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, 1616, 460774 (2020). Methanolic extracts of leaves of Musa acuminata, M. balbisiana and M. sapientum (Musaceae), either from fields or from in vitro cultures or from the plantlets derived from in vitro culture and acclimatized in isolated warm room, were separated on HPTLC silica gel layers with toluene – ethyl acetate – methanol 6:3:1 or ethyl acetate – toluene – formic acid – water 34:5:7:5. 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. Evaluation under white light, UV 254 nm and 366 nm. Derivatization by immersion (2s, 2cm/s) into natural product reagent preceded by heating at 110 °C for 5 min, or into anisaldehyde sulfuric acid reagent, diphenylamine aniline reagent, ninhydrin reagent, followed by the same heating procedure. Besides, plates were neutralized by cold air stream followed with phosphate buffer (8 %, pH 7.5) piezoelectrically sprayed on the plates and automated plate drying. Thereafter, 9 effect-directed assays (EDA) were performed for free radical (DPPH•) scavengers, for enzymatic inhibitors (α-amylase, acetyl- and butyryl-cholinesterase, α- and β-glucosidase), for antimicrobial compounds (Gram-positive Bacillus subtilis assay, Gram-negative Aliivibrio fischeri bioluminescence assay), and for mutagenic compounds (SOS response – UMU-C test using Salmonella typhimurium suspension and 4-nitroquinoline 1-oxide as positive control). The bands of 4 active compounds were eluted with methanol through a TLC-MS interface pump into a quadrupole-Orbitrap mass spectrometer. Full scan mass spectra (m/z 50−800) in the positive and negative ionization modes were recorded using electrospray ionization (ESI, spray voltage 3.3kV, capillary temperature 320°C, collision energy 35 eV). By comparison to a standard, one band present in all samples was identified as linolenic acid. For the other bands, only present in in vitro grown accessions, only raw molecular formulas and phytochemical classes were assigned (a pyrrolidine alkaloid, an amino-acid, a phenolic derivative).

J. Planar Chromatogr. 34, 513-520 (2021). HPTLC of curcumin (1), piperine (2) and ascorbic acid (3) in a combined marketed formulation on silica gel with chloroform - methanol - ether - glacial acetic acid 95:3:1:1. Quantitative determination by absorbance measurement at 254 nm for (3) and in fluorescence mode at 366 nm for (1) and (2). The hRF values for (1) to (3) were 65, 83 and 28, respectively. Linearity was between 620 and 3040 ng/zone for (1), 470 and 2380 ng/zone for (2) and 530 and 2670 ng/zone for (3). Interday and intra-day precisions were below 2 % (n=3). 

J. Planar Chromatogr. 34, 521-530 (2021). HPTLC of piperine in Piper nigrum on silica gel with toluene - ethyl acetate 3:2. Quantitative determination by absorbance measurement at 254 nm. The hRF value for piperine was 63. Linearity was between 200 and 1000 ng/zone. Interday and intra-day precisions were below 1 % (n=3). The LOD and LOQ were 611 and 1778 ng/zone, respectively. Average recovery was 98.3 %.

J. Planar Chromatogr. 34, 543-548 (2021). HPTLC of mangiferin (1) and berberine (2) on silica gel with toluene - acetone - formic acid 7:11:2. Quantitative determination by absorbance measurement at 261 nm. The hRF values for (1) and (2) were 39 and 80, respectively. Linearity was between 400 and 800 ng/zone for (1) and 100 and 500 ng/zone for (2). Interday and intra-day precisions were below 2 % (n=5). The LOD and LOQ were 26 and 79 ng/zone for (1) and 19 and 18 and 56 ng/zone for (2), respectively. Average recovery was 101.2 % for (1) and 101.0 % for (2). The effect of various forced degradation conditions was observed.

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. Planar Chromatogr. 34, 353-359 (2021). HPTLC of alkaloids in the leaves of Solanum retroflexum on silica gel with chloroform - ethyl acetate - methanol 9:8:3. Detection under UV light at 365 nm. Further analysis of extracted zones by ultra-high performance liquid chromatography-quadrupole time-of-flight hyphenated to mass spectrometry (UHPLC‒QTOF‒MS).

J. Planar Chromatogr. 34, 329-336 (2021). HPTLC of piperine in the leaves of Piper trichostachyon on silica gel with n-hexane - ethyl acetate 1:3. Quantitative determination by absorbance measurement at 342 nm. The hRF value for piperine was 50. Linearity was between 100 and 700 μg/μL. LOD was 100 μg/μL. Intermediate precisions were below 3 %. Average recovery was 105.8 %.