J Chromatogr A, 1620, 460970 (2020). Samples were ethyl acetate extracts of Lavandula angustifolia herb and flowers and of aerial parts of other Lamiaceae (Ocimum basilicum, Origanum vulgare, Thymus vulgaris, Rosmarinus officinalis, Salvia officinalis), as well as standards. HPTLC on silica gel (pre-washed with methanol and heated 30 min at 105 °C) with n-hexane – ethyl acetate – acetic acid 70:27:3. Documentation at UV 254 nm and 365 nm and white light before and after A) derivatization with anisaldehyde – sulfuric acid reagent, followed by 10 min heating at 110 °C; B) spraying with DPPH• (0.2 % in methanol), followed by 30 min incubation in the dark; C) α-amylase inhibition assay by immersion into enzyme solution, incubation 30 min at 37 °C, immersion into substrate solution (starch 1 % in water), incubation 20 min at 37 °C and immersion into Gram’s iodine solution for detection (inhibition zones appear blue on white background). Quantification was performed on pictures using image processing software, and expressed as equivalents to the respective standards used for calibration curves: A) β-sitosterol (LOQ 1.5 µg/band), B) gallic acid (LOQ 60 ng/band), C) acarbose (LOQ 8 µg/band). An amylase inhibiting zone (hRF 68) present in all samples (except L. angustifolia), scraped from untreated plates and washed with ethyl acetate, was tentatively identified by ATR-FTIR analysis as oleanolic acid (pentacyclic triterpene).

J Chromatogr A, 1675, 463167 (2022). Samples were ethanol extracts (and their flash chromatography fractions) of Prunus armeniaca leaves (Rosaceae), as well as betulinic, linolenic, maslinic (= crataegolic), oleanolic, ursolic acids and pygenic acids A (= corosolic acid) and B b as standards. When needed, to improve separation of triterpenoids, reversible pre-chromatographic derivatization was performed in situ by applying 10 µL iodine solution (2 % in chloroform) either before development on the deposit band, or for 2D-HPTLC after a first separation up to 60 mm and before a second orthogonal separation. Layers were covered 10 min with glass sheet after iodine application, and then dried 1 min under cold air stream. HPTLC on silica gel with chloroform – ethyl acetate – methanol 20:3:2, 85:9:6, or 15:2:3), followed by 5-10 min drying under cold air stream (eliminating iodine completely). Post-chromatographic derivatization by immersion (time 2 s, speed 3 cm/s) into vanillin – sulfuric acid (40 mg and 200µL, respectively, in 10 mL ethanol), followed by heating 5 min at 110 °C. Antibacterial effect-directed analysis was performed by immersion (time 8 s) into Bacillus subtilis suspension, followed by 2 h incubation at 37 °C, immersion in MTT solution and 30 min incubation at 37 °C. Active bands were eluted from layer with methanol through the oval elution head of a TLC-MS interface pump, into a single quadrupole mass spectrometer to record full scan mass spectra (m/z 200–1200 in both modes) using electrospray ionization (interface temperature 350°C, heat block temperature 400°C, desolvation line temperature 250°C, detector voltage 4.5kV). Five triterpenoids were identified: betulinic, corosolic, maslinic, oleanolic and ursolic acids, acid, as well as two fatty acids: linolenic and palmitic acid.

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.

Drug Standards of China 22 (3), 259-264 (2021). Gentianella acuta (Michx.) Hulten is a herbal traditional Chinese medicine, containing mainly efficacy components like diphenylpyrione, cycloether terpenoids, flavonoids, and triterpenoids. It has liver protection, hypoglycemic, anti-inflammatory and other pharmacological activities, and is used clinically to treat jaundice, headache, fever, dry mouth and bile fever etc. To establish a quality standard of the herb, TLC was used for the investigation of the chemical composition and fingerprints. TLC of methanolic extracts of 10 batches of Gentianella acuta  collected from different regions (A) for cycloether terpene components (gentiopicroside and swertimarin), on silica gel with ethyl acetate - methanol - water 4:1:1, detection under UV 254 nm, identification by comparison of the fingerprints with those of the standards gentiopicroside and swertimarin; (B) for terpenoids (oleanolic acid), on silica gel with chloroform - methanol - ammonium hydroxide 20:6:1, detection under UV 254 nm, identification by comparison of the fingerprints with those of the oleanolic acid standard; (C) for aqueous extracts (water-soluble components such as flavonoids and phenolic acids), on silica gel with 1-butanol - acetic acid - water 9:3:2, detection by spraying with 5 % aluminium trichloride solution and evaluation under UV 366 nm, identification by comparison of the fingerprints with those of the oleanolic acid standard. The results showed that the TLC profiles of 10 batches were very similar, and well consistent with the HPLC fingerprint results. In addition, gentiopicroside, swertimarin and oleanolic acid were identified by TLC in the medicine, thus can be used as the target components of the identification. Therefore, the results of this study can be used as the basis for the authenticity identification and quality evaluation of the medicine.

