J. Planar Chromatogr. 19, 463-466 (2006). Preparative RP-HPTLC of anthocyanin extracts (e. g. malvidine) on silica gel with five-step gradient elution with different concentrations of toluene - acetonitrile - water - formic acid - n-butanol - 2-propanol and resp. addition of tert-butylmethyl ether. After extraction of the third zone from the layer, HPTLC on RP-18 as the best stationary phase with a three-step gradient elution using methanol - water - formic acid in different ratios. Quantitative determination by absorbance measurement at 470 nm.

J. Planar Chromatogr. 23, 230-232 (2010). HPTLC of (+)-catechin, (-)-epicatechin, (-)-epigallocatechin, (-)-epigallocatechin gallate, (-)-epicatechin gallate, procyanidin B2, procyanidin A2, and methylxanthines (theobromine and caffein) on cellulose with n-propanol - water - acetic acid 20:80:1 in a horizontal chamber. Detection by dipping for 1 s into 4-dimethylaminocinnamaldehyde detection reagent. Quantitative determination by absorbance measurement at 655 nm. By densitometry LOD for (-)-epicatechin and procyanidin B2 was 0.2 and 2 ng/zone, respectively; LOQ was 0.4 ng and 4 ng/zone, respectively. These limits were lower by a factor 50 for (-)-epicatechin and by a factor of 10 for procyanidin B2 than those obtained by HPLC. The TLC method gave a more accurate result for the (-)-epicatechin content of baking chocolate than the HPLC method which was also more time-consuming.

Food Chem. 156, 94-99 (2014). TLC of epigallocatechin gallate (1), gallic acid (2) and caffeine (3) on silica gel with dichloromethane - acetone - formic acid 8:7:1. Detection by dipping into 5 % methanol - sulfuric acid reagent, followed by heating at 105 °C for 3 min. Quantitative determination of (1) as gallic acid equivalents by absorbance measurement at 270 nm (epigallocatechin gallate (EPCG) was calculated and expressed as gallic acid equivalents because the EPCG standard is very expensive). The hRF values for (1) to (3) were 54, 69 and 80. Linearity was in the range of 500-5000 ng/zone for (2) and 200-2400 ng/zone for (3). The intermediate/inter-day/intra-day precisions were below 2 % (n=3). The LODs and LOQs were 400 and 500 ng/zone for (2) and 180 and 200 ng/zone for (3), respectively. Recoveries were between 94.9 and 100.0 % for (2).

Journal of Ethnopharmacology 163, 192-202 (2015). TLC of the aqueous extract (crude vs. after tannin removal on a polyamide column) of the kino (red hydrosoluble exudate) of Pterocarpus erinaceus on silica gel with s-butanol – water – acetic acid 14:5:5. Detection with vanillin-hydrochloric acid reagent revealed catechic tannins and related polyphenols as dark pink zones. These compounds showed hRfs between 0 and 40, and above 60 in the case of the crude extract, whereas they almost did not appear in the tannin-free fraction. The extracts were also submitted to HPLC-HRMS, allowing the identification of epicatechin monomer in both extracts and of oligomers in the crude extract only.

J. AOAC Int. 99, 374-379 (2016). HPTLC of glabridin in the roots of Glycyrrhiza glabra on silica gel with hexane – ethyl acetate – chloroform 5:4:3. Quantitative determination by absorbance measurement at 285 nm. The hRF value of glabridin was 48. Linearity was in the range of 50-500 ng/zone. The LOD and LOQ were 10 ng/zone and 30 ng/zone, respectively. Intermediate precisions were below 2 %. Recovery was between 100.6 and 102.0 %. Compared to a validated HPLC method there was no statistically significant difference in the mean values.

J. Ethnopharmacol. 197, 242-249 (2017). Kanakasava is an Indian traditional Ayurvedic formulation containing Datura metel, Adhatoda vasica, Woodfordia fruticosa and Vitis vinifera extracts as major constituents. HPTLC of gallic acid (1) and ethyl gallate (2) on silica gel with toluene – ethyl acetate – formic acid – methanol 35:35:8:5. Quantitative determination by absorbance measurement at 292 nm. The hRF values for (1) and (2) were 43 and 48, respectively.

J. Liq. Chromatogr. Relat. Technol. 41, 329-341 (2018). HPTLC of flavonoids (flavone, apigenin, luteolin, chrysin, quercetin dihydrate, myricetin, kaempferide, kaempferol, naringenin and pinocembrin) in propolis, roasted coffee, rose hip, hibiscus, rosemary and sage on silica gel with n-hexane – ethyl acetate – formic acid 20:19:1. Detection by heating the plate at 110 ºC for 3 min, followed by dipping into NP reagent (1 g of diphenylboric acid 2-aminoethyl ester in 200 mL of ethyl acetate) for 1 s, and after drying into paraffin – n-hexane 1:2 or PEG 4000 for 1 s (for enhancement and stabilization of fluorescent zones), followed by drying for 2 min. Qualitative identification under UV 254 and 366 nm. HPTLC–MS(/MS) analysis was also performed using a TLC-MS interface. Some possible interferences with phenolic acids (chlorogenic acid, rosmarinic acid, protocatechuic acid, gallic acid, syringic acid, ellagic acid, trans-cinnamic acid, o-coumaric acid, m-coumaric acid, p-coumaric acid, caffeic acid, ferulic acid, sinapic acid) were also examined.

Anders. J. Planar Chromatogr. 31, 437-443 (2018). HPTLC of apigenin (1) and luteolin (2) in Hygrophila spinosa on silica gel with toluene – ethyl acetate – formic acid 6:4:1. Quantitative determination by absorbance measurement at 349 nm. The hRF values for (1) and (2) were 64 and 54, respectively. Linearity ranged between 80-560 ng/zone for (1) and 40-280 ng/zone for (2). LOD and LOQ were 6 and 19 ng/zone for (1) and 2 and 7 ng/zone for (2), respectively. The intermediate precision was <3 % (n=3). Recovery was between 99.3 and 100.5 % for (1) and 99.5 and 100.8 % for (2).