J. Planar Chromatogr. 35, 127-138 (2022). HPTLC of fresh fruit peels of some species of the genus Citrus L.: Citrus aurantium L. (bitter orange), C. unshiu Marc. (satsuma mandarin), C. reticulata Blanco (Robinson mandarin), C. sinensis L. (Washington Navel orange), C. limon Brum. (lemon), C. limetta (sweet lime), C. bergamia (bergamot), C. Medica (citron), C. paradisi Macf. (starruby grapefruit), C. maxima (pomelo) and C. maxima x C. paradisi (oroblanco) on silica gel with ethyl acetate - formic acid - acetic acid - water 100:11:11:26. Detection by dipping into a solution of NP (0.5% diphenylborinic acid aminoethyl ester in ethyl acetate), followed by dipping into a PEG (5 % PEG400 in dichloromethane). Tyrosinase inhibition analysis by dipping into 32 % ammonia, followed by drying and spraying with enzyme solution and incubation at room temperature for 10 min. DPPH radical scavenging activity by dipping into a solution of 0.05 % DPPH in methanol, followed by incubation for 30 min in darkness. 

J. Planar Chromatogr. 35, 103-116 (2022). HPTLC of Daqinjiao standard decoction containing the following herbs: Gentianae Macrophyllae Radix (1), Paeoniae Radix Alba (2), Glycyrrhizae Radix et Rhizoma (3), Notopterygii Rhizoma et Radix (4), Saposhnikoviae Radix (5), Angelicae Pubescentis Radix (6), Angelicae Sinensis Radix and Chuanxiong Rhizoma (7), Scutellariae Radix (8) on silica gel with ethyl acetate - methanol - water 15:2:1 for (1) to (5), n-hexane - ethyl acetate 7:3 for (6) and (7) and toluene - ethyl acetate - methanol - formic acid 15:5:1.5:3 for (8). Detection by spraying with 5 % solution of vanillin in sulfuric acid, followed by heating at 105 °C for 5 min for (1) to (3), (5) and (6) and spraying with 2 % iron trichloride for (8). Qualitative identification under UV light at 254 and 366 nm. Reference standards were gentiopicroside for (1), paeoniflorin for (2), liquiritin for (3), nodakenin for (4), 5-O-methylvisammioside for (5), osthole for (6), ligustilide for (7) and baicalein and wogonin for (8). The hRF values for reference standards for (1) to (8) were 40, 35, 46, 28, 24, 37, 65 and 56, respectively.  

J. Planar Chromatogr. 34, 561-567 (2021). HPTLC of Ecuadorian Chenopodium quinoa Willd. leaf extracts on silica gel with formic acid - water - methyl ethyl ketone - ethyl acetate 1:2:4:3. Detection by heating at 105 °C for 60 min, followed by a three step derivatization method: 1) spraying with a 3 mL solution of α-amylase (5 U/mL of α-amylase in ethanol 10 %), followed by incubation at 37 °C for 30 min, 2) a 2 mL solution of starch (1 % of starch in ethanol 10 %) was applied on the plate, followed by incubation at 37 °C for 10 min, and (3) detection using iodine vapors for 2 min (1 g of solid iodine). The method allowed rapid localizing of α-amylase inhibitory compounds in complex plant matrices.

J. Planar Chromatogr. 34, 559-560 (2021). HPTLC fingerprint of Ginkgo biloba finished products on silica gel with n-butyl acetate - methanol - water - formic acid 15:4:2:2. Detection by dipping into anisaldehyde reagent (1 mL of p-anisaldehyde in 200 mL of a mixture of methanol, acetic acid and sulphuric acid 17:2:1). Qualitative identification under UV light at 254 nm and 366 nm. 

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 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.

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.   

Nature - Lab. Invest. 100, 1411–1424 (2020). Samples were chloroform – methanol 1:1 solutions of lipid standards and of liver tissue extracts from wild-type mice (1), from transgenic murine models of hepatic steatosis (2) (mice expressing HBs, hepatitis B virus surface protein), or of cholestasis (3) (mice totally knock-out for the gene of phospholipid translocator ABCB4, ATP-binding cassette subfamily B member 4), or of both (4) (hybrids of mice (2) and (3)). HPTLC on silica gel (preheated at 110°C for 15 min) with n-hexane – diethyl ether – acetic acid 20:5:1. (A) For qualitative analysis, visualization under white light after immersion into anisaldehyde 0.5 % (in sulfuric acid – acetic acid – methanol, 1:2:17), followed by heating at 110°C for 9 min. (B) Identification of lipids was confirmed by elution of the zones of interest with methanol from the HPTLC layer through a TLC-MS interface and a filter frit directly to a quadrupole-orbitrap MS (atmospheric pressure chemical ionization, full HR-MS scan in m/z range 100–1000). (C) For quantitative analysis, visualization at UV 366 nm after derivatization by immersion into primuline reagent (primuline 0.5 g/L in acetone – water 4:1); fluorescence was measured at UV 366 nm (mercury lamp, optical filter for wavelengths above 400 nm, scanning slit 6.0 mm × 0.2 mm, speed 20 mm/s). (A) and (B) allowed the separation and detection of cholesterol, cholesteryl oleate, methyl oleate, free fatty acids (FFA, expressed as oleic acid equivalents) and triacylglycerols (TAG, as triolein equivalents) in liver extracts. (C) showed that TAG was decreased and FFA increased in (3) and (4), compared to (1) and (2). Cholesterol and cholesteryl oleate had no significant changes between groups.