Molecules, 26 (5), 1468 (2021). Summary: Samples were fortified extracts produced with iPowder technology (involving spray-drying of a rich first extract on a new batch of the same plant) from following plants: Camellia sinensis final bud and two leaves (Theaceae), Cynara scolumus leaves and Echinacea purpurea roots (Asteraceae), Eleutherococcus senticosus roots (Araliaceae), Equisetum arvense aerial part (Equisetaceae), Eschscholzia californica aerial parts (Papaveraceae), Humulus lupulus cones (Cannabaceae), Ilex paraguariensis leaves (Aquifoliaceae), Melissa officinalis aerial parts and Rosmarinus officinalis leaves (Lamiaceae), Passiflora incarnata aerial part (Passifloraceae), Raphanus sativus var. niger roots (Brassicaceae), Ribes nigrum leaves (Grossulariaceae), Spiraea ulmaria floral tops (Rosaceae), Valeriana officinalis roots (Caprifoliaceae), Vitis vinifera leaves or pomace (Vitaceae). HPTLC on silica gel with 1) ethyl acetate – toluene – formic acid – water 16:4:3:2,  or 2) cyclohexane – ethyl acetate – formic acid 30:19:1. Detection under white light, UV 254 nm and 366 nm. Extract stability after 2 years was also checked through HPTLC. Neutralization by spraying phosphate-citrate buffer, and drying in cold air stream. Effect-directed analysis using automated piezoelectrical spraying: A) for enzymatic inhibition (acetyl-cholinesterase, glucosidase, glucuronidase, tyrosinase); B) for activity against Gram-negative bacteria (Aliivibrio fischeri bioluminescence assay). Active bands of multipotent compounds were eluted from HPTLC layers 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 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). By comparison to literature, the following compounds were assigned: caffeine, catechins, carnosol, chlorogenic acid, cynaratriol, dicaffeoylquinic acid, feruloyl quinic acid, gallic acid, linoleic and linolenic acids, oleanic or ursolic acid, rosmarinic acid.

J Chromatogr A, 1611, 460602 (2020). Samples were methanolic root macerates of Euthamia graminifolia, Solidago canadensis, S. gigantea, S. rugosa and S. virgaurea (Asteraceae). HPTLC on silica gel with n-hexane – isopropyl acetate – acetone 16:3:1; or (for preparative TLC) on TLC silica gel with n-hexane – acetone 7:3, followed by scraping the layer and eluting with ethanol. When intended for MS experiments, layers were previously washed with methanol – water 4:1 and heated 20 min at 100 °C. Derivatization with vanillin – sulfuric acid reagent. Multivariate image analysis of the derivatized chromatograms allowed clear separation of samples according to species. Effect-directed analysis for: A) enzymatic inhibition by immersion into acetyl- and butyryl-cholinesterase, glucosidase and amylase solutions; B) activity against Gram-negative bacteria using Xanthomonas euvesicatoria chromogenic bioassay, and Aliivibrio fischeri and Pseudomonas syringae maculicola bioluminescence assays; C) activity against Gram-positive bacteria with Bacillus subtilis spizizenii bioassay. Two labdane diterpenes (solidagenone, hRF 47, and presolidagenone, hRF 55) in S. canadensis and two polyacetylenes (matricaria-esters = methyl-decadiene-diynoates, hRF 78 and 87 in HPTLC) in S. virgaurea were identified from multipotent zones by bioassay-guided purification through preparative TLC / HPLC, followed by HRMS and NMR, as well as by HPTLC hyphenated to quadrupole-orbitrap HRMS in 2 ways: A) by eluting with methanol the compounds from the plate through the oval elution head of a TLC-MS interface, with heated electro-spray ionization (HESI, 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); tandem mass spectra were acquired in parallel at fragmentation energy of 15-100 eV; 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 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.