J Chromatogr A, 1625, 461230 (2020). Samples were extracts of Chinese plants: Acorus tatarinowii (= Acorus calamus var. angustatus) rhizomes (Araceae / Acoraceae) (1), Angelica sinensis roots (Apiaceae) (2), Gynura japonica rhizomes (Asteraceae) (3), Phellodendron chinense bark (Rutaceae) (4), Picrasma quassioides twigs and leaves (Simaroubaceae) (5), Rheum sp. roots and rhizomes (R. palmatum, R. tanguticum and/or R. officinale) (Polygonaceae) (6), Sophora flavescens roots (Fabaceae) (7), Dendrobium stems (D. aphyllum, D. aurantiacum var. dennaeanum, D. chrysanthum, D. chrysotoxum, D. gratiosissimum, D. hercoglossum, D. thyrsiflorum, D. trigonopus and D. williamsonii) (Orchidaceae) (8). Standards were: gigantol (from D. sonia); methoxycarbonyl-β-carboline (MCC from (5)); caffeic acid, emodin; senecionine and β-asarone; crategolic acid (= maslinic acid), corosolic acid, oleanic acid, ursolic acid; sesquiterpenoids (atractylenolides I – III) from Atractylodes macrocephala (Asteraceae); flavonoids (baicalein, baicalin, daidzin, hesperidin, wogonin) from Scutellaria baicalensis roots (Lamiaceae). HPTLC on silica gel with 10 mobile phases, depending on the samples. Detection under UV 254 nm and white light. For (3), derivatization with Dragendorff’s reagent (bismuth potassium iodide solution) for visualization of alkaloids. Zones of interest on underivatized plates were identified by a triple-quadrupole ­– linear ion-trap MS, the compounds being removed from the layer by a continuous-wave (445 nm) diode laser pointer through a DART interface (Direct Analysis in Real-Time, helium as gas for plasma-based ambient ionization, discharge needle voltage 1.5 kV, grid voltage 350 V, capillary temperature 300 °C and voltage 40 V, full scan in positive ionization mode in m/z range 150-800). Pigment standards were used for validation of this laser-assisted HPTLC-DART-MS method: malachite green, crystal violet, chrysoidin, auramine O, rhodamine B, Sudan red I – IV, Sudan red G, dimethyl yellow. Afterwards, the same HPTLC-MS method was applied to the origin / species determination of Dendrobium samples, based on the presence of four bibenzyl compounds erianin, gigantol, moscatilin, tristin. Erianin was present only in D. chrysotoxum, whereas none of these were detected in D. hercoglossum. Several components of the extracts were thus identified: asarone (a phenylpropanoid) in (1); phthalide lactones (butenylphthalide, ligustilide and chuanxiong lactone) in (2); co-eluting pyrrolizidine alkaloids (senecionine and seneciphylline) in (3); benzylisoquinoline alkaloid berberine in (4); alkaloids (canthinone alkaloids and MCC) in (5); anthraquinones (rhein, aloe-emodin, emodin, emodin methyl ether, chrysophanol) and (in negative mode) caffeic acid (a hydroxycinnamic acid) and corosolic, maslinic and oleanic acids (triterpenoids) in (6); quinolizidine alkaloids (matrine, oxymatrine, oxysophocarpine, sophoridine) in (7).

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.

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).