J. Planar Chromatogr. 33, 79-87 (2020). HPTLC of vitamin C in the dried fruit of Rosa laxa on silica gel with ethyl acetate - absolute ethanol - water 40:24:15. Quantitative determination by absorbance measurement at 273 nm. The hR_F value for vitamin C was 61. Linearity was between 0.25 and 1.2 µg/zone. Intermediate precisions were below 2 % (n=6). Average recovery was 98.4 %.

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 84(2), 129-134 (2018). TLC of subfractions obtained from normal-phase LC and size-exclusion chromatography of an ethanolic extract of Bougainvillea spectabilis (Nyctaginaceae) stem-bark on RP-18 with methanol – water 2:3 and 1:1 to isolate six flavones (bougainvinones J, K, L, M, and two dimethylflavone derivatives).

Planta Medica 84(1), 59-64 (2018). A multi-step fractionation through silica gel column chromatography (CC) of a methanolic extract of Plectranthus africanus (whole plant, Lamiaceae) was monitored through TLC on silica gel with various solvent mixtures (n-hexane or dichloromethane with either acetone or methanol). Zones were detected under UV and further by spraying with sulfuric acid 20 % and heating at 100°C. For each fraction or TLC profile, the authors provide the CC gradient, the optimal proportions of the solvents used for the TLC mobile phase, as well as the RF values of the molecules isolated by this CC method: new abietane-type diterpenoids (plectranthroyleanones A, B, C), betulinic and oleanolic acids, heterosides of apigenin, rhamnetin and sitosterol.

Planta Medica 84(1), 26-33 (2018). For the monitoring of the multi-step fractionation through VLC (vacuum liquid chromatography) of the chloroform-soluble parts of a methanol – water 7:3 percolate of Hippophae rhamnoides (Eleagnaceae) fruit peels, TLC on silica gel and RP-18, detection by spraying with sulfuric acid and heating. Preparative TLC on silica gel with cyclohexane – dichloromethane – methanol 5:15:1 to isolate, from VLC subfractions, three lignans (nectandrin B, fragransin A2, saucernetindiol) that are diastereoisomers of each other.

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.

J. of Modern Trad. Chinese Med. 20 (8), 975-978 (2018). Panax notoginseng is a traditional Chinese medicinal herb which activates blood circulation, anti-platelet aggregation and anti-thrombosis. TLC for quality control of ginsenoside Rb1 (1), notoginsenoside R1 (2) and ginsenoside Rg1 (3) on silica gel with the lower phase of chloroform – methanol – water 13:7:2 (after standing for 12 h at below 10˚C). Detection by spraying with 10% sulfuric acid in ethanol and heating at 110 ˚C until the zones are visible, evaluation under UV 365 nm. Quantification by densitometric absorption measurement at 510 nm. Validation by investigation of the linearity ranges of 0.5-5.0 µg/zone (r=0.998) for (1), 0.5-5.01 µg/zone (r=0.999) for (2) and 0.5-4.9 µg/zone (r=0.998) for (3). The plate-to-plate precision % RSD (n=12) was 1.5 %, 1.1 % and 1.9 % for (1) to (3). Recovery from standard sample addition was 96.4 % (%RSD 1.4 %, n=6) for (1), 96.9 % (%RSD 0.9 %, n=6) for (2), and 98.9% (%RSD 1.7 %, n=6) for (3).

J. of Chromatogr. A 1534, 170-178 (2018). HPTLC of flavonoid aglycones in eleven commercial Cistus incanus herbal teas using three independent methods (multi-development on amino phase and two two-dimensional developments on silica gel phase). HPTLC on silica gel with chloroform - methanol - ethyl acetate 15:3:2. Detection at UV 254 and 366 nm and by derivatization with aluminium chloride (1 % methanolic solution), ferric chloride (0.5 g FeCl₃ in 2.5 mL water and 47.5 mL ethanol), NP-PEG (0.5 % methanolic NP solution, and after drying, 5 % ethanolic PEG solution), PABA (0.5 g PABA in 18 mL glacial acetic acid diluted with 20 mL water, plus 1 mL o-phosphoric acid and 60 mL acetone), or DPA reagents (1 g aniline and 1 g diphenylamine in 100 mL acetone and 10 mL o-phosphoric acid, heated for 5 min at 110°C). Confirmation of the presence of glucose by HPTLC on amino phase with in situ acid hydrolysis: incubation in HCl vapor followed by heating at 100°C, pre-development with acetonitrile, drying, development with acetonitrile - water 7:3, heating for 20 min at 170°C and dipping in paraffin - n-hexane 1:2 follwed by drying. TLC-direct bioautography by immersion of the developed and dried plates in a bacterial cell suspension of either Bacillus subtilis or Aliivirio fischeri strains. Analysis of the compounds isolated from the bioactive zones by HPLC-diode array detector (DAD)-electrospray ionization (ESI)-MS. The presented TLC/HPTLC platform allowed identification of the antibacterial components apigenin, kaempferide, cis- and trans-tiliroside, and the isomers of the p-coumaric acid-conjugated tiliroside,  all of them inhibiting both B. subtilis and A. fischeri.