 65:25:14. Derivatization by immersing into sulfuric acid (5 % in methanol) and heating at 110°C for 4 min. Densitometric evaluation within 25 min in absorbance mode at 423 nm, which was the optimal wavelength for quantifying simultaneously the triterpenoid gymnemagenin (hRF 27, linearity range 100–1200 ng/band, LOD 32 ng/band, LOQ 53 ng/band) and β-sitosterol (hRF 78, linearity range 200–1200 ng/band, LOD 97 ng/band, LOQ 159 ng/band). Interday and intra-day precisions as well as recovery rates provided relative deviation values below 1 %. This method was used to determine the analyte contents in the tablets (0.041 % gymnemagenin and 0.138 % β-sitosterol), as well as to confirm the stability of the analytes in solution at room temperature after 48h.   

J. Planar Chromatogr. 34, 377-401 (2021). HPTLC of flavonoid glycosides, phloroglucinol glycosides, monoterpene glycosides and monoterpene sugar esters, triterpenoids, phloroglucinols, monomeric phloroglucinols, dimeric phloroglucinols and phloroglucinol-terpene adducts in 15 eucalypts (13 Eucalyptus and 2 Corymbia) on silica gel with multiple mobile phases. Detection by spraying with anisaldehyde-sulfuric acid reagent. Zones were scanned from 200 to 700 nm.