J. Sep. Sci. 46, 2300582 (2023). HPTLC of berberine in Berberis vulgaris, Berberis
aquifolium, and Hydrastis canadensis on silica gel with n-propanol - formic acid - water 95:1:4 (1) and 90:1:9 (2). Detection of (1) by spraying with dragendorff reagent, followed by drying at 100 °C. Qualitative identification under UV light at 254 and 366 nm. The hRF values for berberine in different plants were between 44 and 49.

 J. Pharmacogn. Phytochem. 12(1), 6-14 (2023). TLC silica gel layers were used to monitor the purification through column chromatography (CC) of a chloroform fraction of the methanolic root bark extract of Rauvolfia vomitoria (Apocynaceae). Mobile phases were petroleum ether – ethyl acetate 4:1 (MP1), dichloromethane – methanol 20:1 (MP2), and dichloromethane – methanol 15:1 (MP3). Visualization under UV 254 nm. Preparative TLC on thicker silica gel was performed on two subfractions: (A) with dichloromethane – methanol 100:7 for the isolation of the methyl esters of eudesmic acid and of trimethoxycinnamic acid (hRF values 35 and 28, respectively, in MP1); (B) with MP2 for the isolation of an indole alkaloid: kumujan B (= 1-carbomethoxy-β-carboline, hRF value 40 in MP2). Other indole alkaloids were isolated through CC: ajmaline, mauensine and reserpine (hRF values 35, 13 and 47, respectively, in MP3).

J. Planar Chromatogr. 36, 31-43 (2023). HPTLC of chelerythrine (1) and ethoxychelerythrine (2) in the roots of Zanthoxylum nitidum on silica gel with chloroform - methanol 25:1. Detection under UV light at 365 nm. Direct analysis in real-time mass spectrometry (DART-MS) was used to monitor the chemical changes of (2) into (1) in different solvents, suggesting that a more stable (1) can be considered to replace (2) as quality marker for Zanthoxylum nitidum.

J. Planar Chromatogr. 35, 603-608 (2022). HPTLC of berberine (1) and ursolic acid (2) in an Ayurvedic formulation on silica gel with chloroform - acetone - formic acid 12:7:1. Quantitative determination by absorbance measurement at 330 nm. The hRF values for (1) and (2) were 46 and 68, respectively. Linearity was between 200 and 1000 ng/zone for (1) and 500 and 2500 ng/zone for (2). Intermediate precisions were below 2 % (n=9). The LOD and LOQ were 91 and 175 ng/zone for (1) and 153 and 465 ng/zone for (2), respectively. Recovery was in the range of 98 and 102 % for (1) and (2).

ACS Omega 4, 5038-5043 (2019). HPTLC of Sarcocephalus pobeguinii bark extract on silica gel with toluene - n-butanol - water 35:15:2. Detection under UV 366 nm. Effect-directed detection by dipping into a 0.02 % methanolic DPPH solution, α-glucosidase, and AChE/BChE assays. Fast blue salt B together with 2-naphthyl α-Dglucopyranoside or α-naphthyl acetate was used as substrates for the α-glucosidase or AChE/BChE assays, respectively. For the DPPH reagent, the plate was kept in the dark for 90 s, followed by heating at 60 °C for 90 s. All images were documented in white light illumination. Further analysis by high-resolution mass spectrometry. The method allowed the identification of antidiabetic, cholinesterase inhibiting, and antioxidative activities.

