J. Planar Chromatogr. 17, 84-88 (2004). OPLC of trans-resveratrol on silica gel with chloroform - methanol 10:1 after preconditioning of the plates for 3 h at 120 °C. Detection by immersion of the dried plates in a bacterial suspension (Pseudomonas savastanoi pv. phaseolicola race 6) for 20 s and MTT staining (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide; 80 mg MTT and 100 mg Triton X-100 in 100 mL water) either after a short draining period or after overnight incubation; after staining the time for evaluation varied (e. g. from 1 h to 6 - 9 days or more). First results of the investigation of a complex bioautographic system with special emphasis on the direct effect of the antibiotic trans-resveratrol (fitoalexin) and the function of formaldehyde in relation to antibiotics.

J. Chromatogr. A 1216(20), 4485-4491 (2009). TLC of (+)-catechin and (-)-epicatechin on cellulose with water. Detection with 4-dimethylaminocinnamaldehyde in HCl produced blue bands. Detection with vanillin reagent produced quickly fading red spots. Quantitative determination by absorbance measurement at 655 nm. Linearity was between 2 to 12 ng/zone and a polynomial regression fit from 2 to 30 ng/zone. The repeatability of the separation of 20 ng/zone was 3.5 % (%RSD, n = 6). The visible limit of detection of both standards was 1 ng/zone, the densitometric limit of detection was 0.2 ng/zone. The optimized 4-dimethylaminocinnamaldehyde reagent is superior to the more frequently used vanillin reagent and is applicable also for determination of mixtures containing other catechins, such as (-)-catechin, (-)-epicatechin gallate, (-)-epigallocatechin gallate, procyanidin A2, procyanidin B1 and procyanidin B2.

J. Planar Chromatogr. 24, 93-98 (2011). TLC of eleven phenols (2,6-dimethylphenol, phenol, 4-hydroxybenzaldehyde, 3-methylphenol, phloroglucinol, 2-methoxyphenol, 4-tert-butylphenol, 4-methoxyphenol, 3-nitrophenol, 2-aminophenol, 2,4-dichlorophenol) on RP-18 in a twin-trough chamber after saturation for 20 min at room temperature. 8 aqueous mobile phases (methanol - water 7:3 and 3:2, methanol - water - triethylamine 30:19:1, acetone - water 7:3 and 3:2, acetone - water - triethylamine 30:19:1, acetone - water - tetrahydrofuran 11:8:1, and methanol - water - acetic acid 30:19:1) and 6 non-aqueous mobile phases (acetone - n-hexane 1:4 and 3:7, acetone - n-hexane - triethylamine 9:40:1, tetrahydrofuran - n-hexane 1:4 and 3:7, tetrahydrofuran - n-hexane - triethylamine 9:40:1) were used. Detection under UV light at 254 nm. 2D TLC was performed by developing the plates in the first dimension using aqueous mobile phases and, after drying, non-aqueous mobile phases in the second dimension. The most efficient system was methanol - water - triethylamine 30:19:1 in the first direction and tetrahydrofuran - n-hexane - triethylamine 9:40:1 in the second direction.

Food Res. Int. 65, 13-19 (2014). Review of the challenges and limitations in the analysis of polyphenol-protein interactions. The author described some properties of the HPTLC, such as the level of resolution that can be obtained with 2D-HPTLC and the coupling with mass spectrometry, that make this tool a promising alternative for the analysis of protein-phenol adducts.

J. Planar Chromatogr. 29, 256-263 (2016). HPTLC fingerprinting of flavonoids and phenolic acids in seven different Scutellaria species on silica gel with ethyl acetate – toluene – formic acid 50:49:1 for dichloromethane and methanolic extracts. Dichloromethane extracts were also developed on cyano phase with propan-2-ol – n-heptane – formic acid 50:49:1 and methanol – water – formic acid 60:39:1. The methanolic extracts were developed using methanol – water – formic acid 40:59:1. Detection with anisaldehyde reagent. Evaluation by chemometric processing. The best results for chemometric processing were obtained on the cyano phase.

Planta Medica 83(03/04), 300-305 (2017). Preparative TLC on 1) RP-18 phase with methanol – water, in several proportions from 2:1 to 9:11 and on 2) silica gel with dichloromethane – ethyl acetate, from 5:1 to 10:3 was applied to purify eight phenylethylchromones from subfractions of a methanolic extract of Aquilaria filaria agarwood. Preparative TLC on silica gel with n-hexane – ethyl acetate 2:1 was also used to separate the products of one of these chromones (2-(2-hydroxy-2-phenylethyl)-4H-chromen-4-one) with the (S)- and (R)-MTPA-Cl (α-methoxy-α-trifluoromethyl-phenylacetyl-chloride) needed for the Mosher ester method for asymmetric carbon configuration, allowing, after NMR, the determination of the chromone as an uneven mixture of R- and S-enantiomers (4:1). The enantiomer separation was done after derivatisation into diastereoisomers (no chiral separation).

CBS 118, 5-7 (2017). Presentation of two HPTLC methods for 1) detection and identification of UV filter substances in suncream and 2) detection of phenolic markers in Edelweiss species (Leontopodium spp.). For 1) HPTLC of sun cream samples and standards octocrylene, avobenzone, octisalate and ensulizole on silica gel first with heptane – ethyl acetate 4:1 with chamber saturation, migration distance 70 mm, then with isopropanol, without saturation, migration distance 28 mm. Densitometric evaluation by absorbance measurement at UV 254 nm. Direct elution of target zones into a single quadrupole MS, detection in positive and negative ionization mode. For 2) HPTLC of methanolic and glycerol-based Edelweiss extracts and standards chlorogenic acid, apigenin, luteolin, luteolin-4-O-glucoside, luteoline-7-O-glucoside, leontopodic acids A and B, cynarine, and 3,5-dicaffeoylquinic acid on silica gel with butyl acetate – formic acid – water 280:100:3 with chamber saturation, migration distance 70 mm. Detection by heating the plate at 100 °C for 3 min and immersing (while still hot) into natural products reagent (1 g of 2-aminoethyl diphenylborinate in 200 mL ethyl acetate). Evaluation under UV 366 nm.

J. Planar Chromatogr. 31, 155-162 (2018). HPTLC of lawsone in Lawsonia inermis on silica gel with benzene ‒ ethyl acetate ‒ acetic acid 75:25:1. Quantitative determination by absorbance measurement at 275 nm. The hRf value for lawsone was 33. Linearity was in the range of 50-350 ng/zone. The intermediate precision was below 2 % (n=6). The LOD and LOQ were 16 and 50 ng/zone for lawsone, respectively. Average recovery was 96 %.