Planta Medica 84(6/7), 465-474 (2018). The new concept “Comprehensive HPTLC Fingerprinting” was applied to define specifications for the identification and purity assessment of Angelica gigas roots, and for the quantification of its markers: the coumarins decursin and decursinol angelate. Methanolic root extracts of A. gigas (10 reference materials, 24 commercial samples), of 26 other Apiaceae species (including 10 Angelica, 9 Ligusticum, 2 Notopterygium, 4 Peucedanum, and Levisticum officinale) and of mixtures, were developed with toluene - ethyl acetate - acetic acid 90:10:1 on HPTLC silica gel (at 33% relative humidity, chamber pre-saturated for 20 min with filter paper and developing solvent) and dried for 5 min. Detection under white and UV lights before and after derivatization by dipping into 10% sulfuric acid in methanol and then heating 3 min at 100°C. Quantitative evaluation by densitometry in fluorescence mode at UV 313 nm, and luminance was also calculated from the image pixels. The study showed the presence in A. gigas of nodakenin, decursinol, 7-demethylsuberosin, imperatorin, osthole, and isoimperatorin at hRF 0, 4, 15, 33, 38 and 44 respectively. Z-ligustilide (hRF 59) was absent from A. gigas, allowing 1) to distinguish it from several other Apiaceae species; 2) to identify in mixtures with A. gigas two common adulterants (A. acutiloba, A. sinensis) even at 1% in the root powder. Minimal content of A. gigas fingerprint markers (decursin + decursinol acetate, co-eluting at hRF 27) was assessed as 3% (w/w) based on the quantified peaks from A. gigas reference materials.

Planta Medica 83(17), 1329-1334 (2017). Two acetone-soluble subfractions of an n-hexane maceration of Hypericum denudatum aerial parts (Hypericaceae) were submitted to repeated centrifugal planar chromatography (CPC) on silica gel using n-hexane – ethyl acetate (gradient from 100:0 to 90:10), obtaining four dimeric acylphloroglucinols (denudatin A, hyperbrasilol A, uliginosin B and isouliginosin B), which were purified by crystallisation with n-hexane – dichloromethane 9:1. From the most apolar CPC eluates, a monomer (selancin A) was isolated on preparative TLC silica gel layer by elution with n-hexane – ethyl acetate 97:3. Furthermore, all the purification steps were monitored through TLC on silica gel with n-hexane – ethyl acetate 19:1 or with n-hexane – dichloromethane 1:1. Detection under UV light after derivatization with anisaldehyde – sulfuric acid, monomeric acylphloroglucinols appeared purple, whereas dimers appeared yellow-orange.

Planta Med. 83(14/15), 1233-1241 (2017). HPTLC of standards and methanolic extracts of L. cardiaca, L. japonicus and L. sibiricus (Lamiaceae) acidified with formic acid on silica gel with ethyl acetate – acetic acid – formic acid – water 100:11:11:26, in an automatic development chamber with 48 % humidity (20 min presaturation). Detection under white and UV light, before and after immersion in 1) anisaldehyde – sulphuric acid (followed by heating) for the detection of iridoids; 2) natural product reagent A for phenylpropanoids; 3) modified Dragendorff reagent (bismuth oxynitrate 0.17 %, sulfuric acid 3.5 %, glacial acetic acid 2 %, potassium iodide 4 %) for alkaloids. Ajugoside (hR_F 29) and verbascoside (hR_F 53) were found in L. cardiaca and L. sibiricus, but absent in L. japonicus. The opposite was true for leonurine (hR_F 52), whereas stachydrine (hR_F 14) was found in the three species. This method allows to distinguish L. japonicus from the other species, which have to be distinguished from each other through morphology.

J. Planar Chromatogr. 32, 55-57 (2019). TLC of dimethyl phthalate, diethyl phthalate, di-n-butyl phthalate, diisobutyl phthalate, diallyl phthalate, and bis(2-ethylhexyl) phthalate on silica gel with petroleum ether - ethyl acetate - phosphoric acid 9:1:1. Detection by spraying with 0.1 % 2,6-dichlorophenolindophenol with the instantaneous appearance of pink-colored zones.

J. Planar Chromatogr. 32, 69-71 (2019). HPTLC of oxyfluorfen in visceral tissue on silica gel with hexane - acetone 4:1. Detection by spraying with 5 % stannous chloride solution in hydrochloric acid, followed by heating at 110 ºC for 20 min. After cooling, the plates were sprayed with freshly prepared cooled (0‒5 °C) nitrating mixture of sodium nitrite in hydrochloroc acid, followed by a solution of β-napthol in sodium hydroxide. The hRF value of oxyfluorfen was 61. 

Biomed. Chromatogr. 21 (1), 94-100 (2006). Presentation of a post TLC developing technique to detect substances which can inhibit tyrosinase activity. The TLC plate is sprayed with tyrosinase and l-tyrosine solutions successively. A positive result is detected as white zone against a brownish-purple background. The method is suitable as a quick screening procedure for tyrosinase inhibitor detection, and as a guiding procedure for the isolation of tyrosinase inhibitors from mixtures or natural product extracts.

Science & Culture Jan.-Feb., 22-30 (2008). Isolation and identification of some unique chemical compounds is reported using chemical, chromatographic and spectroscopic methods such as GC-MS, HPTLC and HPLC. The presence of bio-organic molecules such as oxygenated dibenzo-a-pyrones (DBPs), their amino acyl conjugates (DCPs) and polyphenyl benzoquinones (PBQs) was observed in all the four samples of meteorites. HPTLC on silica gel with 1) n-butanol - acetone - acetic acid - water 7:7:2:4 for amino acids, detection with ninhydrine reagent and absorbance measurement at 610 nm; 2) n-butanol - acetic acid - water 3:1:2 for sugars, detection with p-anisidine reagent and absorbance measurement at 380 nm; 3) chloroform - methanol 9:1 for DBPs and absorbance measurement at 240 nm and 360 nm.

Abstract No. 9185, IHCB (2009). HPTLC of hydro alcoholic extracts of Berberis aristata on silica gel with benzene - ethyl acetate - diethyl amine 6:3:1. Detection by spraying with AlCl3 reagent (for estimation of flavonoids) or with Folin Ciocalteu reagent (for total phenolic content). The fingerprint profile was optimized using two different mobile phases: n-butanol - acetic acid - water 14:1:5 and n-propanol - formic acid - water 90:1:9. The extract showed 6 different spots and was found to contain 13.5 % w/w of berberin.