Heliyon 9(2), e13469 (2023). Samples were methanolic extracts of different organs (bark, leaves, fruit pericarps, roots, twigs, seed coats and seedlings) of Dysoxylon binectariferum (= D. gotadhora = D. ficiforme, Meliaceae), as well as rohitukine (chromone piperidine alkaloid) isolated from a bark Soxhlet extract through column chromatography. TLC was used to monitor the purity of rohitukine isolation and to compare the fingerprints of the organ extracts. TLC on silica gel in 2 steps, successively with ethyl acetate – hexane 2:1, and with methanol – chloroform – dichloromethane 4:4:1. Visualization under UV 254 nm and 366 nm. Rohitukine (hRF 16) was very concentrated in bark, but present also in pericarps, leaves, twigs, seed coats and seedlings. (Editors note: Mobile phases and distribution of rohitukine were explained directly by the author (successive 2-step development, not biphasic system). The TLC figures did not show unequivocally the presence in roots, but it was confirmed by the author (and already quantified by other methods in  doi.org/10.1371/journal.pone.0158099).

J Chromatogr A 1638, 461597 (2021). Samples were Isatis tinctoria (= I. indigotica) root extracts (Brassicaceae) and their fractions. Standards were oseltamivir acid (OA), a neuraminidase (NA) inhibitor; pinoresinol (PR, a lignan), β-sitosterol (SS, a sterol), and dihydro-neoascorbigen (DHNA, an alkaloid). HPTLC / TLC on silica gel with (1) petroleum ether – ethyl acetate – acetic acid 48:8:1 for petroleum ether extracts and SS, or 30:40:1 for ethyl acetate extracts, or 10:30:1 for PR; (2) with toluene – ethyl acetate – methanol – formic acid 16:3:1:2 or 10:4:1:2 also for ethyl acetate extracts and DHNA; (3) with n-butanol – acetic acid – water 25:4:3 for butanol extracts. OA was applied but not developed. RP-18, polyamide, cellulose, alumina layers were tested, but the resolution was lower. Derivatization by spraying with sulfuric acid (10 % in ethanol). Enzymatic assay by immersion of the plates into neuraminidase solution (6 U/mL), followed by 1 h incubation at 37 °C and by immersion into chromogenic substrate solution (1.75 mM 5-bromo-4-chloro-3-indolyl-α-D-N-acetylneuraminic acid). After 5 min, NA inhibitors were seen as white zones on blue background. The experiment was previously improved for the following parameters: incubation times, substrate and enzyme concentrations, followed by statistical evaluation and calculations using Box-Behnken design. Quantification by absorbance measurement (detection wavelength 605 nm, reference wavelength 420 nm). In optimal conditions, OA had LOD 300 ng/zone. Zones of interest on underivatized plates were directly submitted to MS, using EFISI (electrostatic-field-induced spray ionisation), as follows. Chromatograms were immersed 1–3 s into dimethicone – n-hexane 1:1 to form a hydrophobic film, and dried 30 min at room temperature; on the analyte spot, a hydrophilic droplet was formed with 5 µL methanol – water 1:1, extracting the analyte from the layer; the analyte was further attracted through a capillary tube (3–4 cm long, made of non-deactivated fused silica) under a strong electrostatic field, into the in-let orifice of the triple-quadrupole ­– linear ion-trap MS (induction voltage 4 kV; capillary voltage 40 V; tube lens voltage 100 V; capillary temperature 200 °C). Full-scan spectra were recorded in m/z range 50 – 1000, helium was used for collision-induced dissociation. 11 active compounds were identified in the extract: SS, 6 alkaloids (including cycloanthranilylproline, DHNA, hydroxy-indirubin, isatindigodiphindoside, isatindinoline A and), 3 lignans (including PR and isolariciresinol), 1 fatty acid (trihydroxy-octadecenoic acid).

Food Chem. 131846 (2022). HPTLC of Trifolium medium L. (1) and Trifolium pratense (2) on silica gel with dichloromethane - methanol - ethyl acetate 5:10:11:20 for (1) and chloroform - ethyl acetate 3:2 for (2). The AChE inhibitory activity of individual compounds was examined by spraying with 1) acetyl cholinesterase, followed by incubation at 37 °C for 20 min, 2) 2 mM acetylthiocholine solution and 3) 2 mM 5,5´-dithiobis-(2-nitrobenzoic acid) solution, and visualized after 20 min.