J. Planar Chromatogr. 33, 27-32 (2020). HPTLC of rutin (1), chlorogenic acid (2) and gallic acid (3) in the seeds of Moringa oleifera on silica gel with ethyl acetate - acetone - water - formic acid 6:3:2:2. Quantitative determination by absorbance measurement at 254 nm. The hR_F values for (1) to (3) were 51, 72 and 83, respectively. Linearity was between 1000 and 7000 ng/zone for (1), 100 and 700 ng/zone for both (2) and (3). Intermediate precisions were below 1 % (n=6). The LOD and LOQ were 5 and 17 ng/mL for (1), 7 and 22 ng/mL for (2) and 7 and 20 ng/mL for (3), respectively. Recovery rate was between 98.1 and 99.5 % for (1), 98.8 and 99.5 % for (2) and 97.6 and 98.6 % for (3).

J. Planar Chromatogr. 33, 33-41 (2020). HPTLC fingerprint of the kernel and seed of Allanblackia parviflora fruit (extracted with methanol - water 4:1) on silica gel with methanol - water - ethyl acetate 33:27:200. Detection by spraying with vanillic acid - sulfuric acid reagent (1 g of vanillic acid in 100 mL of 96 % ethanol, followed by the dropwise addition of 2 mL concentrated sulfuric acid). Different formulations of the derivatization reagent were investigated and the use of vanillic acid instead of the more frequently used vanillin provided a better result. Qualitative determination under UV 254 and 366 nm. Consistent hR_F values of the main zones under UV 254 nm were 39, 35 and 12. For the derivatized plate, consistent hR_F values of the main zones were 39, 34, 31 and 22.

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.

J. Liq. Chromatogr. Relat. Technol. 42, 563-569 (2019). HPTLC of spinosin in the fruits of Ziziphus jujuba on silica gel with ethyl acetate - dichloromethane - methanol - water 18:10:15:5. Quantitative determination by absorbance measurement at 334 nm. The hRF value for spinosin was 38. Linearity was between 10 and 120 ng/mL. Intermediate precision was below 2 % (n=6). The LOD and LOQ were 12 and 35 ng/mL, respectively. Recovery rate was between 98.7 and 101.3 %. The HPTLC method provided similar reproducibility, accuracy and selectivity for the quantitative determination of spinosin compared with a HPLC method.

J. AOAC Int. 102, 1003-1013 (2019). HPTLC of quercetin (1) and berberine (2) in Pushyanuga Churna on silica gel with toluene - ethyl acetate - methanol - formic acid 6:6:2:1. Quantitative determination by absorbance measurement at 254 nm for (1) and 366 nm for (2). The hRF values for (1) and (2) were 63 and 24, respectively. Intermediate precisions were below 2 % (n=3). The LOD and LOQ were 1 and 3 µg/mL for (1) and 0.05 and 0.1 µg/mL for (2), respectively. Recovery rate was between 93.5 and 100.6 % for (1) and 95.2 and 97.6 % for (2).